Perception Of Facial Identity Research Articles

Face Feature Change Detection Ability in Developmental Prosopagnosia and Super-Recognisers.

In non-clinical populations, facial features (eyes, nose, mouth) may vary in their contribution to face identity perception. Changes to whole faces are easier to detect than changes to individual features, and eye changes are typically easier to detect than mouth changes, which in turn are easier to detect than nose changes. However, how this differs for people with face recognition difficulties (developmental prosopagnosia; DP) and for individuals with superior face recognition abilities (super-recognisers; SR) is not clear; although findings from previous studies have suggested differences, the nature of this difference is not understood. The aim of this study was to examine whether differences in the ability to detect feature changes in DPs and SRs were (a) quantitative, meaning that the pattern across feature changes remained the same but there was an overall upwards or downwards shift in performance, or (b) qualitative, meaning that the pattern across feature changes was different. Using a change detection task in which individual face features (eyes, nose, mouth) changed between sequentially presented faces, we found that while prosopagnosics showed a quantitative difference in performance with a downwards shift across all conditions, super-recognisers only showed qualitative differences: they were better able to detect when the face was the same and were marginally (but not non-significantly) worse at detecting when the eyes changed. Further, the only condition which distinguished between the three groups was the ability to identify when the same face was presented, with SRs being better than controls, and controls being better than DPs. Our findings suggest that, in feature-matching tasks, differences for DPs are due to them being overall worse at the task, while SRs use a qualitatively different strategy.

Both identity and non-identity face perception tasks predict developmental prosopagnosia and face recognition ability

Developmental prosopagnosia (DP) is characterised by deficits in face identification. However, there is debate about whether these deficits are primarily perceptual, and whether they extend to other face processing tasks (e.g., identifying emotion, age, and gender; detecting faces in scenes). In this study, 30 participants with DP and 75 controls completed a battery of eight tasks assessing four domains of face perception (identity; emotion; age and gender; face detection). The DP group performed worse than the control group on both identity perception tasks, and one task from each other domain. Both identity perception tests uniquely predicted DP/control group membership, and performance on two measures of face memory. These findings suggest that deficits in DP may arise from issues with face perception. Some non-identity tasks also predicted DP/control group membership and face memory, even when face identity perception was accounted for. Gender perception and speed of face detection consistently predicted unique variance in group membership and face memory; several other tasks were only associated with some measures of face recognition ability. These findings indicate that face perception deficits in DP may extend beyond identity perception. However, the associations between tasks may also reflect subtle aspects of task demands or stimuli.

Familial Transmission of Developmental Prosopagnosia: New Case Reports from an Extended Family and Identical Twins.

Existing evidence suggests that developmental prosopagnosia (DP) is a surprisingly prevalent condition, with some individuals describing lifelong difficulties with facial identity recognition. Together with case reports of multiple family members with the condition, this evidence suggests that DP is inherited in at least some instances. Here, we offer some novel case series that further support the heritability of the condition. First, we describe five adult siblings who presented to our lab with symptoms of DP. Second, for the first known time in the literature, we describe a pair of adult identical twins who contacted us in the belief that they both experience DP. The condition was confirmed in three of the five siblings (with minor symptoms observed in the remaining two) and in both twins. Supplementary assessments suggested that all individuals also experienced some degree of difficulty with facial identity perception, but that object recognition was preserved. These findings bolster the evidence supporting the heritability of DP and suggest that it can be a specific impairment in some cases.

Serial dependence in facial identity perception and visual working memory.

Serial dependence (SD) refers to the effect in which a person's current perceptual judgment is attracted toward recent stimulus history. Perceptual and memory processes, as well as response and decisional biases, are thought to contribute to SD effects. The current study examined the processing stages of SD facial identity effects in the context of task-related decision processes and how such effects may differ from visual working memory (VWM) interactions. In two experiments, participants were shown a series of two sequentially presented face images. In Experiment 1, the two faces were separated by an interstimulus interval (ISI) of 1, 3, 6, or 10 s, and participants were instructed to reproduce the second face after a varying response delay of 0, 1, 3, 6, or 10 s. Results showed that SD effects occurred most consistently at ISI of 1 s and response delays of 1 and 6 s consistent with early and late stages of processing. In Experiment 2, the ISI was held constant at 1 s, and to separate SD from VWM interactions participants were post-cued to reproduce either the first or the second face. When the second face was the target, SD effects again occurred at response delays of 1 and 6 s, but not when the first face was the target. Together, the results demonstrates that SD facial identity effects occur independently of task-related processes in a distinct temporal fashion and suggest that SD and VWM interactions may rely on separate underlying mechanisms.

The impact of eyeglasses on face identity perception

The impact of eyeglasses on face identity perception

Memory matching features bias the ensemble perception of facial identity.

Humans have the ability to efficiently extract summary statistics (i.e., mean) from a group of similar objects, referred to as ensemble coding. Recent studies have demonstrated that ensemble perception of simple objects is modulated by the visual working memory (VWM) task through matching features in VWM. However, few studies have examined the extending scope of such a matching feature effect and the influence of the organization mode (i.e., the way of combining memory matching features with ensemble properties) on this effect. Two experiments were done to explore these questions. We used a dual-task paradigm for both experiments, which included a VWM task and a mean estimation task. Participants were required to adjust a test face to the mean identity face and report whether the irregular objects in a memory probe were identical or different to the studied objects. In Experiment 1, using identity faces as ensemble stimuli, we compared participants' performances in trials where a subset color matched that of the studied objects to those of trials without color-matching subsets. In Experiment 2, we combined memory matching colors with ensemble properties in common region cues and compared the effect with that of Experiment 1. Results of Experiments 1 and 2 showed an effect of the VWM task on high-level ensemble perception that was similar to previous studies using a low-level averaging task. However, the combined analysis of Experiments 1 and 2 revealed that memory matching features had less influence on mean estimations when matching features and ensemble properties combined in the common region than when combined as parts of a complete unit. These findings suggest that the impact of memory matching features is not limited by the level of stimulus feature, but can be impacted by the organization between matching features and ensemble target properties.

Individual differences in serial dependence manifest when sensory uncertainty is high

Perceptual experience in the recent past has been shown to alter subsequent perception. Recently, it has been suggested that this “serial dependence” effect is modulated by sensory uncertainty. In the current study, by overlaying three different levels of visual noise (i.e., no-, low-, or high-noise) on face stimuli, we investigated how serial dependence in face identity perception varies with sensory uncertainty. After learning two facial identities, the faces were combined at various morph levels and participants reported which identity was perceived while noise and noise-free presentations alternated over trials. Results showed that identity perception of noise-free faces was positively biased toward the past when the previous face was noise-free or highly noisy, but not when a low-noise was added. There were considerable individual differences in bias magnitude for trials preceded by high-noise stimuli which reflected individuals’ general bias tendencies. When correlated with the other two conditions, a general bias tendency showed a significant relationship with low-noise trials, but not with no-noise trials. This indicates that the bias tendency of individuals manifests more strongly when the sensory information was uncertain. Therefore, the current findings suggest 1) that sensory uncertainty modulates serial dependence in face identity perception and 2) that an individual’s general bias tendency interacts with sensory uncertainty to alter perception.

Person knowledge shapes face identity perception

Recognition of others' identity through facial features is essential in life. Using both correlational and experimental approaches, we examined how person knowledge biases the perception of others' facial identity. When a participant believed any two individuals were more similar in personality, their faces were perceived to be correspondingly more similar (assessed via mousetracking, Study 1). Further, participants' facial representations of target individuals that were believed to have a more similar personality were found to have a greater physical resemblance (assessed via reverse-correlation, Studies 2 and 3). Finally, when participants learned about novel individuals who had a more similar personality, their faces were visually represented more similarly (Study 4). Together, the findings show that the perception of facial identity is driven not only by facial features but also the person knowledge we have learned about others, biasing it toward alternate identities despite the fact that those identities lack any physical resemblance.

Deep learning of shared perceptual representations for familiar and unfamiliar faces: Reply to commentaries

We recently argued that human unfamiliar face identity perception reflects substantial perceptual expertise, and that the advantage for familiar over unfamiliar face identity matching reflects a learned mapping between generic high-level perceptual features and a unique identity representation of each individual (Blauch, Behrmann and Plaut, 2020). Here we respond to two commentaries by Young and Burton (2020) and Yovel and Abudarham (2020), clarifying and elaborating our stance on various theoretical issues, and discussing topics for future research in human face recognition and the learning of perceptual representations.

Comparing unfamiliar voice and face identity perception using identity sorting tasks.

Identity sorting tasks, in which participants sort multiple naturally varying stimuli of usually two identities into perceived identities, have recently gained popularity in voice and face processing research. In both modalities, participants who are unfamiliar with the identities tend to perceive multiple stimuli of the same identity as different people and thus fail to “tell people together.” These similarities across modalities suggest that modality-general mechanisms may underpin sorting behaviour. In this study, participants completed a voice sorting and a face sorting task. Taking an individual differences approach, we asked whether participants’ performance on voice and face sorting of unfamiliar identities is correlated. Participants additionally completed a voice discrimination (Bangor Voice Matching Test) and a face discrimination task (Glasgow Face Matching Test). Using these tasks, we tested whether performance on sorting related to explicit identity discrimination. Performance on voice sorting and face sorting tasks was correlated, suggesting that common modality-general processes underpin these tasks. However, no significant correlations were found between sorting and discrimination performance, with the exception of significant relationships for performance on “same identity” trials with “telling people together” for voices and faces. Overall, any reported relationships were however relatively weak, suggesting the presence of additional modality-specific and task-specific processes.

Computational insights into human perceptual expertise for familiar and unfamiliar face recognition

Humans are generally thought to be experts at face recognition, and yet identity perception for unfamiliar faces is surprisingly poor compared to that for familiar faces. Prior theoretical work has argued that unfamiliar face identity perception suffers because the majority of identity-invariant visual variability is idiosyncratic to each identity, and thus, each face identity must be learned essentially from scratch. Using a high-performing deep convolutional neural network, we evaluate this claim by examining the effects of visual experience in untrained, object-expert and face-expert networks. We found that only face training led to substantial generalization in an identity verification task of novel unfamiliar identities. Moreover, generalization increased with the number of previously learned identities, highlighting the generality of identity-invariant information in face images. To better understand how familiarity builds upon generic face representations, we simulated familiarization with face identities by fine-tuning the network on images of the previously unfamiliar identities. Familiarization produced a sharp boost in verification, but only approached ceiling performance in the networks that were highly trained on faces. Moreover, in these face-expert networks, the sharp familiarity benefit was seen only at the identity-based output probability layer, and did not depend on changes to perceptual representations; rather, familiarity effects required learning only at the level of identity readout from a fixed expert representation. Our results thus reconcile the existence of a large familiar face advantage with claims that both familiar and unfamiliar face identity processing depend on shared expert perceptual representations.

A proportionally suppressed and prolonged LPP acts as a neurophysiological correlate of face identity aftereffect

The recognition of facial identity is fundamentally important in daily life and social interactions. Here, we asked how the perception of facial identity is influenced by the set of preceding faces that observers are exposed to. We morphed the faces of Adam and Bob to generate a continuum of face images, and asked subjects to judge the identity of those face images to be Adam or Bob after they were exposed to a face image within the continuum. We found that after adaptation to Bob, the subjects were apt to identify a subsequently presented ambiguous face to be Adam, and vice versa, i.e., the face identity aftereffect (FIAE). We simultaneously recorded EEG during the task and analyzed the event-related potentials in response to the test faces, and found that adapting to a face identity (e.g., Bob) suppressed the amplitude, and prolonged the latency, of the late positive potential (LPP) in response to subsequent faces of the same identity (e.g., Bob). Further analyses of the LPP in response to each test face within the continuum revealed a proportional changing trend, i.e., the strongest LPP suppression happened when the adaptor and the test face were the most similar, while the similarity declined, the LPP gradually recovered from suppression. The modulations of LPP amplitude and latency by the identity similarity between the adaptor and test face strongly indicate that the proportionally suppressed and prolonged LPP activity acts as a neurophysiological correlate of FIAE.

Tsinghua facial expression database - A database of facial expressions in Chinese young and older women and men: Development and validation.

Perception of facial identity and emotional expressions is fundamental to social interactions. Recently, interest in age associated changes in the processing of faces has grown rapidly. Due to the lack of older faces stimuli, most previous age-comparative studies only used young faces stimuli, which might cause own-age advantage. None of the existing Eastern face stimuli databases contain face images of different age groups (e.g. older adult faces). In this study, a database that comprises images of 110 Chinese young and older adults displaying eight facial emotional expressions (Neutral, Happiness, Anger, Disgust, Surprise, Fear, Content, and Sadness) was constructed. To validate this database, each image was rated on the basis of perceived facial expressions, perceived emotional intensity, and perceived age by two different age groups. Results have shown an overall 79.08% correct identification rate in the validation. Access to the freely available database can be requested by emailing the corresponding authors.

Bayesian regression-based developmental norms for the Benton Facial Recognition Test in males and females.

Face identity recognition is important for social interaction and is impaired in a range of clinical disorders, including several neurodevelopmental disorders. The Benton Facial Recognition Test (BFRT; Benton & Van Allen, 1968), a widely used assessment of identity recognition, is the only standardized test of face identity perception, as opposed to face memory, that has been normed on children and adolescents. However, the existing norms for the BFRT are suboptimal, with several ages not represented and no established time limit (which can lead to inflated scores by allowing individuals with prosopagnosia to use feature matching). Here we address these issues with a large normative dataset of children and adolescents (ages 5-17, N = 398) and adults (ages 18-55; N = 120) who completed a time-limited version of the BFRT. Using Bayesian regression, we demonstrate that face identity perception increases asymptotically from childhood through adulthood, and provide continuous norms based on age and sex that can be used to calculate standard scores. We show that our time limit of 16 seconds per item yields scores comparable to the existing norms without time limits from the non-prosopagnostic samples. We also find that females (N = 156) score significantly higher than males (N = 362), supporting the existence of a female superiority effect for face identification. Overall, these results provide more robust norms for the BFRT and promote future research on face identity perception in developmental populations.

Anodal tDCS and High-Frequency tRNS Targeting the Occipitotemporal Cortex Do Not Always Enhance Face Perception.

There has been increasing interest in the utility of transcranial electrical stimulation as a tool to enhance cognitive abilities. In the domain of face perception, enhancements have been reported for both transcranial direct current stimulation (tDCS) and high-frequency transcranial random noise stimulation (tRNS) targeting the occipitotemporal cortex. In a series of two experiments, we attempted to replicate these findings for face identity perception, and extend on previous studies, to determine if similar enhancements are also observed for object and facial expression perception. In Experiment 1, using a single blind, between-subjects design in healthy volunteers (N = 53), we examined whether anodal tDCS over the occipitotemporal cortex enhanced performance on tasks involving perception of face identity, facial expression, and object stimuli, when compared to sham stimulation. We failed to replicate previous findings of enhanced performance on face and object perception, nor extend findings to facial expression perception. In Experiment 2, using a single blind, between-subjects design (N = 39), we examined the effect of high-frequency tRNS over the occipitotemporal cortex using the same three tasks employed in Experiment 1. We failed to replicate previous findings of enhanced face perception following high-frequency tRNS over the occipitotemporal cortex, relative to sham stimulation (although we used different stimulation parameters to that employed in a previous study). We also found no evidence of enhanced facial expression and object perception following high-frequency tRNS. The findings align with a growing body of studies that have failed to replicate previously reported enhancements following administration of tDCS and hint for different efficacy of, on first sight, related stimulation protocols. Future studies should explore the foundation of these differential effects in greater detail.

Improving face identity perception in age-related macular degeneration via caricaturing

Patients with age-related macular degeneration (AMD) have difficulty recognising people’s faces. We tested whether this could be improved using caricaturing: an image enhancement procedure derived from cortical coding in a perceptual ‘face-space’. Caricaturing exaggerates the distinctive ways in which an individual’s face shape differs from the average. We tested 19 AMD-affected eyes (from 12 patients; ages 66–93 years) monocularly, selected to cover the full range of vision loss. Patients rated how different in identity people’s faces appeared when compared in pairs (e.g., two young men, both Caucasian), at four caricature strengths (0, 20, 40, 60% exaggeration). This task gives data reliable enough to analyse statistically at the individual-eye level. All 9 eyes with mild vision loss (acuity ≥ 6/18) showed significant improvement in identity discrimination (higher dissimilarity ratings) with caricaturing. The size of improvement matched that in normal-vision young adults. The caricature benefit became less stable as visual acuity further decreased, but caricaturing was still effective in half the eyes with moderate and severe vision loss (significant improvement in 5 of 10 eyes; at acuities from 6/24 to poorer than <6/360). We conclude caricaturing has the potential to help many AMD patients recognise faces.

Caricaturing faces to improve identity recognition in low vision simulations: How effective is current-generation automatic assignment of landmark points?

PurposePrevious behavioural studies demonstrate that face caricaturing can provide an effective image enhancement method for improving poor face identity perception in low vision simulations (e.g., age-related macular degeneration, bionic eye). To translate caricaturing usefully to patients, assignment of the multiple face landmark points needed to produce the caricatures needs to be fully automatised. Recent development in computer science allows automatic face landmark detection of 68 points in real time and in multiple viewpoints. However, previous demonstrations of the behavioural effectiveness of caricaturing have used higher-precision caricatures with 147 landmark points per face, assigned by hand. Here, we test the effectiveness of the auto-assigned 68-point caricatures. We also compare this to the hand-assigned 147-point caricatures.MethodWe assessed human perception of how different in identity pairs of faces appear, when veridical (uncaricatured), caricatured with 68-points, and caricatured with 147-points. Across two experiments, we tested two types of low-vision images: a simulation of blur, as experienced in macular degeneration (testing two blur levels); and a simulation of the phosphenised images seen in prosthetic vision (at three resolutions).ResultsThe 68-point caricatures produced significant improvements in identity discrimination relative to veridical. They were approximately 50% as effective as the 147-point caricatures.ConclusionRealistic translation to patients (e.g., via real time caricaturing with the enhanced signal sent to smart glasses or visual prosthetic) is approaching feasibility. For maximum effectiveness software needs to be able to assign landmark points tracing out all details of feature and face shape, to produce high-precision caricatures.

Investigating the perception of face identity in adults on the autism spectrum using behavioural and electrophysiological measures

In the present study, we investigated face processing in individuals with self-reported Autism Spectrum Disorder (ASD, n = 16) and typically developing control participants (n = 16) using behavioural and electrophysiological measures. As a measure of their face memory, we administered the Cambridge Face Memory Test to participants in the ASD group. The results showed that the scores of the ASD participants were reliably below the age- and gender-matched norms of neurotypical individuals. To measure brain responses to faces, we used the fast periodic visual stimulation method, presenting photographs of a same-identity face (i.e., base face) at a constant frequency of 6 Hz (F) interleaved with different-identity faces (i.e., the oddball faces) presented at 1.2 Hz. The 6 Hz presentation of the base face and 1.2 Hz presentation of the oddball face elicited periodic brain responses corresponding to face detection and face individuation processes, respectively. Participants viewed four blocks of upright faces and four blocks of inverted faces. The results showed an enhanced EEG response to upright base faces at 6 Hz frequency and its harmonics compared to inverted faces, and the response was most focal over medial occipital channels. An enhanced response was found to upright oddball faces at 1.2 Hz and its harmonics compared to the inverted faces, and the response was centred over occipito-temporal channels in the right hemisphere. Critically, no differences or interactions were found between the ASD and typically developing groups in the responses to either the 6 Hz base faces or the 1.2 oddball faces. These results suggest that in individuals with ASD, the earlier stage of face perception, as measured by the fast periodic visual stimulation paradigm, can be dissociated from the later memory stage of face processing, as assessed by the Cambridge Face Memory Test.

Serial dependence promotes the stability of perceived emotional expression depending on face similarity.

Individuals can quickly and effortlessly recognize facial expressions, which is critical for social perception and emotion regulation. This sensitivity to even slight facial changes could result in unstable percepts of an individual's expression over time. The visual system must therefore balance accuracy with maintaining perceptual stability. However, previous research has focused on our sensitivity to changing expressions, and the mechanism behind expression stability remains an open question. Recent results demonstrate that perception of facial identity is systematically biased toward recently seen visual input. This positive perceptual pull, or serial dependence, may help stabilize perceived expression. To test this, observers judged random facial expression morphs ranging from happy to sad to angry. We found a pull in perceived expression toward previously seen expressions, but only when the 1-back and current face had similar identities. Our results are consistent with the existence of the continuity field for expression, a specialized mechanism that promotes the stability of emotion perception, which could help facilitate social interactions and emotion regulation.

Rapid Improvement on a Temporal Attention Task within a Single Session of High-frequency Transcranial Random Noise Stimulation.

This study explored the modulatory effects of high-frequency transcranial random noise stimulation (tRNS) on visual sensitivity during a temporal attention task. We measured sensitivity to different onset asynchronies during a temporal order judgment task as a function of active stimulation relative to sham. While completing the task, participants were stimulated bilaterally for 20 min over either the TPJ or the human middle temporal area. We hypothesized that tRNS over the TPJ, which is critical to the temporal attention network, would selectively increase cortical excitability and induce cognitive training-like effects on performance, perhaps more so in the left visual field [Matthews, N., & Welch, L. Left visual field attentional advantage in judging simultaneity and temporal order. Journal of Vision, 15, 1-13, 2015; Romanska, A., Rezlescu, C., Susilo, T., Duchaine, B., & Banissy, M. J. High-frequency transcranial random noise stimulation enhances perception of facial identity. Cerebral Cortex, 25, 4334-4340, 2015]. In Experiment 1, we measured the performance of participants who judged the order of Gabors temporally imbedded in flickering discs, presented with onset asynchronies ranging from -75 msec (left disc first) to +75 msec (right disc first). In Experiment 2, we measured whether each participant's temporal sensitivity increased with stimulation by using temporal offsets that the participant initially perceived as simultaneous. We found that parietal cortex stimulation temporarily increased sensitivity on the temporal order judgment task, especially in the left visual field. Stimulation over human middle temporal area did not alter cortical excitability in a way that affected performance. The effects were cumulative across blocks of trials for tRNS over parietal cortex but dissipated when stimulation ended. We conclude that single-session tRNS can induce temporary improvements in behavioral sensitivity and that this shows promising insight into the relationship between cortical stimulation and neural plasticity.