Visual Perception Of Biological Motion Research Articles

Making night-time pedestrians safer using innovative clothing designs

Night-time pedestrians, including recreational walkers and runners, remain at significant risk of being killed or seriously injured, because drivers often fail to see them in time to avoid a collision. Clothing incorporating retro-reflective markers on the moveable joints creates a visual perception of biological motion or “biomotion” which has been shown to improve night-time pedestrian conspicuity. This study investigated whether clothing with markings in the biomotion configuration retains its conspicuity if adapted to include thinner or patterned retro-reflective strips making it more acceptable to wear for recreational pedestrians. In a night-time closed road study, the relative conspicuity of pedestrians to 14 young drivers with normal vision (mean age 24.3 ± 3.1 years) was assessed for pedestrians wearing different thicknesses and patterns of biomotion strips and compared with typical clothing worn by night-time pedestrians, including commercially available sports clothing with retro-reflective elements, a fluorescent yellow top, and black clothing. Results showed that all the biomotion configurations resulted in significantly longer recognition distances: around 2 times longer than the sports clothing, 2.5 times longer than the fluorescent top and 4 times longer than the black clothing. Similar trends were found for the distance at which drivers correctly identified pedestrian orientation (towards or sideways to the vehicle), with significantly longer distances for all the biomotion configurations, when compared to the sports, fluorescent top and black clothing. These findings highlight the effectiveness of biomotion clothing, even when using retro-reflective strips as thin as 0.75 cm and have implications for clothing designs for recreational walkers and runners to enhance their night-time safety.

The relevance to social interaction modulates bistable biological-motion perception

Social interaction, the process through which individuals act and react toward each other, is arguably the building block of society. As the very first step for successful social interaction, we need to derive the orientation and immediate social relevance of other people: a person facing toward us is much more likely to initiate communications than a person who is back to us. Reversely, however, it remains elusive whether the relevance to social interaction modulates how we perceive the other's orientation. Here, we adopted the bistable point-light walker (PLW) which is ambiguous in its in-depth orientation. Participants were asked to report the orientation (facing the viewer or facing away from the viewer) of the PLWs. Three factors that are task-irrelevant but critically pertinent to social interaction, the distance, the speed, and the size of the PLW, were systematically manipulated. The nearer a person is, the more likely it initiates interactions with us. The larger a person is, the larger influence it may exert. The faster a person is, the shorter time is left for us to respond. Results revealed that participants tended to perceive the PLW as facing them more frequently than facing away when the PLW was nearer, faster, or larger. These same factors produced different patterns of effects on a non-biological rotating cylinder. These findings demonstrate that the relevance to social interaction modulates the visual perception of biological motion and highlight that bistable biological motion perception not only reflects competitions of low-level features but is also strongly linked to high-level social cognition.

The neural representation of human versus nonhuman bipeds and quadrupeds

How do humans recognize humans among other creatures? Recent studies suggest that a preference for conspecifics may emerge already in perceptual processing, in regions such as the right posterior superior temporal sulcus (pSTS), implicated in visual perception of biological motion. In the current functional MRI study, participants viewed point-light displays of human and nonhuman creatures moving in their typical bipedal (man and chicken) or quadrupedal mode (crawling-baby and cat). Stronger activity for man and chicken versus baby and cat was found in the right pSTS responsive to biological motion. The novel effect of pedalism suggests that, if right pSTS contributes to recognizing of conspecifics, it does so by detecting perceptual features (e.g. bipedal motion) that reliably correlate with their appearance. A searchlight multivariate pattern analysis could decode humans and nonhumans across pedalism in the left pSTS and bilateral posterior cingulate cortex. This result implies a categorical human-nonhuman distinction, independent from within-category physical/perceptual variation. Thus, recognizing conspecifics involves visual classification based on perceptual features that most frequently co-occur with humans, such as bipedalism, and retrieval of information that determines category membership above and beyond visual appearance. The current findings show that these processes are at work in separate brain networks.

Making Sense of the Body: the Role of Vestibular Signals.

The role of the vestibular system in posture and eye movement control has been extensively described. By contrast, how vestibular signals contribute to bodily perceptions is a more recent research area in the field of cognitive neuroscience. In the present review article, I will summarize recent findings showing that vestibular signals play a crucial role in making sense of the body. First, data will be presented showing that vestibular signals contribute to bodily perceptions ranging from low-level bodily perceptions, such as touch, pain, and the processing of the body's metric properties, to higher level bodily perceptions, such as the sense of owning a body, the sense of being located within this body (embodiment), and the anchoring of the visuo-spatial perspective to this body. In the second part of the review article, I will show that vestibular information seems to be crucially involved in the visual perception of biological motion and in the visual perception of human body structure. Reciprocally, observing human bodies in motion influences vestibular self-motion perception, presumably due to sensorimotor resonance between the self and others. I will argue that recent advances in the mapping of the human vestibular cortex afford neuroscientific models of the vestibular contributions to human bodily self-consciousness.

Perceptual Evaluation of Motion Editing for Realistic Throwing Animations

Animation budget constraints during the development of a game often call for the use of a limited set of generic motions. Editing operations are thus generally required to animate virtual characters with a sufficient level of variety. Evaluating the perceptual plausibility of edited animations can therefore contribute greatly towards producing visually plausible animations. In this article, we study observers’ sensitivity to manipulations of overarm and underarm biological throwing animations. In the first experiment, we modified the release velocity of the ball while leaving the motion of the virtual thrower and the angle of release of the ball unchanged. In the second experiment, we evaluated the possibility of further modifying throwing animations by simultaneously editing the motion of the thrower and the release velocity of the ball, using dynamic time warping. In both experiments, we found that participants perceived shortened underarm throws to be particularly unnatural. We also found that modifying the thrower's motion in addition to modifying the release velocity of the ball does not significantly improve the perceptual plausibility of edited throwing animations. In the third experiment, we modified the angle of release of the ball while leaving the magnitude of release velocity and the motion of the thrower unchanged, and found that this editing operation is efficient for improving the perceptual plausibility of shortened underarm throws. Finally, in Experiment 4, we replaced the virtual human thrower with a mechanical throwing device (a ramp) and found the opposite pattern of sensitivity to modifications of the release velocity, indicating that biological and physical throws are subject to different perceptual rules. Our results provide valuable guidelines for developers of games and virtual reality applications by specifying thresholds for the perceptual plausibility of throwing manipulations while also providing several interesting insights for researchers in visual perception of biological motion.

Dynamics of oscillatory changes associated with the perception of human motion

Neurophysiological evidence suggests that a specialized cortical network is involved in the visual perception of biological motion; however, the temporal dynamics underlying this network is largely unexplored. We used magnetoencephalography to determine the spatial distribution and task-related temporal dynamics of the oscillatory activity of random and human motion. We recorded cortical responses in healthy adults while they passively viewed point-light displays of static dots, random, and human motion. By analyzing differences in the time-frequency distributions between pairs of conditions, we found that: (a) the perception of both motion conditions resulted in a significant decrease in the α/β band in the right superior occipital gyrus and a significant decrease in the β band in the right insula and (b) the human motion condition was associated with specific alterations in α, β, and γ bands with significant reductions in the α band in the right superior temporal gyrus, right precuneus, and left inferior parietal lobule, significant reductions in the β band in the bilateral superior temporal gyrus, together with a significant increase in the γ band in the left inferior parietal lobule and superior temporal regions. These data suggest that although the perception of both random and human motion involves desynchronization of oscillatory activity in α and β bands in similar cortical regions, only human motion is associated with a larger network and significant alterations in the α/β band particularly in the right hemisphere.

Anticipating the terminal position of an observed action: Effect of kinematic, structural, and identity information

The ability to visually identify and anticipate motor actions performed by others is thought to be an essential component of social interactions and possibly requires relating visual information with sensorimotor knowledge. Though motor theory of visual perception received convincing evidence from behavioural, neuropsychological, and developmental studies, the nature of the information used for anticipating the terminal location of an observed human action remains still an open issue. In this context, the aim of the present study was to evaluate the role of motor representations on the prediction of the terminal location of an observed manual reaching movement. The stimulus was a two-dimensional point-light display showing the top-view of a right arm moving along the sagittal plane towards targets positioned at different distances. The task was to estimate the terminal location of the reaching movement after the stimulus vanished following 60% of total movement duration. Characteristics of the point-light display could vary according to movement kinematics (biological motion, constant, inverse, or monotonically increased velocity), structural features (all joints visible or only the forefinger tip), and movement identity (self- vs. other-generated action). Results showed that spatial performances improved when presenting “self-generated” actions (identity effect) in the biological motion condition (kinematic effect). Furthermore, reducing the visual stimulus to the forefinger did not affect the performance (structural effect). Considered together, these findings provide further evidence for motor-based visual perception of biological motion and suggest that kinematic but not structural information is crucial to give sense to an observed human action and to anticipate its final location.

Reading action word affects the visual perception of biological motion

In the present study, we investigate whether reading an action-word can influence subsequent visual perception of biological motion. The participant's task was to perceptually judge whether a human action identifiable in the biological motion of a point-light display embedded in a high density mask was present or not in the visual sequence, which lasted for 633 ms on average. Prior to the judgement task, participants were exposed to an abstract verb or an action verb for 500 ms, which was related to the human action according to a congruent or incongruent semantic relation. Data analysis showed that correct judgements were not affected by action verbs, whereas a facilitation effect on response time (49 ms on average) was observed when a congruent action verb primed the judgement of biological movements. In relation with the existing literature, this finding suggests that the perception, the planning and the linguistic coding of motor action are subtended by common motor representations.

BOLD response during visual perception of biological motion in obsessive-compulsive disorder

Although research has shown that deficits in various cognitive functions may underlie obsessive-compulsive disorder (OCD), studies have not yet clarified the specificity and etiology of perception processing, particularly the perception of biological motion that is correlated with social cognition. We used functional magnetic resonance imaging (fMRI) to investigate neural activity associated with the perception of biological motion in OCD patients. The subjects were 15 patients with OCD and 15 age- and IQ-matched healthy volunteers. All subjects participated in a biological motion task in which they performed a one-back task signaling a repeated stimulus with a key press in each block condition to obligate attention to both types of stimuli. The biological motion versus scrambled motion contrast revealed that both OCD patients and healthy controls exhibited increased activation of the superior and middle temporal gyrus, the regions implicated in processing of biological motion, which is consistent with previous studies. However, direct comparison between OCD subjects and healthy controls indicated that patients with OCD exhibited increased activation in the right superior and middle temporal gyrus and the left inferior temporal and fusiform gyrus, and reduced activation in the right postcentral gyrus (BA 40) compared to healthy subjects. OCD patients exhibited increased activation in the ventral visual system, including the inferior temporal and fusiform gyrus. We observed a differential pattern of activity between OCD patients and healthy controls, indicating that OCD patients have functional differences related to the perception of biological motion. The differential activation between OCD patients and healthy subjects might contribute to the pathophysiological understanding of obsessive compulsive disorder.

Selective impairment in visual perception of biological motion in obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is associated with a variety of well-documented cognitive deficits such as deficits in memory and executive functioning, but little is known about basic perceptual concomitants of OCD. This study investigated global, configural processing in OCD using dynamic (moving) and static stimuli with minimal demands on cognitive function. Twenty OCD patients and 16 age- and education-matched healthy control subjects were tested on four perceptual tasks: two motion tasks involved detection and discrimination of human activity portrayed by point-light animations ("biological" motion). The other two tasks involved detection of coherent, translational motion defined by random-dot cinematograms and detection of static global shape defined by spatially distributed contours. OCD patients exhibited impaired performance on biological motion tasks; in contrast, their performance on tasks of coherent motion detection and global form perception were comparable to those of healthy controls. These results indicate that OCD patients have a specific deficit in perceiving biological motion signals, whereas their perception of non-biological coherent motion and static global shape is intact. Because efficient social interactions depend on accurate and rapid perception of subtle socially relevant cues, deficits in biological motion perception may compromise social functioning in people with OCD.

Four-day-old human neonates look longer at non-biological motions of a single point-of-light.

BackgroundBiological motions, that is, the movements of humans and other vertebrates, are characterized by dynamic regularities that reflect the structure and the control schemes of the musculo-skeletal system. Early studies on the development of the visual perception of biological motion showed that infants after three months of age distinguished between biological and non-biological locomotion.Methodology/Principal FindingsUsing single point-light motions that varied with respect to the “two-third-power law” of motion generation and perception, we observed that four-day-old human neonates looked longer at non-biological motions than at biological motions when these were simultaneously presented in a standard preferential looking paradigm.Conclusion/SignificanceThis result can be interpreted within the “violation of expectation” framework and can indicate that neonates' motion perception — like adults'—is attuned to biological kinematics.

Visual perception of biological motion by form: A template-matching analysis

Biological motion perception is referred to as the ability to recognize a moving human figure from no more than a few moving point lights. Such point-light stimuli contain limited form information about the shape of the body and local image motion signals from the moving points. The contributions of form and motion to the vivid perception of point-light displays are subject to controversy in the discussion. While some studies claim that local motion signals are critical, others emphasize the role of global form cues. Here, we present a template-matching approach to investigate the role of global form analysis. We used a template-matching method that derives biological motion exclusively from form information. The algorithm used static postures monitored from walking humans as stored templates. We compared the simulation results to psychophysical experiments with the commonly used point-light walker and a variant point-light walker with near-absent local motion signals. The common result in all experiments was a high correlation between simulation results and psychophysical data. The results show that the limited form information in point-light stimuli might be sufficient to perceive biological motion. We suggest that it is possible for humans to extract the sparse form information in point-light walkers and to use it to perceive biological motion by integrating dynamic form information over time.

A model of biological motion perception from configural form cues.

Biological motion perception is the compelling ability of the visual system to perceive complex human movements effortlessly and within a fraction of a second. Recent neuroimaging and neurophysiological studies have revealed that the visual perception of biological motion activates a widespread network of brain areas. The superior temporal sulcus has a crucial role within this network. The roles of other areas are less clear. We present a computational model based on neurally plausible assumptions to elucidate the contributions of motion and form signals to biological motion perception and the computations in the underlying brain network. The model simulates receptive fields for images of the static human body, as found by neuroimaging studies, and temporally integrates their responses by leaky integrator neurons. The model reveals a high correlation to data obtained by neurophysiological, neuroimaging, and psychophysical studies.

Patterns of fMRI Activity Dissociate Overlapping Functional Brain Areas that Respond to Biological Motion

Accurate perception of the actions and intentions of other people is essential for successful interactions in a social environment. Several cortical areas that support this process respond selectively in fMRI to static and dynamic displays of human bodies and faces. Here we apply pattern-analysis techniques to arrive at a new understanding of the neural response to biological motion. Functionally defined body-, face-, and motion-selective visual areas all responded significantly to "point-light" human motion. Strikingly, however, only body selectivity was correlated, on a voxel-by-voxel basis, with biological motion selectivity. We conclude that (1) biological motion, through the process of structure-from-motion, engages areas involved in the analysis of the static human form; (2) body-selective regions in posterior fusiform gyrus and posterior inferior temporal sulcus overlap with, but are distinct from, face- and motion-selective regions; (3) the interpretation of region-of-interest findings may be substantially altered when multiple patterns of selectivity are considered.

Action Perception: Seeing the World through a Moving Body

Recent evidence suggests that the acquisition of new motor skills can directly influence later visual perception even when an observer's eyes remain 'wide shut' during learning.

Eccentric perception of biological motion is unscalably poor

Accurately perceiving the activities of other people is a crucially important social skill of obvious survival value. Human vision is equipped with highly sensitive mechanisms for recognizing activities performed by others [Johansson, G. (1973). Visual perception of biological motion and a model for its analysis. Perception and Psychophysics, 14, 201; Johansson, G. (1976). Spatio-temporal differentiation and integration in visual motion perception: An experimental and theoretical analysis of calculus-like functions in visual data processing. Psychological Research, 38, 379]. One putative functional role of biological motion perception is to register the presence of biological events anywhere within the visual field, not just within central vision. To assess the salience of biological motion throughout the visual field, we compared the detectability performances of biological motion animations imaged in central vision and in peripheral vision. To compensate for the poorer spatial resolution within the periphery, we spatially magnified the motion tokens defining biological motion. Normal and scrambled biological motion sequences were embedded in motion noise and presented in two successively viewed intervals on each trial (2AFC). Subjects indicated which of the two intervals contained normal biological motion. A staircase procedure varied the number of noise dots to produce a criterion level of discrimination performance. For both foveal and peripheral viewing, performance increased but saturated with stimulus size. Foveal and peripheral performance could not be equated by any magnitude of size scaling. Moreover, the inversion effect––superiority of upright over inverted biological motion [Sumi, S. (1984). Upside-down presentation of the Johansson moving light-spot pattern. Perception, 13, 283]––was found only when animations were viewed within the central visual field. Evidently the neural resource responsible for biological motion perception are embodied within neural mechanisms focused on central vision.

Active processing of biological motion perception: an ERP study

The purpose of this study was to measure event-related potentials (ERPs) to clarify how attention affects neural activity during the visual perception of biological motion (BM). Thirteen healthy subjects observed BM or scrambled motion (SM). For SM, each point had the same velocity vector as in BM, but the initial starting positions were randomized. Each BM and SM was overlaid with ten noise dots and four rectangles. For the rectangles, one was or was not rotated 90° relative to the others. Subjects were required to undertake two kinds of visual tasks. For the attention-to-motion condition, subjects directed their attention to the type of motion. For the attention-to-rectangle condition, subjects directed their attention to the rotational angle of the overlaid rectangles. As in our earlier study, the ERP response to the perception of BM had two negative components at ∼200 ms (N200) and ∼330 ms (N330) in both attentional conditions. Our analysis focused on the amplitude of the second negative component, which was sensitive to BM. There was a significant interaction between attention and the type of motion regarding the amplitude of N330. Specifically, the amplitude of N330 in response to BM was greater in the attention-to-motion condition than in the attention-to-rectangle condition, and was greater than the amplitude of the response to SM in the attention-to-motion condition. These results suggest that in this experimental design, processing of BM is modulated by attention.

Dissociable cortical processing of recognizable and non-recognizable biological movement: analysing gamma MEG activity.

Recognition of biological motion is one of the essential ingredients of human evolutionary survival. When biological motion is revealed solely by a set of light dots on the joints of an invisible human figure, the perceptual system reliably distinguishes it from similar configurations. Here, we assessed the changes in neuromagnetic cortical responses during visual perception of biological motion. Healthy humans saw a randomized set of stimuli consisting of a point-light canonical walker and a scrambled configuration in which the spatial positions of dots were randomly rearranged on the screen. In separate runs, configurations were presented either within an upright or inverted (180 degrees ) orientation in the image plane. Participants performed a one-back repetition task lifting a forefinger in response to the second of two consecutive identical stimuli of each type. Both recognizable upright and non-recognizable inverted walkers evoke enhancements in oscillatory gamma brain activity (25-30 Hz) over the left occipital cortices as early as 100 ms from stimulus onset. Only a recognizable upright walker, however, yields further consecutive peaks over the parietal (130 ms) and right temporal (170 ms) lobes. Scrambled displays do not elicit any increases in the gamma response. The stimulus-specific time course and topographic dynamics of cortical oscillatory activity indicate that the brain rapidly dissociates spatial coherence and meaning revealed through biological movement.

Brain Areas Active during Visual Perception of Biological Motion

Theories of vision posit that form and motion are represented by neural mechanisms segregated into functionally and anatomically distinct pathways. Using point-light animations of biological motion, we examine the extent to which form and motion pathways are mutually involved in perceiving figures depicted by the spatio-temporal integration of local motion components. Previous work discloses that viewing biological motion selectively activates a region on the posterior superior temporal sulcus (STSp). Here we report that the occipital and fusiform face areas (OFA and FFA) also contain neural signals capable of differentiating biological from nonbiological motion. EBA and LOC, although involved in perception of human form, do not contain neural signals selective for biological motion. Our results suggest that a network of distributed neural areas in the form and motion pathways underlie the perception of biological motion.

Biological Motion Shown Backwards: The Apparent-Facing Effect

We examined how showing a film backwards (reverse transformation) affects the visual perception of biological motion. Adults and 6-year-old children saw first a point-light quadruped moving normally as if on a treadmill, and then saw the same display in reverse transformation. For other groups the order of presentation was the opposite. Irrespective of the presentation mode (normal or reverse) and of the facing of the point-light figure (rightward or leftward), a pronounced apparent-facing effect was observed: the perceptual identification of a display was mainly determined by the apparent direction of locomotion. The findings suggest that in interpreting impoverished point-light biological-motion stimuli the visual system may neglect distortions caused by showing a film backwards. This property appears to be robust across perceptual development. Possible explanations of the apparent-facing effect are discussed.