Perception of biological motion by jumping spiders

The body of most creatures is composed of interconnected joints. During motion, the spatial location of these joints changes, but they must maintain their distances to one another, effectively moving semirigidly. This pattern, termed “biological motion” in the literature, can be used as a visual cue, enabling many animals (including humans) to distinguish animate from inanimate objects. Crucially, even artificially created scrambled stimuli, with no recognizable structure but that maintains semirigid movement patterns, are perceived as animated. However, to date, biological motion perception has only been reported in vertebrates. Due to their highly developed visual system and complex visual behaviors, we investigated the capability of jumping spiders to discriminate biological from nonbiological motion using point-light display stimuli. These kinds of stimuli maintain motion information while being devoid of structure. By constraining spiders on a spherical treadmill, we simultaneously presented 2 point-light displays with specific dynamic traits and registered their preference by observing which pattern they turned toward. Spiders clearly demonstrated the ability to discriminate between biological motion and random stimuli, but curiously turned preferentially toward the latter. However, they showed no preference between biological and scrambled displays, results that match responses produced by vertebrates. Crucially, spiders turned toward the stimuli when these were only visible by the lateral eyes, evidence that this task may be eye specific. This represents the first demonstration of biological motion recognition in an invertebrate, posing crucial questions about the evolutionary history of this ability and complex visual processing in nonvertebrate systems.

A Point-Light Display Model for Teaching Motor Skills to Children With Autism Spectrum Disorder: An Eye-Tracking Study

People with autism spectrum disorder (ASD) have limitations in their attention and working memory that affect their motor learning. The aim of current study was to compare point-light display (PLD) to video observation as instructional models for teaching motor skills to children with ASD versus typically developing (TD) children. We randomly assigned 24 children with ASD aged 6-17-years-old and 24 age paired typically developing (TD) children to four groups: (a) ASD-Video, (b) ASD-PLD, (c) TD-Video, and (d) TD-PLD. After twenty training blocks (200 trials), all participants entered into late retention and transfer testing. We recorded all participants’ visual gazes when observing each PLD and Video condition. Both PLD groups had better performance in the acquisition phase, and on retention and transfer tests. Also, gaze recordings revealed that children with ASD paid more attention to relevant demonstration points in the PLD than in the video condition. We discuss possible mechanisms and implications of these findings.

“I Like the Way You Move”: Validating the Use of Point-Light Display Animations in Virtual Reality as a Methodology for Manipulating Levels of Sexualization in the Study of Sexual Objectification

Sexual objectification of others has seen a growing research interest in recent years. While promising, the field lacks standardized stimuli, resulting in a confusion between sexualization and sexual objectification, which limits the interpretability of published results. In this study, we propose to use point-light display (PLD) as a novel methodology for manipulating sexualization levels as a first step toward isolating movement from other visual cues (e.g., clothing or physical appearance) for studying effects of sexual objectification of others. To do so, we first developed 8 virtual reality animations varying on 3 dimensions: 1) nature of movement (dance vs. walk), 2) level of sexualization (low vs. high), and 3) animation speed (slow and fast). Then, we validated these stimuli with perception ratings from 211 participants via an online survey. Using mixed linear regression models, we found evidence that our manipulation was successful: while participants took longer, were less accurate, and less confident in their response when confronted with a dancing, sexualized PLD, they also rated it as significantly more sexualized. This latter effect was stronger for participants perceiving a woman dancing compared to participants who perceived other genders. Overall, participants who reported more frequent sexual objectification behaviors also perceived the animations as more sexualized. Taken together, these results suggest that sexual suggestiveness can be manipulated by rather simple movement cues, thus validating the use of PLD as a stepping stone to systematically study processes of sexual objectification. From there, it is now possible to manipulate other variables more precisely during immersions in virtual reality, whether by adding a skin to the animated skeleton, by situating the PLD into different context, by varying the amplitude and the nature of the movements, or by modifying the context of the virtual environment.

Perception of biological motion in point-light displays by jumping spiders

Over the last 50 years, point-light displays have been successfully used to explore how animals respond to dynamic visual stimuli—specifically, differentiation of the biological from the non-biological. These stimuli are designed to preserve movement patterns while minimizing static detail, with single dots representing each of the main joints of a moving animal. Imposed by their internal skeleton, vertebrate movements follow a specific semi-rigid dynamic pattern, termed “biological-motion”, which can be used to distinguish animate from inanimate objects. Although biological motion detection has not been studied in invertebrates, rigid exoskeletons force many species to also follow semi-rigid movement principles. Due to their highly developed visual system and complex visual behaviors, we investigated the capability of jumping spiders to discriminate biological from non-biological motion using point-light display stimuli. By constraining spiders so that they could rotate but not move directionally, we simultaneously presented two point-light display stimuli with specific dynamic traits and registered their preference by observing which pattern they turned towards. Jumping spiders clearly demonstrated the ability to discriminate between stimuli. However, spiders showed no preference when both stimuli presented patterns with semi-rigid movements, results that are directly comparable to responses in vertebrate systems. This represents the first demonstration of biological motion recognition in an invertebrate, posing crucial questions about the evolutionary history of this ability and complex visual processing in non-vertebrate systems.

Seeing a drummer’s performance modulates the subjective experience of groove while listening to popular music drum patterns

Spontaneous rhythmical movements, like foot-tapping and head-bobbing, often emerge when people listen to music, promoting the enjoyable sensation of ‘being in the groove’. Here we report the first experiment to investigate if seeing the music maker modulates this experience. Across trials we manipulated groove level in the audio beats (high vs low), and manipulated the match between the audio beats and a concurrently observed point-light display (PLD) of the drummer. The visual display was either fully corresponding with the audio beats, or incompatible across three conditions: a static PLD, a corresponding but asynchronous PLD (0.5s time shifted); or a non-corresponding PLD (e.g. high groove audio paired with low groove PLD). Participants (n = 36) rated: (a) their desire to move; and (b) their perceived groove, purely in response to the audio beats, using 8-point Likert scales. The main effects of groove level and visual display were significant in both measurements. Ratings increased for high compared to low groove audio overall, and for the fully corresponding condition compared to the other visual conditions. Ratings of the desire to move also increased in the static compared to the non-corresponding condition, and the two-way interaction was significant. Desire to move significantly increased for high compared to low groove audio in the fully corresponding, static and asynchronous conditions, while this effect was absent in the non-corresponding condition. These findings identify the importance of seeing as well as hearing the musician for an enhanced experience of groove, which necessitates a multimodal account of music perception.

Biological Motion Detection in Rats

This study will examine the rodent visual system by assessing whether they can discriminate between various biological motion point‐light displays. Pilot data suggests that rats can discriminate between a human walker point‐light display walking left and right. Therefore this study will investigate which kind of information rats use to differentiate biological motion; the overall shape of the moving body (conformational theory) versus the local movement of the feet (ballistic motion theory). First, we will train the rats to discriminate between human point‐light displays walking in opposite directions using a modified Morris water maze. Then we will observe their reactions to a backwards‐walking display. If the rats use shape as a visual cue for biological motion, they will swim towards the goal arm that corresponds to the direction the backwards walker is facing. However, if the rats use ballistic motion as a visual cue for biological motion, they will swim towards the goal arm that corresponds to the direction the backwards walker is moving. We hypothesize that rats use the ballistic motion of the feet as a cue for life detection. This is the first study to investigate whether rats can detect biological motion, and will contribute to the theory that animals have evolved an innate ability to quickly detect biological motion of vital importance.