Beyond differences between the body schema and the body image: insights from body hallucinations

The distinction between the body schema and the body image has become the stock in trade of much recent work in cognitive neuroscience and philosophy. Yet little is known about the interactions between these two types of body representations. We need to account not only for their dissociations in rare cases, but also for their convergence most of the time. Indeed in our everyday life the body we perceive does not conflict with the body we act with. Are the body image and the body schema then somehow reshaping each other or are they relatively independent and do they only happen to be congruent? On the basis of the study of bodily hallucinations, we consider which model can best account for the body schema/body image interactions.     

Implicit body representations and the conscious body image

Recent studies have revealed that somatosensory processing relies on a class of implicit body representations showing large distortions of size and shape. The relation between these representations and the conscious body image remains unclear. Dissociations have been reported in the clinical literature on eating disorders between different body image measures, with larger and more consistent distortions found with depictive measures, in which participants compare their body to a visual depiction of a body, than metric measures, in which participants compare their body to some non-body standard. Here, we compared implicit body representations underlying position sense to the body image measured with both depictive and metric methods. The body image was measured using both a depictive method (template matching) in which participants judged whether their hand was wider or more slender than a shown hand picture, and a metric method (line length) in which participants judged whether different parts of their hand were shorter or longer than a presented line. Consistent with previous findings, characteristic distortions were found for the implicit body representation underlying position sense. These distortions were also found in attenuated form for metric - but not depictive - body image measures. While replicating the basic dissociation between implicit body representations and the conscious body image, these results demonstrate that this dissociation is not absolute and specific tasks may utilise both to varying degrees depending on task demands. Metric measures may not be pure measures of body image, but some combination of visual and somatosensory body representations.     

肢体形状和肢体动作表征的早期发展

肢体是社会性信息的重要载体。研究肢体表征的早期发展对于揭示其肢体表征加工的内在机制, 进一步理解婴儿的社会性发展具有重要意义。从肢体形状和肢体动作两个方面来看, 已有研究主要考察了婴儿在处理肢体结构信息和运动信息时的表征方式, 并提出了婴儿肢体表征发展机制的两种理论。未来应进一步明确婴儿肢体表征的具体发展过程及关键期, 并通过脑成像技术探究生物运动偏好对于肢体表征的作用机制。     

Visuo-tactile congruency influences the body schema during full body ownership illusion

Previous research showed that full body ownership illusions in virtual reality (VR) can be robustly induced by providing congruent visual stimulation, and that congruent tactile experiences provide a dispensable extension to an already established phenomenon. Here we show that visuo-tactile congruency indeed does not add to already high measures for body ownership on explicit measures, but does modulate movement behavior when walking in the laboratory. Specifically, participants who took ownership over a more corpulent virtual body with intact visuo-tactile congruency increased safety distances towards the laboratory’s walls compared to participants who experienced the same illusion with deteriorated visuo-tactile congruency. This effect is in line with the body schema more readily adapting to a more corpulent body after receiving congruent tactile information. We conclude that the action-oriented, unconscious body schema relies more heavily on tactile information compared to more explicit aspects of body ownership.     

Specifying the human body configuration

Three experiments investigated the specific spatial relations that define the human body configuration. In Experiment 1, participants searched for scrambled bodies amongst normal distractors. In Experiments 2 and 3 participants were asked to identify whether single body images (upright or inverted) were scrambled or normal. Scrambled bodies had head or limbs displaced to either symmetrical or asymmetrical positions. Experiment 1 showed that asymmetrical violations are recognized faster than symmetrical violations. All three experiments revealed that when the number of structural violations is held constant, head violations are recognized faster than limb violations. Experiment 3 also showed a greater inversion effect for scrambled bodies that maintained head on top and vertical symmetry, providing evidence that these are key spatial relations in the human body configuration. Overall, the results supported our hypothesis that the human body configuration is defined primarily by a head at the apex of a vertically symmetrical body.     

Wanting a body that's better than average: the effect of manipulated body norms on ideal body size perception

We examined the effect of body norms on ideal and current body size perception. In Study One, female participants were randomly assigned to one of three experimental conditions: (1) a thinner body norm, (2) a heavier body norm, or (3) no body norm. Body norms were manipulated by indicating a bogus "population average," and current and ideal body size perception were subsequently measured using a body silhouettes measure. Women had a thinner ideal body size in the thinner norm condition than in the heavier norm condition. Study Two replicated these results, but in a sample of young men and with regards to muscularity rather than thinness. Men had a more muscular ideal body size in the more muscular norm condition than in the less muscular norm condition. Current body size perception was also influenced by body norms, but only for women and after controlling for BMI.     

Threat of the thin-ideal body image and body malleability beliefs: effects on body image self-discrepancies and behavioral intentions

This study examined the effect of the threat aroused by the perception of thin-ideal images combined with beliefs about the malleability of the body on perceived/objective, ideal/objective and ought/objective body image self-discrepancies. An experimental computer program enabled women (N=82) to artificially increase or decrease the shape of their own body (previously photographed) in response to questions about their "actual", "ideal" and "ought" body self-perceptions. As predicted, results showed that women had greater body self-discrepancies when confronted with threatening thin ideals, regardless of their body mass index. The size of this trend depended on the way they were made to think of their body (malleable vs. fixed). Findings also suggested a possible relationship between body self-representations and eating behaviors or intentions. The impact of thin-ideal threats and body malleability beliefs on body perception is discussed.     

My body until proven otherwise: Exploring the time course of the full body illusion

Evidence from the Full Body Illusion (FBI) has shown that adults can embody full bodies which are not their own when they move synchronously with their own body or are viewed from a first-person perspective. However, there is currently no consensus regarding the time course of the illusion. Here, for the first time, we examined the effect of visuomotor synchrony (synchronous/asynchronous/no movement) on the FBI over time. Surprisingly, we found evidence of embodiment over a virtual body after five seconds in all conditions. Embodiment decreased with increased exposure to asynchronous movement, but remained high in synchronous and no movement conditions. We suggest that embodiment of a body seen from a first-person perspective is felt by default, and that embodiment can then be lost in the face of contradictory cues. These results have significant implications for our understanding of how multisensory cues contribute to embodiment.     

Masculine body ideologies as a non-gynocentric framework for the psychological study of the male body

Psychological research of the body disproportionately centers on body-appearance concerns. Grounded in women's experience of objectification, it neglects much of men's bodily experience. To address this we introduce Masculine Body Ideologies (MBI), a set of belief systems that prescribe how men should engage with their bodies. Three MBI ideal-types are identified and situated within broader masculinity ideologies: unattended, functional body ideology associated with traditional masculinity rooted in modern industrial society; metrosexual body ideology associated with post-industrial, consumer masculinity and reemploying signifiers of body functionality to form an objectified body esthetics; and holistic body ideology emphasizing inner-harmony, authenticity and expressivity, manifesting post-industrial trends of self-aware masculinity. As a normative framework, MBI underscores how similar body practices may be motivated by different body concerns associated with alternative body ideologies. This framework can clarify conceptual and empirical inconsistencies in studies of male body-appearance concerns and inform emerging research and mental-health considerations.     

On the methodology of body image assessment: the use of figural rating scales to evaluate body dissatisfaction and the ideal body standards of women

We examined the use of figural rating scales to measure body dissatisfaction and the ideal body standards of women. We also attended to the potential influence of demand characteristics in body assessment research using these measures, a methodological concern largely ignored in this field. We used both within- and between-subjects designs to assess whether women hold different body standards for themselves compared to their same sex peers and whether their own ideal body size (IBS) is different from what they think men prefer. Regardless of the method of data collection (within or between design), we failed to find any differences on separate items of body image ideals. The findings do provide evidence of robust and large effects for the current–ideal discrepancy as measured by figural rating scales, but argue against including multiple questions about ideal body preferences on these types of scales. Concerns about the influence of demand characteristics were not supported by the data.     

A computer-graphic technique for the study of body size perception and body types

We present a novel approach for measuring body size estimation in normal and eating-disordered women and men. Clinical categories of body types were used as prototypes. By comparing the subjective appearance of a person’s body with prototypes, we can understand how different attributes of his or her body shape contribute to perception of body size. After lifelike random distortions have been applied to parts of their body image, individuals adjust their body shapes until they converge on their perceived veridical appearance. Exaggeration and minimization of particular body areas measured with respect to their true shape and with different prototypes can be expressed as numerical deviations. In this way, perceived body size and body attractiveness can be appraised during the course of diagnosis and treatment of eating disorders.     

Avatar body dimensions and men's body image

Two online surveys examined the significance of the visual analogues, or ‘avatars’, men (total N = 266) create and use online. Two-dimensional (adiposity × muscle) somatomorphic matrices revealed that avatars are generally thinner than their creator's actual body and similar to their ideal, but more muscular than either their actual or ideal. Men's ratings of the importance of their avatar's appearance correlated with their actual weight and muscle concerns, and disparity between their avatar and actual body dimensions predicted their offline context body change concerns additional to that accounted for by disparity between their ideal and actual bodies. Together with the observation that men also reported higher self-esteem, less social interaction anxiety and less social phobia while online (which correlated with the time they spent online), these results suggest that the physical dimensions of avatars used in social interactions online may serve a compensatory function.     

Affective intentionality and the feeling body

This text addresses a problem that is not sufficiently dealt with in most of the recent literature on emotion and feeling. The problem is a general underestimation of the extent to which affective intentionality is essentially bodily. Affective intentionality is the sui generis type of world-directedness that most affective states – most clearly the emotions – display. Many theorists of emotion overlook the extent to which intentional feelings are essentially bodily feelings. The important but quite often overlooked fact is that the bodily feelings in question are not the regularly treated, non-intentional bodily sensations (known from Jamesian accounts of emotion), but rather crucial carriers of world-directed intentionality. Consequently, most theories of human emotions and feelings recently advocated are deficient in terms of phenomenological adequacy. This text tries to make up for this deficit and develops a catalogue of five central features of intentional bodily feelings. In addition, Jesse Prinz’s embodied appraisal theory is criticized as an exemplary case of the misconstrual of the bodily nature of affective experience in naturalistic philosophy of mind.

Self awareness and the body image

What mental representations give us the sense of our body as a unique object in the world? We investigated this issue in the context of the rubber hand illusion (RHI), an illusion of body image in which a prosthetic hand brushed synchronously, but not asynchronously, with one’s own hand is perceived as actually being one’s hand. We conducted a large-scale study of the RHI, and used psychometric analysis to reveal the structure of the subjective experience of embodiment [Longo et al. (2008). What is embodiment? A psychometric approach. Cognition,107, 978-998]. Here, we use this dataset to investigate the relation between incorporation of a rubber hand into the body image and the perceived similarity between the participant’s hand and the rubber hand. Objective similarity (as measured by skin luminance, hand shape, and third-person similarity ratings) did not appear to influence participants’ experience of the RHI. Conversely, incorporation of the rubber hand into the body image did affect the similarity that participants perceived between their own hand and the rubber hand. Participants who had experienced the RHI perceived their hand and the rubber hand as significantly more similar than participants who had not experienced the illusion. That is, embodiment leads to perceived similarity, but perceived similarity does not lead to embodiment. Furthermore, similarity ratings following the illusion were selectively correlated with some components of embodiment, but not with others. These results suggest an important role of a mental body image in the perception of the relation between the self and others.