Search

Research suggests that humans have an attentional bias for the rapid detection of emotionally valenced stimuli, and that such a bias might be shaped by clinical psychological states. The current research extends this work to examine the relation between body dissatisfaction and an attentional bias for thin/idealized body shapes. Across two experiments, undergraduates completed a gender-consistent body dissatisfaction measure, and a dot-probe paradigm to measure attentional biases for thin versus heavy bodies. Results indicated that men ( n = 21) and women ( n = 18) show an attentional bias for bodies that correspond to their own gender (Experiment 1), and that high body dissatisfaction among men ( n = 69) and women ( n = 89) predicts an attentional bias for thin same-gender bodies after controlling for body mass index (BMI) (Experiment 2). This research provides a new direction for studying the attentional and cognitive underpinnings of the relation between body dissatisfaction and eating disorders.

OBJECTIVE We examined biological motion perception in Parkinson's disease (PD). Biological motion perception is related to one's own motor function and depends on the integrity of brain areas affected in PD, including posterior superior temporal sulcus. If deficits in biological motion perception exist, they may be specific to perceiving natural/fast walking patterns that individuals with PD can no longer perform, and may correlate with disease-related motor dysfunction. METHOD Twenty-six nondemented individuals with PD and 24 control participants viewed videos of point-light walkers and scrambled versions that served as foils, and indicated whether each video depicted a human walking. Point-light walkers varied by gait type (natural, parkinsonian) and speed (0.5, 1.0, 1.5 m/s). Participants also completed control tasks (object motion, coherent motion perception), a contrast sensitivity assessment, and a walking assessment. RESULTS The PD group demonstrated significantly less sensitivity to biological motion than the control group (p < .001, Cohen's d = 1.22), regardless of stimulus gait type or speed, with a less substantial deficit in object motion perception (p = .02, Cohen's d = .68). There was no group difference in coherent motion perception. Although individuals with PD had slower walking speed and shorter stride length than control participants, gait parameters did not correlate with biological motion perception. Contrast sensitivity and coherent motion perception also did not correlate with biological motion perception. CONCLUSION PD leads to a deficit in perceiving biological motion, which is independent of gait dysfunction and low-level vision changes, and may therefore arise from difficulty perceptually integrating form and motion cues in posterior superior temporal sulcus. (PsycINFO Database Record

The accurate visual perception of an object’s motion requires the simultaneous integration of motion information arising from that object along with the segmentation of motion information from other objects. When moving objects are seen through apertures, or viewing windows, the resultant illusions highlight some of the challenges that the visual system faces as it balances motion segmentation with motion integration. One example is the barber pole Illusion, in which lines appear to translate orthogonally to their true direction of emotion. Another is the illusory perception of incoherence when simple rectilinear objects translate or rotate behind disconnected apertures. Studies of these illusions suggest that visual motion processes frequently rely on simple form cues.

The phenomenon of apparent motion, or the illusory perception of movement from rapidly displayed static images, provides an excellent platform for the study of how perceptual systems analyze input over time and space. Studies of the human body in apparent motion further suggest that the visual system is also influenced by an observer’s motor experience with his or her own body. As a result, the human visual system sometimes processes human movement differently from object movement. For example, under apparent motion conditions in which inanimate objects appear to traverse the shortest possible paths of motion, human motion instead appears to follow longer, biomechanically plausible paths of motion. Psychophysical and brain imaging studies converge in supporting the hypothesis that the visual analysis of human movement differs from the visual analysis of nonhuman movements whenever visual motion cues are consistent with an observer’s motor repertoire of possible human actions.

The main question that Firestone & Scholl (F&S) pose is whether “what and how we see is functionally independent from what and how we think, know, desire, act, and so forth” (sect. 2, para. 1). We synthesize a collection of concerns from an interdisciplinary set of coauthors regarding F&S's assumptions and appeals to intuition, resulting in their treatment of visual perception as context-free.

Typical adult observers demonstrate enhanced behavioral sensitivity to human movement compared to animal movement. Yet, the neural underpinnings of this effect are unknown. We examined the tuning of brain mechanisms for the perception of biological motion to the social relevance of this category of motion by comparing neural response to human and non-human biological motion. In particular, we tested the hypothesis that the response of the right posterior superior temporal sulcus (pSTS) varies according to the social relevance of the motion, responding most strongly to those biological motions with the greatest social relevance (human > dog). During a functional magnetic resonance imaging (fMRI) session, typical adults viewed veridical point-light displays of human, dog, and tractor motions created from motion capture data. A conjunction analysis identified regions of significant activation during biological motion perception relative to object motion. Within each of these regions, only one brain area, the right pSTS, revealed an enhanced response to human motion relative to dog motion. This finding demonstrates that the pSTS response is sensitive to the social relevance of a biological motion stimulus.

To determine whether motor difficulties documented in Asperger's Syndrome (AS) are related to compromised visual abilities, this study examined perception and movement in response to dynamic visual environments. Fourteen males with AS and 16 controls aged 7–23 completed measures of motor skills, postural response to optic flow, and visual sensitivity to static form and coherent motion in random dot kinematograms and point-light walkers. No group differences were found in sensitivity to static form or coherent motion. However, significant group differences were found in visual sensitivity to human movement and postural responsivity to optic flow, which both correlated with motor skills. This may suggest difficulties in perception and production of movement and dysfunctional perceptual-motor linkages in AS.

Zusammenfassung. Wie nimmt das menschliche visuelle System Handlungen wahr? – Traditionelle Modelle der visuellen Wahrnehmung nehmen an, dass bei allen Beobachtern die gleichen visuellen Prozesse der Analyse von visuellen Stimuli unterschiedlicher Art zu Grunde liegen. Dieser theoretische Ansatz sagt vorher, dass unterschiedliche Personen Gegenstände und Handlungen in gleicher Art und Weise wahrnehmen, unabhängig davon, ob sich ihr Bewegungssystem beispielsweise durch krankheitsbedingte Veränderungen oder Trainingsanpassungen unterscheidet. Demgegenüber nehmen Theorien der embodied perception an, dass individuelle Fähigkeiten des Beobachters die visuelle Wahrnehmung beeinflussen. Ausgehend von diesem Ansatz ist das, was man sieht, dadurch bestimmt, was man physisch tun (kann). Menschliche Bewegung wird dabei als eine spezielle Kategorie von visuellen Bewegungsreizen angesehen, da es die einzige Bewegungsart ist, welche der Mensch ausführen und wahrnehmen kann. Der vorliegende Artikel gibt einen Überblick über aktuelle neuro- und verhaltenswissenschaftliche Befunde zur visuellen Wahrnehmung menschlicher Bewegung unter besonderer Berücksichtigung der Rolle des motorischen Systems. Dabei wird auf die Wahrnehmung von Athleten eingegangen, da diese Personengruppe über spezifische motorische und visuelle Fähigkeiten verfügt, welche den Erklärungswert traditioneller Theorien der visuellen Wahrnehmung kritisch hinterfragen.

Successful social behavior requires the accurate perception and interpretation of other peoples' actions. In the last decade, significant progress has been made in understanding how the human visual system analyzes bodily motion. Neurophysiological studies have identified two neural areas, the superior temporal sulcus (STS) and the premotor cortex, which play key roles in the visual perception of human movement. Patterns of neural activity in these areas are reflective of psychophysical measures of visual sensitivity to human movement. Both vary as a function of stimulus orientation and global stimulus structure. Human observers and STS responsiveness share some developmental similarities as both exhibit sensitivities that become increasingly tuned for upright, human movement. Furthermore, the observer's own visual and motor experience with an action as well as the social and emotional content of that action influence behavioral measures of visual sensitivity and patterns of neural activity in the STS and premotor cortex. Finally, dysfunction of motor processes, such as hemiplegia, and dysfunction of social processes, such as Autism, systematically impact visual sensitivity to human movement. In sum, a convergence of visual, motor, and social processes underlies our ability to perceive and interpret the actions of other people. WIREs Cogn Sci 2011 2 68-78 DOI: 10.1002/wcs.88 For further resources related to this article, please visit the WIREs website.

Traditionally, psychological research on autism spectrum disorder (ASD) has focused on social and cognitive abilities. Vision provides an important input channel to both of these processes, and, increasingly, researchers are investigating whether observers with ASD differ from typical observers in their visual percepts. Recently, significant controversies have arisen over whether observers with ASD differ from typical observers in their visual analyses of movement. Initial studies suggested that observers with ASD experience significant deficits in their visual sensitivity to coherent motion in random dot displays but not to point-light displays of human motion. More recent evidence suggests exactly the opposite: that observers with ASD do not differ from typical observers in their visual sensitivity to coherent motion in random dot displays, but do differ from typical observers in their visual sensitivity to human motion. This review examines these apparently conflicting results, notes gaps in previous findings, suggests a potentially unifying hypothesis, and identifies areas ripe for future research.

Mounting neurophysiological evidence indicates that the visual analysis of human movement differs from the visual analysis of other categories of complex movement. If different patterns of neural activity underlie visual percepts of human and nonhuman movement, then psychophysical measures should elucidate different patterns of visual sensitivity to human movement and similarly complex, but nonhuman movement. To test this prediction, two psychophysical studies compared visual sensitivity to human and animal motions. Using a simultaneous masking paradigm, observers performed a coherent motion detection task with point-light displays of human and horse gait, presented upright and inverted. While task performance indicated the use of configural processing during the detection of both human and horse motion, observers demonstrated greater visual sensitivity to coherent human motion than coherent horse motion. Recent experience influenced orientation dependence for both types of motion. Together with previous neurophysiological findings, these psychophysical results suggest that the visual perception of human movement is both distinct from and shares commonalities with the visual perception of similarly complex, nonhuman movement.

Observers can recognize other people from their movements. What is interesting is that observers are best able to recognize their own movements. Enhanced visual sensitivity to self-generated movement may reflect the contribution of motor planning processes to the visual analysis of human action. An alternative view is that enhanced visual sensitivity to self-motion results from extensive experience seeing one's own limbs move. To investigate this alternative explanation, participants viewed point-light actors from first-person egocentric and third-person allocentric viewpoints. Although observers routinely see their own actions from the first-person view, participants were unable to identify egocentric views of their own actions. Conversely, with little real-world experience seeing themselves from third-person views, participants readily identified their own actions from allocentric views. When viewing allocentric displays, participants accurately identified both front and rear views of their own actions. Because people have little experience observing themselves from behind or from third-person views, these findings suggest that visual learning cannot account for enhanced visual sensitivity to self-generated action.

The texture of a rolling circle depicts the translational and rotational components of its motion. In the case of a homogeneous circle, however, visual cues to the rotational component of motion are absent. To examine how the visual system resolves undetermined motion cues, optically neutral circles were displaced so that changes in their orientation were invisible. Contextual cues systematically triggered the perception of illusory rotation, suggesting that the visual system uses contextual cues along with intrinsic surface cues to compute percepts of rolling objects. This might also explain why people rarely experience the perception of ambiguous motion.

We characterized magnetoencephalographic responses during observation of point-light displays of human and object motion. Time courses of grand-mean source estimates were computed and time frequency maps were calculated. For both conditions, activity began in the posterior occipital and mid-parietal areas. Further, late peaks were observed in the parietal, sensory-motor and left temporal regions. Only observation of human motion resulted in activation of the right temporal area. Both viewing conditions resulted in alpha and beta event-related desynchronization over the parietal, sensory-motor and temporal areas. A significant increase in beta activity was seen in the posterior temporal region in the human motion condition. The visual analyses of human and object motion appear to involve both overlapping and divergent patterns of neural activity.

Humans, being highly social creatures, rely heavily on the ability to perceive what others are doing and to infer from gestures and expressions what others may be intending to do. These perceptual skills are easily mastered by most, but not all, people, in large part because human action readily communicates intentions and feelings. In recent years, remarkable advances have been made in our understanding of the visual, motoric, and affective influences on perception of human action, as well as in the elucidation of the neural concomitants of perception of human action. This article reviews those advances and, where possible, draws links among those findings.

Is the visual analysis of human actions modulated by the emotional content of those actions? This question is motivated by a consideration of the neuroanatomical connections between visual and emotional areas. Specifically, the superior temporal sulcus (STS), known to play a critical role in the visual detection of action, is extensively interconnected with the amygdala, a center for emotion processing. To the extent that amygdala activity influences STS activity, one would expect to find systematic differences in the visual detection of emotional actions. A series of psychophysical studies tested this prediction. Experiment 1 identified point-light walker movies that convincingly depicted five different emotional states: happiness, sadness, neutral, anger, and fear. In Experiment 2, participants performed a walker detection task with these movies. Detection performance was systematically modulated by the emotional content of the gaits. Participants demonstrated the greatest visual sensitivity to angry walkers. The results of Experiment 3 suggest that local velocity cues to anger may account for high false alarm rates to the presence of angry gaits. These results support the hypothesis that the visual analysis of human action depends upon emotion processes.

Early intervention approaches for facilitating motor development in infants and children with Down syndrome have traditionally emphasised the acquisition of motor milestones. As increasing evidence suggests that motor milestones have limited predictive power for long-term motor outcomes, researchers have shifted their focus to understanding the underlying perceptual-motor competencies that influence motor behaviour in Down syndrome. This paper outlines a series of studies designed to evaluate the nature and extent of perceptual-motor impairments present in children with Down syndrome. 12 children with Down syndrome between the ages of 8-15 years with adaptive ages between 3-7 years (mean age = 5.6 years +/- 1.45 years) and a group of 12 typically developing children between the ages of 4-8 years (mean age = 5.4 +/- 1.31 years) were tested on their ability to make increasingly complex perceptual discriminations of motor behaviours. The results indicate that children with Down syndrome are able to make basic perceptual discriminations but show impairments in the perception of complex visual motion cues. The implications of these results for early intervention are discussed.

Increasing evidence suggests that the visual analysis of other people's actions depends upon the observer's own body representation or schema. This raises the question of how differences in observers' body structure and schema impact their perception of human movement. We investigated the visual experiences of two persons born without arms, one with and the other without phantom sensations. These participants, plus six normally-limbed control observers, viewed depictions of upper limb movement under conditions of apparent motion. Consistent with previous results (Shiffrar M, Freyd JJ (1990) Psychol Sci 1:257), normally-limbed observers perceived rate-dependent paths of apparent human movement. Specifically, biologically impossible motion trajectories were reported at rapid display rates while biologically possible trajectories were reported at slow display rates. The aplasic individual with phantom experiences showed the same perceptual pattern as control participants, while the aplasic individual without phantom sensations did not. These preliminary results suggest that phantom experiences may constrain the visual analysis of the human body. These results further suggest that it may be time to move beyond the question of whether aplasic phantoms exist and instead focus on the question of why some people with limb aplasia experience phantom sensations while others do not. In this light, the current results suggest that somesthetic representations are not sufficient to define body schema. Instead, neural systems matching action observation, action execution and motor imagery likely contribute to the definition of body schema in profound ways. Additional research with aplasic individuals, having and lacking phantom sensations, is needed to resolve this issue.

Johansson's point-light walker figures remain one of the most powerful and convincing examples of the role that motion can play in the perception of form (Johansson, 1973 Perception & Psychophysics14 201–211; 1975 Scientific American232(6) 76–88). In the current work, we use a dual-task paradigm to explore the role of attention in the processing of such stimuli. In two experiments we find striking differences in the degree to which direction-discrimination performance in point-light walker displays appears to rely on attention. Specifically, we find that performance in displays thought to involve top – down processing, either in time (experiment 1) or space (experiment 2) is adversely affected by dividing attention. In contrast, dividing attention has little effect on performance in displays that allow low-level, bottom – up computations to be carried out. We interpret these results using the active/passive motion distinction introduced by Cavanagh (1991 Spatial Vision5 303–309).

Most studies and theories of object recognition have addressed the perception of rigid objects. Yet, physical objects may also move in a nonrigid manner. A series of priming studies examined the conditions under which observers can recognize novel views of objects moving nonrigidly. Observers were primed with 2 views of a rotating object that were linked by apparent motion or presented statically. The apparent malleability of the rotating prime object varied such that the object appeared to be either malleable or rigid. Novel deformed views of malleable objects were primed when falling within the object's motion path. Priming patterns were significantly more restricted for deformed views of rigid objects. These results suggest that moving malleable objects may be represented as continuous events, whereas rigid objects may not. That is, object representations may be "dynamically remapped" during the analysis of the object's motion.

Depth rotations can reveal new object parts and result in poor recognition of “static” objects (Biederman & Gerhardstein, 1993) . Recent studies have suggested that multiple object views can be associated through temporal contiguity and similarity Edelman & Weinshall, 1991 , Lawson et al., 1994 , Wallis, 1996 . Motion may also play an important role in object recognition since observers recognize novel views of objects rotating in the picture plane more readily than novel views of statically re-oriented objects (Kourtzi & Shiffrar, 1997) . The series of experiments presented here investigated how different views of a depth-rotated object might be linked together even when these views do not share the same parts. The results suggest that depth rotated object views can be linked more readily with motion than with temporal sequence alone to yield priming of novel views of 3D objects that fall in between “known” views. Motion can also enhance path specific view linkage when visible object parts differ across views. Such results suggest that object representations depend on motion processes.

Recovering a reliable 3D percept from the retinal sampling of dynamic images requires the linkage of motion signals across space and time. In this paper, we review recent experimental results that enhance our understanding of the perceptual processes of motion integration, segmentation, and selection that are necessary to solve this inverse optics problem. Simple paradigms involving the presentation of moving contours are used to assess our ability to link sparse motion information. Our results indicate that human motion perception strongly depends on both primitive stimulus characteristics, such as contrast, eccentricity, and duration, as well as higher level characteristics such as feature classification and spatial configurations. Further, the perceived direction of a moving object depends little upon its familiarity. Finally, pursuit eye movements of compositional stimuli are highly correlated with perceived motion coherence. This ensemble of results is analysed within the context of current theories of motion perception.

How do people recognize an object in a novel orientation? Psychophysical and neurophysiological studies have suggested that extensive practice is required before observers can recognize an object that has been rotated to a new orientation Because object orientation frequently varies with object movement, we examined whether observers might more readily recognize a moving object in a new orientation Results from a priming study indicate that motion significantly and readily enhances the recognition of new object orientations when those orientations fall within the path of the motion That is motion promotes view-invariant object recognition without practice

To understand the visual analysis of biological motion, subjects viewed dynamic, stick figure renditions of a walker, car, or scissors through apertures. As a result of the aperture problem, the motion of each visible edge was ambiguous. Subjects readily identified the human figure but were unable to identify the car or scissors through invisible apertures. Recognition was orientation specific and robust across a range of stimulus durations, and it benefited from limb orientation cues. The results support the theory that the visual system performs spatially global analyses to interpret biological logical motion displays.

Previous research demonstrates that meaningfully related sounds enhance visual sensitivity to point-light displays of human movement. Here we report two psychophysical studies that investigated whether, and if so when, this facilitation is modulated by the temporal relationship between auditory and visual stimuli. In Experiment 1, participants detected point-light walkers in masks while listening to footsteps that were either synchronous or out-of-phase with point-light footfalls. The relative timing of auditory and visual walking did not impact performance. Experiment 2 further tested the importance of multisensory timing by disrupting the rhythm of the auditory and visual streams. Participants detected point-light walkers while listening to footstep or tone sounds that were either synchronous or temporally random with regards to point-light footfalls. Heard footsteps improved visual sensitivity over heard tones regardless of timing. Taken together, these results suggest that during the detection of others' actions, the perceptual system makes use of meaningfully related sounds whether or not they are synchronous. These results are discussed in relation to the unity assumption theory as well as recent empirical data that suggest that temporal correspondence is not always a critical factor in multisensory perception and integration.

Accurate interpretations of image motion require the segmentation of motion signals produced by different objects with the simultaneous integration of motion signals produced by the same object. We investigated a motion integration paradigm in which the direction of an object's motion could only be determined from an integration of motion signals across the disconnected object edges. In a series of experiments we show that observers' ability to determine object motion depends significantly upon stimulus duration, luminance contrast and edge width. These effects suggest that the visual system, after some delay, relies upon relatively thick, luminance defined contour discontinuities to segment moving images. Copyright © 1996 Elsevier Science Ltd.

A translating homogeneous edge viewed through an aperture is an ambiguous stimulus, while a translating edge discontinuity is unambiguous. Under what conditions does the visual system use unambiguous velocity estimates to interpret ambiguous velocity estimates? We considered a translating rectangle visible through a set of stationary apertures. One aperture displayed a rectangle edge while the other apertures displayed corners. Observers reported the direction in which the edge appeared to translate. The results suggest that collinearity and terminator proximity determine whether the unambiguous corner velocity was used to interpret the ambiguous edge velocity. These results suggest some of the ways in which the visual system controls the integration of velocity estimates across image space.

To interpret the projected image of a moving object, the visual system must integrate motion signals across different image regions. Traditionally, researchers have examined this process by focusing on the integration of equally ambiguous motion signals. However, when the motions of complex, multi-featured images are measured through spatially limited receptive fields, the resulting motion measurements have varying degrees of ambiguity. In a series of experiments, we examine how human observers interpret images containing motion signals of differing degrees of ambiguity. Subjects judged the perceived coherence of images consisting of an ambiguously translating grating and an unambiguously translating random dot pattern. Perceived coherence of the dotted grating depended upon the degree of concurrence between the velocities of the grating terminators and dots. Depth relationships also played a critical role in the motion integration process. When terminators were suppressed with occlusion cues, coherence increased. When dots and gratings were presented at different depth planes, coherence decreased. We use these results to outline the conditions under which the visual system uses unambiguous motion signals to interpret object motion.

Typical observers exhibit a remarkable sensitivity to the social information conveyed by the body motions of others. Scholars have asserted that successful social behavior depends on successful social perceptions, yet observers of these motions naturally vary in their social skills. This chapter explores how natural variability in social skills—specifically for observers with autism spectrum disorders—provides insights into the relation between social skills and social behaviors by exploring the relation between visual sensitivity and social capabilities.

The study of the human body in motion is a dynamic discipline. Since the earliest observations, techniques have been refined and models rendered more precisely. In spite of this refinement, current research bears a remarkable continuity with the approach utilized in the seminal works of the 1970s. Thus, the study of the human body in motion is characterized by both continuity and progress. This book aims to shed light both on the most recent advances and the common underpinnings in research on the dynamic human body. An overview of the subsequent chapters is presented.

I. Introduction Chapter 1: Making Great Strides: Advances in Research on the Perception of the Human Body Chapter 2: Gunnar Johansson, Events, and Biological Motion II. Psychophysics Chapter 3: Top-Down versus Bottom-up Processing of Biological Motion Chapter 4: Seeing You through Me: Creating Self-Other Correspondences for Body Perception Chapter 5: What Does " Really Mean? Differentiating Visual Percepts of Human, Animal, and Non-biological Motions Chapter 6: Shape-Independent Processing of Biological Motion Chapter 7: Action Perception from a Common Coding Perspective III. Development and Individual Differences Chapter 8: Developmental Origins of Biological Motion Perception Chapter 9: Experience and the Perception of Biological Motion Chapter 10: Variability in the Visual Perception of Human Motion as a Function of the Observer's Autistic Traits Chapter 11: Development of Body Motion Processing in Normalcy and Pathology IV. Social Perspectives Chapter 12: Person (Mis)Perception? On the Biased Representation of the Human Body. Chapter 13: It's the Way You Walk: Kinematic Specification of Vulnerability to Attack Chapter 14: Coordinating Social Beings in Motion Chapter 15: Functionalism Redux: How Adaptive Action Constrains Perception, Simulation, and Evolved Intuitions V. Neurophysiology Chapter 16: Neural mechanisms for action observation Chapter 17: Neural Mechanisms for Biological Motion and Animacy Chapter 18: The How, When, and Why of Configural Processing in the Perception of Human Movement Chapter 19: Brain Mechanisms for Social Perception: Moving towards an Understanding of Autism Chapter 20: From Body Perception to Action Preparation: A Distributed Neural System for Viewing Bodily Expressions of Emotion Chapter 21: Sensory and Motor Brain Areas Subserving Biological Motion Perception: Neuropsychological and Neuroimaging Studies Chapter 22: Computational Mechanisms of the Visual Processing of Action Stimuli Index

For several decades, vision researchers’ use of the term “biological motion” has been used to refer to different things, including the category of all animal movements, the category of all human movements, and, most specifically, the category of human movements depicted in point-light displays. In reviewing data from psychophysical and neurophysiological studies, along with some new perceptual findings, this chapter examines the hypothesis that the visual analysis of human motion does not represent a uniform or bounded perceptual category but rather that analyses of human motion differ in a graded fashion from analyses of nonhuman animal motion. Thus, “biological motion” perception likely defines the perceptual category of human and animal motions organized such that human motion, or, more specifically, the observer’s own motor repertoire, constitutes the prototypical stimulus within the category.

Contains fulltext : 102528.pdf (Publisher’s version ) (Open Access) The action abilities of an individual observer modulate his or her perception of spatial properties of the environment and of objects. The present study investigated how joint action abilities shape perception. Four experiments examined how the intention to lift an object with another individual affects perceived weight. In Experiments 1, 2a, and 2b, participants judged the perceived weight of boxes while expecting to lift them either alone or with a co-actor. In Experiment 3, the co-actor was healthy or injured. Participants intending to lift a box with a co-actor perceived the box as lighter than participants intending to lift the same box alone, provided that the co-actor appeared healthy and therefore capable of helping. These findings suggest that anticipated effort modulates the perception of object properties in the context of joint action. We discuss implications for the role of action prediction and action simulation processes in social interaction. 9 p.

3. B.T. Volpe, J.E. LeDoux, and M.S. Gazzan iga, Information processing of visual stimuli in an extinguished field, Nature, 282, 722-724 (1979). 4. M.S. Gazzaniga, J.D. Holtzman, and CS. Smylie, Speech without conscious awareness, Neu rology, 35, 682-685 (1987). 5. M.S. Gazzaniga, Right hemisphere language following brain bisection: A twenty year perspec tive, American Psychologist, 38, 525-547 (1983). 6. J. Sergent, Furtive incursion into bicameral minds: Integrating and coordinating role of subcor tical structures, Brain, 113, 537-568 (1990). 7. A. Ptito, F. Lepore, M. Ptito, and M. Las sonde, Target detection and movement discrimina tion in the blind field of hemispherectomized pa tients, Brain, 114, 497-512 (1991). 8. C. Kennard, Blindsight Workshop (University of Oxford, Oxford, 1993). 9. A. Cowey and P. Stoerig, The neurobiology of blindsight, Trends in Neurosciences, 14, MO MS (1991). 10. J. Campion, R. Latto, and Y.M. Smith, Is blindsight an effect of scattered light, spared cortex, and near-threshold vision? Behavioral and Brain Sci ences, 6, 423-486 (1983). 11. J.D. Holtzman, Interactions between corti cal and subcortical visual areas: Evidence from hu man commissurotomy patients, Vision Research, 24, 801-813 (1984). 12. R. Balliet, K. Mt Blood, and P. Bach-y-Rita, Visual field rehabilitation in the cortically blind? Journal of Neurology, Neurosurgery, and Psychiatry, 48, 1113-1124(1985). 13. R. Fendrich, CM. Wessinger, and M.S. Gazzaniga, Residual vision in a scotoma: Implica tions for blindsight, Science, 258, 1489-1491 (1992). 14. N.K. Humphrey, A History of the Mind (Si mon & Schuster, New York, 1992). 15. N. Block, Review of Consciousness Ex plained by Dennett, D.C, Journal of Philosophy, 90, 181-193(1993). 16. J.L. Barbur, K.H. Ruddock, and V.A. Wa terfield, Human visual responses in the absence of the geniculo-calcarine projection, Brain, 103, 905 928 (1980); I.M. Blythe, J.M. Bromley, C Kennard, and K.H. Ruddock, Visual discrimination of target displacement remains after damage to the striate cortex in humans, Nature, 320, 619-621 (1986); L. Weiskrantz, A. Harlow, and J.L. Barbur, Factors af fecting visual sensitivity in a hemianopic subject, Brain, 114,2269-2282 (1991). 17. C.A. Marzi, G. Tassinaari, S. Aglioti, and L. Lutzemberger, Spatial summation across the vertical meridian in hemianopics: A test of blindsight, Neu ropsychologia, 24, 749-758 (1986); I.M. Blythe, C Kennard, and K.H. Ruddock, Residual vision in pa tients with retrogeniculate lesions of the visual path ways, Brain, 110, 887-905 (1987).

In demonstrations of apparent motion, observers typically report seeing motion along the shortest possible path between two sequentially presented objects. Recent work has demonstrated that violations of this shortest path rule occur with realistic photographs of a human body displayed for sufficiently long temporal intervals when a longer path is more anatomically plausible than the shortest path. The current set of experiments investigated the mechanisms by which information about biomechanical motion constrains apparent motion perception. In Experiment I, we demonstrated, first, that the availability of extra processing time does not simply—in and of itself—result in the perception of longer paths of apparent motion. Second, we rejected the hypothesis that the perception of biomechanically correct paths of apparent motion depends on biologically appropriate velocities. In Experiment 2, we discovered that the longer the motion path required to satisfy the biomechanical movement limitations of the stimulus, the longer the time needed to construct and therefore perceive that path. These findings together suggest that additional processing time is necessary, but not sufficient, for interpolations of longer paths.

Observers are remarkably sensitive to point-light displays of human movement. The Superior Temporal Sulcus (STS) and premotor cortex are implicated in the visual perception of point-light human actions and the integration of perceptual signals across modalities. These neurophysiological findings suggest that auditory information might impact visual sensitivity to point-light displays of human actions. Previous research has demonstrated that coincident, action-consistent sounds enhance visual sensitivity to the presence of coherent point-light displays of human movement. Here we ask whether visual detection sensitivity is modulated specifically by the meaningfulness of sounds that are coincident with observed point-light actions. To test this hypothesis, two psychophysical studies were conducted wherein participants detected the presence of coherent point-light walkers in a mask under unimodal or audiovisual conditions. Participants in audiovisual conditions heard either tones or actual footfalls coincident with the seen walkers' footsteps. Detection sensitivity increased when visual displays were paired with veridical auditory cues (footfalls), but not when paired with simple tones. The footfall advantage disappeared when the visual stimuli were inverted. These results suggest that the visual system makes use of auditory cues during the visual analysis of human action when there is a meaningful match between the auditory and visual cues.

Successful social behavior requires the accurate detection of other people's movements. Consistent with this, typical observers demonstrate enhanced visual sensitivity to human movement relative to equally complex, nonhuman movement [e.g., Pinto & Shiffrar, 2009]. A psychophysical study investigated visual sensitivity to human motion relative to object motion in observers with autism spectrum disorder (ASD). Participants viewed point-light depictions of a moving person and, for comparison, a moving tractor and discriminated between coherent and scrambled versions of these stimuli in unmasked and masked displays. There were three groups of participants: young adults with ASD, typically developing young adults, and typically developing children. Across masking conditions, typical observers showed enhanced visual sensitivity to human movement while observers in the ASD group did not. Because the human body is an inherently social stimulus, this result is consistent with social brain theories [e.g., Pelphrey & Carter, 2008; Schultz, 2005] and suggests that the visual systems of individuals with ASD may not be tuned for the detection of socially relevant information such as the presence of another person. Reduced visual sensitivity to human movements could compromise important social behaviors including, for example, gesture comprehension.

Individual motion measurements are inherently ambiguous since the component of motion parallel to a homogeneous translating edge cannot be measured. Numerous models have proposed that the visual system solves this ambiguity through the integration of motion measurements across disparate contours. To examine this proposal, subjects observed a translating diamond through four stationary apertures. Since the diamond's motion could not be determined from any single contour, motion integration across contours was required to determine the diamond's direction of motion. We demonstrate that observers have difficulty accurately integrating motion information across space. Performance improved when the diamond stimulus was presented at 7 degrees eccentricity, through jagged apertures, or at low contrast. Taken together, these results imply that integration across space is more likely when the motion of contour terminators is less salient or reliable.

Several studies have shown that the motor system is involved in action perception, suggesting that action concepts are represented through sensory–motor processes. Such conclusions imply that motor system impairments should diminish action perception. To test this hypothesis, a group of 10 brain-damaged patients with hemiplegia (specifically, a lesion at the motor system that affected the contralesional arm) viewed point-light displays of arm gestures and attempted to name each gesture. To create the dynamic stimuli, patients individually performed simple gestures with their unaffected arm while being videotaped. The videotapes were converted into point-light animations. Each action was presented as it had been performed, that is, as having been produced by the observer's unaffected arm, and in its mirror reversed orientation, that is, as having been produced by the observer's hemiplegic arm. Action recognition accuracy by patients with hemiplegia was compared with that by 8 brain-damaged patients without any motor deficit and by 10 healthy controls. Overall, performance was better in control observers than in patients. Most importantly, performance by hemiplegic patients, but not by nonhemiplegic patients and controls, varied systematically as a function of the observed limb. Action recognition was best when hemiplegic patients viewed actions that appeared to have been performed by their unaffected arm. Action recognition performance dropped significantly when hemiplegic patients viewed actions that appeared to have been produced with their hemiplegic arm or the corresponding arm of another person. The results of a control study involving the recognition of point-light defined animals in motion indicate that a generic deficit to visual and cognitive functions cannot account for this laterality-specific deficit in action recognition. Taken together, these results suggest that motor cortex impairment decreases visual sensitivity to human action. Specifically, when a cortical lesion renders an observer incapable of performing an observed action, action perception is compromised, possibly by a failure to map the observed action onto the observer's contralesional hemisoma.

Contains fulltext : 76873.pdf (Publisher’s version ) (Closed access) Studies of deception detection traditionally have focused on verbal communication. Nevertheless, people commonly deceive others through nonverbal cues. Previous research has shown that intentions can be inferred from the ways in which people move their bodies. Furthermore, motor expertise within a given domain has been shown to increase visual sensitivity to other people's movements within that domain. Does expertise also enhance deception detection from bodily movement? In two psychophysical studies, experienced basketball players and novices attempted to distinguish deceptive intentions (fake passes) and veridical intentions (true passes) from an observed individual's actions. Whereas experts and novices performed similarly with postural cues, only experts could detect deception from kinematics alone. These results demonstrate a link between action expertise and the detection of nonverbal deception.

Observers viewed pairs of alternating photographs of a human body in different positions. Shortest-path motion solutions were pitted against anatomically possible movements. With short stimulus onset asynchronies (SOAs), observers tended to report the shortest path despite violations of anatomical constraints. However, with longer SOAs observers became increasingly likely to report the anatomically possible, but longer, paths. This finding, in conjunction with those from a second study, challenges the accepted wisdom that apparent motion paths are independent of the object. Instead, our findings suggest that when given enough time and appropriate stimuli, the visual system prefers at least some object-appropriate apparent motion paths.

Fitts's law is one of the most well-established principles in psychology. It captures the relation between speed and accuracy in performed and imagined movements. The aim of this study was to determine whether this law also holds during the perception of other people's actions. Subjects were shown apparent motion displays of a person moving his arm between two identical targets. Target width, the separation between targets, and movement speed were varied. Subjects reported whether the person could move at the perceived speed without missing the targets. The movement times reported as being just possible were exactly those predicted by Fitts's law (r2 = .96). A subsequent experiment demonstrated the same lawful relation for the perception of a robot arm (r2 = .93). To our knowledge, this makes Fitts's law the first motor principle that holds in imagery and the perception of biological and nonbiological agents.