Emotional modulation of visual remapping of touch

The perception of tactile stimuli on the face is modulated if subjects concurrently observe a face being touched; this effect is termed "visual remapping of touch" or the VRT effect. Given the high social value of this mechanism, we investigated whether it might be modulated by specific key information processed in face-to-face interactions: facial emotional expression. In two separate experiments, participants received tactile stimuli, near the perceptual threshold, either on their right, left, or both cheeks. Concurrently, they watched several blocks of movies depicting a face with a neutral, happy, or fearful expression that was touched or just approached by human fingers (Experiment 1). Participants were asked to distinguish between unilateral and bilateral felt tactile stimulation. Tactile perception was enhanced when viewing touch toward a fearful face compared with viewing touch toward the other two expressions. In order to test whether this result can be generalized to other negative emotions or whether it is a fear-specific effect, we ran a second experiment, where participants watched movies of faces-touched or approached by fingers-with either a fearful or an angry expression (Experiment 2). In line with the first experiment, tactile perception was enhanced when subjects viewed touch toward a fearful face and not toward an angry face. Results of the present experiments are interpreted in light of different mechanisms underlying different emotions recognition, with a specific involvement of the somatosensory system when viewing a fearful expression and a resulting fear-specific modulation of the VRT effect. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Focusing on the bodily self: The influence of endogenous attention on visual body processing

The present study explores whether endogenous attention can modulate body perception. A modified version of the Posner paradigm was used to direct participants' attention toward the appearance of distinct body images, which differed only in detailed idiosyncratic features: one's own and another person's hands. Hand stimuli were preceded by symbolic cues that predicted their identity with high probability, which made it possible to compare the processing of expected (valid) and unexpected (invalid) targets. Results revealed that endogenous attention influenced the processing of participants' own hands by speeding participants' responses to valid in contrast to invalid trials. Crucially, no validity effect was found for the hands of another person. These findings cannot be explained in terms of perceptual familiarity, since an optimization of the processing for both familiar and unfamiliar faces by symbolic cues was observed. In light of these results, it is suggested that participants are able to anticipate particular stimuli within the same perceptual category as long as these stimuli appear to be remarkably distinct to them, which is probably the case for particular faces and their own bodies, in contrast to other people's bodies.     

Visual capture of touch: out-of-the-body experiences with rubber gloves

When the apparent visual location of a body part conflicts with its veridical location, vision can dominate proprioception and kinesthesia. In this article, we show that vision can capture tactile localization. Participants discriminated the location of vibrotactile stimuli (upper, at the index finger, vs. lower, at the thumb), while ignoring distractor lights that could independently be upper or lower. Such tactile discriminations were slowed when the distractor light was incongruent with the tactile target (e.g., an upper light during lower touch) rather than congruent, especially when the lights appeared near the stimulated hand. The hands were occluded under a table, with all distractor lights above the table. The effect of the distractor lights increased when rubber hands were placed on the table, 'holding' the distractor lights, but only when the rubber hands were spatially aligned with the participant's own hands. In this aligned situation, participants were more likely to report the illusion of feeling touch at the rubber hands. Such visual capture of touch appears cognitively impenetrable.     

Holistic face encoding is modulated by perceived face race: Evidence from perceptual adaptation

Human expertise at processing faces relies on how facial features are encoded: as a whole template rather than as a sum of independent features. This holistic encoding is less prominent for other-race faces, possibly accounting for the difficulty one encounters in recognizing these faces (the ‘other-race effect’). Here, we tested the hypothesis that the magnitude of holistic face encoding can be modulated by racial categorization of the face. Caucasian participants performed a face-composite task with ‘racially-ambiguous’ face-stimuli (cross-race morphed faces, equally categorized as Asian or Caucasian faces in an independent task). The perceived race of the ambiguous faces was manipulated using adaptation. Experiment 1 showed that identical morphed face-stimuli were processed more holistically when perceived as ‘same-race’ than as ‘other-race’, i.e., following adaptation to ‘other-race’ versus ‘same-race’, respectively. Experiment 2 ascertained that the determining factor in the observed holistic processing modulation was the race of the racially-ambiguous face as perceived, rather than expected, by the participants, which supports the idea that the holistic processing of the face-stimuli was modulated by their race-categorization at the perceptual level.     

Perceptual asymmetries in face recognition

Four experiments were carried out to investigate perceptual asymmetries in face recognition. Perceptual asymmetries favoring the half-face on the observer's left were found under free viewing conditions for both unfamiliar faces (Experiment 1) and famous faces (Experiment 3). For unfamiliar faces, this asymmetry was not obtained when fixation was controlled by presenting faces tachistoscopically (Experiment 2). For famous faces, the perceptual asymmetry favoring the half-face normally seen on the left did not appear to be retained in memory (Experiments 3 and 4). Asymmetries in face perception have been explained in terms of a direct access model of laterally effects. However, these results raise the possibility that asymmetric scanning or attentional factors may be important.     

Infant brain responses to felt and observed touch of hands and feet: an MEG study

There is growing interest concerning the ways in which the human body, both one's own and that of others, is represented in the developing human brain. In two experiments with 7‐month‐old infants, we employed advances in infant magnetoencephalography (MEG) brain imaging to address novel questions concerning body representations in early development. Experiment 1 evaluated the spatiotemporal organization of infants’ brain responses to being touched. A punctate touch to infants’ hands and feet produced significant activation in the hand and foot areas of contralateral primary somatosensory cortex as well as in other parietal and frontal areas. Experiment 2 explored infant brain responses to visually perceiving another person's hand or foot being touched. Results showed significant activation in early visual regions and also in regions thought to be involved in multisensory body and self–other processing. Furthermore, observed touch of the hand and foot activated the infant's own primary somatosensory cortex, although less consistently than felt touch. These findings shed light on aspects of early social cognition, including action imitation, which may build, at least in part, on infant neural representations that map equivalences between the bodies of self and other.     

Other-race face perception

The other-race effect (or own-race bias or cross-racial identification effect) refers to the finding that recognition memory tends to be better for faces of members of subjects' own race than for faces of members of other races. The current study was designed to test the hypothesis that perceptual skills specific to identifying faces of particular racial groups contribute to this effect. On each of 50 trials, a photograph of a face was tachistoscopically presented for 120 ms, followed by a pattern mask and then a plain-view test pair composed of the previously presented face and a matched foil. As predicted, an other-race effect was obtained on this perceptual task: White subjects performed significantly more poorly on trials involving African American faces than on trials involving White faces, whereas no such difference was obtained among African American subjects.     

Attention to faces modulates early face processing during low but not high face discriminability

In the present study, we investigated whether attention to faces results in sensory gain modulation. Participants were cued to attend either to faces or to scenes in superimposed face—scene images for which face discriminability was manipulated parametrically. The face-sensitive N170 event-related potential component was used as a measure of early face processing. Attention to faces modulated N170 amplitude, but only when faces were not highly discriminable. Additionally, directing attention to faces modulated later processing (~230—300 msec) for all discriminability levels. These results demonstrate that attention to faces can modulate perceptual processing of faces at multiple stages of processing, including early sensory levels. Critically, the early attentional benefit is present only when the “face signal” (i.e., the perceptual quality of the face) in the environment is suboptimal.     

Touching on face space: Comparing visual and haptic processing of face shapes

The idea that faces are represented within a structured face space (Valentine Quarterly Journal of Experimental Psychology 43: 161–204, 1991) has gained considerable experimental support, from both physiological and perceptual studies. Recent work has also shown that faces can even be recognized haptically—that is, from touch alone. Although some evidence favors congruent processing strategies in the visual and haptic processing of faces, the question of how similar the two modalities are in terms of face processing remains open. Here, this question was addressed by asking whether there is evidence for a haptic face space, and if so, how it compares to visual face space. For this, a physical face space was created, consisting of six laser-scanned individual faces, their morphed average, 50 %-morphs between two individual faces, as well as 50 %-morphs of the individual faces with the average, resulting in a set of 19 faces. Participants then rated either the visual or haptic pairwise similarity of the tangible 3-D face shapes. Multidimensional scaling analyses showed that both modalities extracted perceptual spaces that conformed to critical predictions of the face space framework, hence providing support for similar processing of complex face shapes in haptics and vision. Despite the overall similarities, however, systematic differences also emerged between the visual and haptic data. These differences are discussed in the context of face processing and complex-shape processing in vision and haptics.     

Prosthesis embodiment and attenuation of prosthetic touch in upper limb amputees – A proof-of-concept study

Sensory attenuation of self-touch, that is, the perceptual reduction of self-generated tactile stimuli, is considered a neurocognitive basis for self-other distinction. However, whether this effect can also be found in upper limb amputees using a prosthesis is unknown. Thirteen participants were asked to touch their foot sole with a) their intact hand (self-touch), b) their prosthesis (prosthesis-touch), or c) let it be touched by another person (other-touch). Intensity of touch was assessed with a questionnaire. In addition, prosthesis embodiment was assessed in nine participants. Self-touch as well as prosthesis-touch was characterized by significant perceptual attenuation compared to other-touch, while self- and prosthesis-touch did not differ. The more embodied the prosthesis was, the more similar was its elicited touch perception to actual self-touch. These findings – although preliminary – suggest that perceptually embodied prostheses can be represented as an actual limb by the users’ sensorimotor system.     

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.     

The electrophysiological correlates of integrated face and body-part perception

Previous studies have suggested that the human visual system processes faces and bodies holistically—that is, the different body parts are integrated into a unified representation. However, the time course of this integrative process is less known. In the present study, we investigated this issue by recording event-related potentials evoked by a face and two hands presented simultaneously and in different configurations. When the hands were rotated to obtain a biologically implausible configuration, a reduction of the P2 amplitude was observed relative to the condition in which the face and hands were retained in their veridical configuration and were supplemented with visual cues to highlight further the overall body posture. Our results show that the P2 component is sensitive to manipulations affecting the configuration of face and hand stimuli and suggest that the P2 reflects the operation of perceptual mechanisms responsible for the integrated processing of visually presented body parts.     

Touchant-touché: the role of self-touch in the representation of body structure

The "body image" is a putative mental representation of one's own body, including structural and geometric details, as well as the more familiar visual and affective aspects. Very little research has investigated how we learn the structure of our own body, with most researchers emphasising the canonical visual representation of the body when we look at ourselves in a mirror. Here, we used non-visual self-touch in healthy participants to investigate the possibility that primary sensorimotor experience may influence cognitive representations of one's own body structure. Participants used the fingers of one hand (the 'active' hand), to touch the fingers of the other (the 'passive' hand). A conflict between the experience of the active and passive hand was introduced by experimenter interleaving their fingers with the fingers of the participant's passive hand. This led to the active hand experiencing that it touched more fingers than the passive hand felt it was being touched by. The effects on representation of body structure were assessed using an implicit measure based on Kinsbourne and Warrington's 'in-between task'. We found an underestimation of the number of fingers in the central part of the hand specifically linked to the experience of self-touch. This pattern of results corresponds to the experience of the passive hand, but not the active hand. Nevertheless, comparable reorganisation of fingers within the hand representation was found for both active and passive hands. We show that primary sensorimotor experience can modify the representation of body structure. This modification is driven by the passive experience of being touched, rather than by the active experience of touching. We believe this is the first experimental study of effects of self-touch on the mental representation of the body.     

Physical self-similarity enhances the gaze-cueing effect

Important social information can be gathered from the direction of another person's gaze, such as their intentions and aspects of the environment that are relevant to those intentions. Previous work has examined the effect of gaze on attention through the gaze-cueing effect: an enhancement of performance in detecting targets that appear where another person is looking. The present study investigated whether the physical self-similarity of a face could increase its impact on attention. Self-similarity was manipulated by morphing participants' faces with those of strangers. The effect of gaze direction on target detection was strongest for faces morphed with the participant's face. The results support previous work suggesting that self-similar faces are processed differently from dissimilar faces. The data also demonstrate that a face's similarity to one's own face influences the degree to which that face guides our attention in the environment.     

Tactile localization performance in children with developmental coordination disorder (DCD) corresponds to their motor skill and not their cognitive ability

When localizing touches to the hands, typically developing children and adults show a “crossed hands effect” whereby identifying which hand received a tactile stimulus is less accurate when the hands are crossed than uncrossed. This demonstrates the use of an external frame of reference for locating touches to one’s own body. Given that studies indicate that developmental vision plays a role in the emergence of external representations of touch, and reliance on vision for representing the body during action is atypical in developmental coordination disorder (DCD), we investigated external spatial representations of touch in children with DCD using the “crossed hands effect”. Nineteen children with DCD aged 7–11 years completed a tactile localization task in which posture (uncrossed, crossed) and view (hands seen, unseen) were varied systematically. Their performance was compared to that of 35 typically developing controls (19 of a similar age and cognitive ability, and 16 of a younger age but similar fine motor ability). Like controls, the DCD group exhibited a crossed hands effect, whilst their overall tactile localization performance was weaker than their peers of similar age and cognitive ability, but in line with younger controls of similar motor ability. For children with movement difficulties, these findings indicate tactile localization impairments in relation to age expectations, but apparently typical use of an external reference frame for localizing touch.     

Tactile sensitivity in Asperger syndrome

People with autism and Asperger syndrome are anecdotally said to be hypersensitive to touch. In two experiments, we measured tactile thresholds and suprathreshold tactile sensitivity in a group of adults with Asperger syndrome. In the first experiment, tactile perceptual thresholds were measured. Two frequencies of vibrotactile stimulation were used: 30 and 200 Hz. The results demonstrated significantly lower tactile perceptual thresholds in the Asperger group at 200 Hz but not at 30 Hz, thus confirming tactile hypersensitivity but only for one class of stimulus. A second experiment investigated whether self-produced movement affected the perception of touch in a group of adults with Asperger syndrome. A suprathreshold tactile stimulus was produced either by the participant (self-produced condition) or by the experimenter (externally produced condition) and participants were asked to rate the perception of the tactile stimulation. The results demonstrated that, while both Asperger and control groups rated self-produced touch as less tickly than external touch, the Asperger group rated both types of tactile stimulus as significantly more tickly and intense than did the control group. This experiment confirms the finding of tactile hypersensitivity, but shows that the perceptual consequences of self-produced touch are attenuated in the normal way in people with Asperger syndrome. An abnormality in this process cannot therefore account for their tactile hypersensitivity.     

Sensory and affective judgments of skin during inter- and intrapersonal touch

Here we report two experiments that investigated the tactile perception of one’s own skin (intrapersonal touch) versus the skin of other individuals (interpersonal touch). In the first experiment, thirteen female participants rated, along four perceptual attributes, the skin of their own palm and volar forearm, then that of several of the other participants. Ratings were made using visual analogue scales for perceived smoothness, softness, stickiness, and pleasantness. One’s own skin was rated less pleasant than the skin of others. For both intra- and interpersonal touch, the forearm skin was rated smoother, softer, less sticky and more pleasant than the palmar skin. In the second experiment, ten pairs of female participants rated each other’s palm and volar forearm skin, with the skin of the touched individual being assessed before and after the application of skin emollients that alter skin feel. As in the first experiment, the untreated skin of others was rated more pleasant than the participants’ own skin, and the forearm versus palm differences were replicated. However, the emollient had generally larger effects on self-assessments than the assessments of others, and the site effect showed greater positive sensory and pleasantness increases for palm versus volar forearm. The disparate results of the two experiments suggest that attention, influenced by the ecological importance of the stimulus, is more important to assessment of touched skin than ownership of the skin or the contribution to self-touch made by the additional receptors in the passively touched skin. In both experiments, the pleasantness of touched skin was associated with the skin’s perceived smoothness and softness, with weak trends toward negative associations with its perceived stickiness, consistent with prior research using inanimate surfaces (e.g., textiles and sandpapers).     

An ambiguous-race illusion in children's face memory

Adults show better memory for ambiguous faces of their own race than for ambiguous faces of another race, even when the faces are identical and differentiated only by extraneous cues to racial category. We investigated whether similar context effects operate early in development. Young children raised in predominantly White environments were presented with computer-generated White-Black morphed faces, each paired with either the White or the Black face that contributed to its construction, and were told that the two faces in each pair were siblings. The children's subsequent recognition memory was more accurate for faces that had been paired with White siblings than for faces that had been paired with Black siblings. The same effect did not obtain when the ambiguous faces were paired with White or Black faces that did not contribute to their construction and did not look like siblings. These findings suggest that face memory in children is not driven exclusively by visual information present in faces and instead depends on an interplay of categorical and perceptual information about race and relationships.     

Bayesian face recognition and perceptual narrowing in face-space

During the first year of life, infants' face recognition abilities are subject to 'perceptual narrowing', the end result of which is that observers lose the ability to distinguish previously discriminable faces (e.g. other-race faces) from one another. Perceptual narrowing has been reported for faces of different species and different races, in developing humans and primates. Though the phenomenon is highly robust and replicable, there have been few efforts to model the emergence of perceptual narrowing as a function of the accumulation of experience with faces during infancy. The goal of the current study is to examine how perceptual narrowing might manifest as statistical estimation in 'face-space', a geometric framework for describing face recognition that has been successfully applied to adult face perception. Here, I use a computer vision algorithm for Bayesian face recognition to study how the acquisition of experience in face-space and the presence of race categories affect performance for own and other-race faces. Perceptual narrowing follows from the establishment of distinct race categories, suggesting that the acquisition of category boundaries for race is a key computational mechanism in developing face expertise.     

知觉场理论对面孔知觉年龄偏差效应的解释

使用融合面孔范式和倒置面孔范式来研究面孔知觉的年龄偏差效应,检验知觉场能否作为面孔整体加工的指标,并以此发展年龄偏差的整体加工解释。结果发现：（1）成人和儿童在加工正立面孔时的知觉场均大于加工倒置面孔时的知觉场;（2）在加工正立面孔时,成人加工本年龄面孔比加工他年龄面孔的知觉场更大。上述结果表明：（1）知觉场大小可以作为面孔整体加工的指标,且受面孔朝向的影响;（2）知觉场假设可以解释面孔的年龄偏差效应。