Reference frames for orientation anisotropies in face recognition and biological-motion perception

Both face recognition and biological-motion perception are strongly orientation-dependent. Recognition performance decreases if the stimuli are rotated with respect to their normal upright orientation. Here, the question whether this effect operates in egocentric coordinates or in environmental coordinates is examined. In addition to the use of rotated stimuli the observers were also rotated and tested both with a same-different face-recognition task and with a biological-motion detection task. A strong orientation effect was found that depended only on the stimulus orientation relative to the observer. This result clearly indicates that orientation effects in both stimulus domains operate in an egocentric frame of reference. This finding is discussed in terms of the particular requirement of extracting sophisticated information for social recognition and communication from faces and biological motion.     

Two reference frames for visual perception in two gravity conditions

The processing and storage of visual information concerning the orientation of objects in space is carried out in anisotropic reference frames in which all orientations are not treated equally. The perceptual anisotropies, and the implicit reference frames that they define, are evidenced by the observation of 'oblique effects' in which performance on a given perceptual task is better for horizontally and vertically oriented stimuli. The question remains how the preferred horizontal and vertical reference frames are defined. In these experiments cosmonaut subjects reproduced the remembered orientation of a visual stimulus in 1g (on the ground) and in 0g, both attached to a chair and while free-floating within the International Space Station. Results show that while the remembered orientation of a visual stimulus may be stored in a multimodal reference frame that includes gravity, an egocentric reference is sufficient to elicit the oblique effect when all gravitational and haptic cues are absent.     

Egocentric reference frame bias in the palmar haptic perception of surface orientation

The effect of egocentric reference frames on palmar haptic perception of orientation was investigated in vertically separated locations in a sagittal plane. Reference stimuli to be haptically matched were presented either haptically (to the contralateral hand) or visually. As in prior investigations of haptic orientation perception, a strong egocentric bias was found, such that haptic orientation matches made in the lower part of personal space were much lower (i.e., were perceived as being higher) than those made at eye level. The same haptic bias was observed both when the reference surface to be matched was observed visually and when bimanual matching was used. These findings support the conclusion that, despite the presence of an unambiguous allocentric (gravitational) reference frame in vertical planes, haptic orientation perception in the sagittal plane reflects an egocentric bias.     

The effect of face orientation on holistic processing

Holistic processing, a hallmark of face processing, can be measured by the composite face effect: adults have difficulty recognising the top half of a face when it is aligned with a new bottom half, unless holistic processing is disrupted by misaligning the two halves. Like the recognition of facial identity, holistic processing is impaired when faces are inverted. To obtain a more refined measure of the influence of orientation on holistic face processing, we administered the composite face task to adults at each of seven orientations. In both experiment 1 (in which orientations were randomly intermixed) and experiment 2 (in which orientations were blocked), the composite face effect decreased linearly with rotation. We conclude that holistic processing is tuned to upright faces, diminishes as faces deviate from upright, and becomes insignificant once faces reach a sideways orientation. We propose a hierarchical model of face perception in which linear decreases in holistic processing underlie qualitative shifts in other aspects of face perception.     

听障和听力正常人群空间主导性和空间参照框架的交互作用

通过要求被试分别在近处空间和远处空间完成空间参照框架的判断任务, 考察了听障和听力正常人群空间主导性和空间参照框架的交互作用。结果表明：(1)相对于听力正常人群, 听障人群完成自我参照框架判断任务的反应时更长, 而在完成环境参照框架判断任务无显著差异; (2)听障人群和听力正常人群空间主导性和空间参照框架交互作用呈现出相反模式。研究表明, 听障人群在听力功能受损后, 其空间主导性和空间参照框架的交互作用也产生了变化。     

The Thatcher illusion: rotating the viewer instead of the picture

Faces are difficult to recognise when presented upside down. This effect of face inversion was effectively demonstrated with the 'Thatcher illusion' by Thompson (1980 Perception 9 483-484). It has been tacitly assumed that this effect is due to inversion relative to retinal coordinates. Here we tested whether it is due to egocentric (i.e. retinal) inversion or whether the orientation of the body with respect to gravity also influences the face-inversion effect. A 3-D human turntable was used to test subjects in 5 different body-tilt (roll) orientations: 0 degree, 45 degrees, 90 degrees, 135 degrees, and 180 degrees. The stimuli consisted of 4 'normal' and 4 'thatcherised' faces and were presented in 8 different orientations in the picture plane. The subjects had to decide in a yes-no task whether the faces were 'normal' or 'thatcherised'. Analysis of the d' values revealed a significant effect of stimulus orientation and body tilt. The significant effect of body tilt was due to a drop in d' values in the 135 degrees orientation. This result is compared to findings of studies on the subjective visual vertical, where larger errors occurred in body-tilt orientations between 90 degrees and 180 degrees. The present findings suggest that the face-inversion effect relies mainly on retinal coordinates, but that in head-down body-tilt orientations around 135 degrees the gravitational reference frame has a major influence on the perception of faces.     

An egocentric frame of reference in implicit motor sequence learning

We investigated which frame of reference is evoked during implicit motor sequence learning. Participants completed a typical serial reaction time task. In the first experiment, we isolated egocentric and allocentric frames of reference and found that learning was solely in an egocentric reference frame. In a second experiment, we isolated hand-centered space from other egocentric frames of reference. We found that for a one-handed sequencing task, the sequence was coded in an egocentric reference frame but not a hand-centered reference frame. Our results are restricted to implicit learning of novel sequences in the early stages of learning. These findings are consistent with claims that the neural mechanisms involved in motor skill learning operate in egocentric coordinates.     

Haptic parallelity perception on the frontoparallel plane: the involvement of reference frames

It has been established that spatial representation in the haptic modality is subject to systematic distortions. In this study, the haptic perception of parallelity on the frontoparallel plane was investigated in a bimanual matching paradigm. Eight reference orientations and 23 combinations of stimulus locations were used. The current hypothesis from studies conducted on the horizontal and midsagittal planes presupposes that what is haptically perceived as parallel is a product of weighted contributions from both egocentric and allocentric reference frames. In our study, we assessed a correlation between deviations from the veridical and hand/arm postures and found support for the role of an intermediate frame of reference in modulating haptic parallelity on the frontoparallel plane as well. Moreover, a subject-dependent biasing influence of the egocentric reference frame determines both the reversal of the oblique effect and a scaling effect in deviations as a function of bar position.     

空间场景表征中的参照系选取

被试在矩形房间中从两个不同的观察点学习物体场景并在多个朝向上对物体形成的空间关系进行判断,通过控制场景中物体主要内在轴相对于环境结构（房间和地毯）的方向和被试的学习顺序,探讨被试在场景空间表征中采用何种参照系和参照系选取时的影响因素。两个实验结果发现：（1）内在参照系（intrinsic reference systems）和环境参照系均可以用于物体场景的表征,两类参照系之间的关系却是影响被试物体场景表征时参照系选取的重要因素,即当内在参照系与环境参照系方向一致时,被试无论从哪个朝向学习,都选择从垂直于内在参照系和环境参照系的朝向进行表征。反之,当二者方向不一致时,表征时参照系的选择取决于被试的学习经历;（2）无论内在参照系与环境参照系方向是否一致,物体场景本身内在结构的规则性都能够促进空间记忆,即内在结构的规则性既有助于准确编码物体的相对位置,也有助于提高空间关系判断的准确性。     

空间参照框架的产生机制及与认知机能的关系

空间参照框架是个体表征空间方位的方式, 按照表征中心的不同分为自我中心和环境中心两种参照框架。长期对某一参照框架的持续激活可以形成对该空间参照框架的偏好, 不仅会影响个体的神经元结构, 还会对认知机能产生重要影响。偏好环境中心参照框架会增加海马及其附近脑区的灰质, 而偏好自我中心参照框架会增加尾状核的灰质。海马灰质体积增大会增强正常人的空间记忆能力。持续激活环境中心参照框架的个体会增加海马灰质体积, 从而降低患老年痴呆的风险。未来研究应关注, 地域差异、城乡差异等环境差异在空间参照框架与认知机能关系中的影响机制, 并进一步收集空间参照框架训练在老年痴呆病人中干预效果的实证证据。     

Haptic experiences influence visually acquired memories: Reference frames during multimodal spatial learning

In two experiments, we investigated whether reference frames acquired through touch could influence memories for locations learned through vision. Participants learned two objects through touch, and haptic egocentric (Experiment 1) and environmental (Experiment 2) cues encouraged selection of a specific reference frame. Participants later learned eight new objects through vision. Haptic cues were manipulated, whereas visual learning was held constant in order to observe any potential influence of the haptically experienced reference frame on memories for visually learned locations. When the haptically experienced reference frame was defined primarily by egocentric cues, cue manipulation had no effect on memories for objects learned through vision. Instead, visually learned locations were remembered using a reference frame selected from the visual study perspective. When the haptically experienced reference frame was defined by both egocentric and environmental cues, visually learned objects were remembered in the context of the haptically experienced reference frame. These findings support the common reference frame hypothesis, which proposes that locations learned through different sensory modalities are represented within a common reference frame.     

Conscious awareness is required for holistic face processing

Investigating the limits of unconscious processing is essential to understand the function of consciousness. Here, we explored whether holistic face processing, a mechanism believed to be important for face processing in general, can be accomplished unconsciously. Using a novel “eyes-face” stimulus we tested whether discrimination of pairs of eyes was influenced by the surrounding face context. While the eyes were fully visible, the faces that provided context could be rendered invisible through continuous flash suppression. Two experiments with three different sets of face stimuli and a subliminal learning procedure converged to show that invisible faces did not influence perception of visible eyes. In contrast, surrounding faces, when they were clearly visible, strongly influenced perception of the eyes. Thus, we conclude that conscious awareness might be a prerequisite for holistic face processing.     

Effects of visual information regarding allocentric processing in haptic parallelity matching

Research has revealed that haptic perception of parallelity deviates from physical reality. Large and systematic deviations have been found in haptic parallelity matching most likely due to the influence of the hand-centered egocentric reference frame. Providing information that increases the influence of allocentric processing has been shown to improve performance on haptic matching. In this study allocentric processing was stimulated by providing informative vision in haptic matching tasks that were performed using hand- and arm-centered reference frames.     

The relationship perceived between the real body and the mirror image

We analyse here people's perception of their reflections in mirrors placed in different positions. In two experiments, participants looked at their mirror image, in a third experiment they looked at another person's image. In both cases they were asked to answer a series of questions about how the virtual body appeared relative to the real body, focusing on different aspects. In experiment 1, they were asked to decide whether the reflections were identical, similar, different, or opposite in terms of the global relationship, orientation, and lateralisation (left right arm). In experiment 2 they were instructed to make simple gestures and to evaluate if the gestures in the reflection were identical, opposite, similar, or different from theirs. Results show that 'identity' was preferred when the mirror was in front, and 'opposition' was preferred when the mirror was below. When opposition was experienced, it was attributed mainly to the exocentric frame of reference. Egocentric left-right reversal was not a common experience, although it was reported more frequently when the mirror was in front. The different roles of the exocentric and egocentric frames of reference were further tested in experiment 3, in which the condition of an observer looking at another person's reflection was studied. Contrary to the emphasis on the egocentric frame of reference in the literature on the 'mirror question', results presented in this paper demonstrate the importance of the exocentric frame of reference in influencing how observers react to their reflections.     

面孔认知的四个层面及FFA在其中的作用

面孔具有明显不同于其他刺激物的特点,面孔认知的目的也因此与其他物体认知的目的大相径庭。依据面孔认知的目的,本文将面孔认知划分为四个层面：将面孔区别于一般物体的第一层面,对面孔物理属性进行识别的第二层面,对面孔的生物属性进行识别的第三层面和对面孔的社会属性进行识别的第四层面。FFA是面孔加工的一个重要脑区,通过论述它对面孔认知各层面的作用,FFA在面孔加工中的作用被进一步明确。     

The reference frame for encoding and retention of motion depends on stimulus set size

The goal of this study was to investigate the reference frames used in perceptual encoding and storage of visual motion information. In our experiments, observers viewed multiple moving objects and reported the direction of motion of a randomly selected item. Using a vector-decomposition technique, we computed performance during smooth pursuit with respect to a spatiotopic (nonretinotopic) and to a retinotopic component and compared them with performance during fixation, which served as the baseline. For the stimulus encoding stage, which precedes memory, we found that the reference frame depends on the stimulus set size. For a single moving target, the spatiotopic reference frame had the most significant contribution with some additional contribution from the retinotopic reference frame. When the number of items increased (Set Sizes 3 to 7), the spatiotopic reference frame was able to account for the performance. Finally, when the number of items became larger than 7, the distinction between reference frames vanished. We interpret this finding as a switch to a more abstract nonmetric encoding of motion direction. We found that the retinotopic reference frame was not used in memory. Taken together with other studies, our results suggest that, whereas a retinotopic reference frame may be employed for controlling eye movements, perception and memory use primarily nonretinotopic reference frames. Furthermore, the use of nonretinotopic reference frames appears to be capacity limited. In the case of complex stimuli, the visual system may use perceptual grouping in order to simplify the complexity of stimuli or resort to a nonmetric abstract coding of motion information.     

Disrupting perceptual grouping of face parts impairs holistic face processing

Face perception is widely believed to involve integration of facial features into a holistic perceptual unit, but the mechanisms underlying this integration are relatively unknown. We examined whether perceptual grouping cues influence a classic marker of holistic face perception, the “composite-face effect.” Participants made same–different judgments about a cued part of sequentially presented chimeric faces, and holistic processing was indexed as the degree to which the task-irrelevant face halves impacted performance. Grouping was encouraged or discouraged by adjusting the backgrounds behind the face halves: Although the face halves were always aligned, their respective backgrounds could be misaligned and of different colors. Holistic processing of face, but not of nonface, stimuli was significantly reduced when the backgrounds were misaligned and of different colors, cues that discouraged grouping of the face halves into a cohesive unit (Exp. 1). This effect was sensitive to stimulus orientation at short (200 ms) but not at long (2,500 ms) encoding durations, consistent with the previously documented temporal properties of the holistic processing of upright and inverted faces (Exps. 2 and 3). These results suggest that grouping mechanisms, typically involved in the perception of objecthood more generally, might contribute in important ways to the holistic perception of faces.     

The effect of embodying the elderly on time perception

The present study investigated the perception of stimulus durations represented by elderly faces or by young faces. In a temporal bisection task, participants classified intermediate durations as more similar to a short or a long reference duration. The results showed that the durations represented by elderly faces were less often classified as “long” than the durations represented by young faces. According to internal clock models of time perception, this shortening effect is due to a slowing down of the speed of the internal clock during the perception of elderly faces. Analyses also revealed an interaction between sex of face and sex of participant such that this shortening effect occurred only when the participants share the same sex than the stimulus faces. As discussed, this finding is quite consistent with embodied cognition approaches to information processing, but alternatives accounts are also considered.     

Investigating the effects of inversion on configural processing with an audiovisual temporal-order judgment task

Research has shown that inversion is more detrimental to the perception of faces than to the perception of other types of visual stimuli. Inverting a face results in an impairment of configural information processing that leads to slowed early face processing and reduced accuracy when performance is tested in face recognition tasks. We investigated the effects of inverting speech and non-speech stimuli on audiovisual temporal perception. Upright and inverted audiovisual video clips of a person uttering syllables (experiments 1 and 2), playing musical notes on a piano (experiment 3), or a rhesus monkey producing vocalisations (experiment 4) were presented. Participants made unspeeded temporal-order judgments regarding which modality stream (auditory or visual) appeared to have been presented first. Inverting the visual stream did not have any effect on the sensitivity of temporal discrimination responses in any of the four experiments, thus implying that audiovisual temporal integration is resilient to the effects of orientation in the picture plane. By contrast, the point of subjective simultaneity differed significantly as a function of orientation only for the audiovisual speech stimuli but not for the non-speech stimuli or monkey calls. That is, smaller auditory leads were required for the inverted than for the upright-visual speech stimuli. These results are consistent with the longer processing latencies reported previously when human faces are inverted and demonstrates that the temporal perception of dynamic audiovisual speech can be modulated by changes in the physical properties of the visual speech (ie by changes in orientation).     

Impaired holistic and analytic face processing in congenital prosopagnosia: Evidence from the eye-contingent mask/window paradigm

There is abundant evidence that face recognition, in comparison to the recognition of other objects, is based on holistic processing rather than analytic processing. One line of research that provides evidence for this hypothesis is based on the study of people who experience pronounced difficulties in visually identifying conspecifics on the basis of their face. Earlier, we developed a behavioural paradigm to directly test analytic vs. holistic face processing. In comparison to a to be remembered reference face stimulus, one of two test stimuli was either presented in full view, with an eye-contingently moving window (only showing the fixated face feature, and therefore only affording analytic processing), or with an eye-contingently moving mask or scotoma (masking the fixated face feature, but still allowing holistic processing). In the present study we use this paradigm (that we used earlier in acquired prosopagnosia) to study face perception in congenital prosopagnosia (people having difficulties recognizing faces from birth on, without demonstrable brain damage). We observe both holistic and analytic face processing deficits in people with congenital prosopagnosia. Implications for a better understanding, both of congenital prosopagnosia and of normal face perception, are discussed.