Prototyping hyperspectral imaging devices in current biomedical optics research requires taking into consideration various issues regarding optics, imaging, and instrumentation. In summary, an ideal imaging system should only be limited by exposure time, but there will be technological limitations  that should be considered, modeled, and optimized. This can be achieved by constructing a multiparametric model for the imaging system in question. The article describes a rotating-mirror scanning hyperspectral imaging device, its multiparametric model, as well as design and calibration protocols used to achieve its optimal performance. The main objective of the manuscript is to describe the device and review this imaging modality, while showcasing technical caveats, models and benchmarks, in an attempt to simplify and standardize specifications, as well as to incentivize prototyping similar future designs. In the past decade, the advent of embedded computing has produced a new array of imaging systems that, while based upon mature technologies, have and will increase in complexity. Multi- and hyperspectral imaging (MSI/HSI) is an imaging modality capable of obtaining spatially resolved spectral information of a subject of interest, and one of many areas of research that can also exploit these new developments. This technique has been thoroughly employed in remote sensing , crop anThe design modalities of HSI systems are well documented , and theThe main objective of this article, therefore, is to propose a set of metrics that represent scanning devices such that the key variables that define image quality become adequately established, since overall system performance is not only dependent on the properties of its constituent parts, but also on how efficiently these elements are combined together. A second objective is to describe a custom-built HSI prototype, which presents a structure that may constitute a novel approach, and to use these defined benchmarks to optimize its properties and evaluate where it could be improved. The proposed work pursues the optimization of these efficiency metrics, which could also be extrapolated to other HSI imaging modalities, comparing each other in terms of systems efficiency, evaluating imaging artifacts and acquisition delays, or using them with already existing custom multi- and hyperspectral scientific prototypes for debugging and design optimization.The document is structured as follows. Optical subsystem. An optical component will take a line in the field of view (FOV) and break it up into spatial and spectral information, which will be measured by a camera. There will likely be focusing optics, a spectrographic element and their corresponding couplings and interfaces. From a systems perspective, optics will constrain our wavelength range of operation, and the spectrograph and lens will limit the overall spectral resolution, i.e., the minimum spectral distance between two monochromatic signals that can be spatially separated.Imaging device. Light spatially separated by wavelength will reach a camera, which will capture incoming photons across its active pixel sensor. Different wavelengths will, then, be differentiated by their arrival onto different pixels. Consequently, several imaging parameters will depend on sensor characteristics, namely quantum efficiency (and wavelength range of operation), exposure time, camera gain, pixel depth and spectral resolution. While the first parameters will depend on the specific characteristics of the camera, the latter will be also related to the spectrograph’s ability to separate wavelengths. In the case of line-scanning hyperspectral devices, the camera will also specify the spatial resolution for one of the two spatial axes.Actuator subsystem. The actuator subsystem will usually constitute the sole moving part of the imaging device. In pushbroom systems, for example, either the imaging device or the platform where the sample is placed is moved by a large actuator. In the case of rotating mirror scanners, an actuator/motor will drive a mirror fixed to an otherwise free-rotating axle. Depending on the driving mechanism,  there will be mechanical imperfections—such as backlash—as well as delays due to serial communications between the main computer and the actuator controller/driver. Consequently, the main variables at play will be the repeatability of the drive system  and time delays due to serial communications. If using a stepper motor, its properties  will define the actuator system and its ability to produce high-resolution images.Communications and storage. Image acquisition and actuation control must be governed by a main computer, which must communicate with both camera and actuator subsystems, as well as manage data storage and image calibration. Storage must also be sufficiently efficient so that storing acquired spectra does not impose a significant hindrance on the overall system. We will assume that the imaging system must be able to communicate with other instrumentation and computers within a laboratory network. Camera-computer communications will impose a restriction on the total time per measurement, and therefore communication delays as well as driver and application program interface (API) delays will play a significant role in our efficiency models.ImSpector V10E spectrograph  paired with a CS-mount, 10 × 5 mm–50 mm f/1.3 varifocal objective lens with manual iris and zoom, originallly prepared for 1/3” cameras,  and a Mako G-223B NIR CMOS camera . Coupling the CS-mount objective lens onto the ImSpector and a 2.2 megapixel (2048 × 1088) C-mount camera provides a shorter minimum working distance and angle of view, at the expense of losing a few spectral pixels and half of the spatial pixels of the camera, resulting in a 1200 × 1200 px FOV. This ensemble allows the reading of a single hyperspectral line, which can then be swept across the sample with a rotating metal mirror system powered with a NEMA 17 stepper motor and a GT2 pulley array, achieving 19,200 steps per revolution with minimal backlash and CNC-grade  repeatability.The developed device is a custom-built rotating-mirror scanning HSI device with an embedded computer for storage and control, summarized in Odroid XU4  running Ubuntu 16.04. Dedicated Python 3 software was prepared to handle pymba, a Python 3 wrapper for the Vimba 2.1.3 SDK. Camera control within the laboratory can be achieved through a simplified Python webserver running Flask. Gain control is in the 0–25 dB range, and camera exposure can be set anywhere in the 10 ms–2 s time range. Up to 1.4 MP (1200 × 1200 px) image resolution can be achieved if necessary, although smaller images can be stored via software. The number of sensor bins in the spectral axis is 1088 channels in total, but the total number of spectral channels will be given by the spectrograph. Camera aperture, focus and zoom can be controlled manually.Communications are handled by a generic Gigabit Ethernet router, while DHCP services and camera control are handled by an We shall obtain a set of expressions that can serve as adequate overall system performance metrics, as well as calibration and correction protocols for spatial and spectral information. While the former will provide insight into this particular imaging modality, the latter are standard procedure in hyperspectral imaging.Analogous to frames per second (FPS) in conventional systems, it is the inverse of the total time required to measure a single line, namely the exposure time plus additional time delays:Tline represents the total time needed for acquiring a single line, and it is constituted by a combination of various different time delays and intervals that take place during acquisition:Texp, is the time that a sensor will spend capturing photons from a single line of the FOV  of the camera, b is the bit depth (either 8 or 12 bits), bR is the bitrate (in bits/s), and Ω is the overhead of the protocol. In our practical case, where Vimba uses UDP  on a 2048 × 1088 pixel camera with 8 (or 12) bits per pixel connected to a Gigabit Ethernet router, we obtain 18.16 ms and 27.24 ms of transmission time for 8- and 12-bit images, respectively. This will introduce a limitation of about 55.06 and 27.04 frames per second, respectively, since the camera will be the only device sending packets to the main computer, and switching time will be considered negligible.Transfer/receiving time Tapi. Any imaging sensor will be controlled by the computer via an API or driver library. Driver and API delays should be constant delays that an imaging device presents that can be shown to be due to runtime execution of precompiled API dynamic libraries.Camera Application Program Interface (API) delays, Tmcpy. They represent buffer copying delays due to internal bus limitations within the main computer, i.e., between its network interface and memory.Memory buffer copying and transfer times Tact. These comprise delays in serial communications between the main computer and the actuator subsystem, and due to stepper motor movement, which will be negligible for high-resolution images, but noticeable in low-resolution acquisition.Actuator/mirror movement delays Trand. Unless we work with a real-time operating system, there shall be random interruptions during acquisition, due to the OS scheduler setting the measurement API to background due to priority issues. This phenomenon has a stochastic nature and cannot be controlled unless a real-time operating system is used.There will be additional, random delays, mostly due to Operating System (OS) interruptions. We will denote them as In this equation, Textra = Trx + Tapi + Tmcpy + Tact represents all the additional delays in the system that are not random. This value will be estimated as a constant during nonlinear least squares fitting in the following sections.For our model, efficiency of a scanning imaging device can be described as the ratio between the specified exposure time per sensor capture and the actual time per line:ϵ ≤ 1, sinceThe θ is the orientation angle of the mirror with respect to the normal of the object plane, and γ represents the angle between the object plane normal and the incoming light ray. By the definition of the tangent function, we can infer that the line position along the object plane, dy, is given by:r = r − d, with Using a rotating mirror for scaning imposes a curvature distortion on the FOV of the camera, such that the region of space that remains focused is cilindrical, not planar. This nonlinear transformation can be inferred theoretically by considering x, θ) will be linearly distorted by a scaling factor, which is also a nonlinear function of mirror angle θ:Additionally, the width of objects in a line  will correspond to a spatial position , wherex is the spatial resolution of the measured line in millimeters , yπ/4 corresponds to the pixel index where the ray path is fully normal to the object plane , and the angular resolution of the stepper motor Δθ, in our case, will be the total number of steps per revolution times a stepping factor s:Therefore, every pixel in the image (A representation of the complete nonlinear transformation (without defocusing) is illustrated in θ as a linear transformation between mirror angle θ and position dy in the field of view within focus. In particular, for values r/r ≤ 8% . If lens aperture is kept within a range such that optical depth of field remains over Δr, then a clear image can be captured. Any system should be verified in a real context , so that its linear range can be specified.For this approach, the tangent function can be approximated for small values of Once the main distortions due to using a rotating mirror have been considered, there will be additional accuracy noise caused by the remaining mechanical factors, namely backlash and microstepping. We will assume that any remaining errors will be coming from random sources and are Gaussian-distributed, i.e.,  stepper .MIL-STD-150), printed with reference lines with known lengths. Such lines provide a relationship between pixel positions and actual distances in the image plane.Spatial resolution is typically estimated using a resolution test chart. The one we choose to use is a 1951 USAF Resolution Test Chart (λ = P(p), is a least-squares fit that attempts to relate a spectral wavelength λ to its pixel position p within the sensor:Wavelength separation through a spectrograph is known to be non-linear in nature. Generally, since a given spectrograph has a fixed response over time, spectral characterization only needs to be performed once. There are two steps required in order to fully calibrate a hyperspectral system. First, the polynomic response of the spectrograph as a function of pixel position must be found. The characteristic polynomial of a spectrograph, d can be obtained through least-squares regression with d or more reference peaks, λ0, ⋯, dλ, which can be then identified at specific pixel locations, p0, ⋯, dp [Having a material with well-known reflectance peaks, a polynomial of degree 0, ⋯, pd .spectral resolution of the device. This was achieved via a CAL-2000 Mercury–Argon light source  oriented towards the rotating mirror, which shall be kept at a 45° angle. After background substraction, the spectral emission lines of both gasses should be visible. Since their spectral emission lines are well-known, finding the smallest discernible lines will provide a lower bound for spectral resolution.After being able to relate pixels with wavelengths, we can then establish the hot pixels refers to the appearance of bright pixels at long exposure times due to sensor lattice damage; its correction can be achieved via dark image substraction, quite common procedure in astronomical imaging calibration [i, j indicate the pixel’s position in the sensor, ija and ijb are the coefficients that model the linear behavior of the pixel as a function of exposure time Texp, and bg,ijh will be the estimated hot pixel value that should be subtracted to each pixel for every new measurement. This relationship should be occasionally verified, in order to keep track of the number of damaged pixels in the sensor [The term ibration . Hot pixe sensor .Without properly characterizing the main source of optical power, we may incur in inaccuracies in power output and, therefore, in reflectance measurements. Ideally, for biomedical applications it is preferable to use stable and power-controlled devices, such as monochromatic lasers and/or supercontinuum light sources. As a preliminary approach, it is sufficient to use a tungsten halogen lamp in the Vis–NIR range, due mainly to its thermal inertia, which provides light source stability in the millisecond-to-second scale. We shall procure two protocols for analyzing how the signal-to-noise ratio (SNR) of the camera is a function of exposure time and light source optical power.We will use either one or two 1-kW tungsten halogen bulbs for all measurements, depending on the absorption of the sample. For the first experiment, we turn on the light source and take a low resolution snapshot of an illuminated white Spectralon calibration reference. This is repeated several times (20 times in our case), and each snapshot is timestamped and stored. The average Spectralon reflectance value for each timestamp will be calculated, and then plotted as a function of time. If thermal inertia works well under standard temperature conditions, the average value of this Spectralon reference should become constant over time.rxP is the received optical power on that pixel, sP is the optical power coming from the sample, and nP is Additive White Gaussian Noise (AWGN). Under this assumption, the average SNR as a function of wavelength and exposure time can be calculated via the following expected value ratio:x1, ⋯, Nx are several pixels of a reference material measured at a given exposure time and wavelength, The second experiment assumes that the received sensor counts are a function of backscattered optical power. Therefore, the electrical current transformed into a byte in each pixel will be consequence of the sum of two powers:Once all constraints and properties of our model are adequately defined, we must characterize the imaging system and verify that, indeed, it behaves as described. These results have been obtained from the device explained in Measuring time spent in each of the modeled operations is an adequate first step in characterizing system efficiency. In Texp + Textra), being Textra the constant time parameter that we wish to estimate. Additionally, the ideal model, i.e., 1/Texp, is shown as a dotted black line. The different graphs represent the average lines per second when parts of the system are disabled: the red plot represents normal acquisition, while in the case of the blue line the rotating mirror remains static  and, for the green line, only acquisition commands are being executed, and acquired images are discarded (not stored into memory). Driver and API delays are, in theory, constant values that can be shown to be due to runtime execution of precompiled dynamic libraries. Nevertheless, random variations in timing are clearly visible after adjusting for our model, and are related to OS schduler interruptions and multithreading management, since acquisition, actuator control, storage and RAM management are run by different processes. In order to obtain accurate, stable LPS measurements, we must use application-specific circuits, and/or real-time operating systems.By obtaining the inverse of this time per line, we can represent the rate of acquired lines per second of the scanning device. This calculation is shown in Additionally, it must be noted how, regardless of exposure time, all measurements are limited by the maximum FPS rate that the camera and/or network protocol can manage . All measurements are bounded from above from the value given by Equation (Tact ≪ Tmove).A similar approach can be done for the other modalities shown in Since focusing optics are independent from the actuator subsystem in many cases, the object plane will inevitably suffer nonlinearities. A rotating mirror with a stepper motor will incur three types of measurement errors. First, the object plane will be curved, as the focusing distance will be fixed for any mirror angle; this curvature effect must be limited to a linear range, and its effects must be quantified. Second, there will be backlash in the transmission system that connects the motor to the mirror axle; such backlash can damage repeatability, and must be minimized. Third, and finally, there will be microstepping noise due to spurious currents in both driver and stepper rotor; those must be minimized by using an adequate stepper driver and microstepping factor.y axis can be obtained, which allows for edge detection in the grid. The variation in grid cell width can be approximated by the nonlinear scaling factor of r, the total distance to our object, as well as isolating any remaining errors coming from other sources. The result of this calculation is left in x-wise) alignment between grid and camera was achieved by constantly previewing the image and overlaying a series of horizontal lines in a custom-designed graphical user interface (GUI), moving and fixing the stand until centering and alignment of the center dot of the grid was achieved at θ = π/4 . The relationship between position y and angle θ is linear within the range ±π/8 ≈ ±0.3926 and distortions in the x axis can be corrected by an inverse affine transformation.Although we can model theoretical distortion due to mirror rotation and avoid exceeding its linear range of operation, overall distortion and noise can (and should) be characterized by imaging an Amsler grid with various lengths and forcing the rotating mirror to capture a half/quarter rotation at maximum resolution. Then, the first finite difference along the dy can still be accounted for by FFT clipping this signal down to its average noise spectral power density. The results of this experiment are shown in μ and variance σ2. This variability is therefore in the order of σ ≈ 0.2 mm at a distance of 348.73 mm and a FOV size of 120 × 120 mm, which can be considered negligible for far-field measurement.The residual in the right subplot shows a cosine-like pattern that is likely due to misalignment errors that cannot be compensated by the GUI and manual adjustment. While this non-random variation cannot be corrected any further without more precise equipment, random variations in λ(p) = 370.79 + 2.68p − 0.0001p2, with p being one of the 218 channels. This fairly linear response is expected.As specified in the Materials and Methods section, a Wavelength Calibration Standard plate with tabulated absorption peaks was imaged with a tungsten halogen lamp. The result of finding at least 8 tabulated peaks is displayed in A spatially calibrated image of the aforementioned resolution test chart is displayed in The outcomes of the experiments described in Once our image is as clear as possible, spectral information has been calibrated, and timing issues are well characterized, it is time to benchmark overall system performance. While LPS values show the maximum acquisition speed of the system, efficiency values , while lower efficiencies can be sufficient for slower scenarios . Also, they could be used in industrial manufacturing as a way to quantitatively compare camera efficiency the various tradeoffs between resolution, gain, sensor quantum efficiency, network interface, and spectral range of operation, when selecting a sensor in a commercial device or process.Nlines lines measured will be Timg = NlinesTline/ϵavg(Texp), where ϵavg(Texp) is the average measurement efficiency for a given exposure time. Consequently, the higher the efficiency, the smaller the number of uncorrectable artifacts that could be found in an image with an adequate choice of resolution and exposure time.Another interesting conclusion is related to scanning hyperspectral devices as an imaging modality. Artifacts due to subject motion and/or metabolic changes, such as sample oxidation, changes in oxygenation, degradation, or decay will be more severe as the total time spent capturing is increased. While under these conditions other imaging modalities can prove more useful, a fair tradeoff between speed and resolution can be achieved in these systems, since the total time spent in an image with Finally, by assuming that the model takes into account all timing and nonlinearity issues, its final characteristics can be summarized, as in r = 350 mm, Texp = 200 ms, full resolution), as well as some random spectra within the image, can be seen in As for now, we can report on the protyping of a high-resolution, highly efficient hyperspectral imaging system, capable of 1.44 Mpx spatial resolution, 200 wavelength channels over the Vis–NIR range, fully modifiable optics, variable gain, exposure time and acquisition mode for HSI, SFDI, and SSOP measurements  which can be controlled via a RESTful Web Service from any computer within the laboratory network. An HSI image of a hand obtained with this device  which system developers can consider when building devices as described in As reviewed throughout the article, an ideal system will always spend the vast majority of its time performing acquisition, while minimizing all preprocessing, communications, storage and API-based delays as much as possible. In real case scenarios, full control of its specifications  within a local network is also desireable, especially with multi-purpose camera systems that unlock numerous potential biomedical imaging applications.In order to determine how well a specific custom device behaves (and how much it can be improved), methods like measuring timing constraints and metrics such as system efficiency can provide information on how close to ideal, asymptotic behavior the system under test is. Optics-related parameters, such as nonlinear distortions and microstepping noise, have been characterized as well (at least for the case of rotating mirror scanning systems), and in most cases system redesign has been sufficient to keep them as minimized as possible. Some interesting results include the fact that API communications can be the most significant cause of timing innefficiencies in a scanning system, that spatial distortions can be almost completely eliminated by keeping the FOV of the camera within a linear range, and that vertical resolution is limited by microstepping noise.Interesting future lines of research include, among others: (1) applying flatter, more stable light sources, such as supercontinuum laser sources, in order to achieve a flatter SNR with respect to wavelength; (2) using curved mirrors for depth-of-field and focus plane correction; (3) approaching other wavelength ranges, such as NIR-SWIR; (4) using Application-Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), or real-time operating systems for minimizing all the aforementioned delays; (5) using various spectrograph slit sizes and combinations with other focusing optics, such as macro and/or telecentric lenses; (6) evaluating sensor lattice damage with more complex hot-pixel models, since these exhibit slight nonlinear behavior; (7) studying the exact influence of object motion artifacts in this imaging modality; and (8) using profilometry for source intensity correction, especially when using far-field sources, such as structured light projectors. All these possible improvements stem from the evaluation of the described equipment via the proposed methodology.A more general conclusion that can be reached from these experiments is that a full characterization is necessary when it comes to understanding how the different components of an imaging system relate to each other, so that the root causes of imperfections and/or slowdowns in image acquisition can be adequately detected, and design can be improved in further versions, especially when building and testing devices with clinical and surgical applications, where timeliness and precision are fundamental.


Homo sapiens – regardless of small cultural differences – find easy and inherently intriguing.Empirical evidence is reviewed indicating that the extraordinary aspects of the human mind are due to our species’ ability to go beyond simple “dyadic associations” and to process the relations among three items of information simultaneously. Classic explanations of the “triadic” nature of human skills have been advocated by various scholars in the context of the evolution of human cognition. Here I summarize the core processes as found in (i) the syntax of language, (ii) tool-usage, and (iii) joint attention. I then review the triadic foundations of two perceptual phenomena of great importance in human aesthetics: (iv) harmony perception and (v) pictorial depth perception. In all five subfields of human psychology, most previous work has emphasized the recursive, hierarchical complexity of such “higher cognition,” but a strongly reductionist approach indicates that the core mechanisms are triadic. It is concluded that the cognitive skills traditionally considered to be “uniquely” human require three-way associational processing that most non-Primate animal species find difficult or impossible, but all members of  Homo sapiens be biologically so similar to other animal species and yet cognitively1 so different? In the 21st century, there has been a flood of books and articles on this topic. Notably, several concrete hypotheses have been formulated about the “mindful ape” concerning the emergence of (i) language, (ii) tool-usage, and (iii) social cooperation. These are the behaviors where human cognition appears to be most exceptional and consequently which have received the most consideration by many generations of scholars .Two research strategies have become dominant. The first deals with differences in currently existing cognition among human adults, human infants, and various animal species, notably Primates. Interspecies comparisons in particular are notoriously difficult, but potentially provide a means to evaluate human behavior from a non-anthropocentric viewpoint. The second strategy is the study of the evolutionary record. As sparse and as inherently haphazard as the findings of paleoanthropology may be, fossils have the extreme merit of providing an unambiguous chronological sequence of the major events in the evolutionary history of our species  fundamental human skills e.g.,  – each cEfforts have in fact been made to enumerate the “universals” of human cognition e.g., , but Tat“the problem with such lists is that they can never be complete; there’s always something else to add… And none of these features in itself specifies anything about the human condition; we simply can’t know which of them, if any, is the ‘key’ human attribute, the one that was targeted by past natural selection.”H. sapiens.In the essay that follows, I summarize the case for thinking that five of the “universals” of human cognition that others have previously identified, emphasized, and described explicitly as “triadic” do indeed have a cognitive triad at their core. No attempt is made to delimit our triadic talents to these five phenomena alone, but they are, by consensus, arguably the most distinct and, moreover, the talents that researchers interested in animal cognition have the most difficulty relating to the full-blown talents of Frontiers in Psychology, the present essay is clearly an “Opinion” piece – in attempting to bring together five highly contentious subfields of human psychology within a novel triadic hypothesis. At the same time, however, it can be said that the evidence indicating the importance of cognitive triads has already been presented by others in explication of the unusualness of human cognition separately in each of these subfields. In that respect, the present essay can be seen as a “Review” of current ideas in human cognition – with, to be sure, an emphasis on the supporting views of others that have focused on the perceptual/cognitive triads in language, tool-making, social cooperation, art and music. While I am unaware of any academic work that has argued explicitly against the triadic hypothesis, the vast majority of theorizing on the evolution of human cognition does not focus on “triads” – and, in that regard, the present work represents a personal “Opinion” that may or may not withstand the test of time. In any case, it may inspire further debate on the topic of “What Makes Us Human.”In the context of the types of essays published in Here, I outline the view that the “once-only” revolution in human cognition was the emergence of triadic neuronal processing – or the ability to handle the relationships among three items of information at the same time , as distrelationships that are inherent to any set of three items. The numerosity of the cues themselves is not the issue, but research on short-term memory , but the cognitive complexity arises from the number of distinguishable three (well-placed) tones or objects in comparison with only two. Recursively building on the perceptual triad by adding further auditory or visual cues is endlessly enriching , but the leap from “sensation to art” appears to begin at the transition from the perception of 1 isolated correlation (inherent to 2 cues) to the perception of the 3 relationships (among 3 cues).In our own work in empirical musicology , and vis2, but they are attractive in their conceptual simplicity and consequent empirical testability. In effect, the hypothesis of triadic cognition is both “radical” (in claiming to identify the cognitive functions underlying the transition from pre-modern to modern H. sapiens) and also surprisingly “conservative” . While there remain several lacuna of unexplored issues, the basic hypothesis of triadic processing can be easily understood under the following five headings. There may indeed be other fundamental cognitive realms where human capabilities are qualitatively different , but the following are well documented in the literature on human evolution.Having found empirical indications of the importance of specifically triadic processes in our own data, we returned to the literature  in other fields where human “uniqueness” has been a traditional (if somewhat dubious) claim. In tracking the major evolutionary events that led from the mentality of our chimpanzee-like ancestors some 7 million years ago to the human mind today, it became apparent that others have stumbled onto similar cognitive “leaps” – sometimes using the labels of “triadic” vs. “dyadic” associations, but, more commonly, simply noting the inherent explosion of “complexity” as sensory cues proliferate. Hypotheses concerning the number of perceptual/cognitive processes that can be simultaneously held “in mind” are necessarily controversialusage, the auditory modality is known to provide precise temporal information , unprecedented regions of cross-modal associations at the neocortical level emerged. In the modern human brain, the largest region of trimodal cortex can be found in the inferior temporo-parietal cortex phrases . As such, every phrase, every sentence consisting of phrases, and every syntactic manipulation involving phrases is inherently triadic. Linguists will of course note that there is much more to language, in general, and syntax, in particular, but the phrase is the widely accepted starting point for discussions of the apparently unique human talent for understanding grammar. Notably, the modern version of Chomsky’s theory, the Minimalist Program, explicitly maintains that “the core structure assembled by Merge consists of two syntactic objects plus a label” three-way relationship among (i) a tool, (ii) an object to be affected by the tool, and (iii) a concrete material context within which such manipulations can be productive ( Tool-use requires an understanding of the oductive . Contrar(3) Social cooperation requires the “joint attention” of two participants on a common task. Cognitively, this has been described as a “triadic interaction”  among a. While aH. sapiens. Because tools would necessarily have brought people together for common purposes, their importance for cooperative behavior and ultimately for the survival of the species is clear, but the causal relations among tools, cooperation and language remain uncertain. Moreover, the roles of several other unusual skills may also have played a role in human socialization on an evolutionary timescale. Particularly in light of the cave paintings and fossilized relics of musical instruments from more than 30,000 years ago, paleoanthropologists have speculated that art and music may underlie the enculturation of our ancestors into truly human communities. For this reason, scholars interested in rather high-level aesthetic issues have been able to ask concrete questions concerning what cognitive capacities underlie both the “art instinct” three distinct tones (see the “Harmony Perception” section below). [Note that the creation of rhythms – as distinct from an underlying “beat” – also requires a minimum of three pulses illusory 3D structure of scenes depicted in 2D pictures  – and are perceived by many species. But the techniques known as linear perspective and chiaroscuro (the artistic use of shadows and shading) are demonstrably triadic in relying on the presence of a minimum of three independent visual cues to give static 2D visual images an illusory depth dimension “into” the canvas  of two-tone intervals was a consequence of not simply the difference in frequency between two fundamental pitches , but also a consequence of the frequency differences among all combinations of their overtones . It thencoustics .triads are encountered that the characteristic emotional twinge of the major and minor modes is experienced. Harmonic triads are where music begins to become interesting because even simple harmonies are the affective triggers, used in nearly all types of music, that make music emotionally meaningful. If we include the “atonal mode” heavily employed in modern classical and jazz styles, then moment-by-moment musical compositions can be described in terms of their ability to elicit the positive or negative emotional responses of the major or minor keys or, alternatively, to deliver us into a state of unresolved tension through atonal melodies and harmonies. Note that most of analytic music theory is concerned with more complex notions of tension and release, expectation and resolution, and the ebb and flow of relatively large musical phrases .Importantly, it is not until pitch  phrases , but thewhy quite simple three-tone melodies or chords typically elicit emotional reactions. On the one hand, it was understood that the relatively “stable,” “sonorous” and “beautiful”  major and minor chords contain structurally asymmetrical three-tone combinations , whereas the less stable tension chords contain an abundance of symmetrical triads  . The unresolved character inherent to symmetrical triads was already noted by Vincenzo Galilei (the astronomer’s father) in 1581  tones e.g., , 2017. Sacoustical basis for the worldwide popularity of the stable major and minor chords relative to the  unstable tension chords . In other words, the popularity of the major and minor triads need not be dismissed as ineffable, aesthetic phenomena of arbitrary cultural origin, because both their overall sonority and their positive/negative valence can be calculated directly from definable acoustical properties . The second concerns the harmonic sonority and modality of triads . The atonal tension triads are typically used to enhance the unresolved ambiguity of pitch combinations, and then subsequently resolved to either the major or minor mode by pitch rises or falls.Although a cultural interpretation of “Western” harmony is currently fashionable, we have shown that the emotional “tug” of both melodies and harmonies is based on two acoustical principles. The first concerns the familiar notion of not explained solely by the avoidance of small dissonant intervals. Why are triads with interval structure 3&4, 4&5, or 5&3 semitones heard as minor, whereas 4&3, 3&5, or 5&4 are heard as major? The properties of isolated dyads provide no insight, but, as noted above, the size ratio of upper and lower intervals in pitch triads  provides quantitative answers. As a consequence, it can be concluded that the classification of any chord as major, minor or tension has an acoustical basis , and no longer an aesthetic “mystery” left over from the Renaissance.not confusing the 2D picture with 3D reality, but, for that same reason, they fail to understand, enjoy, and utilize the fantasy world of 3D space represented on 2D surfaces that makes visual art and graphical design both interesting and useful for H. sapiens.In the visual arts, the techniques of linear perspective and chiaroscuro can provide a strong and coherent illusion of 3D structure in scenes depicted on a 2D canvas – an artistic effect that was generally absent prior to the 15th century. Interestingly, the near-universal human enthusiasm for believing that we actually “see” the 3D depth implied in the 2D picture is not shared with most other species – trained chimpanzees and gorillas being important exceptions. The implication is that, while capable of recognizing 2D shapes on a 2D surface, most animals do not interpret those shapes as representing objects in an imaginary  3D world. They are, of course, literally correct in So, just what is the cognitive mechanism that underlies our “clever gullibility” to see 3D structure in 2D paintings? The answer, in a word, is perspective. Discovered and developed as an artistic technique in the early Renaissance, the theory of perspective is surprisingly complex, still debated by specialists  and stilFigure 3, the depth relationship between two non-overlapping shapes in a 2D picture  is inherently ambiguous . But, if there is overlap (“occlusion”) of one shape on the other , the depth configuration becomes obvious to all normal observers. There are then two objects plus an explicit relationship between them. Regardless of the relative size or relative vertical position of the objects on the 2D canvas, the occluding shape is seen to be closer and the occluded shape is perceived as further away: an illusion of “depth” has been created.Moreover, we now know from experimental work on the elements of perspective drawing that the inference of an illusory third dimension is made possible by the alignment of quite small numbers of visual cues . As showFigures H). There is a strong inference of depth when at least three shapes (as distinct from two) lie in the extremely low probability configuration of linear alignment on a 2D plane (F). If the difference in size of the three objects (taken two at a time) produces convergence of perspective lines on a common horizon line, then a depth interpretation is again favored. However, a random distribution of three similar shapes of different sizes would not imply a gradual decrease in size with distance and not imply a unique vanishing point on the horizon (H). Therefore, the “chance” alignment of three such shapes – with  or without (E) drawn perspective lines – is correctly inferred to be a highly significant (low probability) arrangement.Unlike those dyadic examples, the depth perception of (non-overlapping) triads of shapes is more subtle. Specifically, the relative positioning of all three shapes on the 2D canvas determines the perception of the depth structure of the scene  can never be “unaligned” in pictorial depth: it is necessarily the case that perspective lines joining the edges of, for example, two spheres converge and create a vanishing point on the horizon. As a consequence, the fact of their convergence (on or off of the canvas) provides no information: the probability of convergence is 1.0 and the likelihood of that particular configuration in 3D space cannot be calculated. The convergence of the six lines that join three shapes drawn in linear perspective tells a very different story. Their meeting at a unique vanishing point (F) or on a unique horizon line (G) is such a low probability occurrence that the human brain normally infers that there is a cause  for these linear relationships.In contrast, a priori probabilities in visual perception. In brief, the depth perception of visual scenes containing two non-overlapping shapes  is inherently uncertain, but there are both low-probability (E–G) and high-probability (H) configurations of scenes containing three non-overlapping shapes. On the basis of accumulated visual experience, the human brain detects low-probability events – and  automatically draws (depth) conclusions from the apparently non-random alignment of the visual cues on a 2D canvas.Such findings are consistent with the ideas of Figure 4A), and has often been noted by commentators on the artistic use of shadows using examples from Renaissance art and astronomy  and (ii) converging lines to convey distance to an illusory vanishing point , their repetitive use produced unprecedented  parallel lines to depict shadows  entails the “merging” of two words through a connecting “head” .The cognitive triad that lies at the heart of modern linguistic theory is the “phrase” – advocated since the 1950s by Noam Chomsky in the form of “transformational grammar” (1965) [later called “head-driven phrase structure grammar”  in recogFigure 5, right), we immediately know of the kinds of events that might be conveyed through such language, but without a familiarity with the arbitrary rules of phrase-ordering, we do not know who did what to whom. Dyadic associations do not suffice for explicating causality.The task that all language users repeatedly face when producing or hearing speech is to determine the unique meaning that corresponds to a specific combination of words organized into such discrete phrases. English-speakers pay attention primarily to the word-order within and between phrases. In other languages, the prefixes and suffixes of words and their agreement among the parts of speech can be more important than word-order, but in all languages comparable rules of syntax must be followed to indicate the relationships among words organized into phrases with specific – normally unique – meanings. As not hard-wired, but learned – language-by-language, individual-by-individual, sentence-by-sentence .In triadic phrases, words are necessarily connected two at a time in a temporal sequence (because of the linear ordering demanded by speech), but the human ability to understand the “chunking” of lexical units into phrases is still a deep mystery. According to sentence . As mostnot instinctual at the level of word-order. Indeed, in the world’s ∼6000 languages, every possible sequencing of subject (S), verb (V) and object (O) is used as the default structure. Most (90%) begin with subjects (SOV and SVO), but verb-initial languages (VSO and VOS) are not uncommon (Hawaiian and Celtic languages) and sentences beginning by default with direct objects are also known .With locally agreed-upon rules of sequencing, individual phrases have “correct” or “incorrect” temporal order to convey a specific meaning, but they can be rotated at will to agree with the sequencing rules of other languages to produce, once again, meaningful sentences with unambiguous semantics. Moving an adjective from its position before a noun (as in English) to after it (as in Thai), or transplanting a verb from its early position in English to its end position in Japanese or Latin may seem “unnatural” to English speakers, but those are precisely the kinds of syntactic rules that every young child absorbs from a language community, and soon masters. Because of such syntactic variability, successful translation therefore requires more than a one-to-one replacement of words with their lexical equivalents in a foreign tongue. The more challenging syntactic task (for second language learners) is to rotate the branches in a linguistic tree so that the same meaning is conveyed in a different language – often using a radically different sequence of spoken words , animals proceed to dyadic associations without an intrinsic sequential order – and their repetition. Failing to grasp the triadic principles of phrase structure – through which causality, as distinct from simple correlation, can be conveyed – grammatically “complex” linguistic structures remain a challenge to all species except H. sapiens.Where do other species stand in their understanding of language? Remarkably, chimpanzees can learn the meaning of several hundred arbitrary symbols  and minoFigures 7, 8).The newest insights into cognitive triads have come from the oldest field of study concerned with human evolution: the construction and use of primitive stone-tools . From obFigure 8B) is that these animals have learned skills in the wild that require consideration of not just one or two, but three objects simultaneously. One-object talents are not uncommon – and grabbing a morsel to eat is easy enough if the animal is equipped with a dexterous hand, beak or paw. Two-object talents, such as scooping out edible bugs with a stick, are far less common and require that the animal keep track of both the bugs and the stick. But three-object talents are extremely rare. Small groups of capuchin monkeys in South America, chimpanzees in Africa, and Pacific sea otters have spontaneously learned that placing (1) an edible nut with a hard shell onto (2) a firm, horizontal surface that will serve as an anvil, and striking it from above with (3) a hammer stone will result in a nutritious snack. Clearly, this task requires that the tool-user maintain three perceptually distinct objects in mind. Mastering the triadic skill demands practice over several years, and has been found to be transmitted from generation to generation . Although it is clearly a long journey to the building of empires, the products of human civilization are, without exception, consequences of large-scale, prolonged social cooperation. As others have coherently demonstrated, social cooperation is, for each participating individual, cognitively triadic.If indeed we are not only tool-users and language-users (and artists and musicians), but even more importantly social beings, just what is the cognitive trick that has allowed us to master the art of social cooperation? The key is not simply empathetic recognition of our own species , but rather the employment of, once again, fundamentally triadic cognitive mechanisms. Human beings normally and habitually empathize with other human beings by “reading their minds,” speculating on the other’s motivations, and then acting accordingly . The elenot simply the summation of several dyads, but are themselves primitives with their own meaning that can then be employed in more complex associational phenomena.I have outlined the hypothesis that the core talents underlying the “higher” cognition in diverse fields of human psychology are a consequence of three-way mental associations. Such cognition is rare among animals, in general , but is the essence of the way in which human beings normally and habitually “think.” A simpler form of cognition, i.e., one-to-one associations, is essentially dyadic. Dyadic cognition is of course extremely useful and an understanding of correlations is often sufficient for the purposes of biological survival . In contrast, triadic processes require an additional cognitive effort – not merely a third element, but a tripling of the dyadic associations inherent to a triad of cues and the introduction of an “emergent property” in the form of a novel three-way pattern. That complexity produces an unprecedented and notably slow “mindfulness” that is the unspoken pride and joy – and arguably the source of much disputation – for humankind. Unlike the two-element associational processes, of which all animal nervous systems are capable, a triad involves an association between, to begin with, two elements, but now with a minimal context provided by the third element. The dyadic association then becomes context-dependent, and the meaning of the dyadic relationship is necessarily affected by the context. As a consequence, by their very nature, triads are In that respect, it is relevant to note that cognitive dyads are additive, but triads are inherently recursive and hierarchical, insofar as each element in a triad can itself be replaced by a triad – leading to conceptual structures the complexity of which is limited only by the capacity of short-term memory. The recursive nature of language is well known and easily studied using imbedded relative clauses. The hypothesis of triadic cognition still requires considerable refinement. The five categories discussed above are the best known, most-widely discussed candidates of “higher” human cognition, but there may be other multimodal or unimodal triadic operations involving, for example, purely proprioceptive (athletics) or gustatory (cuisine) cues. More precise definitions of the relationships among cues  will also be needed. Finally, reformulation of the familiar concepts of “folk” psychology in terms of the formal “ternary operations” of Boolean algebra will undoubtedly be necessary. Already we know that any ternary operation can be stated in terms of the logistician’s definitions of “meet,” “join,” and “complement” e.g., . In prinintelligence. It is this trick that has allowed our species to sometimes transcend the dictates of strictly dyadic, correlational behaviorism and to enjoy the mindfulness of higher-order, context-dependent, cognitive complexity.Normal human beings can easily juggle three quasi-independent stimuli  in exercising the talents discussed above. By taking the relationships among all three stimuli into consideration simultaneously, we find meaning in the three-way interaction that is not apparent from the summation of multiple two-way interactions. In contrast, while animals can accurately perceive the same sensory stimuli and learn the same dyadic associations between pairs of stimuli, they apparently find no inherent meaning in the triad itself. Because of the stark difference between dyadic associations and triadic relations, it appears that triadic processing – breaking the world into bite-size triads – is the essence of human The author confirms being the sole contributor of this work and approved it for publication.The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Evidence suggests that stigma against people with mental illness remains high. This demands innovative approaches to reduce stigma. One innovative stigma reduction method is participatory video (PV), whereby marginalized people come together to script, film and produce bottom-up educational videos about shared issues. These videos are then shown to target groups. This paper has two objectives (i) to examine the feasibility of using participatory video with people with severe mental illness (SMI); and (ii) to assess viewer impressions of the resultant videos and subsequent subjective impact.We conducted a participatory action research study with three workgroups of people with severe mental illness situated in different Canadian cities, who set out to create and disseminate locally-grounded mental-health themed videos. This involved process and outcome evaluation to assess feasibility and impact. Specifically, we (i) observed fidelity to a co-designed action-plan in all three workgroups; (ii) distributed brief purpose-built questionnaires to viewers at organized screenings to assess preliminary impact; and (iii) conducted focus groups with viewers to elicit further impressions of the videos and subsequent subjective impact.N = 1104, response rate 72%) indicated that viewers reported that their understandings had improved after watching the videos. Four themes emerged from six viewer focus groups (N = 30), with participants frequently noting that videos were (i) educational and informative; (ii) real and relatable; (iii) attention-grabbing; and (iv) change-inducing.The three workgroups achieved high-fidelity to the action-plan. They successfully produced a total of 26 videos, over double the targeted number, during an 18-month period. Likewise, the workgroups organized 49 screenings at a range of venues attended by 1542 people, again exceeding the action-plan targets. Results from the viewer questionnaires (To our knowledge, this study is the first large-scale multi-site project examining the feasibility and impact of a participatory video program for people with severe mental illness. The results indicate that participatory video is a feasible method in this population and gives preliminary evidence that resultant videos can reduce viewer stigma. Thus, participatory video should be considered a promising practice in the ongoing effort to reduce mental illness stigma. Evidence suggest that community stigma against people with mental illness remains high across the world , 2. VariFor example, Stip et al.  surveyedOther research indicates that such views are often held by important decision-makers including employers, journalists and even health care providers , 9, 10. Hence, stigma reduction has become a key target for mental health advocates in various jurisdictions across the world , 14. In In these sessions, people with mental illness present their personal recovery journey to select audiences from a first-person perspective , 18. NumParticipatory Video (PV). In a PV project, a group of marginalized people come together to script, film and produce bottom-up educational videos about shared issues affecting them. The videos are rooted in a local context, and the workgroup has complete editorial control over content and themes  being the central theme and discussion of the video”.Other participants praised the videos for the multi-dimensional in-depth portrayal of people with mental illness, with one stating that “what worked is we actually got to see her as a person. We got to see her life, her transitions, her talents, you know, her relationships, and that’s what drove it home”. A similar sentiment was expressed by a student participant who stated that “you kind of learn about these concepts in more of an abstract form, and you rarely get to see how it affects someone… but the videos just give you a very different perspective and makes it more human”.Others noted that a strength of the videos was their well-rounded and normative portrayal of people, moving beyond the mental illness label to show individuals as active citizens. For example, one participant declared that one video about a man in recovery was “Marvelous! Just it shows him as a human being, it shows him as a brilliant artist. It shows him as a member of a community; it shows him as a citizen, you know? It was just wonderful”.Indeed, participants regularly praised the focus on local ordinary people and the depiction of people with mental illness in a multi-faceted positive manner. As one participant aptly stated, “I like these videos because they use ordinary people – I can’t identify with a multimillionaire, but I can identify with someone who is like me”. Another participant noted approvingly that “the videos were made by someone with their own experiences…I just retain it better…it impacts you more strongly than if it’s some like fictional thing or an abstract article”.You can relate…as everyone comes to forks in the road in their life. And I’ve had lucky breaks but if I would have had an unlucky break you look at these people and you think ‘God, that could’ve been me’.Similarly, participants noted that the videos often helped narrow social distance, with one mental health worker stating that “these videos, the ways that they kind of get into the personal lives of those people, it really bridges a distance”. Another participant stated:I think it was amazing…this impression that there’s no road to recovery is really the worst part of the stigma…So, I, I find that – I found that part incredibly relatable, as my brother has improved throughout his life…And to be honest, there’s been points in my life where I wondered how close I could have been to being in a shelter…I thought they were all very relatable.This view is encapsulated by a participant whose brother had schizophrenia, who noted that the videos were educational, relatable and thought-provoking all in one. This participant talked about a screening thus:Focus group participants regularly reported that the screenings grabbed their attention and left a memorable impression, leading them to further engage with the videos and their content. For example, one said that the videos were “very good…It had my attention the whole time. And it made me want to watch more of them. So I think you hit the ball out of the park on that one!”.I really liked that video because it just was so well done from like a production point of view. You can tell they had a storyboard, and, you know, they obviously – they shot out of order, and they had different sequences acted out. And, you know, the editing was – Like there wasn’t any point where I felt like the editing has stopped me from the story. I think it was just really well done…Relatedly, participants often noted that the videos were produced with a high level of skill and professionalism, with one participant stating that they “were excellent…like industry standard, you know. It looked like professional, you never would’ve guessed that these were people who 12 months before hardly knew anything about cameras or videos”. Indeed, some focus group participants had experience in videography, and they were particularly impressed, with one stating that:It is powerful to put the camera and the storytelling in the hands of the person who is, who has lived the experience of mental health…seeing someone – hearing a story from the perspective of someone who has, you know, lived this life and is able to tell it – tell it cleanly and really – really well, in that way, is just – I mean, there’s nothing else like it.Participants also highlighted the novelty value of the bottom-up emphasis on lived experience of mental illness, which offered unique (and under-reported) perspectives and storylines. In fact, many participants enjoyed the films and found them attention-grabbing specifically for these reasons. For example, one participant described their experience as such:Likewise, some participants reflected positively on the granular-level technicalities of the videos; including discussion of animation, accompanying music and filming locations. For example, one film, ‘Off-Suit’, included extensive animation. One participant found this memorable, stating that “I found I haven’t seen very much [animation] recently and just to sort of have it stick in my head as like a different visual. That was really, really nice.” Another participant stated “some of that music, I can still hear…and I mean the settings that they chose to show themselves in as well and how they moved within those settings, like their body language…It was really rich”.I think [the videos] are good…I thought they were amazing…I was impressed by the level of craft in the videos. They were very watchable, and um engaging…And I think that the films are like a really interesting way of letting people show exactly what [mental illness] means in reality. Like we talk about this idea of stigma and mental health and how like, I don’t know, It ends up being like kind of theoretical…until you’re faced with a human being that has to deal with those stigmas and all those labels. And the way that they manifest in reality is so different from how you ever read about itIn short, many participants perceived the videos as high-quality, gripping productions; this allowed them to engage fully with the core issues under discussion such as stigma and recovery. This subjective experience is neatly encapsulated in the quote below:I think having the videos is your best opportunity to being able to reduce stigma with other people because I know, like I said, watching it myself it brought me down to the level of being like “Okay. This is like a real human thing that you actually – that people go through, right?”. I think there’s a perception that people with mental illness, there’s no – they’re never gonna get better, they’re just, they’re not trying to work on it…but from my perception, I can see how people work on it. And so for me, the stigma went down a little bit watching some of the videos and seeing that…it reduced my judgment mindset.As previously discussed, the videos were frequently considered educational and informative. Moreover, participants reported that they contained relatable characters, and that the production was professional and attention-grabbing. All this interacted, leading to reported changes in understandings, attitudes and even behaviours. For example, one participant described how her own levels of stigma towards people with mental illness decreased after watching the videos:Similarly, some participants described how the videos led them to reframe their perspectives about people with mental illness, which led to increased empathy and understandings. For example, one participant stated that the videos were enlightening as they showed people “in a recovery path. So, you could see that while you’re not totally cured…you’re able to function in society and, you know, be just like everyone else”. Another stated that her experience at a screening “increases your empathy and makes you realize all of these things you don’t think about”, while another participant described how it made them realize that people with mental illness “are suffering…it’s affecting their brain or something else. But they’re not bad people. In fact, they’re artists, and they’re, you know, doctors, lawyers, engineers, whatever else”.I teach at university, so one of the videos about psychiatric medication side effects, said that people get drowsy, you know. It doesn’t mean they’ve stayed up all night partying or, or that people yawn, sometimes fall asleep. So, I see that happen in class and after watching that video, uh, I would say to myself ‘that poor person probably has like mental illness, and they’re on psychiatric medication and they’d much rather be sitting listening to me teach, but the medication is so strong’. Whereas before I watched that video I’d be more like ‘ugh’ and think like ‘God, how dare they sleep when I’m talking’ (laughs). So, at a practical level the videos have actually changed some of my empathy.Notably, some participants implied that the videos changed their behaviours towards people with mental illness for the better. This was often related to the development of empathy, which could prompt kinder and more engaging behaviours. For example, one participant discussed their experience viewing a video entitled “Psychotropic Side Effects 101”, stating that:I think showing shorts [short videos]…I think it is good…I think it is actually like good clickbait because like you watch it, and you’re like, “Oh! This is actually like really lovely and humanizing, and I no longer fear people with schizophrenia or whatever.” You know? Hopefully.Others made similar remarks, which were often centered around the wider theme that the videos ‘humanized’ or ‘personalized’ mental illness and its associated challenges, leading to changes in empathy and understanding. For example, one participant noted the positive change-inducing value of these videos, which contained hopeful stories of recovery, in contrast to Hollywood-type violent dramas which commonly induce fear by misrepresenting schizophrenia:To close the results section, we would like to note that the researchers did not independently identify any other major themes that are not integrated into the results section above. That said, we did note a very small amount of less positive comments. A few people stated that some videos were too long thereby making them less effective, preferring the shorter videos. Also, a few participants stated that the videos could have included more documentary-style facts or statistics. However all researchers agreed that this did not constitute a theme, as the less-positive comments were very rare, and in fact were completely absent from some of the focus groups.There are two key findings to this study. Firstly, the results indicate that participatory video with people with mental illness is a feasible anti-stigma intervention. Secondly, the data suggests that the resultant videos and organized screenings positively affect viewers and could be an effective means of stigma reduction.These results have policy implications. As stated, stigma reduction has become a key target for mental health policy in various jurisdictions across the world , 14. In Importantly, the PV screenings detailed in this study integrated many of the recommended evidence-based critical ingredients of contact-based sessions. For example, Chen et al.  note thaAt the PV screenings, at least two members of the workgroup participated in the panel discussion and question period, answering questions and interacting with audience members. Likewise, the videos frequently presented stories of personal recovery from a first-person perspective, which was re-emphasized in the panel discussion. This gave a clear and hopeful message that viewers found educational and informative, dispelling myths and stereotypes in the process. As witnessed in the results, this also increased viewer empathy, which has been identified as a powerful mediator of prejudice reduction in a seminal meta-analysis .Notably, the adopted PV approach also contained important additional elements which are not necessarily captured in a traditional contact-based session. For example, many focus group participants expressed surprise and amazement at the high-quality of the videos. By the same token, the videos frequently went ‘behind the scenes’ to show people with SMI competently performing everyday activities in their workplace, homes or community spaces. All this could further help dispel myths and disabuse viewers of stereotypical notions that people with SMI are violent, incurable or inept . In shorSimilarly, videos produced by PV programs have a wider potential reach than contact-based sessions. This could be especially important in large countries such as Canada and Australia where significant portions of the population live in rural and remote regions, often with specific mental health challenges, including stigma . This reGiven this experience, we have packaged the process into a discreet intervention that we call the RADAR model, which can be implemented by people with mental illness elsewhere. To assist others with implementation, we are creating a short toolkit and manual in lay language, which will shortly be available at the project website . Such imThe RADAR model has five key components. Firstly, an action-plan should be developed in a bottom-up manner with feasible deadlines and targets. Secondly, workgroups must be provided with appropriate video equipment and training in both camera work as well as analytical thinking. Thirdly, workgroups should be supported by a facilitator with videography skills during the production and editing phase. Fourthly, participant-led screenings should be organized that include an introduction, video screenings, question period and panel discussion. Fifthly, videos should be disseminated on dedicated social media channels and websites, then shared with relevant organizations and local media.Of note, the study points to three critical ingredients that make videos effective in reducing stigma. First, videos should aim to educate and inform, shedding light on underlying issues such as stigma, recovery and social challenges associated with mental illness. Second, videos should be grounded in the realities of everyday life with mental illness, using relatable local people in recovery as mainstays of the videos. Third, videos must be attention-grabbing and engaging through high-quality production. All this may ultimately induce viewer change.Importantly, the feasibility targets for the number of screenings to the general public were not met at two sites. In fact, it proved considerably easier to organize screenings within our existing networks, mainly by taking slots at pre-existing routine events, such as a class in a university course or a local hospital grand round. This indicates that dissemination may be most successful where workgroups exploit existing networks and piggy-back on pre-existing routine events.Indeed, the workgroups opportunistically organized several screenings to mental health service user groups and organizations as word of the project spread through local networks. This deviation from the action-plan was considered a sign of success, as the workgroups deployed agency and initiative by organizing screenings to an important audience. It is also consistent with the wider PV approach, which demands participant control over dissemination , 25, 27.There are a number of limitations to the present study. First, the quantitative measure of impact was purpose-built and relatively simple, and was not administered before the screening. This approach only gives limited information about the effect of video viewing on external stigma. However, this project was primarily feasibility research of an understudied intervention in an understudied population, meaning that the gathering of preliminary evidence for impact is warranted. This was also a preference of the participants during co-design. Future research should test more formally the impact of such videos longitudinally through repeated measures with validated instruments.Second, we collected and analyzed viewer data generically, without stratification, in order to assess general impact. For example, each focus group included a heterogenous mix of viewers- including students, health care providers, mental health service users and the general public. Homogenous focus groups of each category may have given different results, however this proved impractical due to the tight schedules of potential participants. By the same token, we did not stratify the quantitative feedback from the video screenings by age, gender or other variables. This was not an a priori aim of the study, and such post-hoc analysis may risk inferential error due to issues of sample size, power and multiple testing . SimilarThird, there is a possibility of bias in various aspects of the study. For example, selection bias may have affected screening attendance, as these were arranged opportunistically at sympathetic venues  and likely included people who were already receptive to mental health issues. Similarly, there is a possibility of response bias, especially in the focus groups, as participants may have given socially desirable answers given the presence of other people in the group- some of whom introduced themselves as mental health advocates or people with mental illness. This could have inhibited the expression of less positive comments, which may have emerged through a more private methodology such as in-depth interviews. Moreover, it should be noted that questionnaire and focus group respondents were mostly young female students, with a minority of men and older adults. This sampling bias places some limits on generalizability. Future research should purposely test the impact of PV on groups who are traditionally hard to reach in stigma research, such as men and older adults.Fourth, we did not formally measure variables such as level of functioning, specific diagnosis or educational background, as this was considered inconsistent with our inclusive recovery-oriented approach during co-design. This may limit the generalizability of the results to other groups of people with mental illness. That said, all participants regularly attended a psychosocial rehabilitation centre and self-identified as in recovery from a SMI. Moreover, the content of the resultant videos indicates that participants had experienced a range of serious issues including homelessness, hospitalization and unemployment . This meFifth, this paper focuses on the impact on viewers, and does not report the impact on the workgroup members with SMI who actually made the videos. Theoretically, involvement in the process may have led to a reduction in self-stigma and an increase in empowerment among workgroup members , 20, 22.To our knowledge, this study is the first large-scale multi-site project examining the feasibility and impact of a participatory video program for people with mental illness. The results indicate that PV is a feasible method, as participants with mental illness exceeded the vast majority of targets in terms of project participation, video production and screening organization. The questionnaire and focus group data give preliminary evidence that these videos can reduce stigma in viewers. As such, participatory video should be considered a promising practice in the ongoing struggle to raise awareness and reduce stigma.