Libertarians are an increasingly prominent ideological group in U.S. politics, yet they have been largely unstudied. Across 16 measures in a large web-based sample that included 11,994 self-identified libertarians, we sought to understand the moral and psychological characteristics of self-described libertarians. Based on an intuitionist view of moral judgment, we focused on the underlying affective and cognitive dispositions that accompany this unique worldview. Compared to self-identified liberals and conservatives, libertarians showed 1) stronger endorsement of individual liberty as their foremost guiding principle, and weaker endorsement of all other moral principles; 2) a relatively cerebral as opposed to emotional cognitive style; and 3) lower interdependence and social relatedness. As predicted by intuitionist theories concerning the origins of moral reasoning, libertarian values showed convergent relationships with libertarian emotional dispositions and social preferences. Our findings add to a growing recognition of the role of personality differences in the organization of political attitudes. Libertarian ideology prescribes a unique pattern of moral concerns that cannot be readily classified on the standard left-right dimension, but as with differences between liberals and conservatives, these unique sensibilities should be measurable using existing psychological scales. In this paper, we empirically address the question of what dispositional traits, emotions, and social preferences predict self-identification as libertarian. Based on the stated beliefs of libertarian intellectual leaders, as well as previous research on the social and intuitive origins of moral beliefs th and 18th century who argued that states, laws, and governments exist for the benefit of the people. The individual is the unit of value, and the liberty of the individual is the essential precondition for human flourishing. John Locke wrote: “the great and chief end, therefore, of men's uniting into commonwealths and putting themselves under government is the preservation of their property” , tyrannical (because it violates the negative liberty of some people to promote the positive liberty of others), and wasteful (because governments rarely achieve the efficiencies generated by the competition of private firms).Seen in this light it becomes clear why American libertarians are sometimes called “classical liberals,” and in Europe, the term liberal is often used in the same way that “classical liberal” is used in the United States. It also becomes clear why libertarian thought is now associated with anti-government and anti-progressive movements. Libertarianism provides an ideological narrative whereby the opposition to high taxes and big government is not just an “economic” position: it is a The most obvious psychological characteristic of libertarian ideology is the value placed on negative liberty as an overriding moral principle, as can be seen in this quote concerning a law outlawing online gambling, from U.S. Congressman Ron Paul The most basic principle to being a free American is the notion that we as individuals are responsible for our own lives and decisions. We do not have the right to rob our neighbors to make up for our mistakes, neither does our neighbor have any right to tell us how to live, so long as we aren't infringing on their rights…. There are those that feel online gambling is morally wrong and financially irresponsible, which I do not argue with, but they also feel that because of this, the government should step in and prevent or punish people for taking part in these activities. This attitude is anathema to the ideas of liberty.Libertarians appear to have a coherent moral philosophy, which includes a general opposition to forcing any particular moral code upon others. Note that Paul is not saying that gambling is morally acceptable. Rather, he is saying that (negative) liberty has a moral value that supersedes other moral considerations. Libertarians seem willing to reject both liberal concerns for social justice But what might explain the libertarian focus on liberty to the exclusion of other moral concerns? Recent work in moral psychology suggests that moral attitudes arise, at least in part, from low-level “dispositional traits” feel traditional moral concerns less than do most other people. Tetlock, et al. This work suggests that one explanation for the unique moral profile of libertarians is that they The Fountainhead, Ayn Rand Finally, emotional reactions, and the moral principles that derive from them, serve interpersonal functions why libertarians may hold their unique pattern of moral beliefs.In this paper, we let libertarians speak for themselves. We report the results of 16 surveys in which a total of 11,994 self-identified libertarians participated. We show how self-described libertarians differ from self-described liberals and conservatives not just on their moral beliefs, but on a variety of personality measures that, given previous research on the emotional Our goal, however, was not just to describe the moral intuitions and dispositional traits of libertarians. Our second goal was to provide further evidence for the dispositional origins of ideology To apply this model to the study of libertarians, we first show that libertarians do indeed have a distinct profile of moral concerns (Study 1). We then show that dispositional traits relate to ideological identification, and that this relationship is often mediated by moral intuitions, which can be thought of as a type of characteristic adaptation in McAdams' terminology (Study 2). In Study 3, we show that specific moral concerns relate to distinct styles of social functioning, and that libertarians' unique moral profile relates to their social preferences. Consistent with theories of parallel constraint satisfaction We begin with three general predictions.Libertarians will value liberty more strongly and consistently than liberals or conservatives, at the expense of other moral concerns. This expectation is based on the explicit writings of libertarian authors .Libertarians will rely upon emotion less – and reason more – than will either liberals or conservatives. This expectation is based upon previous research on the affective origins of moral judgment Reason.Libertarians will be more individualistic and less collectivist compared to both liberals and conservatives. This expectation is based upon previous research concerning the social function of moral judgment We evaluate these predictions in three studies using large web-based samples and a variety of measures related to morality, cognition, emotion, and social relatedness. Each “study” is actually a collection of separate studies that were conducted via a data collection website (described below), but for presentation purposes, we group them together based on the predictions they address.The analyses presented are based on data from 157,804 participants  who visited YourMorals.org and participated in one or more studies between June 2007 and January 2011. Results replicate within sub-samples collected before and after January 2010, indicating that the findings of this paper were not greatly affected by current events that occurred during data collection. Only participants who were raised in the United States until at least the age of 14 were included in these analyses. YourMorals.org is a data collection platform where, after providing basic demographics, participants are invited to take part in any of 6–8 featured and 30–40 overall studies, each described with a title and a brief one sentence description. Before each study, participants were presented with an IRB approved information sheet, detailing our contact information, participant rights, and study details, to which they were asked to agree. Upon completion of each scale, a graph including the participant's own score in comparison to others is provided. Participants usually find YourMorals.org through publicity about psychological research or by typing keywords related to morality into a search engine. Most participants took one or two surveys, but 37% completed more than two, and 15% completed more than five.YourMorals.org offers a unique opportunity to examine libertarian morality because, unlike most major surveys , it allows participants to choose the label “libertarian” as a self-descriptor, rather than forcing them to select a point on the liberal-conservative spectrum. As of January 2011, 11,994 American visitors to YourMorals.org had self-identified as “libertarian”. Because our sample is not representative, we do not claim to describe the absolute percentage of libertarians who hold any particular belief or share any particular trait. Rather, our goal is to compare libertarians to liberals and conservatives on a variety of personality traits, in order to examine whether the relationships found between dispositions, values, and social functioning in previous research are also found within self-described libertarians.Our main dependent variable is political self-identification, which we use to compare ideological groups within each specific study. Upon registration, participants were asked “When it comes to politics, do you usually think of yourself as liberal, moderate, conservative, or something else?” Options available on a dropdown menu included “very liberal,” “liberal,” “slightly liberal,” “moderate/middle of the road,” “slightly conservative,” “conservative,” “very conservative,” “don't know/not political”, “libertarian,” and “other.” The libertarian option was chosen by 7.6%  of American visitors; 13.5%  chose one of the three conservative options, 11.1%  chose “moderate,” while the majority  chose one of the three liberal options.Examining libertarians' responses on social versus economic issues indicated that our participants' understanding of the term “libertarian” converged with our expectations that they would be fiscally conservative and socially liberal. When asked “how liberal or conservative” they were on “economic issues” on a 1  to 7 (very conservative) scale, libertarians indicated that they were even more conservative (M = 6.10) than conservatives (M = 5.93), and far more conservative than liberals (M = 2.83). When asked the same question about “social issues”, libertarians characterized themselves as much more liberal than self-identified conservatives (M's = 2.49 vs. 5.16), though not as liberal as liberals themselves (M = 1.66). Self-identified libertarians in our sample also reported specific political attitudes that were consistent with the expected pattern of relative social liberalism. For example, 59% of libertarians felt that “abortion should be generally available to those who want it” compared with 18% of conservatives, and 69% of libertarians felt “same sex couples should be allowed to legally marry” compared with 21% of conservatives . Parallel analyses using social liberalism combined with fiscal conservatism as a proxy for libertarianism in this sample replicated the main findings of this paper. Analysis of the values of a statistically extracted cluster see  also repThe specific sub-sample that elected to take each study is described along with each measure. The full libertarian sample was mostly white (87.5% of those who answered our ethnicity question), male (79.6%), well educated (79.3% were in college or had earned a college degree), and diverse on age . Libertarians were comparable to other participants in terms of education, ethnicity, and age, but were much more likely to be male (79.6%) compared to both liberals  and conservatives . Because of this difference and because many of the distinguishing characteristics of libertarians turn out to be traits on which there are substantial gender differences, we include tables that show the effects separately for males and females.p values in the text, though they are indicated in d scores in these tables to allow comparisons of effect sizes across scales and genders. Any time we say that one group scored higher or lower than another group, the difference was significant at p<.01, and usually at p<.001. In describing our effects, we generally follow Cohen's d = .10 to .39), medium/moderately (d = .40 to .69), or large/substantially (d>.70), but give the exact d statistic when differences are very small or very large. Rather than describing each measure in a single method section, we provide a short description of each scale and its sample, followed by the results for that scale, and a brief discussion of how the results help us evaluate our three predictions. Finally, after each set of measures, many of which have a great deal of psychological overlap, we include multivariate analyses designed to help the reader synthesize each set of measures presented.Due to our large sample sizes and the many differences between liberals and conservatives, virtually all measures produced highly significant contrasts. Because the degree of significance is not as important as the overall pattern of differences, we do not discuss If any civilization is to survive, it is the morality of altruism that men have to reject.- Ayn RandOur first prediction was that, compared to liberals and conservatives, the morality of libertarians would be characterized by strong endorsement of individual liberty at the expense of other moral considerations. We addressed this question by examining several measures designed to give a broad overview of a person's values and morals, in particular the Moral Foundations Questionnaire The Moral Foundations Questionnaire (MFQ) measures the degree to which a person relies on each of five moral foundations: harm/care, fairness/reciprocity, ingroup/loyalty, authority/respect, and purity/sanctity. The scale has two parts. The first measures abstract assessments of moral relevance  and the second measures agreement with more specific moral statements . The MFQ has been shown to be reliable and valid, and to predict a variety of moral and political attitudes, independent of political ideology d scores indicating how libertarians differed from liberals and conservatives on the MFQ . If libertarians have indeed elevated self-direction as their foremost guiding principle, then they may see the needs and claims of others, whether based on liberal or conservative principles, as a threat to their primary value.Once again, we see that libertarians look somewhat like liberals, but assign lower importance to values related to the welfare or suffering of others–the benevolence value  and universalism . It is also noteworthy that the highest mean for any Schwartz Value dimension was libertarians' endorsement of self-direction . Self-Direction was the most strongly endorsed value for all three groups, but for libertarians the difference was quite large compared to the next most endorsed value, achievement (The Ethics Position Questionnaire d = .58), and similar but lower than liberals (d = −.25), on moral relativism.According to Forsyth's The Good-Self Assessment The results suggest that libertarians are less likely to see moral traits as important to their core self, compared to liberals and conservatives. At the same time they are just as likely as these two groups to base their self-concept around positive non-moral characteristics, such as being funny or outgoing. Notably, libertarians were the only group to report valuing pragmatic, non-moral traits more than moral traits. Libertarians may hesitate to view traits that engender obligations to others  as important parts of who they are because such traits imply being altruistic In the original conception of Moral Foundations Theory, concerns about liberty (or autonomy or freedom) were not measured. But as we began to collect data on libertarians and to hear objections from libertarians that their core value was not well represented, we created questions related to liberty in the style of the Moral Foundations Questionnaire. We generated 11 items about several forms of liberty see  and colld = 2.56). On lifestyle liberty, libertarians scored substantially higher than both liberals (d = .81), and conservatives (d = 1.19).Libertarians are not unconcerned about all aspects of morality, as suggested by their scores on the MFQ and several other widely used morality scales. Rather, consistent with their self-descriptions, they care about liberty. Like conservatives, they endorse a world in which people are left alone to enjoy the fruits of their own labor, free from government interference. They also exceed both liberals and conservatives  in endorsing personal or lifestyle liberty.We conducted two analyses to answer this question, in addition to the above comparisons. First, we conducted a cluster analysis of participants using Moral Foundations Questionnaire sub-scale scores, to see if we could statistically extract libertarians based on their pattern of responses concerning their values, rather than on their self-identification. Second, we conducted a principal components analysis of the measures included in Study 1 in order to see if the values that libertarians espouse did indeed form a coherent factor.A hierarchical cluster analysis was conducted on all participants who completed both the basic Moral Foundations Questionnaire sub-scale scores, as well as the Liberty Foundation scores , using Ward's Method to calculate the distance between participants. Visual analysis of the resulting dendogram indicated that a major third cluster split occurs at a significant distance from further divisions, and we therefore classified all participants based on this three-cluster solution. Mean scores and the composition of each group are given in Principal components analysis using all measures from Study 1, except for the Good-Self Scale, was conducted on 374 participants  who completed these measures. Scree plot analysis The above analyses suggest that libertarians indeed hold an empirically distinct set of values, compared to liberals and conservatives. Given that liberty values form an empirically distinct value cluster that has pragmatic utility in differentiating groups and is distinct from other self-oriented concerns such as power and achievement, it is likely that concerns about liberty represent a moral intuition previously unmeasured in Moral Foundations Theory. A cluster analysis of participants yielded a 3-group solution where members of this third group endorsed libertarian values more and liberal/conservative values less, and were also more likely to be libertarian see . PrincipOur results suggest that libertarians are a distinct group that places lower value on morality as typically measured by moral psychologists. This pattern was replicated across a variety of largely separate samples with moral concerns measured using several different approaches. Our measures were not overtly political in content, and there were few questions about the role of government. Rather, we used measures of general values and moral beliefs, and found that libertarians were consistently less concerned than other groups about the individual-level, other-oriented concerns that most theorists place at the heart of morality: harm, benevolence, and altruism. The contrast here was starkest with liberals, but we also found that libertarians were much less concerned than conservatives with group-level moral issues  that are typically associated with conservative morality This is not to say, however, that libertarians are devoid of moral concerns. Contemporary moral psychology has paid little attention to the valuation of negative liberty as a specifically moral concern. Independence may be seen as a pragmatic value Therefore, our first prediction was strongly supported: libertarians value liberty more strongly and consistently than liberals or conservatives, at the expense of other moral concerns. We now turn to the question of libertarian dispositions. In particular, might libertarians simply feel the emotional pull of most moral concerns more weakly than other people do? Might libertarians generally be dispositionally more rational and less emotional? Study 2 tests whether these dispositional traits (level 1) may lead libertarians to certain values (level 2) and then to the endorsement of certain ideological narratives (level 3), which tie these values together in the form of an ideology “Every aspect of Western culture needs a new code of ethics - a rational ethics - as a precondition of rebirth.”- Ayn RandIn Study 2, we sought to examine cognitive and emotional differences among libertarians, liberals, and conservatives. Psychologists have long theorized that values evolve from the interaction of heritable dispositions, childhood learning, and social-contextual factors In place of a system of morality deriving from emotion, libertarians have explicitly sought a “rational ethics” These considerations led us to our second prediction: Libertarians will reveal a cognitive style that depends less on emotion– and more on reason– than will either liberals or conservatives. We expected this cognitive style to relate to the distinct moral profile described in Study 1, leading to libertarian self-identification.The Big Five Personality Inventory The libertarian pattern on the Big 5 complements our findings on their explicit values in Study 1. Libertarians report lower levels of the traits that indicate an orientation toward engaging with and pleasing others . Low scores on agreeableness in particular have been said to indicate a lack of compassion and a critical, skeptical nature The Interpersonal Reactivity Index IRI  is a 28-According to Davis The Disgust Scale Revised Previous research has shown that liberals are less disgust-sensitive than conservatives The Hong Reactance scale The high levels of reactance expressed by libertarians fit well with the value they place on liberty as a moral foundation. It is of course possible that libertarians' responses to the scale are primarily expressions of their current political beliefs, but it is also possible that people who have the strongest visceral reactions to interference from others are also the people most drawn to the ideals and identity of libertarianism. Reactance may in fact function as a moral emotion that draws individuals toward the ideal of negative liberty. Reactance scores were negatively correlated with measures of empathy  that are most associated with conceptions of positive liberty The Empathizer-Systemizer scale  judgments are more likely to be reached via “hot” affective processes e.g., , our resThe Cognitive Reflection Task The cognitive reflection task provides a behavioral validation of the hypothesis that libertarians have a more reasoned cognitive style. In our dataset, this measure inter-correlates with both Need for Cognition  and Baron-Cohen Systemizer  scores, with libertarians scoring higher than both liberals and conservatives on all three measures. Taken together, a convergent picture of the rational cognitive style of libertarians emerges .Consistent with McAdams' personality model Using AMOS 19, three structural equation models were created and compared: 1. a partial mediation model whereby dispositional variables affect libertarian self-identification directly as well as mediated by values see , 2. a fuWe also tested these mediation models using a procedure developed by Baron & Kenny As predicted, libertarians showed lower levels of emotional responsiveness on standard measures of the moral emotions of disgust and empathy . MultivaLibertarians did display high scores, however, on one measure of emotional reactivity, the Hong Reactance scale , which wThe use of liberty rhetoric may have different psychological origins in different political groups. Autonomy is posited to be a universal basic human psychological need Consistent with their stated preference for rationality, libertarians seem to enjoy effortful and thoughtful cognitive tasks . In combIn conclusion, we found strong support for our second prediction, that libertarians will rely upon emotion less – and reason more – than will either liberals or conservatives. Further, multi-variate models suggest that these emotional differences may lead to certain value orientations which in turn predispose individuals toward libertarian self-identification. In the next section we explore how these value orientations may also have roots in specific patterns of (and attitudes about) social relationships, consistent with theories about the social function of moral reasoning To say ‘I love you’ one must first be able to say the ‘I.’”“- Ayn Rand (1943)One of the primary purposes of moral concerns such as conformity, tradition, authority, and group-loyalty is to bind individuals together libertarians will be more individualistic and less collectivist compared to both liberals and conservatives, suggesting that their moral concern for liberty may represent the conversion of this preference into a value Study 3 tests the idea that The Individualism-Collectivism scale Libertarians appear more individualistic and less collectivistic than both liberals and conservatives. The relative preference for individualism occurs in both hierarchical and non-hierarchical circumstances.The Identification with All of Humanity Scale Consistent with the libertarian desire for personal liberty, libertarians feel relatively low levels of connection to their community, country, and people globally. This pattern suggests that libertarians are likely to join conservatives in opposing transnational humanitarian undertakings, and they are likely to join with liberals in opposing projects and legislation that are aimed at strengthening national identity.The Different Types of Love scale Consistent with the results on the Identification with All of Humanity scale, the libertarian independence from others is associated with weaker loving feelings toward friends, family, romantic partners, and generic others. It is noteworthy that differences between liberals and conservatives were generally small (except toward generic others). Libertarians were the outliers.In order to answer this question, we conducted a principal component analysis to determine if these variables could be grouped into common ‘sociality’ factors and if libertarians do indeed score low on them. Further, we wanted to relate these factors to value clusters from Study 1.Principal component analysis using the Individualism-Collectivism Scale, Identification with All Humanity Scale, and Different Types of Love Scale was conducted on 630 participants who completed all three measures. The scree plot r = .60, p<.001, MFQ-fairness: r = .42, p<.001, MFQ-authority: r = −.18, p<.001, MFQ-ingroup: r = −.14, p<.01, MFQ-purity: r = −.07, p = .07), while variables indicative of “Conservative Values” correlated positively with the tight social connection factor .Of these participants, 590 also completed the Moral Foundations Questionnaire. Variables indicative of “Other Oriented Values” correlated positively with the broad social connection factor . If “moral thinking is for social doing” Libertarians will value liberty more strongly and consistently than liberals or conservatives, at the expense of other moral concerns.While not all libertarians endorse the views of Ayn Rand, our findings can be summarized by the three quotations we have presented from her work. We began Study 1 with Rand's exhortation to reject “the morality of altruism,” and we showed that libertarians do indeed reject this morality, as well as all other moralities based on ideas of obligation to other people, groups, traditions, and authorities. Libertarians scored relatively high on just one moral concern: liberty. The libertarian pattern of response was found to be empirically distinct from the responses of liberals and conservatives, both in our cluster analysis of participants and in our principal components analysis of measures. We found strong support for our first prediction: We introduced Study 2 with Rand's claim that Western culture can only be reborn when it can be founded on “a rational ethics.” Consistent with Rand's writing and psychological research concerning the intuitive origins of moral reasoning Libertarians will rely upon emotion less – and reason more – than will either liberals or conservatives.We also found that libertarians showed a strong preference for and enjoyment of reasoning . We think it is worth repeating that libertarians were the only one of our three groups for which systemizing scores were higher, in absolute terms, than their empathizing scores, suggesting that libertarians are the only group that may be psychologically prepared for the Randian revolution of “rational ethics.” Thus, we found strong support for our second prediction: Libertarians will be more individualistic and less collectivist compared to both liberals and conservatives.We introduced Study 3 with Rand's condemnation of love that is not based on a strong sense of self. We found that libertarians do indeed have a strong sense of self and the self's prerogatives, and a correspondingly lower sense of attachment to others. They exhibit a high degree individualism, a low degree collectivism, and generally report feeling less bonding with others, less loving for others, and less feelings of a sense of common identity with others. Libertarians have a lower degree of the broad social connection that typifies liberals as well as a lower degree of the tight social connections that typify conservatives. These social preferences were related to their moral attitudes suggesting that libertarians have less functional use for moral concerns. We found strong support for out third prediction: The current research extends past comparisons between liberals and conservatives to a third ideological group — libertarians. Our findings are consistent with the emerging view that personality plays a crucial role in the formation of ideology. As is the case with liberals and conservatives The current research not only describes an important ideological group, but also tells a coherent story about how and why some people become libertarians while others become liberals or conservatives. While we cannot establish causality with our correlational data, we can see several cross-level links of the sort described by McAdams and Pals A related way to describe the links between personality and morality is found in Rozin's The current research examined a specific ideological group in the United States, but just as research on other distinctive groups such as patients with brain lesions This set of studies has two main limitations: our findings rely almost exclusively on self-report measures, and our sample is not representative of the general population. Our reliance on self-report measures is partially mitigated by the fact that we used diverse measures that converge on an extremely consistent picture of libertarianism. The fact that libertarian performance on the Cognitive Reflection Task and their responses to classic moral dilemmas converges with libertarian self-report of their cognitive and emotional style also mitigates some of this concern. Because so little has been written about libertarian psychology, we believe that our very large set of self-report measures is an important first step in characterizing libertarian psychology upon which more methodologically advanced work can build Our use of a volunteer internet sample means that we must be cautious in generalizing our findings to the broader population. However, our results generally replicate across gender see , and 4, Our sample, while far more diverse than most college samples Our use of a volunteer internet sample gave us at least three benefits in terms of data quality. First, because volunteers are often more educated and motivated, such samples often show less random measurement error, less survey satisficing, and less social desirability bias compared to nationally representative samples While our sample represents a large number of libertarians, it may or may not represent the majority. Not withstanding our cluster analysis in Study 1, libertarianism may also be studied as a dimension that an individual may endorse to varying degrees rather than as a discrete kind of person, which may be one of the reasons that national surveys typically do not measure identification as libertarian. Self-identification as ‘libertarian’ can change meaning over time, further complicating the issue. William James Political and social psychologists often study ideology on a unidimensional liberal-conservative spectrum, but the real world is clearly more complex. As psychologists advance in studying the personality traits associated with liberalism and conservatism, our findings confirm the value of this approach and extend its reach by describing a heretofore-neglected yet politically important group – libertarians. Libertarians have a unique moral-psychological profile, endorsing the principle of liberty as an end and devaluing many of the moral concerns typically endorsed by liberals or conservatives. Although causal conclusions remain beyond our current reach, our findings indicate a robust relationship between libertarian morality, a dispositional lack of emotionality, and a preference for weaker, less-binding social relationships. These findings are consistent with previous research on the dispositional origins of moral judgment. By focusing on one understudied ideological group, the findings provide further evidence concerning the closely intertwined nature of personality, values, and political ideology.Appendix S1Liberty Items.(DOC)Click here for additional data file.


Cardiovascular surgery, also known heart surgery is a stressful profession where surgical skills and experience can make the difference between life and death for the cardiac patient. The cardiac surgeon must acquire numerous years of education, training and surgical expertise. Open heart surgical operations are lengthy taking 4 - 6 hours or longer to complete. The surgeon has to be on call all the time because emergencies can occur anywhere, anytime, preoperatively or postoperatively without warning. The cardiac surgeon has to work with a very experienced team; even a small mistake may lead to a tragic unexpected cascade of events, resulting in a disaster. Thus, stress is an integral part of cardiovascular surgery. It is not surprising that surgeons practicing this stressful profession aged 45 and older have suicidal rates 1.5 to 3 times that of the general population . These sA competent cardiovascular surgeon should be able to battle stress, “keep his cool” under pressure, “think on his feet” and improvise “on-the-spot” in case something unexpectedly goes awry during the course of the surgery. Moreover, the task of a cardiovascular surgeon does not end in the operatory. It is imperative that he or she has good bedside manners in order to effectively communicate with heart patients and their guardians in the ward, discuss treatment options preoperatively as well as help the patients recover postoperatively. The surgeon should also be in good physical shape to be able to stand for hours without fatigue. Thus, regular exercise is also important. Mentality, psyche and self-confidence are equally vital to combat the inherent stress of open heart surgery. However, for the cardiac surgeon preferring a stress-less work environment, teaching may be a good albeit less lucrative alternative -5.


To fully define the grammar of American Sign Language (ASL), a linguistic model of its nonmanuals needs to be constructed. While significant progress has been made to understand the features defining ASL manuals, after years of research, much still needs to be done to uncover the discriminant nonmanual components. The major barrier to achieving this goal is the difficulty in correlating facial features and linguistic features, especially since these correlations may be temporally defined. For example, a facial feature  occurring at the end of the movement of another facial feature , may specify a Hypothetical conditional, but only if this time relationship is maintained. In other instances, the single occurrence of a movement  can be indicative of the same grammatical construction. In the present paper, we introduce a linguistic–computational approach to efficiently carry out this analysis. First, a linguistic model of the face is used to manually annotate a very large set of 2,347 videos of ASL nonmanuals (including tens of thousands of frames). Second, a computational approach is used to determine which features of the linguistic model are more informative of the grammatical rules under study. We used the proposed approach to study five types of sentences – Hypothetical conditionals, Yes/no questions, Wh-questions, Wh-questions postposed, and Assertions – plus their polarities – positive and negative. Our results verify several components of the standard model of ASL nonmanuals and, most importantly, identify several previously unreported features and their temporal relationship. Notably, our results uncovered a complex interaction between head position and mouth shape. These findings define some temporal structures of ASL nonmanuals not previously detected by other approaches. Sign languages provide a window for the study of what formal, highly abstract and minimally required properties constitute human linguistic knowledge e.g., e.g., head, brows, eye lids, eye gaze, nose, mouth, cheeks, chin, shoulders), the options available to each , and the multiple combinations in which they interact.. Thus, sorting through all the possibilities and testing each for what may be subtle differences in meaning is a complex problem with many variables. While it is well known how the handshape, hand movement and palm orientation form the fundamental building blocks of the manual component of the sign The sign language literature has made it clear that although affective and linguistic expressions may co-occur, they are nonetheless easily distinguished by their articulation onsets and offsets with respect to the signs made on the hands, with linguistic expressions tightly coordinated with the syntactic constituents that they relate to To better understand the need of computational tools for the linguistic analysis of nonmanuals, let us review their use in sign languages. The nonmanuals used in sign languages serve a variety of functions similar to those performed by intonation or word order changes in a spoken language like English. For example, to make a question from the English statement “Sarah is having a party this weekend,” the intonation pattern can be changed from falling at the end to rising at the end “Sarah is having a party this weekend?” (an echo question) or the word order can be changed to give “Is Sarah having a party this weekend?” (a yes/no question). To make similar questions, American Sign Language (ASL), like some spoken languages, does not use the option of changing the word order but instead adds nonmanual markers. In this example, the nonmanual marker is that of a “Yes/no question.” Such a marker is used to denote questions that can be readily answered with a simple “yes” or “no.” This is in contrast, for instance, to “Wh-questions” which start with a “wh”-word  such as “which,” “when,” “how,” etc; in ASL Wh-questions are made with both the addition of nonmanual markers and optional word order changes. But each of these markers, for “Yes/no question” or “Wh-question,” may consist of multiple articulations, the most prominent being the position of the eyebrows, but with secondary articulations that may turn out to have their own meanings which combine with the primary meaning, or that may have emphasizer effects on the primary meaning, or that may be signer-specific, or even accidental and irrelevant To identify nonmanual markers, sign language researchers will typically manually annotate head movements and facial expression changes observed in a large number of video sequences. Tools such as ELAN e.g., for conditionals, a sign with the meaning ‘if’ may be used but is not required) i.e., positive versus negative) seems to be marked with nonmanuals; there is no regular sign for indicating positive polarity as this is the default interpretation in all languages, and negative signs for negative polarity are optional if the nonmanual for negation is present To date, research in ASL has identified that Hypothetical conditionals, Yes/no questions and Wh-questions are marked primarily by nonmanuals and secondarily by optional signs , and first-order co-occurrences , as, for example, one facial or head articulation occurring before another . Note that the term “discriminant” goes beyond a characterization of the nonmanual. While characterization defines the production of a nonmanual, discriminant features are those produced during one grammatical construction  but absent elsewhere. This proposed approach will thus be used to test the hypothesis that nonmanual markers discriminate among the following nine classes of sentences: Hypothetical conditionals, Yes/no questions, Wh-questions, Wh-questions postposed, Assertions and their polarities (positive and negative).The present paper describes a linguistic-computational approach to This proposed approach not only validates some known nonmanuals but, most importantly, identifies a large variety of previously unsuspected nonmanual markers for each of the nine sentence types of ASL considered in the present paper. For example, as expected, our results show a systematic relationship between eyebrow position and grammatical constructions. As predicted by previous literature, ‘brows move up’ is prominent in Hypothetical conditionals (89.1%) and Yes/no questions (92.3%). Similarly, ‘brows move down’ occurs systematically in Wh-questions (89.5%) and Wh-questions with the Wh-sign postposed (99.2%). However, our results reveal a complex interaction between head position and mouth shape that has not been previously reported in the literature. This finding is extremely relevant because it shows how co-articulations of facial components are employed as grammatical constructions and hence emphasizes the importance of complex interaction of nonmanual markers in sign language.The results summarized in the preceding paragraph would have been difficult to attain using a visual analysis of manual annotations. In contrast, the proposed computational approach can search for all possible first-order feature relationships and calculate which consistently co-occur in a given grammatical construct but rarely happen elsewhere. The approach and algorithms described in this paper have been incorporated into ELAN and can hence be readily used by other researchers to replicate and expand on the results reported herein.e.g., spoken English and Turkish Sign Language both allow negative Yes/no questions We investigate the role of nonmanuals in five (5) types of sentences: Hypothetical conditionals, Yes/no questions, Wh-questions, Wh-questions postposed and Assertions; in addition we consider their polarities: positive and negative. This yields a total of 9 classes because Yes/no-questions are neutral, meaning they cannot be associated with a specific polarity , for a total of We recorded fifteen (15) Deaf native users of ASL signing more than The signers were recorded using two high quality Sony DCR-VX2100 cameras. These cameras are equipped with 3 1/3″ CCDs for fast capture of color images in our studio conditions. All human subjects signed a consent form, granting permission for the use of their video sequences in research and the replication of these in scientific articles. The research and consent forms were approved by the IRB boards at The Ohio State University and Purdue University.The first camera recorded the upper-body (including the head) of the signer. The second camera captured a close-up of the face. This second camera provides high-quality video of the nonmanuals, For consistency check, the annotations of each recorded sentence were visually validated by a native Deaf ASL signer and an experienced sign language researcher who were members of the American Sign Language Linguistics Laboratory at Purdue University. In particular, we made sure all video clips in the database correctly expressed its target sentence and that it was clearly visible and understood. Video clips not passing this test were eliminated from the database.The video clips and manual annotations described in this section will be made publicly available to those wishing to extend on the results reported herein.e.g., nose on top of the mouth), while second-order specify between-feature distances. Shape features means that facial features are in a specified position . These descriptions are correlated with facial movement that may also be defined using other coding systems Research in face perception has demonstrated that facial expressions are coded and recognized by the cognitive system using configural Similarly, sign language research has shown that such options as brow position, closed/open mouth and flat/round lips, teeth showing, and head turns are potential building blocks of nonmanual markers All video clips are displayed with the ELAN discriminative facial features. A possible solution is to treat a feature as a time varying function, where each category has some numerical value e.g., headshakes, left to right turns, etc. We resolve these problems using Allen's Temporal Logic (ATL).The qualitative manual annotations described above must then be quantified in order to determine the most event A happens before event Bbefore, meets, overlaps, equals, starts, during and finishes. To show the use of the above defined propositions, consider the examples in A and B. A is said to be before B, when A happens disjointly before B, A could be head turns right and B head turns left. Here, we would write head turns right before head turns left. This could be the case when a subject is signing a negative statement with negation marked with a headshake.ATL is a framework that allows us to analyze relative temporal information, such as A happens immediately before B, then A is said to meet B, before and meets is that before requires a non-empty time interval between both events. For example, when nodding, the head moves up and down without a visual pause, which could be written as, A meets B. Obviously, in practice, two events involving different articulations would only perfectly follow one another by chance. To accommodate for small natural variabilities , we define meets as B occurring after a very brief interval A. The value of In the case that A is said to overlap B when A starts before B and A finishes during B, equals means that both events, A and B, share the same time interval, e.g., to indicate that the brows move up once, as in Yes/no questions A finishes before B, then A is said to start with B, A and B finish at the same time but A starts after B, then A is said to finish at B, during means that A's time interval happens within B's time interval, When both events start at the same time but i.e., “Brad is cooking/cooks fish on the grill”). The resulting coding using ATL relations is shown in e.g., In summary, the Allen's Temporal Logic defined above is composed of a set of binary propositions. Formally, we denote this set as e.g., brows move up equals brows move down) giving a total The 17 feature categories  form a se.g., while a single headshake may not carry any grammatical meaning, multiple headshakes can be a marker of negation or Wh-questions It is also important to encode the number of consecutive occurrences for a given ATL relation. This might be important for some discriminant features, Formally, we represent a sentence as e.g., Yes/no-questions versus the others), we need to use a feature extraction algorithm that uncovers the features or combinations of them that best discriminate between sentence types. In pattern recognition, such approaches are called discriminant analysis The histogram representation of the ALT described thus far provides a convenient numerical representation of the nonmanual events we wish to study. To determine the time relations that best discriminate a grammatical structure from the rest .Formally, RLDA finds the projection vector Solving for (1) yields, discriminative if its corresponding absolute magnitude in i.e., i.e., An ATL relation is hence defined as hypothesis is that nonmanual markers can be used to discriminate among the nine classes of sentences described above. More specifically, we hypothesize that first-order temporal relations of facial movements are sufficient to code for such grammatical structure. To test this hypothesis, we use all the video sequences in our database except one to find the discriminant facial features (as described in the Methods section) and test whether the resulting model correctly classifies the left out sentence. This approached is known as Leave-One-Sentence-Out (LOSO) test.Our i.e., Classification of the left out (test) sample In addition to the above, we included the commonly used sensitivity index d′ to measure the distance between signal and noise for the most discriminative features. Here, d′ measures the performance of a single feature in isolation and, hence, does not provide information on co-occurring features or their temporal structures.i.e., the discriminant features. To achieve this, we run a one-versus-all experiment. This means that, for each class , we use the linguistic-computational approach described in the Methods section to find the discriminant features that are common to that class but are not descriptive of the other classes.First, we wish to determine the nonmanuals that best discriminate each structure, The resulting discriminant features need to distinguish between the grammatical structures under study. These features are those providing the highest classification accuracies in the LOSO test described above. They are in i.e., i.e., i.e., In discriminant the feature is. Some discriminant features will of course be more common and, hence, will successfully discriminate more samples of finishes brows move up” in not a Hypothetical conditional (with classification accuracy at 97.6%). In comparison, “Brows move up” is a better nonmanual marker of conditionals , but is also employed elsewhere . Thus, this second nonmanual is not as robust as the previous one. As expected, the result of averaging the last two columns in The numbers in these last two columns (labeled “% Classification”) specify how many of our sentences can be correctly classified using each single feature Additionally, we tested for the statistical significance of our results. This was done by comparing our results with those given by a randomization of the class labels. That is, we compare the results obtained with the proposed approach to the results one observes when the class labels for each of the samples Let us now describe the results of this study in detail for each of the 5 classes under consideration.With respect to the Hypothetical conditionals , the higfinishes brows move up” in 19% of the Hypothetical conditionals suggests a head thrust at the end of the conditional clause Most notably, during brows move up,” which may reflect the establishment of a space to the left of the signer at head level to mark clauses containing content that is uncertain, hypothetical, or otherwise irrealis. The use of space for linguistic pragmatic functions has been recently reported for Catalan Sign Language (LSC) during brows move up” in Hypothetical conditionals is Lackner's observation of the signers' reference to a “mental” space or “space of thoughts,” which may be coded by pointing, gazing up, or moving the chin up.Another frequent head behavior is “head turns left during brows move up” occurs very frequently in clauses containing negation (negative polarity), as part of the negative headshake  teeth touch the (bottom) lip at the end of the articulation of “if.” In contrast, the high frequency of “teeth open” in non-Hypotheticals is not accompanied by high occurrence of “teeth touch lip during brows move up” and “teeth touch lip during mouth open.” Instead, “teeth open” is the result of the inclusion of lexical items such as FISH in the stimuli. As reported in e.g., pronouns, verbs). Thus, it is not unusual that a noun sign like FISH would be accompanied by the articulation of “fish” or at least the first part of it that involves articulation of “f” or “fi.” Both Hypothetical conditionals and non-Hypotheticals have a high occurrence of “teeth open” in From In contrast, “brows move up” occurs in few Wh-questions (10.6%) but is very frequent in other constructions (70.5%), which includes the Hypothetical conditionals discussed above and Yes/no questions (discussed below), both of which are associated with raised brows. “Brow move up” may also be associated with some occurrences of Wh-questions with Wh-sign postposed. This allows for very high classification rates of Wh-questions and other constructions even when they are using this single feature.starts brows move down,” which occurs frequently in Wh-questions (43.1%) but not in other constructions (0.5%). This cue is likely associated with the presence of mouthing of “who” at the beginning of some Wh-questions. This is also the case for “mouth shape round.”The remaining discriminative cue is “mouth shape round starts brows move down” for Wh-questions.From the results in meets brows move down,” with the brows up on the non-question part and the brows down on the Wh-word. This “brows up meets brows down” pattern in ASL Wh-questions postposed is noted in A “Wh-question postposed” is one in which the Wh-word has been produced at the end of the question instead of at the beginning  in Wh-questions postposed, and may be related to mouthing of other Wh-words, such as “which,” “why,” and “where.” Note the classification rate, for Wh-questions postposed and others is 94% when combining the features.The mouth is also active in relation to “brows move down,” with “mouth shape round overlaps brows move down” occurred in 16.9% of these as compared to only 2.5% in other constructions. Periodic blinks, the kind that are associated with eye-wetting, are well-known as a marker of the end of intonational phrases and syntactic constituents in ASL inside the clause. This supports the suggestion that they are deliberate blinks, which are used to emphasize a sign, because signs in final position in a clause are already emphasized/stressed One articulation in Wh-questions postposed that did not show up in other constructions is the occurrence of blinks. “Blink Yes/no questions are distinguished primarily by “brows move up,” although this cue also occurs frequently in other constructions, which include Hypothetical conditionals  and Assebefore brows move down” does not occur in Yes/no questions, since the brow raise is expected to span the entire question before brows move down” does occur in other constructions, namely those in which a Topic or Hypothetical conditional clause (brows up) precedes a Wh-question.Note that, as expected, “brows move up starts brows move up” occurs in 33.5% of Yes/no questions but only 6.9% of other constructions. Half of the Yes/no questions are preceded by a topic; according to “Head moves up finishes brows move up” occurs in 32.9% of the Yes/no questions as compared to only 3.4% of the other constructions, with a clear classification accuracy for the latter (97.2%). This is a truly surprising result which undoubtedly suggests further investigations in this direction as, to our knowledge, no function for flat mouth in ASL has been assigned in the existing literature. Since it spans the full duration of brows up  and ends when the brows up ends, these results suggest that this is a question mouth marker, although the issue is then raised as to why it is only not more frequent.“Mouth shape flat Assertions have been traditionally viewed as not marked by specific nonmanuals, leaving the articulators free to reflect ones that accompany nonmanually marked lexical signs as well as to reflect the signer's emotional status. The cues identified as distinctive in i.e., Hypothetical conditionals, Wh-questions, Wh-questions postposed and Assertions.The study of polarity follows the same procedure described above. The discriminant features selected by the LOSO approach are given in Here, we also performed the statistical significant analysis described in Experiment 1 section. All our results were again statistically significant with: Let us look at each of these results in more detail.From When we dig into the details of the temporal behavior of head turns, we identify linguistic interactions that have not been available to impressionistic analysis so far. We believe this is an improvement our algorithm has made possible for sign language research. In this sense, the findings with the ordering and the relation of head turns alert us to two previously unrealized findings about negative polarity in ASL.meets the opposite head turn” which kinematically correlates to a fast paced headshake. That the defining relation is “meets” rather than a head turn preference on either side of the relation is proved when we compare meets head turns right” discriminant feature. On the other hand, what gives us the fast paced headshake in meets head turns left” discriminant feature. The commonality turns out to be the abstract linguistic relation “a head turn meets the opposite head turn.” The kinematic realization of this abstract linguistic property is a fast paced headshake.The first finding is that the defining relation for negative polarity is “a head turn meets the opposite head turn.” There is a widespread linguistic assumption that Assertions are the most basic, simplest clause type, and this is where we see the negative headshake start with “head turns right.”The second finding is that we can generalize that negation normally begins with “head turns right.” Because this does not always occur, we state the general nonmanual marking as “a head turn during brows move up” is the discriminant feature for conditionals. As we will see in discriminant features for polarity in assertions, the primary indicator of fast paced negative headshake “head turns right meets head turns left” in Assertions, the most basic clause, starts with head turn to the right. In Hypothetical conditionals, the “head turns left” dominates the negative, and the fast paced negative headshake is modified to start on the left, yielding “head turns left meets head turns right”, the most active nonmanual marker in negative Hypothetical conditions , leading to In addition to these two findings we also need to note that the headshakes reflected by “head turns right/left Beyond the results above, our results further highlight the role of the mouth in nonmanuals. Note the frequency of “mouth shape other”  during (overlapping with) “head turns right” in a large number of negative Hypothetical conditionals.meets head turns right” gives us a strong cue for differentiating negative polarity from positive polarity in the conditional sentences. When this result is evaluated with “head turns right overlaps mouth shape other,” we come up with the pattern in As we noted above, the fast paced “head turns left Next, note that the percentage of “mouth shape other” (46.3% vs. 17.9%) is strong enough not to be associated with a combined effect of lexical mouth-shapes of random signs in negative sentences. The contrast in discriminant percentages indicates that the mouth is actively involved in the expression of negation in ASL. This finding  is consistent with results reported in The fact that “mouth shape other” is not as frequent as headshake is another interesting finding. There are two ways to interpret this finding. First, although “mouth shape other” is present for almost half of the negative sentences, it could be a redundant or secondary prosodic cue, similar to the findings in The discriminant features that distinguish negative and positive polarity in Wh-questions are more varied than those of Hypothetical conditionals and seem to be less clearly reflective of general negative marking. That is, they generally do not indicate head turns. Instead, a number of the features relate to mouth and teeth positions. In addition, there is no clear pattern of occurrence such as that seen with Hypothetical conditionals, where strong markings were seen for negatives as compared to positives. Here, sometimes a mouth or teeth feature is more prevalent in negatives and sometimes the reverse is true. This suggests that while Wh-questions can be clearly marked by brows down, when Wh-questions are negative, nonmanuals alone may not be able to carry both semantic functions. Such a conclusion is in keeping with two other observations in the literature. One is that both Wh-marking and negation use headshakes; the negative headshake is somewhat larger and slower starts mouth open” is highly classificatory (91.9%) for positive Wh-questions by its absence. While “brows move down” is clearly related to Wh-questions, mouth open could be related to some of the Wh-words being mouthed  and given the higher occurrence in negatives, possibly also ‘not.’ Another mouth cue with a high classification value (89%) for positives by its absence, “teeth open overlaps head turns right,” is almost three times more prevalent in negatives than in positives. Similarly, “mouth closed meets teeth open” is twice as prevalent in negatives as in positives and has a high classification value – its absence from positives yields correct classification 90.2% of the time despite its rare occurrence in Wh-questions in general. When such negative evidence (9.8%) is combined with positive evidence (30.8%), we may thus suggest that “mouth closed meets teeth open” is a candidate to discriminate between negative and positive polarity in Wh-questions. The computational model of this interaction is given in Moreover, the current results define several interesting interactions in Wh-questions and polarity. “Brows move down As we have discussed in the section above regarding negative conditionals, there is evidence of “mouth closed” as a marker of negation. The fact that it meets “teeth open” 30.8% of the time suggests that this cue may be interrupted by some lexical interference (mouthing of English words) tucked into the flow of prosody due to certain lexical items.Another mouth feature that has a high classification value for negative Wh-questions is “teeth touch lip,” which occurs in 25.2% of positives versus only 6.7% of negatives. This is likely the result of three of the positive Wh-questions containing signs that can be accompanied by mouthing of English words beginning with ‘f’ .In contrast to regular Wh-questions, there is a clearer pattern to negative marking for Wh-questions postposed, with discriminant features all occurring more frequently in the negatives than in the positives. This pattern seems to support the argument above concerning regular Wh-questions. The basic difference between Wh-questions with and without Wh-sign postposing is that when the Wh-sign occurs at the end of the question, the material that occurs before the Wh-sign does not have to be covered by Wh-marking. As discussed in discriminant features for polarity in Wh-questions, the material prior to the Wh-sign can sometimes be considered an Assertion, meaning that Wh-marking and negation marking would not come into conflict. Hence, Like regular Wh-questions, we see increased prominence of mouth and teeth positions which will require further research to explain, such as the interaction of mouth gestures with mouthing the English words when certain signs are produced The results for polarity marking of Assertions also show clear nonmanual marking of negation, as all discriminant features occur more often in negatives than in positives. The primary cue in all discriminant features is head turn, reflecting negative headshakes. The only other discriminant cue is “brows move up,” which occurs before “head turns right;” this is the result of those Assertions that begin with a topic or are preceded by a conditional clause, both of which are marked with brows up, followed by a negative Assertion marked with headshake.In sum, with the exception of Wh-questions, the marking of negative polarity is clear on the constructions included in this study, and Wh-questions themselves are known to differ from the other constructions in needing a manual Wh-sign most of the time. The surprises in the data are related to mouth and teeth positions, which seem to gain prominence as nonmanual marking becomes more complex when multiple semantic functions are expressed simultaneously.Uncovering the discriminant features of the linguistic model governing nonmanuals in sign languages has proven to be an extremely hard problem. The present paper shows how this can be resolved using a linguistic-computational approach. In this approach a linguistic representation of the face is first obtained. A computational approach is then employed to determine the combination of these features consistently observed in each class but not with others. The resulting linguistic model proves to be able to discriminate between nine different classes of sentences – Hypothetical conditionals, Wh-questions, Wh-questions postposed and Assertions in their two polarities and Yes/no questions in positive polarity.The analyses described above strongly suggest that there are discriminant features that can be used to separate conditionals from non-conditionals, Yes/no questions from non-Yes/no-questions, Wh-questions and Wh-questions with postposed Wh-signs from non-Wh-questions, and Assertions from non-Assertions. In addition, for each of these except Yes/no questions which do not form negative in ASL, the discriminant features separate the negative structures from their positive counterparts. From the model , the resi.e., a faster paced headshake.In addition, the algorithm gives temporal relations that are striking with respect to head turns, where there are both expected and important novel results. The use of multiple head turns as headshakes has been well-documented for ASL and other sign languages as a major nonmanual marker of negation i.e., headshake, may very well be instantiated in more than one articulatory combination given the left and right directions of articulation, as well as temporal possibilities; a priori there is no reason to expect other sign languages which employ “headshake” as the major nonmanual cue to behave the same way as ASL does. On the big picture, this path also opens up an exciting agenda, both for ASL and cross-linguistic research, for quantitatively detecting nuances in the behavior of certain nonmanual markers which look the same on the surface even to the eye of an experienced sign language annotator.This opens a new venue for the study of headshakes. For instance, with regard to negative head turns it will be important to determine whether all negative headshakes are faster under all conditions across multiple sign languages. This possibility is raised in observations on Austrian Sign Language In addition to the insights about negation reported here, the approach presented in the present work also revealed that head turn left is a discriminant feature in conditionals. Again, work on Austrian Sign Language Lastly, the results also highlight the important role that the mouth and teeth play in negation. It is noted in As a final note, it should be noted that the methodology described herein  will most probably find applications beyond the studies of sign language. Elan is a generic tool used in several disciplines and the statstistical analysis described in the present paper is equally valid in these studies.Appendix S1Supporting Tables S1–S5.(TEX)Click here for additional data file.


Dynamic modeling of lymphocyte behavior has primarily been based on populations based differential equations or on cellular agents moving in space and interacting each other. The final steps of this modeling effort are expressed in a code written in a programing language. On account of the complete lack of standardization of the different steps to proceed, we have to deplore poor communication and sharing between experimentalists, theoreticians and programmers. The adoption of diagrammatic visual computer language should however greatly help the immunologists to better communicate, to more easily identify the models similarities and facilitate the reuse and extension of existing software models. Since immunologists often conceptualize the dynamical evolution of immune systems in terms of “state-transitions” of biological objects, we promote the use of unified modeling language (UML) state-transition diagram. To demonstrate the feasibility of this approach, we present a UML refactoring of two published models on thymocyte differentiation. Originally built with different modeling strategies, a mathematical ordinary differential equation-based model and a cellular automata model, the two models are now in the same visual formalism and can be compared. The perspective is to encourage immunologists involved into mathematical modeling or software productions, to adopt a visual graphical language, here mainly the unified modeling language (UML) “state-transition” diagram to ease the communication, the reuse and the extension of their models.The immune system is a complex biological adaptive, highly diversified, robust and resilient system, characterized by complexity at different levels. Lymphocytes are the central actors of the immune system, in the middle of a multi-scale biological organization, “from molecule to organism”. Multi-scale modeling remains a challenge, as for other biological systems . DespiteSystem dynamics models deal with time, formalized with two distinct concepts as “discrete time,” by a succession of time points and intervals, or as “continuous time” . Models The evolution of homogeneous mathematical model of cell populations  toward “Although in Immunology there is more than 20-years tradition of software and mathematical modeling, very few of them have been the object of further exploitation once published and made available . Models Immunologists often conceptualize the dynamical evolution of their systems in terms of “state-transitions” of biological objects and do it by means of personalized and informal graphical illustrations. Thus, the adoption of a more formal and standard type of state-transition diagram could improve the current situation to not only help biologists to better understand each other but also to facilitate the production and the reading of software code executing these visual transitions, at level of populations or agents .in silico experiments.Thus, in this paper, we promote the development and usage of a visual, computational approach more comprehensible than mathematical equations and programing instructions. This should improve our understanding of lymphocyte dynamics, the exchange on this understanding and simplify the implementation of models by non-specialists delivered from the production of executable code or mathematical equations, to concentrate to A model describes a complex system from the “real word” and thus requires abstraction. This abstraction is performed as the immunologist decides about an experimental protocol in order to observe selected objects at different scales and to follow them in time and space. For example, the capacities of the immune system to preserve the homeostasis and to provide rapid adaptation to an antigen and anamnestic responses can be observed at the organism level, through physiological or pathological clinical observations that relate to lower scale levels. At molecular level, the somatic generation of the diversity of an immuno-receptor, as the TCR, allows for a dynamic network of interactions with antigens. At the cell level, this leads to clonal selection, activation and division. At the organ level, the fluidity of the system insures constant tissue redistribution of cells and molecules, cell migration from thymus to spleen and lymph nodes.Thus, models of lymphocyte population dynamics and turnover consist in reconstructing the components or “entities” of the system across various scales, from molecules to organisms, to determine the relations/interactions through space (varying from micrometer to meters) and “processes” through time (varying between microseconds to years) as explained below. However, the formalization and abstraction of the immune objects as entities undergoing processes, with the help of spatial and dynamic ontologies, respectively defined as SNAP and SPAN , as wellThe immune “entities” could be described according to the language used by the modeler. A cell exists in one “state”: it could be quiescent or in a given phase of the cell cycle or dead. In addition the phenotype and/or a function of a cell define a given state, as CD4 helper T cells. Cells are “located” in various tissues and are in “relation” with other entities. Finally, cells can be considered at various level of “granularity.” For example, T lymphocyte populations are “aggregation” of T cells according to criteria of phenotype, structure or function, although heterogeneity still prevails inside these populations at lower granularity. Accordingly, cells can be modeled at population level (with continuous model as ordinary equation) or at cell level according to space (with discrete model as automata or multi-agent system).According to ontologies, cells participate to various processes, such as division, activation, differentiation, interaction, clonotype selection, apoptosis or migration. According to the states of the cells, their evolution can thus be modeled as “state-transition” that can be applied to various processes in parallel: for example, a thymocyte can differentiate while migrating in cortex and medulla. Note that processes at other levels like molecular or organ levels can similarly be described and modeled. Finally, all these process will determine the global cell dynamics and turnover.“High-level programing languages” are based on abstraction and use of natural language that is easier to understand as compared to “low level programing language,” based on codes. Thus, visual modeling language considers biological-object as conceptual abstract-objects that endure processes. The level of abstraction allowed by these diagrams makes possible to distinguish more easily the “entities” as T cells and the “processes” that occur at different levels such as differentiation, migration and cell cycle. Moreover, such “state-transition diagrams” allow computing parallel pathways at various scales to avoid redundancy that is inherent in the formal description of multi-level, heterogeneous and concurrent systems and to model heterogeneity in a very simplified and economical form  .We have To convince the immunologist of the feasibility of this approach as well as the benefit gained by adopting it, we sketch in the rest of the paper how existing “low level programed” immune models should gain in readability and accessibility by adopting a “high-level graphical” representation under the form of “state-transition diagrams.” We present a “refactoring” of two published models of T cell biology in the thymus. Refactoring consists in restructuring the code or equations of a model to improve its expression, readability and extensibility, without changing its external behavior. One model consists in cell population differentiation modeling with differential equations (continuous model). The other one is a discrete model. Originally it was an automata model consisting of a discrete lattice, where each site (cell) in a given state, follows some rules in space and time that depends on local neighbors . It has p, d, and u represent proliferation, death, and differentiation, respectively, and ix represents the ith stage. The model mainly consists of constant hematopoietic progenitor influx in thymus (Sn); differentiation between thymocyte developmental phenotypes DN and double-positive (DP) cells differentiation into CD4+ or CD8+ cells, then egression of SP stage, either, to the periphery ; proliferation ; positive and negative selection ; and natural cell death . In parallel, the “cell cycle” is represented: the cell switches between quiescence (G0) and cycle with division (S/M). The parameter γ set to 1 represents the cell division into two daughter cells. There is the possibility to induce a perturbation into the system through the specific depletion of T cells entering the S/M cycle phase (p), if γ is set to 0. This represents the presence or absence of a pharmaco-genetic conditional treatment by ganciclovir that induces apoptosis related to the incorporation of a nucleotide analog during DNA elongation. This rule applies to all cell populations except in late DP quiescent cells as indicated in the schema. The “proliferation” depicts that the daughters of a proliferating cell transit into the next generational compartment, except during treatment (γ = 0) when dividing cells die by apoptosis and are lost from the model. The parameter u is an increasing function of generation (G1 to n), making cells more likely to differentiate between phenotypic compartments as they progress through the cell generations.The original model  is a comThe parallelism in this graphical model largely simplifies the original formulation of ODEs while remaining faithful to it. Hierarchy and compound states are present again clearly reducing the diagram clutter. Other representation of the model depicting the differentiation with linear cell generations is also possible .The original model  is a disIt is important to notice that both refactored models, population-based and ABM can now be compared, are directly executable and can provide simulations of physiology, pathologies, and treatment, while not being the scope of this paper. Moreover, their parameters can be automatically tuned to fit experimental data. Any ABM model can also be run as a population version to save time in simulation . Moreover, the flexibility of these diagrams allows assembling the parts of the biological puzzle piece after piece and improving the models.in silico” experiments to predict and explain the puzzling T cells dynamics and the effect of immunological perturbations.As shown here, state-transition diagrams can represent high-level semantics suitable to clarify immunological concepts and to aid communication among interdisciplinary researchers. It can also represent low levels quantitative information suitable for individual-based ABM and population-based ODE modeling. Organization of immune knowledge using a standardized, diagrammatic formal language should greatly improve knowledge integration at multi-scale levels and sharing between experimentalist and theoretician collaborators, rendering their software more readable, scalable, and usable. We are currently working on ways of automatically generating executable code out of these state-transition diagrams. State-transition diagrams supports the extension and interoperability of published models. This will help for dynamic computational modeling of lymphocyte behavior in health and diseases, and for “Véronique Thomas-Vaslin and Hugues Bersini designed the project and wrote the article, Adrien Six and Jean-Gabriel Ganascia participated to discussions.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.


The discussion about nomothetic and idiographic approaches is one of the main philosophical debates in the field of psychological sciences Schafer, .The term “nomothetic” comes from the Greek word “nomos” that means “usage, custom, law” and in psychology is referred to the objective classification under similar conditions, to in establish generalizations, such as diagnoses. The term “idiographic” derives from the Greek word “idios”, meaning “pertaining to self; one's own, private or separate” and is referred to the aspects of subjective experience that makes each person unique.In the clinical psychology, the debate deals about the classification of personality and other taxonomies, as well as the use of diagnosis. At the intervention level, the discussion is about the use of individualistic treatment techniques or treatment derived from research where the focus is a group of people with a similar condition, where  efficacy is tested with aggregated statistics. For example, evidence-based research indicates that the cognitive-behavioral therapy has a positive impact toward the anxiety disorders , this debate is very important and sometimes is at risk of being underestimated. The human tendency toward generalization, together with a superficial approach to research findings, may lead us to stereotypical beliefs about a person living with severe disease. In the case of ALS, an incurable terminal illness with a potentially steep decline in physical function and erosion of independence, it could easily be assumed that “if a person has ALS, than he/she must be depressed and have a low quality of life” questionnaire, though care should be taken when selecting a questionnaire for this purpose. QoL is defined by the World Health Organisation as a “broad ranging concept affected in a complex way by the person's physical health, psychological state, level of independence, social relationships, personal beliefs, and their relationship to salient features of their environment”  (Hickey et al.,