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Anxiety prepares us to deal with unpredictable threats, such as the approaching of an unknown person. Studies have shown our innate tendency to see approaching motion in ambiguous walkers in what was termed facing-the-viewer (FTV) bias. Here we investigated if anxiety states further contributed to this bias, hypothesizing that such states would increase overall FTV biases. Throughout three Experiments, we asked participants to judge the motion direction of ambiguous point-light walkers and measured their respective FTV biases under safe and anxiety-related conditions induced via imagery (Experiment 1), screaming sounds (Experiment 2), and threat of shock (Experiment 3). Across all experiments, we showed that anxiety does not affect our tendency to perceive an approaching behavior in ambiguous walkers. Based on our findings, and the discrepancies found in the literature, we emphasize the need for future studies to paint a clearer picture on the nature and aspects capable of affecting this bias. [ABSTRACT FROM AUTHOR]

Extensive research in social perception and biological motion has converged on the finding that humans are particularly accurate in identifying gender from the gait of minimal visual conspecific stimuli (e.g., point-light walkers). Despite the preponderance of evidence in favor of this ability, we return to the original paradigm and vary a single parameter—weight. Across nine pre-registered studies, participants (N = 3,196) were assigned to view the gait of point-light walkers based on actual human motion patterns. We find a decline in the accuracy of identifying the gender of female point-light walkers as their weight increases. However, as the weight of female walkers decreases, gender identification accuracy is recovered. These findings carry implications for the gendered nature of weight bias and the role of weight in human perception. [ABSTRACT FROM AUTHOR]

Recently, approach-avoidance tendencies and visual perception biases have been increasingly studied using bistable point-light walkers (PLWs). Prior studies have found a facing-the-viewer bias when one is primed with general threat stimuli (e.g. angry faces), explained by the "error management theory", as failing to detect a threat as approaching is riskier than the opposite. Importantly, no study has explored how disease threat – linked to the behavioural immune system – might affect this bias. This study aimed to explore whether disease-signalling cues can alter how we perceive the motion direction of ambiguous PLWs. Throughout 3 experiments, participants indicated the motion direction of a bistable PLW previously primed with a control or disease-signalling stimuli – that is, face with a surgical mask (Experiment 1), sickness sound (Experiment 2), or face with a disease cue (Experiment 3). Results showed that sickness cues do not significantly modulate the perception of approach-avoidance behaviours. However, a pattern emerged in Experiments 2 and 3, suggesting that sickness stimuli led to more facing away percepts. Unlike other types of threat, this implies that disease-related threat stimuli might trigger a distinct perceptual bias, indicating a preference to avoid a possible infection source. Nonetheless, this finding warrants future investigations. [ABSTRACT FROM AUTHOR]

Human point-light displays consist of luminous dots representing human articulations, thus depicting actions without pictorial information. These stimuli are widely used in action recognition experiments. Because humans excel in decoding human motion, point-light displays (PLDs) are often masked with additional moving dots (noise masks), thereby challenging stimulus recognition. These noise masks are typically found within proprietary programming software, entail file format restrictions, and demand extensive programming skills. To address these limitations, we present the first user-friendly step-by-step guide to develop visual noise to mask PLDs using free, open-source software that offers compatibility with various file formats, features a graphical interface, and facilitates the manipulation of both 2D and 3D videos. Further, to validate our approach, we tested two generated masks in a pilot experiment with 12 subjects and demonstrated that they effectively jeopardised human agent recognition and, therefore, action visibility. In sum, the main advantages of the presented methodology are its cost-effectiveness and ease of use, making it appealing to novices in programming. This advancement holds the potential to stimulate young researchers' use of PLDs, fostering further exploration and understanding of human motion perception.

To perceive, identify and understand the action of others, it is essential to perceptually organize individual and local moving body parts (such as limbs) into the whole configuration of a human body in action. Configural processing—processing the relations among features or parts of a stimulus—is a fundamental ability in the perception of several important social stimuli, such as faces or biological motion. Despite this, we know very little about how human infants develop the ability to perceive and prefer configural relations in biological motion. We present two preferential looking experiments (one cross-sectional and one longitudinal) measuring infants' preferential attention between a coherent motion configuration of a person walking vs. a scrambled point-light walker (i.e., a stimulus in which all configural relations were removed, thus, in which the perception of a person is impossible). We found that three-month-old infants prefer a coherent point-light walker in relation to a scrambled display, but both five- and seven-month-old infants do not show any preference. We discuss our findings in terms of the different perceptual, attentional, motor, and brain processes available at each age group, and how they dynamically interact with selective attention toward the coherent and socially relevant motion of a person walking during our first year of life. [ABSTRACT FROM AUTHOR]

Language comprehension requires rapid and flexible access to information stored in long-term memory, likely influenced by activation of rich world knowledge and by brain systems that support the processing of sensorimotor content. We hypothesized that while literal language about biological motion might rely on neurocognitive representations of biological motion specific to the details of the actions described, metaphors rely on more generic representations of motion. In a priming and self-paced reading paradigm, participants saw video clips or images of (a) an intact point-light walker or (b) a scrambled control and read sentences containing literal or metaphoric uses of biological motion verbs either closely or distantly related to the depicted action (walking). We predicted that reading times for literal and metaphorical sentences would show differential sensitivity to the match between the verb and the visual prime. In Experiment 1, we observed interactions between the prime type (walker or scrambled video) and the verb type (close or distant match) for both literal and metaphorical sentences, but with strikingly different patterns. We found no difference in the verb region of literal sentences for Close-Match verbs after walker or scrambled motion primes, but Distant-Match verbs were read more quickly following walker primes. For metaphorical sentences, the results were roughly reversed, with Distant-Match verbs being read more slowly following a walker compared to scrambled motion. In Experiment 2, we observed a similar pattern following still image primes, though critical interactions emerged later in the sentence. We interpret these findings as evidence for shared recruitment of cognitive and neural mechanisms for processing visual and verbal biological motion information. Metaphoric language using biological motion verbs may recruit neurocognitive mechanisms similar to those used in processing literal language but be represented in a less-specific way.

When one walks toward a crowd of pedestrians, dealing with their biological motion while controlling one's own self-motion is a difficult perceptual task. Limb articulation of a walker is naturally coupled to the walker's translation through the scene and allows the separation of optic flow generated by self-motion from the biological motion of other pedestrians. Recent research has shown that if limb articulation and translation mismatch, such as for walking in place, self-motion perception becomes biased. This bias may reflect an illusory motion attributed to the pedestrian crowd from the articulation of their limbs. To investigate this hypothesis, we presented observers with a simulation of forward self-motion toward a laterally moving crowd of point-light walkers and asked them to report the perceived lateral speed of the crowd. To investigate the dependence of the crowd speed percept on biological motion, we also included conditions in which the points of the walker were spatially scrambled to destroy body form and limb articulation. We observed illusory crowd speed percepts that were related to the articulation rate of the biological motion. Scrambled walkers also produced illusory motion but it was not related to articulation rate. We conclude that limb articulation induces percepts of crowd motion that can be used for interpreting self-motion toward crowds., Competing Interests: The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2024.)

Motion plays an important role in recognising animate creatures. This research supports a distinction between intrinsic and extrinsic motions in their relationship to identifying information about the characters performing the motions. Participants viewed events involving costumed human characters. Intrinsic motions involved relative movements of a character’s body parts, whereas extrinsic motions involved movements with respect to external landmarks. Participants were later tested for recognition of the motions and who had performed them. The critical test items involved familiar characters performing motions that had previously been performed by other characters. Participants falsely recognised extrinsic conjunction items, in which characters followed the paths of other characters, more often than intrinsic conjunction items, in which characters moved in the manner of other characters. In contrast, participants falsely recognised new extrinsic motions less often than new intrinsic motions, suggesting that they remembered extrinsic motions but had difficulty remembering who had performed them. Modelling of receiver operating characteristics indicated that participants discriminated old items from intrinsic conjunction items via familiarity, consistent with conjoint representations of intrinsic motion and identity information. In contrast, participants used recollection to distinguish old items from extrinsic conjunction items, consistent with separate but associated representations of extrinsic motion and identity information. [ABSTRACT FROM AUTHOR]

Our ability to see meaningful actions when presented with pointlight traces of human movement is commonly referred to as the perception of biological motion. While traditionalexplanations have emphasized the spontaneous and automatic nature of this ability, morerecent findings suggest that attention may play a larger role than is typically assumed. Intwo studies we show that the speed and accuracy of responding to point-light stimuli is highly correlated with the ability to control selective attention. In our first experiment we measured thresholds for determining the walking direction of a masked point-light figure, and performance on a range of attention-related tasks in the same set of observers. Mask-density thresholds for the direction discrimination task varied quite considerably from observer to observer and this variation was highly correlated with performance on both Stroop and flanker interference tasks. Other components of attention, such as orienting, alerting and visual search efficiency, showed no such relationship. In a second experiment, we examined the relationship between the ability to determine the orientation of unmasked point-light actions and Stroop interference, again finding a strong correlation. Our results are consistent with previous research suggesting that biological motion processing may requite attention, and specifically implicate networks of attention related to executive control and selection.

Participants diagnosed with mild cognitive impairment (MCI), dementia and controls completed measures that required decoding emotions from point-light displays of bodily motion, and static images of facial affect. Both of these measures tap social cognitive processes that are considered critical for social competency. Consistent with prior literature, both clinical groups were impaired on the static measure of facial affect recognition. The dementia (but not the MCI) group additionally showed difficulties interpreting biological motion cues. However, this did not reflect a specific deficit in decoding emotions, but instead a more generalized difficulty in processing visual motion (both to action and to emotion). These results align with earlier studies showing that visual motion processing is disrupted in dementia, but additionally show for the first time that this extends to the recognition of socially relevant biological motion. The absence of any MCI related impairment on the point-light biological emotion measure (coupled with deficits on the measure of facial affect recognition) also point to a potential disconnect between the processes implicated in the perception of emotion cues from static versus dynamic stimuli. For clinical (but not control) participants, performance on all recognition measures was inversely correlated with level of semantic memory impairment. (JINS, 2012, 18, 1–8) [ABSTRACT FROM PUBLISHER]

Abstract: Personality trait attribution can underpin important social decisions and yet requires little effort; even a brief exposure to a photograph can generate lasting impressions. Body movement is a channel readily available to observers and allows judgements to be made when facial and body appearances are less visible; e.g., from great distances. Across three studies, we assessed the reliability of trait judgements of point-light walkers and identified motion-related visual cues driving observers’ judgements. The findings confirm that observers make reliable, albeit inaccurate, trait judgements, and these were linked to a small number of motion components derived from a Principal Component Analysis of the motion data. Parametric manipulation of the motion components linearly affected trait ratings, providing strong evidence that the visual cues captured by these components drive observers’ trait judgements. Subsequent analyses suggest that reliability of trait ratings was driven by impressions of emotion, attractiveness and masculinity. [Copyright &y& Elsevier]

Assessing intentions, direction, and velocity of others is necessary for most daily tasks, and such information is often made available by both visual and auditory motion cues. Therefore, it is not surprising our great ability to perceive human motion. Here, we explore the multisensory integration of cues of biological motion walking speed. After testing for audiovisual asynchronies (visual signals led auditory ones by 30 ms in simultaneity temporal windows of 76.4 ms), in the main experiment, visual, auditory, and bimodal stimuli were compared to a standard audiovisual walker in a velocity discrimination task. Results in variance reduction conformed to optimal integration of congruent bimodal stimuli across all subjects. Interestingly, the perceptual judgements were still close to optimal for stimuli at the smallest level of incongruence. Comparison of slopes allows us to estimate an integration window of about 60 ms, which is smaller than that reported in audiovisual speech. [ABSTRACT FROM AUTHOR]

Abstract: There is evidence that human observers are more sensitive to the direction-of-heading of point-light walkers defined by first-order than second-order motions. We addressed this question by measuring the minimum direction difference (azimuth) that observers could discriminate when the dots composing the walkers were conveyed by first or second-order motions. Sensitivity to azimuth differences for four stimulus types (two first-order and two second-order) was tested at a range of stimulus sizes and at eccentricities of 0–16° in the right visual field. We find that for most stimulus types and eccentricities any azimuth threshold can be obtained by an appropriate adjustment of stimulus size. To achieve a given azimuth threshold second-order stimuli must be larger than the corresponding first-order stimuli. Therefore, stimulus magnification equates sensitivity to walker direction and we may say that sensitivity to walker direction is generally cue-independent. Similarly, in most cases stimulus magnification is sufficient to eliminate eccentricity dependent variability from the azimuth thresholds. Interestingly, the magnification required match peripheral to foveal thresholds increases faster with eccentricity for first-order stimuli than for second-order stimuli, while at the same time thresholds for first-order stimuli are lower than those for second-order stimuli at corresponding sizes and eccentricities. [Copyright &y& Elsevier]

Abstract: 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 walker-direction 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. [Copyright &y& Elsevier]

Biological motion perception—our capacity to perceive the intrinsic motion of humans and animals—has been implicated as a precursor of social development in infancy. In the adult brain, several biological motion neural correlates have been identified; of particular importance, the right posterior superior temporal sulcus (rpSTS). We present a study, conducted with fNIRS, which measured brain activations in infants' right posterior temporal region to point-light walkers, a standard stimulus category of biological motion perception studies. Seven-month-old infants (n = 23) participated in a within-subject blocked design with three experimental conditions and one baseline. Infants viewed: an intact upright point-light walker of a person approaching the observer; the same point-light walker stimulus but inverted; and a selected frame from the point-light walker stimulus, approaching the viewer at constant velocity with no articulated motion, close to object motion. We found activations for both the upright and the inverted point-light walkers. The rigid moving point-light walker frame did not elicit any response consistent with a functional activation in this region. Our results suggest that biological motion is processed differently in the right middle posterior temporal cortex in infancy, and that articulated motion is a critical feature in biological motion processing at this early age. • We measured infants' right temporal responses to biological motion using fNIRS. • Seven months old viewed a coherent point-light walker, an inverted point-light walker and a rigid moving point-light walker display. • The observation of both upright and inverted point-light walkers were associated to functional activations. • Infant's rSTS region responds to biological motion as early as 7-months. [ABSTRACT FROM AUTHOR]

When people walk side-by-side, they often synchronize their steps. To achieve this, individuals might cross-modally match audiovisual signals from the movements of the partner and kinesthetic, cutaneous, visual and auditory signals from their own movements. Because signals from different sensory systems are processed with noise and asynchronously, the challenge of the CNS is to derive the best estimate based on this conflicting information. This is currently thought to be done by a mechanism operating as a Maximum Likelihood Estimator (MLE). The present work investigated whether audiovisual signals from the partner are integrated according to MLE in order to synchronize steps during walking. Three experiments were conducted in which the sensory cues from a walking partner were virtually simulated. In Experiment 1 seven participants were instructed to synchronize with human-sized Point Light Walkers and/or footstep sounds. Results revealed highest synchronization performance with auditory and audiovisual cues. This was quantified by the time to achieve synchronization and by synchronization variability. However, this auditory dominance effect might have been due to artifacts of the setup. Therefore, in Experiment 2 human-sized virtual mannequins were implemented. Also, audiovisual stimuli were rendered in real-time and thus were synchronous and co-localized. All four participants synchronized best with audiovisual cues. For three of the four participants results point toward their optimal integration consistent with the MLE model. Experiment 3 yielded performance decrements for all three participants when the cues were incongruent. Overall, these findings suggest that individuals might optimally integrate audiovisual cues to synchronize steps during side-by-side walking., (Copyright © 2017 Elsevier B.V. All rights reserved.)

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.