How do people estimate the orientation of other people's faces? We observed that two... more How do people estimate the orientation of other people's faces? We observed that two images of a face seen from the same orientation, but illuminated from different angles, appeared to have different orientations. The first experiment was designed to document and quantify this phenomenon with respect to the average orientation of the face. The images were rendered on a black background that made it impossible to discriminate the shadowed facial parts from the background. We determined the physical orientation shift necessary ...
A little more than 30 years ago, the Swedish psychologist Gunnar Johansson (1973; 1976) fascinate... more A little more than 30 years ago, the Swedish psychologist Gunnar Johansson (1973; 1976) fascinated the vision science community with an arresting demonstration of the organizational efficiency of the human visual system: He attached small light bulbs to the major joints of a human figure dressed entirely in black. Filming the movement of that figure created a highly reduced display that consisted only of a small number of white dots moving against a black background. Yet, it created the vivid and immediate percept of a human figure in action. Less than 10 dots and 150 ms of display time were sufficient for a human observer to perceptually organize the dots into a fully coherent, articulated shape of a human figure, implicating the involvement of a highly specialized perceptual process. Today, we call Johansson's phenomenon biological motion perception and the point-light displays he first used to demonstrate it have become recognized as a very effective research tool for studying the mechanisms upon which it is based. A demonstration of point-light displays and their potential to convey information about a walking person can be found at http://www.biomotionlab.ca/Demos/BMLwalker.html. J E x p P s y c h o l H u m P e r c e p t P e r f o r m , 3 1 ( 5 ) , 1 0 9 6 -1 1 0 6 .
Male pigeons show species-specific courtship displays in front of female pigeons. The present stu... more Male pigeons show species-specific courtship displays in front of female pigeons. The present study examined whether visual information, without auditory or tactile input, could trigger such courtship displays. The study also examined which technical measures could be used to present the visual stimuli. We studied the behaviors of male pigeons in response to video-taped and computer-animated stimuli presented on a computer monitor. The subjects did show courtship displays in front of video-taped and computer-animated ...
Detection and Interpretation of Animacy, Agency, and Intention, 2013
The study of biological motion perception was introduced into vision research some 40 years ago b... more The study of biological motion perception was introduced into vision research some 40 years ago by Swedish psychologist Gunnar Johansson. Since that time, the questions and approaches have changed considerably. While early work on biological motion perception was primarily concerned with mechanism of perceptual organization, the more recent research emphasizes on the social significance of human and animal motion. In tracing the evolution of the term "biological motion" and its use, this chapter attempts to characterize and classify the different questions and experimental paradigms that have dominated research on biological motion perception over the last few decades.
Biological motion—that is, the movement patterns of animals and humans—provides a rich source of ... more Biological motion—that is, the movement patterns of animals and humans—provides a rich source of information that helps us to quickly and reliably detect the presence of another living being; to identify it as a predator, prey, or conspecific; and to infer its actions and intentions in order to respond with adequate behavior. Once we know that we are being confronted with another person, we are able to use motion as a source of information about identity, gender, age, emotional state, and personality traits and as a complex means for ...
Visual motion, a critical cue in communication, can be manipulated and studied using video playba... more Visual motion, a critical cue in communication, can be manipulated and studied using video playback methods. A primary concern for the video playback researcher is the degree to which objects presented on video appear natural to the non-human subject. Here we argue that the quality of motion cues on video, as determined by the video's image presentation rate (IPR), are of particular importance in determining a subject's social response behaviour. We present an experiment testing the effect of variations in IPR on pigeon (Columbia livia) response behaviour towards video images of courting opposite sex partners. Male and female pigeons were presented with three video playback stimuli, each containing a different social partner. Each stimulus was then modified to appear at one of three IPRs: 15, 30 or 60 progressive (p) frames per second. The results showed that courtship behaviour became significantly longer in duration as IPR increased. This finding implies that the IPR signi...
Biological motion stimuli, such as orthographically projected stick figure walkers, are ambiguous... more Biological motion stimuli, such as orthographically projected stick figure walkers, are ambiguous about their orientation in depth. The projection of a stick figure walker oriented towards the viewer, therefore, is the same as its projection when oriented away. Even though such figures are depth-ambiguous, however, observers tend to interpret them as facing towards them more often than facing away. Some have speculated that this facing-the-viewer bias may exist for sociobiological reasons: Mistaking another human as retreating when they are actually approaching could have more severe consequences than the opposite error. Implied in this hypothesis is that the facing-towards percept of biological motion stimuli is potentially more threatening. Measures of anxiety and the facing-the-viewer bias should therefore be related, as researchers have consistently found that anxious individuals display an attentional bias towards more threatening stimuli. The goal of this study was to assess w...
Orthographically projected biological motion point-light displays are generally ambiguous with re... more Orthographically projected biological motion point-light displays are generally ambiguous with respect to their orientation in depth, yet observers consistently prefer the facing-the-viewer interpretation. There has been discussion as to whether this bias can be attributed to the social relevance of biological motion stimuli or relates to local, low-level stimulus properties. In the present study we address this question. In Experiment 1, we compared the facing-the-viewer bias produced by a series of four stick figures and three human silhouettes that differed in posture, gender, and the presence versus absence of walking motion. Using a paradigm in which we asked observers to indicate the spinning direction of these figures, we found no bias when participants observed silhouettes, whereas a pronounced degree of bias was elicited by most stick figures. We hypothesized that the ambiguous surface normals on the lines and dots that comprise stick figures are prone to a visual bias that...
Non-visual photoreceptors with diverse photopigments allow organisms to adapt to changing light c... more Non-visual photoreceptors with diverse photopigments allow organisms to adapt to changing light conditions. Whereas visual photoreceptors are involved in image formation, non-visual photoreceptors mainly undertake various non-image-forming tasks. They form specialised photosensory systems that measure the quality and quantity of light and enable appropriate behavioural and physiological responses. Chromatophores are dermal non-visual photoreceptors directly exposed to light and they not only receive ambient photic input but also respond to it. These specialised photosensitive pigment cells enable animals to adjust body coloration to fit environments, and play an important role in mate choice, camouflage and ultraviolet (UV) protection. However, the signalling pathway underlying chromatophore photoresponses and the physiological importance of chromatophore colour change remain under-investigated. Here, we characterised the intrinsic photosensitive system of red chromatophores (erythr...
Child neuropsychology : a journal on normal and abnormal development in childhood and adolescence, Jan 7, 2014
Biological motion perception can be assessed using a variety of tasks. In the present study, 8- t... more Biological motion perception can be assessed using a variety of tasks. In the present study, 8- to 11-year-old children born prematurely at very low birth weight (<1500 g) and matched, full-term controls completed tasks that required the extraction of local motion cues, the ability to perceptually group these cues to extract information about body structure, and the ability to carry out higher order processes required for action recognition and person identification. Preterm children exhibited difficulties in all 4 aspects of biological motion perception. However, intercorrelations between test scores were weak in both full-term and preterm children-a finding that supports the view that these processes are relatively independent. Preterm children also displayed more autistic-like traits than full-term peers. In preterm (but not full-term) children, these traits were negatively correlated with performance in the task requiring structure-from-motion processing, r(30) = -.36, p <...
The silhouette illusion published online a number of years ago by the Japanese Flash designer Nob... more The silhouette illusion published online a number of years ago by the Japanese Flash designer Nobuyuki Kayahara has received substantial attention from the online community. One feature that seems to make it interesting is an apparent rotational bias: Observers see it spinning more often clockwise than counter-clockwise. Here, we show that this rotational bias is in fact due to the visual system's preference for viewpoints from above rather than from below.
There is conflicting evidence about whether stimulus magnification is sufficient to equate the di... more There is conflicting evidence about whether stimulus magnification is sufficient to equate the discriminability of point-light walkers across the visual field. We measured the accuracy with which observers could report the directions of point-light walkers moving ±4°from the line of sight, and the accuracy with which they could identify five different point-light walkers. In both cases accuracy was measured over a sevenfold range of sizes at eccentricities from 0°to 16°in the right visual field. In most cases observers (N = 6) achieved 100% accuracy at the largest stimulus sizes (20°height) at all eccentricities. In both tasks the psychometric functions at each eccentricity were shifted versions of each other on a log-size axis. Therefore, by dividing stimulus size at each eccentricity (E) by an appropriate F = 1 + E/E 2 (where E 2 represents the eccentricity at which stimulus size must double to achieve equivalent-to-foveal performance) all data could be fit with a single function. The average E 2 value was .91 (SEM = .19, N = 6) in the walkerdirection discrimination task and 1.34 (SEM = .21, N = 6) in the walker identification task. We conclude that size scaling is sufficient to equate discrimination and identification of point-light walkers across the visual field.
The International journal of eating disorders, 2007
The aim of the present study was to find out whether in bulimia nervosa the perceptual component ... more The aim of the present study was to find out whether in bulimia nervosa the perceptual component of a disturbed body image is restricted to the overestimation of one's own body dimensions (static body image) or can be extended to a misperception of one's own motion patterns (dynamic body image). Participants with bulimia nervosa (n = 30) and normal controls (n = 55) estimated their body dimensions by means of a photo distortion technique and their walking patterns using a biological motion distortion device. Not only did participants with bulimia nervosa overestimate their own body dimensions, but also they perceived their own motion patterns corresponding to a higher BMI than did controls. Static body image was correlated with shape/weight concerns and drive for thinness, whereas dynamic body image was associated with social insecurity and body image avoidance. In bulimia nervosa, body image disturbances can be extended to a dynamic component.
How do people estimate the orientation of other people&amp;#x27;s faces? We observed that two... more How do people estimate the orientation of other people&amp;#x27;s faces? We observed that two images of a face seen from the same orientation, but illuminated from different angles, appeared to have different orientations. The first experiment was designed to document and quantify this phenomenon with respect to the average orientation of the face. The images were rendered on a black background that made it impossible to discriminate the shadowed facial parts from the background. We determined the physical orientation shift necessary ...
A little more than 30 years ago, the Swedish psychologist Gunnar Johansson (1973; 1976) fascinate... more A little more than 30 years ago, the Swedish psychologist Gunnar Johansson (1973; 1976) fascinated the vision science community with an arresting demonstration of the organizational efficiency of the human visual system: He attached small light bulbs to the major joints of a human figure dressed entirely in black. Filming the movement of that figure created a highly reduced display that consisted only of a small number of white dots moving against a black background. Yet, it created the vivid and immediate percept of a human figure in action. Less than 10 dots and 150 ms of display time were sufficient for a human observer to perceptually organize the dots into a fully coherent, articulated shape of a human figure, implicating the involvement of a highly specialized perceptual process. Today, we call Johansson's phenomenon biological motion perception and the point-light displays he first used to demonstrate it have become recognized as a very effective research tool for studying the mechanisms upon which it is based. A demonstration of point-light displays and their potential to convey information about a walking person can be found at http://www.biomotionlab.ca/Demos/BMLwalker.html. J E x p P s y c h o l H u m P e r c e p t P e r f o r m , 3 1 ( 5 ) , 1 0 9 6 -1 1 0 6 .
Male pigeons show species-specific courtship displays in front of female pigeons. The present stu... more Male pigeons show species-specific courtship displays in front of female pigeons. The present study examined whether visual information, without auditory or tactile input, could trigger such courtship displays. The study also examined which technical measures could be used to present the visual stimuli. We studied the behaviors of male pigeons in response to video-taped and computer-animated stimuli presented on a computer monitor. The subjects did show courtship displays in front of video-taped and computer-animated ...
Detection and Interpretation of Animacy, Agency, and Intention, 2013
The study of biological motion perception was introduced into vision research some 40 years ago b... more The study of biological motion perception was introduced into vision research some 40 years ago by Swedish psychologist Gunnar Johansson. Since that time, the questions and approaches have changed considerably. While early work on biological motion perception was primarily concerned with mechanism of perceptual organization, the more recent research emphasizes on the social significance of human and animal motion. In tracing the evolution of the term "biological motion" and its use, this chapter attempts to characterize and classify the different questions and experimental paradigms that have dominated research on biological motion perception over the last few decades.
Biological motion—that is, the movement patterns of animals and humans—provides a rich source of ... more Biological motion—that is, the movement patterns of animals and humans—provides a rich source of information that helps us to quickly and reliably detect the presence of another living being; to identify it as a predator, prey, or conspecific; and to infer its actions and intentions in order to respond with adequate behavior. Once we know that we are being confronted with another person, we are able to use motion as a source of information about identity, gender, age, emotional state, and personality traits and as a complex means for ...
Visual motion, a critical cue in communication, can be manipulated and studied using video playba... more Visual motion, a critical cue in communication, can be manipulated and studied using video playback methods. A primary concern for the video playback researcher is the degree to which objects presented on video appear natural to the non-human subject. Here we argue that the quality of motion cues on video, as determined by the video's image presentation rate (IPR), are of particular importance in determining a subject's social response behaviour. We present an experiment testing the effect of variations in IPR on pigeon (Columbia livia) response behaviour towards video images of courting opposite sex partners. Male and female pigeons were presented with three video playback stimuli, each containing a different social partner. Each stimulus was then modified to appear at one of three IPRs: 15, 30 or 60 progressive (p) frames per second. The results showed that courtship behaviour became significantly longer in duration as IPR increased. This finding implies that the IPR signi...
Biological motion stimuli, such as orthographically projected stick figure walkers, are ambiguous... more Biological motion stimuli, such as orthographically projected stick figure walkers, are ambiguous about their orientation in depth. The projection of a stick figure walker oriented towards the viewer, therefore, is the same as its projection when oriented away. Even though such figures are depth-ambiguous, however, observers tend to interpret them as facing towards them more often than facing away. Some have speculated that this facing-the-viewer bias may exist for sociobiological reasons: Mistaking another human as retreating when they are actually approaching could have more severe consequences than the opposite error. Implied in this hypothesis is that the facing-towards percept of biological motion stimuli is potentially more threatening. Measures of anxiety and the facing-the-viewer bias should therefore be related, as researchers have consistently found that anxious individuals display an attentional bias towards more threatening stimuli. The goal of this study was to assess w...
Orthographically projected biological motion point-light displays are generally ambiguous with re... more Orthographically projected biological motion point-light displays are generally ambiguous with respect to their orientation in depth, yet observers consistently prefer the facing-the-viewer interpretation. There has been discussion as to whether this bias can be attributed to the social relevance of biological motion stimuli or relates to local, low-level stimulus properties. In the present study we address this question. In Experiment 1, we compared the facing-the-viewer bias produced by a series of four stick figures and three human silhouettes that differed in posture, gender, and the presence versus absence of walking motion. Using a paradigm in which we asked observers to indicate the spinning direction of these figures, we found no bias when participants observed silhouettes, whereas a pronounced degree of bias was elicited by most stick figures. We hypothesized that the ambiguous surface normals on the lines and dots that comprise stick figures are prone to a visual bias that...
Non-visual photoreceptors with diverse photopigments allow organisms to adapt to changing light c... more Non-visual photoreceptors with diverse photopigments allow organisms to adapt to changing light conditions. Whereas visual photoreceptors are involved in image formation, non-visual photoreceptors mainly undertake various non-image-forming tasks. They form specialised photosensory systems that measure the quality and quantity of light and enable appropriate behavioural and physiological responses. Chromatophores are dermal non-visual photoreceptors directly exposed to light and they not only receive ambient photic input but also respond to it. These specialised photosensitive pigment cells enable animals to adjust body coloration to fit environments, and play an important role in mate choice, camouflage and ultraviolet (UV) protection. However, the signalling pathway underlying chromatophore photoresponses and the physiological importance of chromatophore colour change remain under-investigated. Here, we characterised the intrinsic photosensitive system of red chromatophores (erythr...
Child neuropsychology : a journal on normal and abnormal development in childhood and adolescence, Jan 7, 2014
Biological motion perception can be assessed using a variety of tasks. In the present study, 8- t... more Biological motion perception can be assessed using a variety of tasks. In the present study, 8- to 11-year-old children born prematurely at very low birth weight (<1500 g) and matched, full-term controls completed tasks that required the extraction of local motion cues, the ability to perceptually group these cues to extract information about body structure, and the ability to carry out higher order processes required for action recognition and person identification. Preterm children exhibited difficulties in all 4 aspects of biological motion perception. However, intercorrelations between test scores were weak in both full-term and preterm children-a finding that supports the view that these processes are relatively independent. Preterm children also displayed more autistic-like traits than full-term peers. In preterm (but not full-term) children, these traits were negatively correlated with performance in the task requiring structure-from-motion processing, r(30) = -.36, p <...
The silhouette illusion published online a number of years ago by the Japanese Flash designer Nob... more The silhouette illusion published online a number of years ago by the Japanese Flash designer Nobuyuki Kayahara has received substantial attention from the online community. One feature that seems to make it interesting is an apparent rotational bias: Observers see it spinning more often clockwise than counter-clockwise. Here, we show that this rotational bias is in fact due to the visual system's preference for viewpoints from above rather than from below.
There is conflicting evidence about whether stimulus magnification is sufficient to equate the di... more There is conflicting evidence about whether stimulus magnification is sufficient to equate the discriminability of point-light walkers across the visual field. We measured the accuracy with which observers could report the directions of point-light walkers moving ±4°from the line of sight, and the accuracy with which they could identify five different point-light walkers. In both cases accuracy was measured over a sevenfold range of sizes at eccentricities from 0°to 16°in the right visual field. In most cases observers (N = 6) achieved 100% accuracy at the largest stimulus sizes (20°height) at all eccentricities. In both tasks the psychometric functions at each eccentricity were shifted versions of each other on a log-size axis. Therefore, by dividing stimulus size at each eccentricity (E) by an appropriate F = 1 + E/E 2 (where E 2 represents the eccentricity at which stimulus size must double to achieve equivalent-to-foveal performance) all data could be fit with a single function. The average E 2 value was .91 (SEM = .19, N = 6) in the walkerdirection discrimination task and 1.34 (SEM = .21, N = 6) in the walker identification task. We conclude that size scaling is sufficient to equate discrimination and identification of point-light walkers across the visual field.
The International journal of eating disorders, 2007
The aim of the present study was to find out whether in bulimia nervosa the perceptual component ... more The aim of the present study was to find out whether in bulimia nervosa the perceptual component of a disturbed body image is restricted to the overestimation of one's own body dimensions (static body image) or can be extended to a misperception of one's own motion patterns (dynamic body image). Participants with bulimia nervosa (n = 30) and normal controls (n = 55) estimated their body dimensions by means of a photo distortion technique and their walking patterns using a biological motion distortion device. Not only did participants with bulimia nervosa overestimate their own body dimensions, but also they perceived their own motion patterns corresponding to a higher BMI than did controls. Static body image was correlated with shape/weight concerns and drive for thinness, whereas dynamic body image was associated with social insecurity and body image avoidance. In bulimia nervosa, body image disturbances can be extended to a dynamic component.
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