Intact Faces Research Articles

Working memory for gaze benefits from the face context.

Retaining gaze in working memory (WM) is essential for successfully navigating through the social world. In the current study, we investigated how WM stores gaze direction by focusing on the role of face context in gaze WM. To address this question, we propose two competing hypotheses. The independence hypothesis predicts that eye gaze is stored independently and is not susceptible to the influence of the surrounding face context. Conversely, the embedding hypothesis claims that gaze WM involves face context and that disruption of holistic face processing would also impair memory for embedded gaze. In three experiments, we adopted different manipulations to disrupt holistic face processing and compared WM performance for gaze within and without face context. In Experiments 1 and 2, we tested WM for gaze direction with schematic upright or inverted faces. We found better performance for gaze within upright faces (vs. inverted faces) by increasing the probability of being remembered. In Experiment 3, we replaced schematic faces with photographic faces, and disrupted holistic processing by using scrambled faces. Results replicated our previous findings, showing that photographic gaze within intact faces was better remembered than gaze presented alone or gaze within scrambled faces. These findings indicate that gaze memory is face-dependent and support the embedding hypothesis.

Discrepancies in perceived humanness between spatially filtered and unfiltered faces and their associations with uncanny feelings.

Human and artificial features that coexist in certain types of human-like robots create a discrepancy in perceived humanness and evoke uncanny feelings in human observers. However, whether this perceptual mismatch in humanness occurs for all faces, and whether it is related to the uncanny feelings toward them, is unknown. We investigated this by examining perceived humanness for a variety of natural images of robot and human faces with different spatial frequency (SF) information: that is, faces with only low SF, middle SF, and high SF information, and intact (spatially unfiltered) faces. Uncanny feelings elicited by these faces were also measured. The results showed perceptual mismatches that LSF, MSF, and HSF faces were perceived as more human than intact faces. This was particularly true for intact robot faces that looked slightly human, which tended to evoke strong uncanny feelings. Importantly, the mismatch in perceived humanness between the intact and spatially filtered faces was positively correlated with uncanny feelings toward intact faces. Given that the human visual system performs SF analysis when processing faces, the perceptual mismatches observed in this study likely occur in real life for all faces, and as such might be a ubiquitous source of uncanny feelings in real-life situations.

Measuring the Contributions of Perceptual and Attentional Processes in the Complete Composite Face Paradigm.

Theories of holistic face processing vary widely with respect to conceptualizations, paradigms, and stimuli. These divergences have left several theoretical questions unresolved. Namely, the role of attention in face perception is understudied. To rectify this gap in the literature, we combined the complete composite face task (allowing for predictions of multiple theoretical conceptualizations and connecting with a large body of research) with a secondary auditory discrimination task at encoding (to avoid a visual perceptual bottleneck). Participants studied upright, intact faces within a continuous recognition paradigm, which intermixes study and test trials at multiple retention intervals. Within subjects, participants studied faces under full or divided attention. Test faces varied with respect to alignment, congruence, and retention intervals. Overall, we observed the predicted beneficial outcomes of holistic processing (e.g., higher discriminability for Congruent, Aligned faces relative to Congruent, Misaligned faces) that persisted across retention intervals and attention. However, we did not observe the predicted detrimental outcomes of holistic processing (e.g., higher discriminability for Incongruent, Misaligned faces relative to Incongruent, Aligned faces). Because the continuous recognition paradigm exerts particularly strong demands on attention, we interpret these findings through the lens of resource dependency and domain specificity.

Visual input to the left versus right eye yields differences in face preferences in 3-month-old infants.

From birth, infants prefer looking at faces over scrambled faces. This face input is important for the development of face processing: individuals who experienced early visual deprivation due to congenital cataracts have long-lasting face processing deficits. Interestingly, the deficits are eye-specific such that left eye cataracts disrupt the development of face processing, whereas right eye cataracts do not. This raises the question of whether infant face preferences are driven primarily by faces observed through the left eye. To investigate this, we presented 3-month-old infants with intact faces paired with scrambled faces. Infants viewed the moving stimuli binocularly, only with their left eye, or only with their right eye. Infants viewing stimuli binocularly or with only the left eye spent significantly more time looking at intact faces than scrambled faces, but this effect was equivocal in infants viewing stimuli through only their right eye. Infants in the binocular group had the greatest preference for faces, and this preference was greater than the right eye group's preference for faces. The left eye group's preference for faces was not statistically different from the other two groups' preference for faces, but additional analyses revealed a correlation between preference for faces and age for the right eye group only, indicating that preference for faces seen with the right eye increase from 3 to 4months of age. These results indicate that the left eye plays a special role in face processing at, or before 3months of age, but a preference for faces through the right eye emerges soon after.

Unitization of internal and external features contributes to associative recognition for faces: Evidence from modulations of the FN400

Associative recognition requires discriminating between old items and conjunction lures constructed by recombining elements from two different study items. This task can be solved not only by recollection but also by familiarity if the to-be-remembered stimuli are perceived as a unitized representation. In two event-related potential (ERP) studies, we provide evidence for the integration of internal and external facial features by showing that the early frontal old-new effect (considered a correlate of familiarity) is modulated by the specific combination of facial features. Participants studied faces consisting of internal features (eyes, eyebrows, nose, and mouth) paired with external features (hair, head shape, and ears). During the testing phase, intact, recombined, and new faces were presented. Recombined faces consisted of internal and external features taken from two different studied faces. The results showed that at the frontal sites, during the time window from 300 to 500 ms, ERPs to intact faces were more positive than those to new and recombined faces; the latter two did not differ from one another. The late parietal effect was observed only after a more extended study phase in Experiment 2. We take the modulation of the early frontal old-new effect as evidence for the contribution of familiarity to associative recognition for combinations of internal and external facial features.

Never forget a face: Verbalization facilitates recollection as evidenced by flexible responding to contrasting recognition memory tests.

Verbal facilitation occurs when describing a face improves its subsequent recognition; but there are several theoretical explanations debated in the literature. The results of the present studies support a relatively unrestricted, parsimonious theory that verbal facilitation occurs because describing a face supports recollection of several different facets of the face-viewing experience. This recollection is then demonstrated by flexibly responding to two competing types of recognition task demands. Participants studied a list of faces and, following each face, performed a nonverbalization task (Experiment 1) or described its features or traits (Experiment 2). Two subsequent recognition tests included intact faces, new faces, and conjunctions (each of which recombined features of two studied faces). Inclusion test instructions emphasized featural information: respond "yes" to both intact and conjunction faces (both of which contained studied features), but "no" to new faces. Exclusion test instructions emphasized configural information: respond "yes" only to intact faces (which were the only test items that matched studied configurations), and "no" to both conjunctions and new faces. Both yes/no responses and confidence ratings supported our hypothesis that verbalization improved discrimination between (a) conjunctions and new faces in the inclusion test, and (b) intact faces and conjunctions in the exclusion test. Additional secondary responses about face type elucidated that verbalization at study improves the ability to recollect either featural or configural information, depending on which type of response the recognition test required. We discuss these findings about practical applications of improved face memory in real-world contexts.

Increased Early Sensitivity to Eyes in Mouthless Faces: In Support of the LIFTED Model of Early Face Processing.

The N170 ERP component is a central neural marker of early face perception usually thought to reflect holistic processing. However, it is also highly sensitive to eyes presented in isolation and to fixation on the eyes within a full face. The lateral inhibition face template and eye detector (LIFTED) model (Nemrodov et al. in NeuroImage 97:81-94, 2014) integrates these views by proposing a neural inhibition mechanism that perceptually glues features into a whole, in parallel to the activity of an eye detector that accounts for the eye sensitivity. The LIFTED model was derived from a large number of results obtained with intact and eyeless faces presented upright and inverted. The present study provided a control condition to the original design by replacing eyeless with mouthless faces, hereby enabling testing of specific predictions derived from the model. Using the same gaze-contingent approach, we replicated the N170 eye sensitivity regardless of face orientation. Furthermore, when eyes were fixated in upright faces, the N170 was larger for mouthless compared to intact faces, while inverted mouthless faces elicited smaller amplitude than intact inverted faces when fixation was on the mouth and nose. The results are largely in line with the LIFTED model, in particular with the idea of an inhibition mechanism involved in holistic processing of upright faces and the lack of such inhibition in processing inverted faces. Some modifications to the original model are also proposed based on these results.

The "parts and wholes" of face recognition: A review of the literature.

It has been claimed that faces are recognized as a "whole" rather than by the recognition of individual parts. In a paper published in the Quarterly Journal of Experimental Psychology in 1993, Martha Farah and I attempted to operationalize the holistic claim using the part/whole task. In this task, participants studied a face and then their memory presented in isolation and in the whole face. Consistent with the holistic view, recognition of the part was superior when tested in the whole-face condition compared to when it was tested in isolation. The "whole face" or holistic advantage was not found for faces that were inverted, or scrambled, nor for non-face objects, suggesting that holistic encoding was specific to normal, intact faces. In this paper, we reflect on the part/whole paradigm and how it has contributed to our understanding of what it means to recognize a face as a "whole" stimulus. We describe the value of part/whole task for developing theories of holistic and non-holistic recognition of faces and objects. We discuss the research that has probed the neural substrates of holistic processing in healthy adults and people with prosopagnosia and autism. Finally, we examine how experience shapes holistic face recognition in children and recognition of own- and other-race faces in adults. The goal of this article is to summarize the research on the part/whole task and speculate on how it has informed our understanding of holistic face processing.

Perceptual face processing in developmental prosopagnosia is not sensitive to the canonical location of face parts

Individuals with developmental prosopagnosia (DP) are strongly impaired in recognizing faces, but it is controversial whether this deficit is linked to atypical visual-perceptual face processing mechanisms. Previous behavioural studies have suggested that face perception in DP might be less sensitive to the canonical spatial configuration of face parts in upright faces. To test this prediction, we recorded event-related brain potentials (ERPs) to intact upright faces and to faces with spatially scrambled parts (eyes, nose, and mouth) in a group of ten participants with DP and a group of ten age-matched control participants with normal face recognition abilities. The face-sensitive N170 component and the vertex positive potential (VPP) were both enhanced and delayed for scrambled as compared to intact faces in the control group. In contrast, N170 and VPP amplitude enhancements to scrambled faces were absent in the DP group. For control participants, the N170 to scrambled faces was also sensitive to feature locations, with larger and delayed N170 components contralateral to the side where all features appeared in a non-canonical position. No such differences were present in the DP group. These findings suggest that spatial templates of the prototypical feature locations within an upright face are selectively impaired in DP.

An Enhanced Default Approach Bias Following Amygdala Lesions in Humans

Approach and avoidance constitute a basic dimension of all animal behavior. Although a large number of studies have investigated approach and avoidance elicited by specific sensory stimuli, comparatively little is known about default approach biases when stimulus information is absent or reduced. The amygdala is well known to contribute to approach and avoidance behaviors in response to specific sensory stimuli; we tested whether the amygdala’s role might extend to situations in which stimulus information is reduced. In a novel task, 3 patients with rare bilateral amygdala lesions (and control subjects) made approach-related judgments about photos of intact faces and of the same faces with all internal facial features occluded. Direct comparisons of the judgments of these stimuli isolated a default bias. The patients showed a greater tendency than the control subjects to rate occluded faces as more approachable than whole faces. These findings suggest that the amygdala’s role in approach behavior extends beyond responses to specific stimuli.

How do neural responses to eyes contribute to face-sensitive ERP components in young infants? A rapid repetition study

Several face-sensitive components of the event-related potential (ERP) have been identified in infants, such as the posterior N290 and P400 components. The contribution of eye-sensitive neurons to these components is still unclear, however. A rapid repetition ERP paradigm was used to test 4-month-olds’ responses to faces with and without eyes (preceded by houses, i.e., unprimed) and faces with eyes that were preceded by faces with or without eyes (i.e., primed). N290 latency was reduced and P400 amplitude was increased for unprimed faces without eyes compared to intact faces. In addition, N290 latency was reduced for faces preceded by intact faces compared to faces preceded by faces without eyes. Thus, processing speed at the level of the N290 and amplitude of the P400 are affected by the absence of eyes in a face supporting the notion that eye-sensitive neurons contribute to these components in infancy. Findings are discussed in relation to the early development of face processing and infant and adult ERP responses to faces and eyes.

Forming first impressions of others in schizophrenia: Impairments in fast processing and in use of spatial frequency information

Individuals form first impressions of others all the time, which affects their social functioning. Typical adults form threat impressions in faces with neutral expressions quickly, requiring less than 40ms. These impressions appear to be mediated by low spatial frequency (LSF) content in the images. Little is known, however, about mechanisms of first impression formation in schizophrenia. The current study investigated how quickly individuals with schizophrenia can form consistent impressions of threat compared with controls and explored the mechanisms involved. Patients and controls were presented intact, LSF- or high spatial frequency (HSF)-filtered faces with durations that varied from 39 to 1703ms and were asked to rate how threatening each face was on a scale from 1 to 5. In order to assess the speed of impression formation for intact faces, correlations were calculated for ratings made at each duration compared to a reference duration of 1703ms for each group. Controls demonstrated a significant relation for intact faces presented for 39ms, whereas patients required 390ms to demonstrate a significant relation with the reference duration. For controls, LSFs primarily contributed to the formation of consistent threat impressions at 39ms, whereas patients showed a trend for utilizing both LSF and HSF information to form consistent threat impressions at 390ms. Results indicate that individuals with schizophrenia require a greater integration time to form a stable “first impression” of threat, which may be related to the need to utilize compensatory mechanisms such as HSF, as well as LSF, information.

Implicit Binding of Facial Features During Change Blindness

Change blindness refers to the inability to detect visual changes if introduced together with an eye-movement, blink, flash of light, or with distracting stimuli. Evidence of implicit detection of changed visual features during change blindness has been reported in a number of studies using both behavioral and neurophysiological measurements. However, it is not known whether implicit detection occurs only at the level of single features or whether complex organizations of features can be implicitly detected as well. We tested this in adult humans using intact and scrambled versions of schematic faces as stimuli in a change blindness paradigm while recording event-related potentials (ERPs). An enlargement of the face-sensitive N170 ERP component was observed at the right temporal electrode site to changes from scrambled to intact faces, even if the participants were not consciously able to report such changes (change blindness). Similarly, the disintegration of an intact face to scrambled features resulted in attenuated N170 responses during change blindness. Other ERP deflections were modulated by changes, but unlike the N170 component, they were indifferent to the direction of the change. The bidirectional modulation of the N170 component during change blindness suggests that implicit change detection can also occur at the level of complex features in the case of facial stimuli.

An Eye-tracking Research on Featural, Configural and Holistic Processing Strategies in Face Perception

There were two main hypotheses attempting to explain the mechanisms of face perception. One was the holistic approach which claimed that faces were stored as relatively undifferentiated wholes, without explicitly representing the facial parts. The other was the dual-code view which claimed that faces were processed on the basis of featural and configural information and that the respective representations were stored in isolation. Indeed, neither of the two approaches could provide a detailed explanation of the mechanisms of face perception. Therefore integrated approaches were proposed. The present study in favor of these integrated systems aims at exploring featural, configural and holistic strategies during face perception. The presence of different eye movement patterns would imply how important information is extracted from facial stimuli. In the two experiments we explored the scanning behavior during face perception. In experiment 1, modified faces with primarily featural(scrambled faces) or configural(blurred faces) information were used as cue stimuli so as to manipulate the way participants processed intact faces which were presented soon afterwards. In a series of matching-to-sample tasks, participants decided whether the identity of an intact test face matched a precedent scrambled or blurred cue face. Analysis of eye movements for test faces showed more interfeatural saccades when preceded by blurred faces, and longer gaze duration within the same feature when preceded by scrambled faces. In experiment 2, a similar paradigm was used except that test faces were cued by intact faces, low-level blurred faces, or slightly scrambled faces. The results suggested that in the intact condition participants performed fewer interfeatural saccades than in low-level blurred condition and had shorter gaze duration than in slightly scrambled condition. Moreover, a few fixations in the center of the face were performed to grasp the information from the whole face. The results suggest a differentiation between featural, configural, and holistic processing strategies, which can be associated with specific patterns of eye movements. By inducing different processing strategies in experiment 1, we provided further evidence that faces can be recognized on the basis of both featural and configural information. In experiment 2 a holistic strategy characterized by the grasp of the whole face was applied, while in experiment 1 a configural strategy was adopted when the information from different locations was integrated by performing a high number of saccades between different features. In conclusion, the present study shows that three modes of face processing strategies coexist in face perception.

Pedicle length in the inferiorly based buccinator myomucosal island flap: a cadaveric study

The inferiorly based buccinator myomucosal island flap is a useful reconstructive option for medium-sized intraoral mucosal defects. The pedicle length of this flap has not yet been determined. Thirteen fresh cadavers (26 sides) with intact faces were studied. An inferiorly based buccinator myomucosal island flap was elevated. Various measurements were taken, including pedicle length, paddle area, and pedicle length after dissection of the facial artery through the submandibular salivary gland; the presence of the facial artery or vein in the pedicle and the number of perforators were also evaluated. The mean pedicle lengths in the right and left sides were 4.8±0.6cm and 4.9±0.6cm, respectively. The mean pedicle lengths after dissection of the facial artery through the submandibular salivary gland were 7.8±0.7cm (right side) and 7.7±0.6cm (left side). The pedicle contained only the facial artery in six sides. There were two to three perforator branches from the facial artery to the mucosal paddle. Paddle sizes of the flap were in the range of 2.2×2.1cm to 3.5×3cm. This flap is suitable for the reconstruction of the floor of the mouth and tongue. Pedicle length can be increased significantly by dissecting the facial artery through the submandibular salivary gland.

A smile biases the recognition of eye expressions: Configural projection from a salient mouth

A smile is visually highly salient and grabs attention automatically. We investigated how extrafoveally seen smiles influence the viewers' perception of non-happy eyes in a face. A smiling mouth appeared in composite faces with incongruent non-happy (fearful, neutral, etc.) eyes, thus producing blended expressions, or it appeared in intact faces with genuine expressions. Attention to the eye region was spatially cued while foveal vision of the mouth was blocked by gaze-contingent masking. Participants judged whether the eyes were happy or not. Results indicated that the smile biased the evaluation of the eye expression: The same non-happy eyes were more likely to be judged as happy and categorized more slowly as not happy in a face with a smiling mouth than in a face with a non-smiling mouth or with no mouth. This bias occurred when the mouth and the eyes appeared simultaneously and aligned, but also to some extent when they were misaligned and when the mouth appeared after the eyes. We conclude that the highly salient smile projects to other facial regions, thus influencing the perception of the eye expression. Projection serves spatial and temporal integration of face parts and changes.

The role of the eyes in processing an intact face and its scrambled image: A dense array ERP and low-resolution electromagnetic tomography (sLORETA) study

The aim of the present study was to test whether the eyes of an intact face produced a specific brain response compared to the mouth, nose, or hair and whether their specificity was also maintained in a scrambled face. Fifteen subjects were asked to focus visual attention on global and single elements in intact faces and in their scrambled image. EEG data were recorded from 256-Hydrocel Geodesic Sensor-Net200. Event-related potentials (ERPs) analyses showed a difference between the intact face and the scrambled face from N170 component until 600 ms on the occipito-temporal montage and at 400–600 ms on the frontal montage. Only the eyes showed a difference between conditions (intact/scrambled face) at 500 ms. The most activated source detected by sLORETA was the right middle temporal gyrus (BA21) for both conditions and for all elements. Left BA21 resulted in significantly more activation in response to eyes in the intact face compared to the eyes in the scrambled face at 500 ms. The left BA21 has a central role in high-level visual processing and in understanding others' intentions. These findings suggest a specificity of the eyes and indicate that the eyes play the social and communicative role of comprehending the nonverbal intentions of others only when inserted in an intact face.

Assessing temporal processing of facial emotion perception with transcranial magnetic stimulation

The ability to process facial expressions can be modified by altering the spatial frequency of the stimuli, an effect that has been attributed to differential properties of visual pathways that convey different types of information to distinct brain regions at different speeds. While this effect suggests a potential influence of spatial frequency on the processing speed of facial emotion, this hypothesis has not been examined directly. We addressed this question using a facial emotion identification task with photographs containing either high spatial frequency (HSF), low spatial frequency (LSF), or broadband spatial frequency (BSF). Temporal processing of emotion perception was manipulated by suppressing visual perception with a single-pulse transcranial magnetic stimulation (TMS), delivered to the visual cortex at six intervals prior to (forward masking) or following (backward masking) stimulus presentation. Participants performed best in the BSF, followed by LSF, and finally HSF condition. A spatial frequency by forward/backward masking interaction effect demonstrated reduced performance in the forward masking component in the BSF condition and a reversed performance pattern in the HSF condition, with no significant differences between forward and backward masking in the LSF condition. Results indicate that LSF information may play a greater role than HSF information in emotional processing, but may not be sufficient for fast conscious perception of emotion. As both LSF and HSF filtering reduced the speed of extracting emotional information from faces, it is possible that intact BSF faces have an inherent perceptual advantage and hence benefit from faster temporal processing.

Behavioral and electrophysiological correlates of intact and scrambled body perception

ObjectiveIntact faces and bodies elicit two prominent electrophysiological components (P100 and N170). The N170 is thought to be related to the structural encoding and configural processing of faces and bodies. The aim of the present study was to investigate whether intact faces and bodies as well as scrambled faces and bodies elicit the same component. This would imply that similar as faces, bodies are encoded as a whole. MethodsWe used a matching to sample task and two manipulations validated as an assessment of configural processing in previous studies: the inversion effect and intact versus scrambled stimulus presentation. ResultsFor both categories, performance was better for intact compared to scrambled stimuli. Additionally, stimulus distortion seems to abolish the body but not the face inversion effect. On the electrophysiological level, we found enhanced N170 amplitudes for intact faces and bodies compared to scrambled stimuli. The opposite pattern engaged in the time-window of the P100. Furthermore, for the N170 we observed an inversion effect for intact but not scrambled bodies. ConclusionsFirst-order relational information are important for the perception of bodies and might be processed in the N170 time-window. Disrupting this information interacts with the inversion effect. SignificanceThe current data suggest that faces and bodies might be processed by distinct mechanisms as the experimental manipulation affected faces in a different way than bodies.

A Smile Radiates Outwards and Biases the Eye Expression

This study investigated how extrafoveally seen smiles influence the viewers' perception of non-happy eyes in a face. A smiling mouth appeared in composite faces with incongruent (angry, fearful, neutral, etc.) eyes, thus producing blended expressions, or they appeared in intact faces with genuine expressions. Overt attention to the eye region was spatially cued, foveal vision of the mouth was blocked by gaze-contingent masking, and the distance between the eyes and the mouth was varied. Participants evaluated whether the eyes were happy or not. Results indicated that the same non-happy eyes were more likely to be judged as happy, and more slowly to be judged as not happy, in presence more than in absence of a smile. As (a) the smiling mouth was highly salient regardless of type of eyes, (b) the influence on the eyes increased gradually as a function of eye-mouth proximity, and (c) the effect occurred in the absence of fixations on the mouth, we conclude that a salient smile radiates outwards to other face regions through a projection mechanism, thus making the eye expression look happy.