Configural processing in body posture recognition: an eye-tracking study

Intermodulation responses show integration of interacting bodies in a new whole

People are often seen among other people, relating to and interacting with one another. Recent studies suggest that socially relevant spatial relations between bodies, such as the face-to-face positioning, or facingness, change the visual representation of those bodies, relative to when the same items appear unrelated (e.g., back-to-back) or in isolation. The current study addresses the hypothesis that face-to-face bodies give rise to a new whole, an integrated representation of individual bodies in a new perceptual unit. Using frequency-tagging EEG, we targeted, as a measure of integration, an EEG correlate of the non-linear combination of the neural responses to each of two individual bodies presented either face-to-face as if interacting, or back-to-back. During EEG recording, participants (N = 32) viewed two bodies, either face-to-face or back-to-back, flickering at two different frequencies (F1 and F2), yielding two distinctive responses in the EEG signal. Spectral analysis examined the responses at the intermodulation frequencies (nF1±mF2), signaling integration of individual responses. An anterior intermodulation response was observed for face-to-face bodies, but not for back-to-back bodies, nor for face-to-face chairs and machines. These results show that interacting bodies are integrated into a representation that is more than the sum of its parts. This effect, specific to body dyads, may mark an early step in the transformation towards an integrated representation of a social event, from the visual representation of individual participants in that event.

Inversion Effect of Hand Postures: Effect of Visual Experience Over Long and Short Term

Some researchers argue that holistic processing is unique to face recognition supported by the face inversion effect. However, findings such as the body inversion effect challenge the face processing-specificity hypothesis, thus supporting the expertise hypothesis. Few studies have explored a possible hand inversion effect which could involve special processing similar to the face and body. We conducted four experiments to investigate the time course and flexibility of the hand posture inversion effect. We utilized a same/different discrimination task (Experiments 1 and 2), an identification task (Experiment 3), and a training paradigm involving the exposure of different hand orientations (Experiment 4). The results show the hand posture inversion effect (with fingers up as upright orientation) was not initially observed during the early phase of testing, but occurred in later phases. This suggests that both lifetime experience and recent exposure affect the hand posture inversion effect. We also found the hand posture inversion effect, once established, was stable across days and remained consistent across different tasks. In addition, the hand posture inversion effect for specific orientations could be obtained with short-term training of a given orientation, indicating the cognitive process is flexible.

A multilevel Bayesian meta-analysis of the body inversion effect: Evaluating controversies over headless and sexualized bodies

Face and body perception rely on specialized processing mechanisms to interpret social information efficiently. The body inversion effect (BIE), refers to an inversion effect for bodies, such that recognition of bodies is impaired by inversion. The BIE, like the face inversion effect (FIE), is particularly important because a disproportionate BIE relative to inversion effects for objects could be interpreted in much the same way as the disproportionate FIE has often been characterized; that is, as evidence of specialized, configural processing. However, research supporting the BIE is marked by methodological heterogeneity and mixed findings. Our multilevel Bayesian meta-analysis addresses inconsistencies in the literature by pooling data from numerous studies to estimate the magnitude of the BIE across various methodological and stimulus properties. We included 180 effect sizes from 41 empirical articles representing data from 2,274 participants. Overall, we found that the BIE was moderate-large in magnitude (Hedges' g = 0.75). Importantly, the inversion effect was larger for bodies than objects (b = 0.42); however, the inversion effect for faces was larger than for bodies (b = 0.34). We tested the role of discrimination dimension, stimulus type, face/head inclusion, stimulus sexualization, and sexualized stimulus sex as moderators of the BIE. We found that the BIE was moderated by discrimination dimension, stimulus type, stimulus sexualization, and sexualized stimulus sex. By synthesizing the existing literature, we provide a better theoretical understanding of how underlying visual processing mechanisms may differ for different types of social information (i.e., bodies vs. faces).

Body-Posture Recognition by Undergraduate Students Majoring in Physical Education and Other Disciplines

Humans are more proficient at processing visual display of body posture when the body is in upright orientation, compared to when inverted (inversion effect). Here we investigated whether extensive exposure or expertise on body posture recognition would affect the efficiency with which body-posture is processed. Using whole-body and piecemeal-body postures as stimuli, we performed two experiments to investigate whether body-posture recognition differed between two groups of participants: undergraduates majoring in physical education (PE) and those in other subjects (non-PE), respectively. These two groups differed significantly in the frequency and intensity of exercise per day and/or accumulated exercise time. In our experiments, following initial presentation of an image of a body posture, participants were shown the same or a different stimulus and were asked to report whether or not they had been previously shown the same image. The orientations of the body postures were also varied between trials. Our results showed that, in Experiment 1, for whole-body posture recognition, both the PE and non-PE groups showed a robust body-inversion effect in terms of both error rate and reaction time (RT), but the magnitude of the body-inversion effect in the RT measure was greater in the PE than the non-PE group. In Experiment 2, for piecemeal-body postures, both groups showed the inversion effect in terms of both error rate and RT measures and the PE group made fewer overall errors than the non-PE group. These cumulative results suggest that a superiority effect exists for PE participants compared with non-PE participants. Our results are generally consistent with the expertise hypothesis.

Visual exploration of emotional body language: a behavioural and eye-tracking study

Bodily postures are essential to correctly comprehend others' emotions and intentions. Nonetheless, very few studies focused on the pattern of eye movements implicated in the recognition of emotional body language (EBL), demonstrating significant differences in relation to different emotions. A yet unanswered question regards the presence of the "left-gaze bias" (i.e. the tendency to look first, to make more fixations and to spend more looking time on the left side of centrally presented stimuli) while scanning bodies. Hence, the present study aims at exploring both the presence of a left-gaze bias and the modulation of EBL visual exploration mechanisms, by investigating the fixation patterns (number of fixations and latency of the first fixation) of participants while judging the emotional intensity of static bodily postures (Angry, Happy and Neutral, without head). While results on the latency of first fixations demonstrate for the first time the presence of the left-gaze bias while scanning bodies, suggesting that it could be related to the stronger expressiveness of the left hand (from the observer's point of view), results on fixations' number only partially fulfil our hypothesis. Moreover, an opposite viewing pattern between Angry and Happy bodily postures is showed. In sum, the present results, by integrating the spatial and temporal dimension of gaze exploration patterns, shed new light on EBL visual exploration mechanisms.

Perceived match between own and observed models' bodies: influence of face, viewpoints, and body size

People are generally unable to accurately determine their own body measurements and to translate this knowledge to identifying a model/avatar that best represents their own body. This inability has not only been related to health problems (e.g. anorexia nervosa), but has important practical implications as well (e.g. online retail). Here we aimed to investigate the influence of three basic visual features—face presence, amount of viewpoints, and observed model size—on the perceived match between own and observed models’ bodies and on attitudes towards these models. Models were real-life models (Experiment 1) or avatar models based on participants’ own bodies (Experiment 2). Results in both experiments showed a strong effect of model size, irrespective of participants’ own body measurements. When models were randomly presented one by one, participants gave significantly higher ratings to smaller- compared to bigger-sized models. The reverse was true, however, when participants observed and compared models freely, suggesting that the mode of presentation affected participants’ judgments. Limited evidence was found for an effect of facial presence or amount of viewpoints. These results add evidence to research on visual features affecting the ability to match observed bodies with own body image, which has biological, clinical, and practical implications.

Character drawing style in cartoons on empathy induction: an eye-tracking and EEG study

In its most basic form, empathy refers to the ability to understand another person’s feelings and emotions, representing an essential component of human social interaction. Owing to an increase in the use of mass media, which is used to distribute high levels of empathy-inducing content, media plays a key role in individual and social empathy induction. We investigated empathy induction in cartoons using eye movement, EEG and behavioral measures to explore whether empathy factors correlate with character drawing styles. Two different types of empathy-inducing cartoons that consisted of three stages and had the same story plot were used. One had an iconic style, while the other was realistic style. Fifty participants were divided into two groups corresponding to the individual cartoon drawing styles and were presented with only one type of drawing style. We found that there were no significant differences of empathy factors between iconic and realistic style. However, the Induced Empathy Score (IES) had a close relationship with subsequent attentional processing (total fixation length for gaze duration). Furthermore, iconic style suppressed the fronto-central area more than realistic style in the gamma power band. These results suggest that iconic cartoons have the advantage of abstraction during empathy induction, because the iconic cartoons induced the same level of empathy as realistic cartoons while using the same story plot (top-down process), even though lesser time and effort were required by the cartoon artist to draw them. This also means that the top-down process (story plot) is more important than the bottom-up process (drawing style) in empathy induction when viewing cartoons

The perception of (naked only) bodies and faceless heads relies on holistic processing: Evidence from the inversion effect

Faces and bodies are more difficult to perceive when presented inverted than when presented upright (i.e., stimulus inversion effect), an effect that has been attributed to the disruption of holistic processing. The features that can trigger holistic processing in faces and bodies, however, still remain elusive. In this study, using a sequential matching task, we tested whether stimulus inversion affects various categories of visual stimuli: faces, faceless heads, faceless heads in body context, headless bodies naked, whole bodies naked, headless bodies clothed, and whole bodies clothed. Both accuracy and inversion efficiency score results show inversion effects for all categories but for clothed bodies (with and without heads). In addition, the magnitude of the inversion effect for face, naked body, and faceless heads was similar. Our findings demonstrate that the perception of faces, faceless heads, and naked bodies relies on holistic processing. Clothed bodies (with and without heads), on the other side, may trigger clothes-sensitive rather than body-sensitive perceptual mechanisms.

Where You Look Matters for Body Perception: Preferred Gaze Location Contributes to the Body Inversion Effect

The Body Inversion Effect (BIE; reduced visual discrimination performance for inverted compared to upright bodies) suggests that bodies are visually processed configurally; however, the specific importance of head posture information in the BIE has been indicated in reports of BIE reduction for whole bodies with fixed head position and for headless bodies. Through measurement of gaze patterns and investigation of the causal relation of fixation location to visual body discrimination performance, the present study reveals joint contributions of feature and configuration processing to visual body discrimination. Participants predominantly gazed at the (body-centric) upper body for upright bodies and the lower body for inverted bodies in the context of an experimental paradigm directly comparable to that of prior studies of the BIE. Subsequent manipulation of fixation location indicates that these preferential gaze locations causally contributed to the BIE for whole bodies largely due to the informative nature of gazing at or near the head. Also, a BIE was detected for both whole and headless bodies even when fixation location on the body was held constant, indicating a role of configural processing in body discrimination, though inclusion of the head posture information was still highly discriminative in the context of such processing. Interestingly, the impact of configuration (upright and inverted) to the BIE appears greater than that of differential preferred gaze locations.

Behavioral and electrophysiological measures of the body inversion effect: the contribution of the limb configurations

Previous behavioral and electrophysiological studies examining the body inversion effect, where inversion of a body stimulus reduces its recognition, suggested that information regarding human bodies is processed configurally. However, few studies to date have examined how the magnitude of the body inversion effect may be impacted by varying degrees of configural information present in a stimulus of interest. In the current study, upright and inverted body stimuli were presented across three body posture conditions, the whole body, piecemeal body (without head and trunk), and random body posture conditions, while response times, error rates, and event-related potentials were recorded. Behavioral measures and assessment of the N170 component, particularly at occipital-temporal site, revealed a robust difference between upright and inverted postures for both the whole body and piecemeal body posture conditions, which was not observed in the random body posture condition. The behavioral measure showed less errors and faster reaction times for upright compared with inverted orientation; however, the N170 component only showed typical effect of orientation (more negative and more delayed peak in waveform for the inverted compared with upright orientation) in the left hemisphere. The magnitude and direction of these differences were comparable for whole body and piecemeal postures. Overall, these results were consistent with the notion that it is the first-order information of body posture rather than the presence of the head (and trunk) that determines the body inversion effect.

Dissociation between the behavioural and electrophysiological effects of the face and body composite illusions

Several studies have reported similarities between perceptual processes underlying face and body perception, particularly emphasizing the importance of configural processes. Differences between the perception of faces and the perception of bodies were observed by means of a manipulation targeting a specific subtype of configural processing: the composite illusion. The composite face illusion describes the fact that two identical top halves of a face are perceived as being different if they are presented with different bottom parts. This effect disappears, if both halves are laterally shifted. Crucially, the effect of misalignment is not observed for bodies. This study aimed to further explore differences in the time course of face and body perception by using the composite effect. The present results replicated behavioural effects illustrating that misalignment affects the perception of faces but not bodies. Thus, face but not body perception relies on holistic processing. However, differences in the time course of the processing of both stimulus categories emerged at the N170 and P200. The pattern of the behavioural data seemed to be related to the P200. Thus, the present data indicate that holistic processes associated with the effect of misalignment might occur 200 ms after stimulus onset.