Mage = 26.3 years, SDage = 7.67, range 15–38) who participated in different team sports . Data were analyzed using an inductive thematic analytic procedure. The results revealed four themes of shared stressors involving issues relating to social pressure, relationships between teammates, performance, or logistics and organization; and four themes of communal coping, namely: problem-focused communal efforts, relationship-focused coping, communal management of emotions, and communal goal withdrawal. The results provided empirical support to the communal coping model (Although sport psychology research has mainly focused on stress and coping as intrapersonal processes, stressful circumstances are often experienced in social groups and coping emerges as a combination of individual and group effort , 2014. Bng model  and exteng model , 2000a.  Successful adaptation in sport settings requires effective cognitive, behavioral, and emotional self-regulation skills . A critiMuch of the research on stress and coping within sport psychology is based on Lazarus’s cognitive-motivational-relational theory (CMRT) of emotion , 2000a. There is also a clear need to explore how appraisal of stressors by athletes influences and is influenced by other team members during their common unfolding team activity and to what extent sources of stress are shared by teammates during sport encounters . mastery coping, including strategies that involve athletes attempting to take control of a stressful situation and thus eliminate the stressor ; (b) internal regulation coping, in which athletes attempt to manage internal responses to stress ; and (c) goal coping withdrawal, referring to athletes ceasing their efforts to achieve goals .Traditionally, coping is defined as constantly changing “cognitive and behavioral efforts to manage specific external and/or internal demands that are appraised as taxing or exceeding the resources of the person” , p. 141.Coping processes, like sources of stress, have been studied almost exclusively from an individualistic perspective . For exaCommunal coping represents a novel perspective through which to examine athletes’ collective efforts to deal with stressors in a team or group context. It refers to a process whereby stressors are appraised and acted upon in the context of close relationships, and describes the efforts of individuals in a group as they collectively cope with stressors . To dateConsidering the widespread use of the CMRT of emotion , 2000a, Mage = 26.3 years, SDage = 7.67, range 15–38), gender , years of practice , levels of practice, and who participated in different team sports. The diversity of the sample allowed us to collect a wide range of information. In addition to these criteria, the 10 participants were selected based on their key roles in their respective teams (see Table 1). After eight interviews, when two further interviews had been conducted with no new themes emerging, we defined this as the point of data saturation (Table 1 for full information). The protocol was also approved by the scientific committee of the French National Association of Research and Technology (ANRT).We purposefully sampled French male and female team sport athletes who varied in terms of age  participated in first interviews to pilot the interview guide. These pilot interviews allowed the interviewer to become familiar with the interview guide and helped her to find effective ways to help athletes verbalize notions of sharing. For example, it was agreed that athletes should be prompted to explicitly verbalize their team’s coping strategies immediately after the enunciation of each shared stressors, and not to separate the parts of the interview inquiring about shared stressors and communal coping strategies. In addition, for those athletes who had difficulty expressing shared stressors, they have been invited to remind them of recent match scenarios.M = 49 min, SD = 8.7) and was conducted by the first author, a sport psychologist accustomed to interview techniques. Interviews were audio recorded and transcribed verbatim, resulting in 152 pages of typed data.The final version of the guide comprised three parts: (a) general information about the athlete’s background  and team social context ; (b) shared sources of stress within the team experienced during competitions ; and (c) communal coping strategies used by the team to deal with shared stressors . Each athlete was questioned at an interpersonal level on his/her perception of his/her team’s experiences and functioning when faced stressful situations during competitions. General questions were asked to obtain detailed descriptions of team’s experiences and functioning in these situations. For example, athletes were asked, “During a game, what specific incidents or events caused you and your teammates to feel collectively stressed?”, “What disturbed the functioning of your team as a whole?”, and “What were your thoughts and actions immediately after collectively experiencing this unpleasant event?”. In this line, athlete’s use of ‘we-talk’ was thought as an indicator of communal coping and his/her perception that their team collectively deal with stressors . InterviWhen we see that our best players are beaten, whether it’s in a fight, speed or during play, it’s really difficult for us,” A8, MIH). In the same way, when athletes reported actions involving the sharing of resources and combining the efforts of several teammates . Between each interview coding, the first and third authors shared their coding and discussed their results until agreement was reached.The research was conducted from a critical realist position, where the reality is assumed to exist but to be only imperfectly apprehendable because of basically flawed human intellectual mechanisms and the fundamentally intractable nature of phenomena . Througheammates , the iteThen, codes related to shared stressors and communal coping strategies were collated into potential themes, gathering all data relevant to each potential theme. The themes were checked depending on the identification of common features and adaptive functions. For example, communal coping strategies such as analysis and action planning, information sharing, refocusing, going back to basics and effort expenditure were grouped together on the basis that they shared a problem-focused communal effort function. The shared stressors and communal coping strategies’ themes, were labeled using procedures of constant comparison between the coded narratives, the related developed theories and the conceptualizations of the findings. Even though the analysis was inductively conducted, congruence between existing literature on stress and coping and concepts identified in our analysis was examined to label the different codes and themes . When prAs a final step in the analysis, we tabulated the number of meaning units (MUs) to observe the distribution of stressors and communal coping strategies among the 10 participants. To specify the distribution, coders counted each of the shared stressors and communal coping strategies, and the number of informants that reported each stressor or coping strategy.Several precautions were taken to follow a list of criteria such as credibility and critical researcher . Indeed,The data analysis procedure revealed 272 MUs comprising 143 MUs related to shared sources of stress and 129 MUs related to communal coping strategies.n = 50), “Relationship between teammates issues” , “Performance issues” , and “Logistical and organizational issues” .The thematic analysis revealed four themes of shared stressors: “Social pressure issues”  and negative social interactions between teammates. These interactions can be verbal  or non-verbal . This theme is illustrated by the following quotes:A1, WFB: The captain, she didn’t act the way she should, she kept telling us off…and that created conflict between the girls.A6, MVB: There’s one player in the team who spends all his time waving his arms in the air – to complain – he’s the coach’s favorite, and the public’s too. But I think it bothers the whole team.Other athletes, such as A3, MR, described a situation in which relationships within their team were threatened by the reflection of one of the teammates:A3, MR: Let’s take the example of a scrum. If we (the forward) are packed into a scrum and the prop is beaten by his opposite number… it’s difficult for him, it hurts his pride, it’s a big thing. And if, in addition, the number 10 then says to him “he’s getting you sideways, you can’t keep doing that,” he’s going to take it badly. He’s already suffered a scrum, maybe even a penalty, and then, as well as all that, his teammate doesn’t support him and doesn’t try to make him feel any better about it… […] And well, when you’re a forward and you hear that… It’s like you’re having a go at your own team.This theme encapsulated the stressors associated with the team’s performance level. It includes stressors linked to the low controllability of the situation and the score, the domination of the opponents and the decrease in the perception of team-efficacy. A9, WBB, A4, MR, and A8, MIH referred to these stressors in the following terms:A9, WBB: We were all over the place, the others were counter-attacking all the time.A4, MR: When you feel you’re not going to make it, even the things you can normally do don’t work. For example, if it’s 2 against 1 and you don’t manage the pass at the right time. Take the Perpignan away match, we knocked on in the in-goal area! At Montpellier, in the first half we were down 30 points to 3… We were being beaten in every area: scrums, passing, kicks, defense… it was a disaster, in the first half we were nowhere!A8, MIH: When the team is… – traumatized is too strong- but the team is a bit …well, psychologically vulnerable, you really feel it. When it’s tricky psychologically and you’re beaten, you feel it. Everyone feels it. […] When you’re physically swamped by the opposition, that’s the hardest. When we see that our best players are beaten, whether it’s in a fight, speed or during play, it’s really difficult for us.This theme encapsulated the stressors associated with the organizational aspects of competitions, such as travel or equipment. This theme is illustrated by the following quotes:A7, MVB: We have a very specific routine on match days, and sometimes, if the journey doesn’t go to plan, we can’t follow it. That can affect us in the evening match.A5, WVB: We’ve played in some gyms where there were leaks in the roof. Once, someone suggested we play in gloves, it was so cold.Table 2).The 129 communal coping strategies used resulted in 13 categories, which then fitted into four overarching communal coping dimensions: “Problem-focused communal efforts”; “Relationship-focused coping”; “Communal management of emotions”; and “Communal goal withdrawal” (see Table 2). Five communal coping strategies were identified in this dimension. (a) Analysis and action planning, consisting of analyzing a problematic situation together and organizing a communal action plan, as shown in the following quotes from two athletes whose teams were then down:This dimension included communal coping strategies aimed at managing and solving problems encountered by several teammates during the competitive event in a collective way  Information sharing, consisting of seeking or providing information support to teammates in order to resolve the problem. For example, two athletes said:A1, WFB: When something like an injury happens I try to give technical advice. […]. I talk to those who were around to give practical advice: “Keep it simple,” “Don’t get worked up,” “If you see it starting to get heated, move away. Until we get a substitution.”During team out- We ask the girls on the bench, as they have a different perspective […] we go and ask their advice.A5, WVB: -(c) Refocusing, consisting of teammates keeping the team’s attention on task-relevant cues when they are facing a problem, as highlighted below:After a lost set – We move on, as if we’re starting a new match. What’s done is done, we focus on what we have to do.A6, MVB: - A10, MBB: We could easily have moved the focus away from the referee, saying, “OK, that’s it, we’re going to stop talking about the refereeing now, we’re just going to play.(d) Going back to basics, consisting of returning to fundamentals, simple game plans, which the team knows inside-out. The following quotes illustrated this strategy:A5, WVB: We gave a lot in the 1st set. In the 2nd set we started out at the same pace and at a certain moment we decided that maybe we shouldn’t overdo it and we should go back to basics a bit and play a more traditional game.A8, MIH: Instead of skating about all over the place, we’re going to try and refocus on simple, effective things.(e) Effort expenditure, consisting of mobilizing the physical and mental resources of the team in order to act together directly on the stressful situation, as highlighted by the following quotes:A5, WVB: We didn’t even talk. We fought to the very end.A10, MBB: It means that, on the contrary, we’re going to go all out, we’re going to be accurate in everything we do so that all the players can enjoy playing basketball well! That’s the most important thing!Table 2). Three communal coping strategies were identified in this theme: (a) Motivational support, consisting of one or more teammates providing encouragement through behavioral or verbal actions to one or more players in order to sustain the relationship between teammates. For example, two athletes said:This dimension included coping strategies using cognitive and behavioral efforts to manage and sustain relationships within the team during the stressful episode  Compensation, consisting of adapting the team play to relieve a teammate in difficulty and compensate for his or her weaknesses, as shown in the following quotes:A7, MVB: If a player is struggling, we say “No, don’t worry, we’ll adapt, we’ll make up for it.” We’ll adapt and even if he doesn’t play quite as well or if his distribution of the ball isn’t as good, we’ll make up for all that until he gets back into the game.A5, WVB: They try to compensate if they can. Certain players try to make up for me so that you can’t actually see that I’m not really in it. But actually if you know where to look, it shows because they don’t compensate very well.When the point guard has difficulty- So it means we have to spread the marking out a bit better between the other players.A9, MBB: - (c) Social joining, consisting of physically joining forces to deal with the situation. This strategy is illustrated by the following quotes:A3, MR: We huddle in the in-goal area, for example, when they score a try.A1, WFB: When we group together, that cuts us off even further from the outside world, in fact it’s a bubble. We’re sort of in a bubble that is the game. We go back into the team bubble.A9, WBB: For example, when there are free throws, we have what we call “middles”: that’s when we huddle together on the court. The five players get together, and the captain  talks to the team.Table 2). Three communal coping strategies were identified in this dimension. (a) Interpersonal emotional regulation, consisting of inhibiting one’s own emotions to protect teammates, to regulate a teammate’s emotions or to use the group to regulate one’s own emotions, as highlighted below:This dimension represented communal coping strategies aimed at regulating team emotions generated by the confrontation with shared stressors  Reassurance, consisting of helping a teammate in trouble with his/her skill, as highlighted by the following quotes:-To a player who has just come into play- We had to reassure him. Tell him that he knows all the fundamental moves, that he can do it, and it’ll be fine.A3, MR: A7, MVB: His mates are around and they’re going to try and go over to him and try to reassure him and give him confidence. Later, it might also be up to the coach to do that but it’s the teammates who are on the court. So the first port of call on the court is the rest of the team: we try to reassure him.(c) De-dramatization, consisting of defusing the situation together, as illustrated by the following quotes:A7, MVB: The team laughs about the pressure, we make a joke of it. But afterwards, there’s enormous pressure, we make a little bit of a joke of it. We joke about it between partners a bit, we make a joke of it so it’s easier to deal with.-When their goal keeper is continuously angry- We muck about generally. We defuse the situation.A8, MIH: Table 2). Two communal coping strategies were identified in this dimension. (a) Task-disengagement, in which teammates collectively cease their efforts to achieve communal goals. For example, two athletes said:This dimension represented the strategies through which a team withdraws from the process of actively striving toward the realization of desirable outcomes  Venting emotions, in which teammates collectively express and ventilate unpleasant emotional tensions, as highlighted by the following quotes:A4, MR: I could see the whole team was about to boil over and complain.A10, MBB: Well, everyone was angry, yeah. Everyone was angry, they were all complaining and saying “It’s rubbish!”.The purpose of the present study was to explore team sport athletes’ perceptions how their team collectively cope with shared stressors during competitive encounters. This study provides empirical support for recent research perspectives on stress and coping within teams in sport settings . The finThe team sport athletes experienced numerous stressors during games, which appeared to affect the team’s functioning as a whole. Specifically, the team sport athletes reported communal sources of stress appraised as “our” problem, related to social pressure issues , relationships between teammates , performance issues , or logistical and organizational issues . Overall, the results complemented findings from previous research using an intrapersonal perspective to explore team sport athletes’ individual sources of stress e.g., , 2009. IIn response to shared stressors, team sport athletes used a variety of communal strategies to deal with them. The communal coping strategies identified can be grouped into four main communal coping dimensions: problem-focused communal efforts ; relationship-focused coping ; communal management of emotions ; and communal goal withdrawal . The identification of these four coping dimensions at the team level represents an important step in the understanding of communal coping in team sports by offering a new perspective on how teams cope when dealing with communal stressors. Indeed, these communal coping strategies concretely describe the collective actions teammates use to cope with shared stressors . While these communal coping strategies share some similarities with individual coping functions see , the oriSome of these communal coping strategies identified in the present research have been reported in previous studies conducted on communal coping in different contexts and social groups e.g., . For exaFurthermore, our results also revealed one dimension unique to communal coping, which differs from any existing individual coping dimensions  and has not been previously highlighted at individual level in a sport context. Relationship-focused coping strategies seem to be used in order to maintain and develop the relationship within the team and to obtain collective benefit during the game . In the This research is at the early stages of investigation into the interpersonal dimensions of stress and coping in sport and performance contexts e.g., . AlthougOur findings also provide a response to researchers who have highlighted the need for further study of how communal coping operates across different types of social groups e.g.,  and acroOn a practical level, these results reinforce the suggestions made by some authors who have underlined the importance for athletes of coping with social stressors and developing inter-player communication skills or supportive behavior as a team coping strategy . To dateAlthough this study observed a rigorous methodology, some limitations should be raised. The main limitation is that shared stressors and communal coping strategies of team sport were investigated through the perceptions of one member of a team without necessarily taking into account the team as a whole. We made this choice in order to be able to interview athletes from different teams, different sports, of different ages and different levels and thus span a wide range of information without being limited to a single team and its standards. Furthermore, we chose to interview athletes with specific roles  that gave him/her a good knowledge of his/her team and that allowed us to have access to a perception of the collective phenomena that could take place within a team. However, this choice has prevented us from verifying with certainty the collective aspect of stressors and the strategies cited. The second limitation is related to the method used . Although this method maximized the ability to extract in-depth information, we were unable to verify the synchronization of the athletes’ responses within their teams. Future research could use Despite these limitations, this study represents a first step in the study of stress and coping at team level. It highlights the interpersonal nature of the stress and coping processes in team sports. Although this study provides an initial insight, future research could continue the investigation of these collective processes by checking how they are shared, by whom they are initiated and how to train athletes in their use. It could also be useful to examine the antecedents  and the consequences  of communal coping. Furthermore, it would be interesting to develop specific ways to assess communal coping strategies in sport.The protocol was approved by the local ethic committee of the French Football Federation and of the two Universities associated to the project. All subjects gave written informed consent in accordance with the Declaration of Helsinki.CL, FD’A-L, and JD conceived the study. CL collected the data and mainly analyzed them with JD. All authors participated in the manuscript redaction. All authors had complete access to the study data that support the publication and approved the manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


We investigate individual heterogeneity in the tendency to under-respond to feedback (“conservatism”) and to respond more strongly to positive compared to negative feedback (“asymmetry”). We elicit beliefs about relative performance after repeated rounds of feedback across a series of cognitive tests. Relative to a Bayesian benchmark, we find that subjects update on average conservatively but not asymmetrically. We define individual measures of conservatism and asymmetry relative to the average subject, and show that these measures explain an important part of the variation in beliefs and competition entry decisions. Relative conservatism is correlated across tasks and predicts competition entry both independently of beliefs and by influencing beliefs, suggesting it can be considered a personal trait. Relative asymmetry is less stable across tasks, but predicts competition entry by increasing self-confidence. Ego-relevance of the task correlates with relative conservatism but not relative asymmetry.The online version of this article (10.1007/s11166-018-9277-3) contains supplementary material, which is available to authorized users. The ability and willingness to take into account feedback on individual performance can influence important choices in life. Mistakes in incorporating feedback may lead to the formation of under- or overconfident beliefs that are known to be associated with inferior decisions. Reflecting the importance of the topic, there is a substantial literature in psychology and economics on Bayesian updating and the role of feedback in belief formation, which we review in more detail below. This literature shows that people are generally “conservative”, i.e. they are less responsive to noisy feedback than Bayesian theory prescribes. Möbius et al.  beliefs for individuals with many bad (good) signals by 10 percentage points on average. A standard deviation in relative asymmetry raises beliefs for any feedback, and by up to 22 percentage points for subjects with a similar number of positive and negative feedback signals.Moreover, feedback responsiveness explains subjects’ willingness to compete with others, a decision that is predictive of career choices outside of the lab (see the literature review below). We measure willingness to compete on a final task, composed from exercises similar to each of the previous tasks. Subjects choose whether they want to get paid on the basis of an individual piece rate, or on the basis of a winner-takes-all competition against another subject. We find that relative conservatism predicts entry into competition both through influencing final beliefs and independently of beliefs. Relative asymmetry also predicts entry by raising final beliefs. Thus, being more conservative and asymmetric is good for high-performing subjects with an expected gain from competition, and bad for the remaining subjects.To our knowledge, this paper provides the most in-depth investigation so far of the importance of individual feedback responsiveness for beliefs about personal ability and economic decisions. Our findings suggest that individual differences in conservatism and, to a lesser degree, asymmetry help explain differences in self-confidence and willingness to compete. In the conclusion, we provide a range of domains in which we expect these attributes to affect people’s decisions and discuss how our study can help to reduce the negative effects of faulty updating.A sizable literature in psychology on belief updating has identified that people are generally “conservative”, meaning they are less responsive to noisy feedback than Bayesian theory suggests  procedure, also known as “matching probabilities” or “reservation probabilities”. Participants were asked to indicate which probability Subjects then were introduced to the first of three different tasks. Each task was composed of a series of puzzles, and subjects were asked to complete as many puzzles as they could within a time frame of five minutes. Their score on the task would be the number of correct answers minus one-half times the number of incorrect answers. The first task, which we will refer to as “Raven”, consisted of a series of Raven matrices, where subjects have to select one out of eight options that logically completes a given pattern ”). In the second task, which we will refer to as “Anagram”, subjects were asked to formulate an anagram of a word displayed on the screen, before moving to the next word (subjects were told that “this exercise is designed to measure your ability for languages”). In the third task, which we will refer to as “Matrix”, subjects were shown a 3×3 matrix filled with numbers between 0 and 10, with two decimal places. The task was to select the two numbers that added up to 10 .5The order of tasks was counterbalanced between sessions, in order to account for effects of depletion or boredom. The details for each task were explained only after the previous task had been completed. Subjects earned 8 DKK for each correct answer and lost 4 DKK for each incorrect answer. We explained to them that their payment could not fall below 0.After each task, we elicited subjective beliefs about a subject’s relative performance. Specifically, we asked participants for their belief that they were in the top half of their group using the BDM procedure described above. After participants submitted their initial beliefs, we gave them a sequence of noisy but informative feedback signals about their performance. Participants were told that the computer would show them either a red or a black ball. The ball was drawn from one of two virtual urns, each containing 10 balls of different colors. If their performance was actually in the top half of their group, the ball would come from an urn with 7 black balls and 3 red balls. If their performance was not in the top half, the ball would come from an urn with 7 red balls and 3 black balls. Thus, a black ball constituted “good news” about their performance, a red ball “bad news”. After subjects observed the ball, they reported their belief about being in top half for a second time. This process was repeated five more times, resulting in six updating measurements for each participant for each task, and 18 belief updates overall. The prize at stake in the belief elicitation task was 10 DKK in each round of belief elicitation.After the third task, subjects were informed about the rules of the fourth and final task, which consisted of the same kind of puzzles as the previous three tasks, mixed in equal proportions. Before performing this task, subjects were offered a choice between two payment systems, similar to Niederle and Vesterlund’s  “Task 3”After the competition choice, subjects were asked to fill out a (non-incentivized) questionnaire. Among other things, we asked how relevant participants thought the skills tested in each of the three tasks were for success in their field of study. We will use the answers to these questions as an individual measure of ego relevance of the tasks. Subjects also completed a narcissism scale, based on Konrath et al. , and ansaggregate patterns of asymmetry and conservatism. To get a feeling for the aggregate distribution of beliefs, Fig. In this section, we answer the question of whether people update in a Bayesian fashion, and focus on R2 = 0.30) than in the Anagram task (R2 = 0.21) or the Raven task (R2 = 0.14). In each task, we find that the R2 of the model increases between 7 and 9 percentage points between the first and last round of belief elicitation. Thus, on average feedback does indeed succeed in providing a tighter fit between actual performance and beliefs over time.To understand whether beliefs have become better calibrated we run OLS regressions of initial and final beliefs in each task on the actual performance rank of subjects. In the initial round, we find that ranks explain more of the variation in beliefs in the Matrix task .We first look at one of the most basic requirements for updating, namely whether people change their beliefs in the right direction. Figure positive rather than negative feedback. Using the same test as for wrongly signed signals, we find that this difference is highly significant .The right panel of Fig. Thus, overall about one-third of our observations display qualitative deviations from Bayesian updating. Importantly, both zero and wrongly signed updates increase in the final updating rounds of each task. Whatever the reason for this pattern ,y-axis) and prior beliefs (x-axis) presented as dots, excluding updates in the wrong direction. The dashed line presents the Bayesian or rational benchmark, showing that updates should be largest for intermediate priors that represent the largest degree of uncertainty. The solid line presents the best quadratic fit to the data, with a 95% confidence interval around it.We now focus on the relation between updates and prior beliefs. Figure The left panel of Fig. It therefore appears that, in contrast to the Bayesian prescription, subjects on average update a constant absolute amount, without conditioning on prior beliefs.μint represents the posterior belief for person i in task n ∈{Anagram, Raven, Matrix} after signal in round t ∈{1,2,3,4,5,6}, and μin,t− 1 represents the prior belief (i.e. the posterior belief in the previous round). Thus, our belief data have a panel structure, with variation both across individuals and over rounds. λH is the natural log of the likelihood ratio of the signal, which in our case is 0.7/0.3 = 2.33, and λH = −λL. To investigate asymmetry and conservatism more systematically, we follow MNNR in estimating the regression model of a linearized version of Bayes’ formula given byδ,βH,βL = 1 correspond to perfect Bayesian updating (see MNNR for more details). Conservatism occurs if both βH < 1 and βL < 1, i.e. subjects place too little weight on either signal. If βH≠βL, this implies “asymmetry”, i.e. subjects place different weight on good signals compared to bad signals. MNNR find that βH > βL on an IQ quiz, but not on a neutral updating task.From the logistic transformation of Bayes’ rule one can derive that The first column of Table 10In each of the three columns, we see clear evidence for conservatism: both the coefficients on the positive and negative signal are very far from unity, the coefficient consistent with Bayesian updating. This implies that most subjects in our sample are indeed conservatively biased in their updating.In the We find that subjects deviate systematically from Bayesian updating:about 10% of updates are in the wrong direction, and such mistakes aremore likely after a negative signal,one quarter of the updates are of size zero, and zero updates happenmore often after a positive signal,among the updates that go in the right direction, updates are a)not sufficiently sensitive to the prior belief, b) too conservative and c)symmetric with respect to positive and negative signals.RA) and “relative conservatism” (RC), to reflect the nature of the interpersonal comparison. We use the absolute size of deviations, since using the relative size leads to large variations in our measures for individuals with extreme priors where average updates are small.13We now turn to the heterogeneity in updating behavior across subjects. In this section, we therefore define individual measures of asymmetry and conservatism. To quantify subjects’ deviations from others, we use the distance of each update from the average update by people with the same prior and the same signal. We call the resulting measures “relative asymmetry”  flexibility to our predicted average updates compared to the quadratic fit shown in Fig. To calculate individual deviations, we use residuals of the following regression model, which is run separately for positive and negative signals.i and for each round t and task n, regression residuals from Eq. 𝜖int. Our measure of relative asymmetry in task n is then defined asRAin is the sum of the average residual after a positive and the average residual after a negative signal. It is positive if an individual updates a) upwards more than the average person after a positive signal, and/or b) downwards less than the average person after a negative signal.For each individual To obtain an overall individual measure for relative asymmetry we calculate an analogous measure across all 3 tasks, spanning 18 updating decisions.i on task n is defined asRCin is the average residual after a negative signal minus the average residual after a positive update. Thus, RCin is positive if an individual updates upward less than average after a positive signal and updates downward less than average after a negative signal. To obtain an overall individual measure of conservatism we calculate an analogous measure across all 3 tasks, spanning 18 updating decisions.Correspondingly, relative conservatism for person These measures are similar to the ones developed by Möbius et al. . One difRC from RA for those with only positive or only negative signals.Finally, updates in the wrong direction pose a problem for the computation of our relative measurements. An update of the wrong sign has a potentially large impact on our measures, as it is likely to result in a large residual. However, as it seems likely that such updates at least partly reflect “mistakes”, this may unduly influence our measures. To mitigate this effect, we treat wrongly signed updates as zero updates in the calculation of our individual measures. Note also that we only calculate our measures for subjects who receive at least one positive and at least one negative signal as it is impossible to distinguish We now analyze these measures of responsiveness, looking in turn at their consistency across tasks, their variation across ego-relevance and their impact on post-feedback beliefs.RC and RA across tasks. Table RC, we find highly significant correlations in the range of 0.22–0.37. For RA, correlations are smaller, and the only significant correlation is that between RA in the Matrix and Anagram tasks. This latter result is puzzling, as these tasks are very different from each other and are seen as relevant by different people.An important motivating question for our research is whether feedback responsiveness can be considered a trait of the individual. To answer this question, we look at the consistency of For a given individual, relative conservatism displays robust correlation overtasks, whereas relative asymmetry does not.We now turn to an analysis of heterogeneity in feedback responsiveness related to task and subject characteristics. In turn, we discuss the role of ego-relevance and gender.Past research suggests that the ego-relevance of a task changes belief updating, and can trigger or increase asymmetry and conservatism , we add individual fixed effects to compare more and less relevant tasks within subject, disregarding between-subject variation. The effect is equally strong, indicating that the same subject is more conservative in tasks that measure skills which are more ego-relevant.To test the extent to which ego-relevance can explain the variation in feedback responsiveness across tasks, we regress Combined with the positive effect of relevance on initial beliefs, the results are consistent with the idea that people deceive themselves into thinking that they are good at ego-relevant tasks and become less responsive to feedback in order to preserve these optimistic beliefs.We find that the self-reported ego relevance of the task is positively correlatedwith initial beliefs and relative conservatism. We do not find a correlationbetween ego relevance and relative asymmetry.Earlier studies have consistently found that women are less (over)confident than men, especially in tasks that are perceived to be more masculine  When observing unbalanced feedback with many more positive than negativesignals or vice versa, a one standard deviation change in relative conservatismor asymmetry changes final beliefs by a little over 10 percentage points. Forbalanced feedback with similar amounts of both positive and negative signals,a one standard deviation change in asymmetry changes final beliefs by about20 percentage points. Controlling for feedback content, relative conservatismand asymmetry jointly explain an additional 21 percentage points of thebetween-subjects variation in final beliefs.In this section we investigate the predictive power of feedback responsiveness for the choice to enter a competition. Competition was based on the score in the final task of the experiment, which consisted of a mixture of Matrix, Anagram and Raven exercises. Before they performed this final task, subjects decided between an individual piece-rate payment and entering a competition with another subject, as described in Section The posterior beliefs about the performance in the previous tasks are likely to influence this decision, which implies that our measures of feedback responsiveness should matter. Specifically, we would expect that relative asymmetry raises the likelihood of entering a competition because it inflates self-confidence. The hypothesized effect of relative conservatism is more complex. Conservatism raises final beliefs, and supposedly competition entry, for those who have many negative signals. However, it should depress competition entry for those who received many positive signals. In addition to this belief channel, it may be that updating behavior is correlated with unobserved personality traits that affect willingness to compete.RA and RC, controlling for ability. We also include gender, as it has been shown that women are less likely to enter a competition  entry decision on RC with the amount of positive signals. The estimated coefficients show that for a person with no positive signals, an increase of one standard deviation in RC raises the probability of entry by 22 percentage points, an effect that is larger than the gender effect. If we compare the coefficient of the interaction term with the coefficient of the number of positive signals in Column (2), we see that an increase in RC reduces the effect of a positive signal by about 75% (0.018/0.024). The estimated total effect of RC is negative for someone with large amounts of positive signals. The effect of more positive signals and its interaction with RC disappear when we control for initial and final beliefs (Column 5), confirming that these effects indeed go through beliefs. However, RC still exerts a large positive direct effect. Together, Columns (4) and (5) clearly suggest that, in addition to its effect on final beliefs, there is an effect of RC that may be a part of a person’s personality. Controlling for the relevance that subjects attach to the three tasks does not alter any of the results.16In order to better understand the effect of conservatism, we interact Relative asymmetry raises the probability of competition entry by increasingfinal beliefs. Relative conservatism raises the probability of competition entryfor people with many negative signals, and diminishes it for those with manypositive signals. Conservatism also has an independent, positive effect on entry,suggesting it may be correlated with competitive aspects of personality.This paper contains a comprehensive investigation of Bayesian updating about beliefs in own ability. We investigate both aggregate patterns of asymmetry and conservatism and individual heterogeneity in these dimensions. On aggregate, we find strong evidence for conservatism and little evidence for asymmetry. Our individual measures of relative feedback responsiveness deliver a number of new insights about individual heterogeneity. We find that differences in relative conservatism are correlated across tasks that measure different cognitive skills, indicating that they can be considered a characteristic or trait of the individual. The same cannot be said about relative asymmetry, which is not systematically correlated across tasks. We also find that individuals are more conservative, but not more asymmetric, in tasks that they see as more ego-relevant. Both measures have substantial explanatory power for post-feedback confidence and competition entry. Relative conservatism affects entry both through beliefs and independently, whereas relative asymmetry increases entry by biasing beliefs upward. Finally, we find that women are significantly more conservative than men.Our study demonstrates both the strengths and limitations of our measurements of asymmetry and conservatism. Measuring updating biases is complex. There is noise in our measures, and their elicitation is relatively time consuming. Future research could investigate whether simpler or alternative measures could deliver similar or better predictive power. Another approach would be to vary the belief elicitation mechanism  business, as well as a range of risky behaviors in which confidence plays a central role. In doing so, it could follow research that has linked laboratory or survey measurements of personal traits to behavior outside the lab. For instance Ashraf et al. , Meier a(PDF 837 KB)Below is the link to the electronic supplementary material.


A recent hypothesis purports that spinal manipulation may cause changes at a brain level. Functional Neurology, a mainly chiropractic approach, promotes the use of spinal manipulation to improve ‘brain function’ as if it were a proven construct. No systematic review has been performed to investigate how well founded this hypothesis is.To investigate whether spinal manipulation has an effect on ‘brain function’ that is associated with any clinical benefits.In this systematic review, the literature was searched in PubMed, Embase, and PEDro . We included randomized or non-randomized controlled studies, in which spinal manipulation was performed to any region of the spine, applied on either symptomatic or asymptomatic humans, and compared to a sham or to another type of control. The outcome measures had to be stated as direct or proxy markers of ‘brain function’. Articles were reviewed blindly by at least two reviewers, using a quality checklist designed for the specific needs of the review. Studies were classified as of ‘acceptable’, ‘medium’, or ‘low’ methodological quality. Results were reported in relation to (i) control intervention  and (ii) study subjects , taking into account the quality. Only results obtained from between-group or between-intervention comparisons were considered in the final analysis.Eighteen of 1514 articles were included. Studies were generally of ‘low’ or ‘medium’ methodological quality, most comparing spinal manipulation to a control other than a sham. Thirteen out of the 18 studies could be included in the final analysis. Transitory effects of different types of ‘brain function’ were reported in the three studies comparing spinal manipulation to sham (but of uncertain credibility), in “subclinical neck/spinal pain” subjects or in symptomatic subjects. None of these three studies, of ‘medium’ or ‘acceptable’ quality, investigated whether the neurophysiological effects reported were associated with clinical benefits. The remaining 10 studies, generally of ‘low’ or ‘medium’ quality, compared spinal manipulation to ‘inactive control’ or ‘another physical stimulus’ and similarly reported significant between-group differences but inconsistently.The available evidence suggests that changes occur in ‘brain function’ in response to spinal manipulation but are inconsistent across and - sometimes - within studies. The clinical relevance of these changes is unknown. It is therefore premature to promote the use of spinal manipulation as a treatment to improve ‘brain function’.The online version of this article (10.1186/s12998-019-0265-8) contains supplementary material, which is available to authorized users. Spinal manipulation (SM) is widely used by various health practitioners, including physiotherapists, osteopaths and chiropractors, to treat mainly musculoskeletal conditions, but some also use it for a variety of other health-related problems , 2. WhilThis lack of evidence contrasts with claims of some therapists, including (but not restricted to) those who practice using the theoretical concepts of Functional Neurology (FN), a mainly chiropractic approach, founded by a chiropractor, FR Carrick . In addiIn line with FN, a current hypothesis is that the clinical benefits observed following SM would be, at least partially, due to neurophysiological changes within the brain , 7. SomeWithin the scientific literature, differently framed hypotheses exist in relation to the potential mechanisms involving the brain, which could explain clinical benefits following SM , 8, 9. TPotential neurophysiological effects of SM on the brain have been the focus of several recent experimental studies. As the brain is involved in a multitude of functions, its activities or alteration of activities after an intervention can be explored in several ways. Not surprisingly then, the studies in this field of research use various approaches and outcome measures to test the hypothesis that SM has an effect on ‘brain function’. For example, some studies investigated the potential effect of SM on brain areas involved in pain processing  and autoIn relation to sham controlled studies, i.e. ‘effect’studies:Is there an effect of SM on ‘brain function’?If there is an effect, for how long does it last?If there is an effect, is it associated with any clinical benefits?In relation to other controlled studies , i.e. the ‘differences in outcome’studies:4 - Is there a difference in ‘brain function’ after SM vs. an ‘inactive control’?5 - Is there a difference in ‘brain function’ after SM vs. ‘another physical stimulus’?Because studies are quite heterogeneous, it is difficult to understand and interpret the evidence in this area. Nevertheless, this task is needed to understand if assertions of the ‘brain-mediated’ hypothesis proponents are substantiated by scientific evidence. A narrative review on the topic by Haavik and Murphy was published in 2012 . In thisData analysis and synthesis).A systematic critical review of the literature was carried out to shed light on the research questions above. The review was registered in the PROSPERO international prospective register of systematic reviews (CRD42017074966). Some deviations from the original protocol were required in response to the material available in the reviewed articles, which was unknown at the time of planning the review. These were: (i) the wording of the research questions was improved, (ii) the review was restricted to spinal manipulative therapy (i.e. did not include extremities), and (iii) the results were analyzed depending on three categories of study subjects instead of the two we planned. Regarding the latter, it was initially planned to analyze the results depending on whether study subjects were (i) healthy or (ii) symptomatic. However, a third type of study subjects was identified, namely “subclinical neck/spinal pain” subjects. Further details on these study subjects are given in a subsequent section . The search strategy was initially developed for PubMed , i.e. the only difference between the study groups being that one group was subjected to the tested intervention  but not the other (i.e. pain medication only), the article could be included.effect of SM (i.e. effect specific to SM) on the brain and could therefore be used to answer the search questions 1 to 3 of the present review. The control was considered as ‘another physical stimulus’ when it involved at least a manual contact , or when it included other forms of manual therapies . ‘Inactive control’ would consist of, for example, placing the study subject in side posture without manual contact or just resting.The control group could be subjected to a sham procedure, an ‘inactive control’, or ‘another physical stimulus’ (other than SM). However, only studies using a sham as comparator could be considered to investigate the Given our overall aim, the inclusion criteria were not limited to specific outcome measures or to specific measurement procedures. Studies were included if their authors stated that the outcome measures were used to assess ‘brain function’, meaning this was not necessarily expected that the outcome measures were valid or markers exclusive of ‘brain function’. This lenient criterion was chosen for two reasons: (i) some outcome measures are known also to depend on segmental activity (e.g. the V-wave)  and (ii)There was no restriction in relation to the date of publication of the studies but only articles in English or French were included.Eligibility criteria were applied twice to the titles by the first author, who also searched the reference lists of the included full texts for additional relevant studies. Thereafter, the abstracts and then the relevant full texts were read independently by two authors (ALM and CLY) to determine if they could be included in the review.Three types of specific checklists were developed for this review relating to: main descriptive features of included articles Tables , 2 and 3Main descriptive features of the included articles were reported in three tables, one for each type of control, i.e. sham, ‘inactive’, and ‘another physical stimulus’ , with an expertise in at least one of the outcomes used in the included studies, provided comments in relation to the methodology and technical aspects of the studies they assessed. These comments could be used to discuss the findings in relation to each research objectives. Some of these comments have been included in this report . Data were later compared to minimize extraction errors. Discrepancies were planned to be resolved by discussion between the authors.The outcomes of the selected studies were reported in three tables . In crossover designs, differences should be tested between-types of interventions. This means that results of studies that did not perform and clearly report comparisons between-groups or, in the case of crossover studies, failed to report between-types of interventions would not be taken into consideration to answer our research questions. Therefore, if authors reported only significant within-groups or within-types of interventions, without taking into account the difference between readings of the two interventions, this would be ignored.In accordance with the recommendations of Bland and Altman (2011) , we planbetween-groups or between-types of intervention analysis.However, our review revealed both unusual and confusing statistical reporting. We therefore decided to take into consideration also some results in a ‘benefit of the doubt’ approach, such as instances when none of the reviewers was able to decide whether the authors had, in fact, performed an appropriate Only the primary outcomes of the included studies were considered.Each article was checked for each quality item, giving either half of a point or one point for each fulfilled item as described in Additional file The various tables were used to report narratively the main findings in relation to our five research questions, taking into account the methodological quality of the individual studies, so that we would have more confidence in the studies of better quality than those with additional methodological deficiencies.For each type of control, the findings were reported by type of study subjects: healthy, symptomatic, or “subclinical neck/spinal pain’” subjects. Following the definition given by the authors of the respective studies, the “subclinical neck/spinal pain” subjects appeared to us as an independent category of study subjects, neither healthy nor in pain at the time of study. Although this latter definition changes somewhat from one publication to another, study subjects were usually described as having a history of “mild intermittent spinal pain, ache or tension , and evidence of dysfunction in the spinal and/or pelvic joints” ; spinal/n = 10), all on “subclinical neck/spinal pain” subjects, were conducted by research teams that included one specific author [Figure c author , 23–28.All articles reported an ethics approval from an ethics committee or from a review board, with or without an identification number of the application and approval. As for conflict of interest, 11 studies declared to have none , 26, 28,Detailed descriptive information of each study is available in Tables The size of the study samples of the 18 included studies ranged from 10 to 72. Ten were conducted on “subclinical neck/spinal pain” subjects Tables , four onn = 14) and mostly conducted using a crossover design (n = 10). Only one study reported the dates and duration of data collection [All the included studies were controlled trials, including two to three experimental groups, most of them with a random allocation ’ or as suggesting some type of ‘brain function(s)’, meaning that some outcomes could also reflect, for example, neurophysiological changes at a segmental level  [after intervention or control, presumably for ethical reasons [before and after intervention at various time points. However, six studies did not specify the time of re-assessment at all and four did not report it clearly.The outcomes of all these studies were either described as periods) , 34. The reasons , 19. As The four studies conducted on symptomatic subjects described in their Methods section that they also assessed clinical outcomes, mainly pain intensity  or ‘medium’ (n = 8), except for three articles that were considered to be of ‘acceptable’ quality (see Table effect’ studies), (ii) no clear reporting whether the study was conducted on naïve subjects (most of the ‘differences in outcome’ studies), (iii) no reporting whether the assessor was blinded to treatment group (most studies), and (iv) no reporting whether the person who analyzed the data was blinded to treatment group (most studies). In addition, the experts  sometimes commented on unusual procedures  Symptomatic subjects (n = 1)One study of ‘acceptable’ methodological quality , conduct“Subclinical neck/spinal pain” subject (n = 2)Two studies on “subclinical neck/spinal pain” subjects , 15, botSymptomatic subjects (n = 1)The effect reported by Sparks et al. 2017  The effect reported by Baarbé et al. 2018  (in a stSymptomatic subjects (n = 1)The study by Sparks et al. 2017  on subje“Subclinical neck/spinal pain” subjects (n = 2)None of the two studies on “subclinical neck/spinal pain” subjects , 15, botOther types of controls, specifically ‘inactive control’ (Table ) or ‘another physical stimulus (Table ), i.e the (‘differences in outcome’ studies (n = 10)changes on ‘brain function’ in response to SM by using varied outcome measures and/or experimental protocols, which makes comparisons between studies difficult.Seven studies could be used for the fourth research question , 21, 29,Summary of findings in relation to the fourth research questiondifferences in outcome between SM and the controls but not necessarily in the same direction. When brain areas were compared, differences were found, but again with some conflicting results. Detailed results are reported in the next section.In these studies, of ‘low’ or ‘medium’ methodological quality, there were, in general, statistically significant Healthy subjects (n = 4)In healthy subjects, an immediate and transient increase of motor-evoked potential amplitudes after lumbar SM was reported in two studies , 18, wheA fourth study , of ‘medSymptomatic subjects (n = 2)The two studies conducted on symptomatic subjects were from the same research team and both of ‘low’ methodological quality , 19; the“Subclinical neck/spinal pain” subjects (n = 1)between-group differences for the other somatosensory evoked potential peak ratios they investigated.In a study on “subclinical neck pain subjects” of ‘medium’ methodological quality , the autFour articles were able to be used in relation to our fifth research question , 26, 28.Summary of findings in relation to the fifth research questiondifferences in outcome between SM and the controls were reported but results were mixed, in studies of ‘low’ to ‘acceptable’ methodological quality. Detailed results are reported in the next section.Some statistically significant Healthy subjects (n = 1)One study of ‘low’ methodological quality , conduct“Subclinical neck/spinal pain” subjects (n = 3)between-group differences for the other somatosensory evoked potential peak ratios investigated.One study on “subclinical neck/spinal pain” subjects , of ‘medbetween-group differences for two other variables they studied.Haavik et al. 2016 , in a stChristiansen et al. 2018 , in a stThis systematic review consists of 18 relevant articles. Once classical risk of bias aspects, necessary in this type of experimental design, had been taken into account, most of these articles were considered of ‘low’ or ‘medium’ methodological quality. In addition, their statistical methods and results sections were often difficult to interpret because of unclear and/or unusual descriptions. For methodological reasons, the results of only 13 of these 18 articles were considered for final analysis.effect on ‘brain function’ compared to a sham intervention, and (ii) whether SM alters ‘brain function’ in a different way compared to an ‘inactive control’ or ‘another physical stimulus’, and this on different type of study subjects. Based on the studies using a sham intervention as comparator to SM, it seems that SM does have an effect on ‘brain function’. As a result, we also studied our two other main objectives, namely (i) how long this effect would last, and (ii) whether this effect was associated with clinical benefits.These 13 articles reported on (i) whether SM has an effects. It was thus shown that SM seems to have the potential to transiently alter (i) somatosensory integration of afferent inputs from the upper limb [effects were lasting and none investigated whether these were associated with any clinical benefits. Also, according to the authors of these three studies, what these effects mean for the brain remains to be established.The three studies using a sham intervention as comparator, two of ‘medium’ and one of ‘acceptable’ methodological quality, provided some evidence to support the hypothesis that SM has supra-segmental neurophysiological per limb , (ii) ceper limb , both onper limb . Howeverbetween-group differences but not necessarily in the same direction and also not systematically for each of the outcomes they studied. Most of these studies reported on healthy or on “subclinical neck/spinal pain” subjects.The 10 studies not using a sham intervention as comparator, most of which were of ‘low’ or ‘medium’ methodological quality, also reported statistically significant effect’ studies and the ‘differences in outcome’ studies, it seems that something does indeed happen within the brain in response to SM. However, what this means remains elusive both in the brain and at a clinical level, and the researchers provide only hypotheses rather than interpretations. In addition, the reported findings have to be interpreted with caution given the general level of methodological quality (‘low’ or ‘medium’) of the included studies.In summary, based on both the ‘effect on ‘brain function’ must thus be put into perspective by comparing it to effects in response to other types of (comparable) physical stimuli or other types of treatment. The question is therefore: Are the findings in relation to ‘brain function’ specific to SM? For various methodological reasons, none of the studies could clearly answer this question. Furthermore, in order to claim brain involvement in the effects of SM it should be expected that changes in ‘brain function’ following SM can be shown related to the desired clinical effects of SM. However, no information related to any clinical significance of such findings was unearthed in this review.Showing that SM is reflected by brain activity does not necessarily mean that something ‘positive’ and clinically relevant happens in response to SM. The significance of any putative Three databases were searched and only one author applied eligibility criteria to the titles. Thus, it is possible that not all relevant articles on the topic were found. Nevertheless, the additional search of reference lists produced only three additional titles. All the following steps of the screening process and of the data extraction were made independently by at least two of the reviewers.Most of the articles we obtained reported on experimental studies, in which no clinical outcomes were included. Studies of this type are not strictly comparable to ordinary clinical studies using the randomized clinical trial design, for which well-established critical appraisal tools exist. The quality checklist used in the present review was therefore not standard. For example, some usual risk of bias items, such as allocation concealment were not assessed, as they were judged less relevant for non-clinical randomized controlled trials. Regarding allocation concealment, we assumed that it would be difficult to predict which study subjects would react how regarding the outcome variables used in the included studies. Nevertheless, most of the items we selected consisted of accepted items to evaluate risk of bias , 32. Thebetween-groups or between-types of interventions. However, such exceptions were noted explicitly in the Results section, either in the text [Because several of the statistical analyses and/or reporting were unclear and/or unusual, we finally resorted to a ‘benefit-of-the-doubt’ approach. Thus, after many discussions and attempts at interpreting some confusing reports, we deviated from our previous criterion, which was to include in the data synthesis only results of the studies that reported clearly differences the text  or in Tathe text .Studies were included also when the outcome variables they tested were not necessarily a reflection of ‘brain function’ only, i.e. some would depend on both segmental and supra-segmental changes  , 34. ThiMany different outcome variables are used in research to measure brain activity, and this was also the case for the articles we included. Their heterogeneity in relation to (i) study subjects , (ii) outcome variables (16 different outcome variables for 18 articles), (iii) experimental protocols for each single variable, and (iv) generally rather low methodological quality, makes comparison of studies difficult and one or several meta-analyses impossible.The methodological quality was quite low in relation to well accepted risk of bias items. Admittedly, these types of studies require a lot of knowledge on technical aspects but this must not remove focus from the fundamental methodological requirements of research, namely the necessity to collect and interpret data in an objective manner.placebo effect implies complex neurophysiologic responses involving the brain [For example, the studies considered to be of ‘low’ and ‘medium’ methodological quality often failed to report using either a credible sham comparator or having been conducted on naïve subjects. As suggested by Fryer and Pearce , the blihe brain . In our effect’ studies must be considered uncertain for two and was recognized as such by the participants in the third. Thus it cannot be ruled out that the effect of SM on ‘brain function’ was the result of contextual factors, rather than truly caused by the SM, as discussed by Rossettini et al. 2018 [According to this review, the credibility of the sham comparator used in the three ‘al. 2018 . This waal. 2018 , where tdifference in outcome’ studies, the origin of the study subjects was reported in only a few cases. Thus we do not know if they had any preconceived ideas/expectations with respect to the study outcomes. This problem could be compounded if several studies were conducted on the same study subjects.In relation to the ‘Another example was that the blinding of the assessor and of the person who analyzed the data was generally poorly reported. Although it is fair to recognize that this reporting may be unusual in some fields of research (e.g. neuroimaging studies), some authors were transparent in relation to this point, which should encourage other researchers also to do the same.In addition, comments were provided by our experts, suggesting that several of the experimental protocols of these reports lacked some of the standards, specific to such studies. Several comments were also provided from the experts on the statistical analyses, indicating that this was an area of concern, as the statistical analysis is at the heart of the validity of any statistically significant findings.Neuroimaging studies, which produce ‘visual’ answers, are perhaps easier to interpret for people without specific knowledge in neurological testing. Nevertheless, they present a challenge for formal analysis. For example, quantification of data is difficult. There are many analytic techniques available for these types of studies and there is a lack of consensus with respect to the most appropriate statistical thresholds to be used . Therefochanges observed at the brain level would result  from a ‘bottom-up’ mechanism, due to altered afferent inputs in response to SM [The rationale for investigating whether SM acts through modulation of ‘brain function’ was generally not clear in the included studies. Nevertheless, most studies proposed that se to SM , 23–28. effects or changes they measured in the SM groups reflect improvement of ‘brain function’ [Articles, in which Haavik was one of the authors, included “subclinical neck/spinal pain” subjects in their studies , 23–28. unction’ , 23–28. Additionally, these studies rest on the assumption that it is possible to detect ‘subluxations’ in people with “subclinical neck/spinal pain”; a concept that remains hypothetical. Overall, it is our considered opinion that some clarifications are needed regarding this “subclinical neck/spinal pain” with ‘subluxations’ concept to ensure appropriate interpretation of the results of these studies.FN practitioners use SM as a treatment of ‘brain lesions’  despite Based on this systematic review, we conclude that there is presently no evidence indicating that SM has a beneficial effect on ‘brain function’ or that the diverse findings identified in this review would be in any way indicators of a health benefit in general. It is therefore premature for authors of this type of research to promote clinical benefits. Nevertheless, this can be observed in at least some commercial videos  and in aIn an example of this overreach, Haavik wrote in her book: “Having your spine checked regularly, to ensure your brain is accurately aware of what is going on in and around your body, should be just as common as exercising every day and brushing your teeth. Everyone should have access to chiropractic care right from birth through to the day they pass away. I believe a lot of suffering could be prevented if this was the case.” .Study Considerations” of that article [Another example is extracted from one of Haavik’s commercial videos , which i article  obviousl article .The clinical relevance of any brain changes should be investigated using symptomatic study subjects. Also, clinical outcomes should be included and the correlation between these and brain changes should be tested to establish if there is some type of benefits.To study the specific effect of SM, proper sham procedures must be adopted and checked for success after the intervention to control for any unspecific effects, including placebo responses.Appropriate methodology in relation to randomized controlled trials, with appropriate attention to the potential sources of bias  should be respected.In relation to the technical procedures, standard protocols should be employed to ensure reproducibility of the outcome measures.Appropriate statistical methods and thresholds should be used.Any conflict of interest should be reported.Results should be replicated by independent research teams before their clinical acceptance.Further research should be undertaken in this area and we recommend attention to the following:Presently, the chiropractic profession might wish to consider the potential consequences of encouraging undergraduate- and postgraduate courses on chiropractic approaches relating to the treatment of the brain via the spine. Obviously, this is also true for other health care providers who may be tempted to practice following such concepts in relation to SM. Moreover, statements aimed at the public relating to this phenomenon should be discussed as findings of unknown clinical effect.According to the results of the present systematic review, it is premature to promote the use of SM as a treatment to improve ‘brain function’ from a clinical point of view.Further, studies on this topic should (i) include symptomatic subjects, (ii) relate to the clinical significance by using outcomes relevant to test associations with neurophysiological changes, and (iii) take into consideration basic methodological and technical requirements pertaining to this type of randomized controlled trials.Additional file 1:Search strategy developed for PubMed for a systematic critical review of the literature on the effect of spinal manipulation on ‘brain function’ (DOCX 126 kb)Additional file 2:Items selected for the quality checklists and their rationale in relation to a systematic critical review on the effect of spinal manipulation on ‘brain function’ (DOCX 22 kb)Additional file 3:The various ways used in the scientific literature for testing the hypothesis that spinal manipulation would have an effect on ‘brain function’ (DOCX 83 kb)Additional file 4:Commercial announcement of a chiropractic seminar entitled “Adjusting the Brain” (PDF 1462 kb)


Most importantly, because researchers treat raters as items, Cronbach’s α is inflated by larger sample sizes even when agreement between raters is fixed. Here, we considered several alternative measures and investigated whether these better discriminate between traits that were predicted to show low , intermediate , and high  levels of agreement. Importantly, the level of inter-rater agreement has not previously been studied for many of these traits. In addition, we investigated whether familiar faces resulted in differing levels of agreement in comparison with unfamiliar faces. Our results suggest that alternative measures may prove more informative than Cronbach’s α when determining how well raters agree in their judgements. Further, we found no apparent influence of familiarity on levels of agreement. Finally, we show that, like attractiveness, both trustworthiness and dominance show significant levels of private taste , although shared taste (perceptions shared with other raters) explains similar levels of variance in people’s perceptions. In conclusion, we recommend that researchers investigating social judgements of faces consider alternatives to Cronbach’s α but should also be prepared to examine both the potential value and origin of private taste as these might prove informative.Researchers have long been interested in how social evaluations are made based upon first impressions of faces. It is also important to consider the level of agreement we see in such evaluations across raters and what this may tell us. Typically, high levels of inter-rater agreement for facial judgements are reported, but the measures used may be misleading. At present, studies commonly report Cronbach’s  It has often been argued that we ‘automatically’ form first impressions from photos of faces. Evidence for this automaticity comes from studies which have shown that impressions can be reliably formed at very short exposure durations ,2, and aα to show high agreement between raters. This, however, is not necessarily the best way of measuring agreement, or even the correct use of Cronbach’s α. Here, we will first review evidence for inter-rater agreement in first impressions across age, race, and culture. We will then discuss the most widely-used measure of agreement in the social literature, Cronbach’s α, and finally focus on alternative measures of rater agreement with the potential to address additional aspects of rating agreement such as individual participant reliability.One interesting and commonly reported aspect of social evaluation is that people seem to agree with each other’s social trait ratings despite limited evidence supporting their accuracy . High inter-rater agreement in the attribution of social traits has been reported as early as the 1920s. In an attempt to refute the study of phrenology using statistical evidence, and thus discourage businesses from using it as a recruitment tool, Cleeton and Knight  had membHigh inter-rater agreement has been reported consistently for a number of social traits  measure for ratings of attractiveness showed that even when Cronbach’s α was very high (α = .95), there could be an equal contribution of shared and private variance in ratings [Cronbach’s Hönekopp  points o ratings . Indeed, ratings . Such fiα and Hönekopp’s bi as measures used for quantifying inter-rater agreement. However, there are several additional candidates that have been reported previously by researchers, although far less frequently than Cronbach’s α. We therefore provide further details on all the measures we include in the current work.We have introduced both Cronbach’s α as a measure of reliability among raters. This value is equivalent to the intraclass correlation coefficient  for a tide, see . One canide, see ,32. As nα ignores any absolute differences and only considers consistency. For consideration, we report values of absolute agreement–ICC–for comparison with Cronbach’s α, which is also termed ICC.It is important to consider the difference between consistency and absolute agreement. Raters may agree on the general order of faces with respect to a particular trait (face A is more attractive than face B) but they may also show systematic differences in terms of the absolute ratings they give . Whether researchers are interested in these absolute differences or not, given that ratings are typically averaged across raters, will depend on the particular question under investigation. If the purpose is to rank faces using their average ratings and choose the highest and lowest subset, for example, then the difference among raters may have little effect as long as consistency is high. However, if the purpose is to select faces which are rated above or below a predefined absolute score, or to consider their absolute (mean) rating in some other way, then raters need to show absolute agreement for this to be meaningful. Readers should be aware that Cronbach’s Another method for quantifying inter-rater agreement is to correlate each participant’s ratings with the mean of the remaining participants –44. If wW, which is proportional to the average rank-order correlation among all pairs of raters. This nonparametric statistic produces higher values for raters that demonstrate higher agreement, and has previously been used to show that likeness ratings demonstrate little agreement across raters [Kendall ,46 devels raters .One important issue to consider when measuring the agreement among raters is their agreement with themselves. If an individual rater is unreliable or inconsistent across different sessions, for example, then this places limitations on how much other raters can hope to agree with them. We are able to quantify within-person reliability here by asking each rater to provide two sets of ratings for the same images. By correlating each rater’s first and second responses, we can obtain a measure of test-retest reliability .If we were to consider only two raters, we could simply correlate the two sets of ratings using either the values or their rank orders and this would provide a measure of their agreement. Extending this idea to groups of raters, we can use modern computing power to allow us to calculate the correlation between every possible pair of raters–the average inter-rater agreement ,42,49,50bi in line with Hönekopp’s [Based on generalisability theory , Hönekopnekopp’s  approachα), along with a statement that the observed amount justifies consideration of only the average rating for each face. As mentioned above, using the average rating in subsequent analyses can result in conclusions that may be misleading or even meaningless if individual differences are both large and potentially informative.Researchers often assume high rater agreement, with only a passing consideration as to the level of agreement across raters and whether it is meaningful . Where aIn the current work, we focus on issues that are rarely considered in depth in the social evaluation literature: 1) are people consistent in their trait ratings of faces? 2) do people agree with others on seemingly subjective impressions? 3) how best might we quantify inter-rater agreement in first impressions? and 4) what is the proportion of shared compared with private variance in ratings of socially-important traits other than attractiveness? We collected ratings on six traits  that were expected to vary significantly in their levels of inter-rater agreement.Ratings of gender and age are both based on cues contained in the physical appearance of the face which leads to highly consistent as well as accurate judgements on those traits –56. We tFor different social traits, there may be reason to predict different levels of shared compared with private variance in ratings. Dominance attribution has been closely associated with face structure, where faces with a higher width-to-height ratio are generally perceived as more dominant and aggressive ,58. TherFinally, parental resemblance was specifically selected to produce lower inter-rater agreement. Here, participants were asked to rate how much each image resembled their own parents. We expect much lower agreement compared to all other traits, as well as a higher contribution of private taste, because there is no reason for participants’ parents to each resemble the rated faces to the same extent.In addition, we consider the potential influence of familiarity on levels of agreement for the first time. Much research has now established how important face familiarity is when performing recognition or matching tasks . HoweverM = 19.1 years, SD = 0.86 years), 57 reported their ethnicity as White or White mixed.In order to include a participant’s data, we required that they recognise at least 50 familiar identities of the 100 viewed. For each of six traits that were rated (with each participant rating one trait only), we continued to collect data until a sample of 10 participants fulfilled this criterion. In total, this meant that 71 students participated. All were undergraduates at the University of York, and took part in exchange for a monetary payment or course credits. Of our final sample of 60 participants  was collected. Two hundred were chosen to be familiar to participants and included international actors, singers, etc., while the other 200 included unfamiliar identities . After initial pilot testing with colleagues to confirm familiarity, we produced a final set of images comprising 50 familiar women, 50 familiar men, 50 unfamiliar women, and 50 unfamiliar men. Although age was not available for these identities at the time the images were taken, we estimate a range of approximately 20–70 years old.All images were broadly front facing, upright, and displayed neutral or smiling expressions. In all other ways, they were unconstrained. Each image was cropped to include only the head and background see . FinallyWe used a fully crossed design, common to many studies in this field, where all images were rated by all raters for a given trait. Each participant was asked to rate all 200 images , presented in a random order, for one trait only. It was important that each participant only rated one trait in order that we would obtain independent measures of agreement for the six traits. In experimental designs where participants each rate images along several dimensions, there is the likelihood of contamination, whereby judging a face as attractive may influence subsequent judgement of that face on trustworthiness, for instance. Participants were assigned to traits based on the order in which they took part–collection on one trait continued until completion and then participants were assigned to the next.The instruction presented onscreen throughout the experiment read “in this particular photograph, how X does the person look?” where X referred to the specific trait being rated. Five of the traits were gender , age , attractiveness , trustworthiness , and dominance . The final trait was resemblance to a parent, so “in this particular photograph, how much does the person look like your mum/dad?” The instruction (“mum” or “dad”) was tailored to the particular sex of that image, and the rating scale was labelled ‘1 = not at all, 7 = very much’. In an attempt to avoid unwanted agreement simply due to age influences , for images where the identity was older or younger than their parents, participants were instructed to imagine how much the person onscreen resembled their parent if that parent were a similar age.a priori reason for participants to agree. The prediction that these traits will yield differing levels of agreement gives us a testable prediction against which to compare the results of our different analysis measures.These specific traits were chosen because we have reason to believe from prior literature that these traits should yield differing levels of agreement. Age and gender, where the cues are entirely in the facial structure, should yield the highest agreement, followed by dominance, attractiveness and trustworthiness, and finally parental resemblance, where there is no After rating every image once, participants were instructed that there would be a second block of ratings, and could have a short break if they wished. Participants then carried out the same ratings task for a second time. That is, every image was rated on the same trait once more, with images presented in a new random order. Participants were not aware beforehand that they would be required to rate the images for a second time, in order to minimise the likelihood that they would try to remember and reproduce their first responses.Upon completion of the two blocks of ratings, participants were shown every image once more  and were asked to identify the person in the photograph. Specifically, we instructed participants to type in the person’s name or some identifying information that demonstrated recognition of the identity. We explained that simply typing “actor”, for example, would not be sufficient and that we required information particular to that person, e.g., the name of a film they starred in, the name of their spouse, etc. Participants were told that accuracy in spelling was not a concern. For those identities that were not recognised, participants were instructed to press the return key and continue to the next photograph. Both this task and the previous ratings tasks were self-paced.Participants were unable to identify any of the unfamiliar people. However, for the familiar images, there were a number of identities that were not recognised. While each individual identified the majority of the 100 images, the specific images that were not recognised differed across participants. In order to carry out our ‘familiar’ analyses, we were only able to include images that all participants were familiar with. This was because many reliability measures require a fully crossed design , and so we necessarily avoided missing values for particular images due to a lack of familiarity. The final number of images  varied for each trait and is reported in Below, we summarise our findings for seven different statistical measures. We present four of these in For many of the measures in Figs α. Age and gender clearly show high values, as one would expect. Interestingly, attractiveness is higher than both dominance and trustworthiness. Finally, and again as expected, parental resemblance shows the lowest reliability. It is worth noting that even this final trait shows a moderate level of reliability (0.48 for unfamiliar images) on this measure.α significantly differ, F = 1.75, p = .005 [One of our focusses in the current work is whether the traits in our three tiers are well differentiated in line with predictions. Although age, which we expected to demonstrate high inter-rater agreement, falls very close to attractiveness (expected to show intermediate agreement) for unfamiliar faces, we find that statistically, these two values of Cronbach’s p = .005 .α of 0.90 if 80 raters were used. This is because simply increasing the number of raters will lead to an increase in the resulting reliability value [α was originally intended as a measure of test reliability, whereby lengthening a test produces a more reliable measure. When using Cronbach’s α in its current context as a measure of rater agreement, the number of test items is equivalent to the number of raters. This issue is one of the important criticisms of the use of this measure, where many researchers and readers may simply assume that a large value denotes high levels of agreement across raters. In contrast, no one would argue that an average inter-rater agreement of 0.10 demonstrated high agreement.We find the expectedly lower reliability of parental resemblance, in comparison with the other five traits, using only ten raters in the current experiment. However, as Hönekopp  noted, ety value . It is iα has a limited definition. As already mentioned, this value refers to the reliability of the average rating and not single raters. In most cases, this is the appropriate measure, as researchers often average across raters to produce a value for each face [It is important to realise that Cronbach’s ach face ,68–70. Hach face . Simply,A,k)—in α. Here, we find that absolute agreement is typically similar but slightly lower than consistency.Another consideration is the difference between consistency and absolute agreement, as mentioned in the introduction. We report values of absolute agreement—ICC for attractiveness that, along with previous research [We also investigated Hönekopp’s  beholderresearch ,42,50, dresearch ), and thresearch  should rbi1 for judgements of unfamiliar face attractiveness in the current work (0.31) is notably lower than Hönekopp’s [Although our measure of nekopp’s  estimatenekopp’s  and 0.36nekopp’s ). It mayBoth the average inter-rater agreement and the beholder index allow us to quantify the amount of variance in ratings due to shared taste for each of the six traits. However, the former is a correlation and requires the value to be squared, while the latter quantifies private taste and we must therefore calculate the complementary percentage. For this reason, we present these derived values in It is reassuring, as illustrated in As Figs While the general pattern of results is similar for familiar and unfamiliar images, we find that raters show consistently higher retest reliability for familiar identities see . ParticiIn the present work, we considered several methods of calculating inter-rater agreement, and quantified such measures for a variety of traits. We expected to see our six traits fall into three tiers regarding the amount of agreement–high , intermediate , and low . For the most part, our measures supported this clear distinction, although not in all cases.α  showed the least ability to discriminate between these three trait categories (with the exception of item retest). Although this measure is the most widely used in the face perception literature as a method for quantifying inter-rater agreement, we know that simply increasing the number of raters will lead to an increase in the resulting reliability value [If we consider the results summarised in Figs ty value . Here, oW, average leave one out) clearly differentiate between traits that we expected to show high, intermediate, and low levels of agreement. Indeed, the fact that all these measures identified this pattern provides further validation regarding our initial predictions when selecting these traits. Comparison across measures is difficult, and there remains no clear way to justify the use of one over the others. However, our results suggest that any one of these may prove suitable as an indicator of inter-rater agreement, while reporting all measures can only serve to inform readers and those carrying out future research.All four remaining measures of inter-rater agreement  attractiveness. While dominance and trustworthiness show similar levels of private taste with each other and with attractiveness , perhaps there is some suggestion that both traits may be a little more ‘private’ than attractiveness see . There aThat we see no clear effect of familiarity on measures of inter-rater agreement is perhaps surprising. On the one hand, more familiar faces may activate shared representations across raters, resulting in higher levels of agreement. On the other, each rater may have their own unique experiences with familiar faces, influencing their perceptions and causing lower agreement. To illustrate, my specific exposure to Liam Neeson (perhaps only his recent action roles) may result in my rating his image as more dominant in comparison with someone whose exposure is based solely on his earlier characters. Here, we found no clear pattern as a result of manipulating familiarity beyond higher retest reliability for familiar faces. This may be because 1) familiarity has little effect on inter-rater agreement; 2) familiarity affects different traits in different ways; or 3) participants were able to ignore their previous experiences with familiar faces and successfully limit their ratings to the specific photographs (as they were instructed to do in the current task). Perhaps asking participants to rate the person rather than the photograph may have led to stronger familiarity effects, and we suggest this as an interesting extension for the future.In line with previous research, we found that attractiveness ratings were influenced by both shared and private taste, although perhaps less so by the latter ,50. ThisIn the current work, we consider the agreement or consistency in ratings across raters. We do not address the separate issue of the validity, or accuracy, in ratings–that is, how closely the ratings measure the actual trustworthiness, age, etc., of the people in the photographs. Previous research has shown that unfamiliar observers are able to accurately estimate age from face photographs , and theα as a metric. Further, several alternatives are described, all of which appear to provide better measures of inter-rater agreement in that they more successfully discriminated between traits that should a priori demonstrate different levels of agreement. In addition, we show that familiarity does not appear to influence inter-rater agreement. Finally, we provide the first investigation of the importance of shared versus private taste with regard to the fundamental social evaluation dimensions, trustworthiness and dominance, with our results suggesting levels comparable with attractiveness, and marginally more influence of shared taste (as measured with bi) in all three traits. Given the increasing popularity of research involving face perception and social traits, we strongly recommend the use of alternative/additional measures of inter-rater agreement, while being open to the idea that raters may not show high levels of agreement and that this might prove informative of itself.In conclusion, our results highlight some of the issues associated with assuming/reporting high inter-rater agreement based solely on the use of Cronbach’s S1 Table(DOCX)Click here for additional data file.S2 Table(DOCX)Click here for additional data file.S1 Dataset(XLSX)Click here for additional data file.