Depth perception from point-light biological motion displays

 

 

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Depth perception from point-light biological motion displays

via Journal of Vision recent issues by de Lussanet, M. H. E., Lappe, M. on 10/22/12

Abstract Humans have a clear impression of facing in depth for point-light biological motion. However, this has not been measured systematically nor is it known on which cues humans rely for their judgment. In the present study subjects judged the facing orientation-in-depth of point-light displays. The displays represented natural walking and modified versions in which the time sequence was reversed, action was perturbed, the limbs and joints were nonrigid, the temporal sequence was scrambled, or the joint positions were scrambled. We found that the subjects were best at judging the facing direction of normal and reversed walking with an accuracy of 6° and 10° precision. The results show that pendular motion of the limb segments and the implicit knowledge of the human body play an important role for the precision of the judgment. Three further factors were relevant for the judgment of facing direction: (a) the discrimination of the front and back side, (b) the facing bias, and (c) the impression of depth from the display, probably due to the kinetic depth effect. The latter influences the accuracy, which differed strongly between subjects. The results suggest that the facing bias, to perceive the figure as facing toward the observer rather than away, is not related to the recognition of a human figure but rather to the presence of oscillating movements of the dots in the display.

 

 

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Biological Motion Processing as a Hallmark of Social Cognition

 

 

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Biological Motion Processing as a Hallmark of Social Cognition

via Cerebral Cortex - current issue door Pavlova, M. A. op 17-4-12

Visual processing of biological motion (BM) produced by living organisms is of immense value for successful daily-life activities and, in particular, for adaptive social behavior and nonverbal communication. Investigation of BM perception in neurodevelopmental disorders related to autism, preterm birth, and genetic conditions substantially contributes to our understanding of the neural mechanisms underpinning the extraordinary tuning to BM. The most prominent research outcome is that patients with daily-life deficits in social cognition are also compromised on visual body motion processing. This raises the question of whether performance on body motion perception tasks may serve a hallmark of social cognition. Overall, the findings highlight the role of structural and functional brain connectivity for proper functioning of the neural circuitry involved in BM processing and visual social cognition that share topographically and dynamically overlapping neural networks.

 

 

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Dynamics of walking adaptation aftereffects induced in static images of walk...

 

 

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Dynamics of walking adaptation aftereffects induced in static images of walking actors

via ScienceDirect Publication: Drug Discovery Today on 3/3/12

Publication year: 2012
Source: Vision Research, Available online 2 March 2012
Nick E. Barraclough, Jennifer Ingham, Stephen A. Page
Visual adaptation to walking actions results in subsequent aftereffects that bias perception of static images of walkers in different postures so that they are interpreted as walking in the opposite direction to the adapting actor. It is not clear, however, if the walking aftereffect is comparable to other well studied low- and high-level visual aftereffects. We therefore measured the dynamics of the walking aftereffect in order to assess the characteristics of the adapting mechanism. We found that walking aftereffects showed similar characteristic dynamics as for face aftereffects and some motion aftereffects. Walking aftereffects could be induced in a broad range of different static images of walking actors and were not restricted to images of actors in any particular posture. Walking aftereffects increased with adapting stimulus repetition and declined over time. The duration of the aftereffect was dependent upon time spent observing the adapting stimulus and could be well modelled by a power-law function that characterises this relationship in both face and motion aftereffects. Increasing the speed of the adapting stimulus by increasing actor walk speed increased aftereffect magnitude, as seen for some motion aftereffects. The nature of the aftereffects induced by observing walking actors indicates that they behave like traditional high-level visual aftereffects.

Highlights

► We test dynamics of aftereffects from observing walking actions. ► Walking adaptation biases all static postures so that they appear to walk in opposite direction. ► Aftereffects increase with adaptor duration and speed, and decline over time.

 

 

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The time to passage of biological and complex motion

 

 

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The time to passage of biological and complex motion

via Journal of Vision recent issues by Mouta, S., Santos, J. A., Lopez–Moliner, J. on 2/27/12

A significant part of human interactions occur with other human beings and not only with inanimate objects. It is important in everyday tasks to estimate the time it takes other people to reach (time to contact) or pass us (time to passage). Surprisingly, little is known about judging time to contact or time to passage of biological or other complex motions. In two experiments, rigid and non-rigid (biological, inverted, scrambled, and complex non-biological) motion conditions were compared in a time-to-passage judgment task. Subjects could judge time to passage of point-light-walker displays. However, due to relative and opponent movements of body parts, all articulated patterns conveyed a noisier looming pattern. Non-rigid stimuli were judged as passing sooner than rigid stimuli but reflected more uncertainty in the judgments as revealed by precision judgments and required longer reaction times. Our findings suggested that perceptual judgments for complex motion, including biological patterns, are built on top of the same processing channels that are involved on rigid motion perception. The complexity of the motion pattern (rigid vs. non-rigid) plays a more determinant role than the "biologicity" of the stimulus (biological vs. non-biological), at least concerning time-to-passage judgments.

 

 

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Local-to-global form interference in biological motion perception

Abstract
Point-light walkers have been useful to study the contribution of form
and motion to biological motion perception by manipulating the
lifetime, number, or spatial distribution of the light points. Recent
studies have also manipulated the light points themselves, replacing
them with small images of objects. This manipulation degraded the
recognizability of biological motion, particularly for local images of
human bodies. This result suggests an interference of body form
information in the local images with the body form analysis necessary
for global biological motion recognition at the global level. We
further explored this interference with respect to its selectivity for
body orientation and motion. Participants had to either discriminate
the facing direction (left/right) or the walking direction
(forward/backward) of a global walker composed of local stick figures
that could face left or right and either stand still or walk forward
or backward. Local stick figures interfered stronger with the facing
direction task if they were facing in the same direction as the global
walker. Walking (forward/backward/static) of the stick figures
influenced neither the facing direction task nor the walking direction
task. We conclude that the interference is highly specific since it
concerns not only the category (human form), but even the facing
direction.

http://www.springerlink.com/content/r6536225h0427703/

Healthy older observers cannot use biological-motion point-light information...

 

 

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Healthy older observers cannot use biological-motion point-light information efficiently within 4 m of themselves. Isabelle Legault, Nikolaus F Troje, Jocelyn Faubert

via i-Perception by Pion on 2/21/12

Healthy aging is associated with a number of perceptual changes, but measures of biological-motion perception have yielded conflicting results. Biological motion provides information about a walker, from gender and identity to speed, direction, and distance. In our natural environment, as someone approaches us (closer distances), the walker spans larger areas of our field of view, the extent of which can be underutilized with age. Yet, the effect of age on biological-motion perception in such real-world scenarios remains unknown. We assessed the effect of age on discriminating walking direction in upright and inverted biological-motion patterns, positioned at various distances in virtual space. Findings indicate that discrimination is worse at closer distances, an effect exacerbated by age. Older adults' performance decreases at distances as far away as 4 m, whereas younger adults maintain their performance as close as 1 m (worse at 0.5 m). This suggests that older observers are limited in their capacity to integrate information over larger areas of the visual field and supports the notion that age-related effects are more apparent when larger neural networks are required to process simultaneous information. This has further implications for social contexts where information from biological motion is critical.

 

 

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Evidence for AuditoryVisual Processing Specific to Biological Motion

 

 

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Evidence for AuditoryVisual Processing Specific to Biological Motion

via Latest Issue of Seeing and Perceiving by Meyer, Georg F. on 2/7/12

 

 

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