Unfamiliar Face Identity Research Articles

Preserved unfamiliar face identity discrimination ability in Alzheimer’s disease: electrophysiological evidence

AbstractBackgroundWhile Alzheimer Disease (AD) patients’ difficulty to recognize face identity (Werheid & Clare, 2007) has been mainly attributed to episodic and semantic memory impairments, these patients can also show abnormal difficulties at matching of unfamiliar faces for their identity, suggesting impaired perceptual function (Lavallée et al., 2016). However, since this latter evidence is based on explicit behavioural measures, the difficulties of AD patients can be due to many factors (e.g., task understanding, stress, motivation, attention, decision making…).MethodsTo obtain an objective and implicit measure of face identity discrimination ability we coupled electroencephalographic (EEG) recordings and fast periodic visual stimulation (FPVS). FPVS consists in the presentation of visual stimuli at a defined frequency that produces EEG responses at the exact same stimulated frequency. 22 diagnosed AD patients (CSF‐positive for AD, MMSE ≤27) and 22 healthy controls matched in sex and age (Fig.1) were tested with a well‐validated FPVS paradigm (>30 published studies) consisting in the presentation of a same identity face 6 times per second (base frequency: 6Hz) with variable other identities presented every fifth image (i.e., oddball frequency: 6/5 = 1.2Hz)(Fig.2). EEG responses at 1.2 Hz reflect an individual’s identity discrimination ability (e.g., Liu‐Shuang et al. 2014, Neuropsychologia; Rossion et al., 2020, Eur. J. Neurosci.).ResultsAt the 1.2 Hz oddball frequency and harmonics, a highly significant amplitude response was found at bilateral occipito‐temporal site for both groups (Fig.3; AD: 0.43 µV, p <.001; CTR: 0.58 µV, p <.001). Since this response becomes negligible when the same faces images are presented upside down (AD: 0.02 µV, p>.05; CTR:0.0009 µV, p >.05), the 1.2 Hz response reflect high‐level cognitive processes. ANOVA analyses revealed a significant effect of Condition (i.e., upright vs. inverted; p<.001). However, despite a lower response overall in AD patients (Fig.3), there was no significant effect of Group (p = .53) or interaction (p = .07).ConclusionThese results provide evidence with an implicit and objective neural measure that unfamiliar face identity discrimination ability is largely preserved in AD, suggesting that abnormal difficulties at matching pictures of unfamiliar faces for their identity in this population is due to other factors than visual discrimination.

The neural basis of human unfamiliar face identity recognition with fMRI frequency-tagging

The neural basis of human unfamiliar face identity recognition with fMRI frequency-tagging

Intracerebral recordings evidence that unfamiliar face-identity recognition is supported by face-selective neural populations in the human ventral occipito-temporal cortex

Intracerebral recordings evidence that unfamiliar face-identity recognition is supported by face-selective neural populations in the human ventral occipito-temporal cortex

Intracerebral electrical stimulation of the right anterior fusiform gyrus impairs human face identity recognition

Brain regions located between the right fusiform face area (FFA) in the middle fusiform gyrus and the temporal pole may play a critical role in human face identity recognition but their investigation is limited by a large signal drop-out in functional magnetic resonance imaging (fMRI). Here we report an original case who is suddenly unable to recognize the identity of faces when electrically stimulated on a focal location inside this intermediate region of the right anterior fusiform gyrus. The reliable transient identity recognition deficit occurs without any change of percept, even during nonverbal face tasks (i.e., pointing out the famous face picture among three options; matching pictures of unfamiliar or familiar faces for their identities), and without difficulty at recognizing visual objects or famous written names. The effective contact is associated with the largest frequency-tagged electrophysiological signals of face-selectivity and of familiar and unfamiliar face identity recognition. This extensive multimodal investigation points to the right anterior fusiform gyrus as a critical hub of the human cortical face network, between posterior ventral occipito-temporal face-selective regions directly connected to low-level visual cortex, the medial temporal lobe involved in generic memory encoding, and ventral anterior temporal lobe regions holding semantic associations to people's identity.

Harnessing fast periodic visual stimulation to study face cognition: Sub-processes, brain-behavior relationships, and objectivity.

Rossion et al. (2020) review over a decade of work investigating the neural basis of unfamiliar face individuation (FI) - the brain's ability to distinguish unfamiliar face identity - using fast periodic visual stimulation (FPVS). Though FPVS measures rapid, automatic processing, its value for studying vision and face cognition could be increased by addressing three important aspects.

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.

Neural responses in a fast periodic visual stimulation paradigm reveal domain-general visual discrimination deficits in developmental prosopagnosia

We investigated selective impairments of visual identity discrimination in developmental prosopagnosia (DP), using a fast periodic identity oddball stimulation paradigm with electroencephalography (EEG). In Experiment 1, neural responses to unfamiliar face identity changes were strongly attenuated for individuals with DP as compared to Control participants, to the same extent for upright and inverted faces. This reduction of face identity discrimination responses, which was confirmed in Experiment 2, provides direct evidence for deficits in the visual processing of unfamiliar facial identity in DP. Importantly, Experiment 2 demonstrated that DPs showed attenuated neural responses to identity oddballs not only with face images, but also with non-face images (cars). This result strongly suggests that rapid identity-related visual processing impairments in DP are not restricted to faces, but also affect familiar classes of non-face stimuli. Visual discrimination deficits in DP do not appear to be face-specific. To account for these findings, we propose a new account of DP as a domain-general deficit in rapid visual discrimination.

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.

Immediate stimulus repetition abolishes stimulus expectation and surprise effects in fast periodic visual oddball designs

Oddball designs are widely used to investigate the sensitivity of the visual system to statistical regularities in sensory environments. However, the underlying mechanisms that give rise to visual mismatch responses remain unknown. Much research has focused on identifying separable, additive effects of stimulus repetition and stimulus appearance probability (expectation/surprise) but findings from non-oddball designs indicate that these effects also interact. We adapted the fast periodic visual stimulation (FPVS) unfamiliar face identity oddball design (Liu-Shuang et al., 2014) to test for both additive and interactive effects of stimulus repetition and stimulus expectation. In two experiments, a given face identity was presented at a 6 Hz periodic rate; a different identity face (the oddball) appeared as every 7th image in the sequence (i.e., at 0.857 Hz). Electroencephalographic (EEG) activity was recorded during these stimulation sequences. In Experiment 1, we tested for surprise responses evoked by unexpected face image repetitions by replacing 10% of the commonly-presented oddball faces with exact repetitions of the base rate face identity image. In Experiment 2, immediately repeated or unrepeated face identity oddballs were presented in high and low presentation probability contexts (i.e., expected or surprising contexts), allowing assessment of expectation effects on responses to both repeated and unrepeated stimuli. Across both experiments objective (i.e., frequency-locked) visual mismatch responses driven by stimulus expectation were only found for oddball faces of a different identity to base rate faces (i.e., unrepeated identity oddballs). Our results show that immediate stimulus repetition (i.e., repetition suppression) can reduce or abolish expectation effects as indexed by EEG responses in visual oddball designs.

Wisdom of the social versus non-social crowd in face identification.

Face identification is more accurate when people collaborate in social dyads than when they work alone (Dowsett & Burton, 2015, Br. J. Psychol., 106, 433). Identification accuracy is also increased when the responses of two people are averaged for each item to create a 'non-social' dyad (White, Burton, Kemp, & Jenkins, 2013, Appl. Cogn. Psychol., 27, 769; White etal., 2015, Proc. R. Soc. B Biol. Sci., 282, 20151292). Does social collaboration add to the benefits of response averaging for face identification? We compared individuals, social dyads, and non-social dyads on an unfamiliar face identity-matching test. We also simulated non-social collaborations for larger groups of people. Individuals and social dyads judged whether face image pairs depicted the same- or different identities, responding on a 5-point certainty scale. Non-social dyads were constructed by averaging the responses of paired individuals. Both social and non-social dyads were more accurate than individuals. There was no advantage for social over non-social dyads. For larger non-social groups, performance peaked at near perfection with a crowd size of eight participants. We tested three computational models of social collaboration and found that social dyad performance was predicted by the decision of the more accurate partner. We conclude that social interaction does not bolster accuracy for unfamiliar face identity matching in dyads beyond what can be achieved by averaging judgements.

Dominance of texture over shape in facial identity processing is modulated by individual abilities.

For face recognition, observers utilize both shape and texture information. Here, we investigated the relative diagnosticity of shape and texture for delayed matching of familiar and unfamiliar faces (Experiment 1) and identifying familiar and newly learned faces (Experiment 2). Within each familiarity condition, pairs of 3D-captured faces were morphed selectively in either shape or texture in 20% steps, holding the respective other dimension constant. We also assessed participants' individual face-processing skills via the Bielefelder Famous Faces Test (BFFT), the Glasgow Face Matching Test, and the Cambridge Face Memory Test (CFMT). Using multilevel model analyses, we examined probabilities of same versus different responses (Experiment 1) and of original identity versus other/unknown identity responses (Experiment 2). Overall, texture was more diagnostic than shape for both delayed matching and identification, particularly so for familiar faces. On top of these overall effects, above-average BFFT performance was associated with enhanced utilization of texture in both experiments. Furthermore, above-average CFMT performance coincided with slightly reduced texture dominance in the delayed matching task (Experiment 1) and stronger sensitivity to morph-based changes overall, that is irrespective of morph type, in the face identification task (Experiment 2). Our findings (1) show the disproportionate importance of texture information for processing familiar face identity and (2) provide further evidence that familiar and unfamiliar face identity perception are mediated by different underlying processes.

Effects of Caricaturing in Shape or Color on Familiarity Decisions for Familiar and Unfamiliar Faces.

Recent evidence suggests that while reflectance information (including color) may be more diagnostic for familiar face recognition, shape may be more diagnostic for unfamiliar face identity processing. Moreover, event-related potential (ERP) findings suggest an earlier onset for neural processing of facial shape compared to reflectance. In the current study, we aimed to explore specifically the roles of facial shape and color in a familiarity decision task using pre-experimentally familiar (famous) and unfamiliar faces that were caricatured either in shape-only, color-only, or both (full; shape + color) by 15%, 30%, or 45%. We recorded accuracies, mean reaction times, and face-sensitive ERPs. Performance data revealed that shape caricaturing facilitated identity processing for unfamiliar faces only. In the ERP data, such effects of shape caricaturing emerged earlier than those of color caricaturing. Unsurprisingly, ERP effects were accentuated for larger levels of caricaturing. Overall, our findings corroborate the importance of shape for identity processing of unfamiliar faces and demonstrate an earlier onset of neural processing for facial shape compared to color.

Face shape and face identity processing in behavioral variant fronto-temporal dementia: A specific deficit for familiarity and name recognition of famous faces.

Deficits in face processing have been described in the behavioral variant of fronto-temporal dementia (bvFTD), primarily regarding the recognition of facial expressions. Less is known about face shape and face identity processing. Here we used a hierarchical strategy targeting face shape and face identity recognition in bvFTD and matched healthy controls. Participants performed 3 psychophysical experiments targeting face shape detection (Experiment 1), unfamiliar face identity matching (Experiment 2), familiarity categorization and famous face-name matching (Experiment 3). The results revealed group differences only in Experiment 3, with a deficit in the bvFTD group for both familiarity categorization and famous face-name matching. Voxel-based morphometry regression analyses in the bvFTD group revealed an association between grey matter volume of the left ventral anterior temporal lobe and familiarity recognition, while face-name matching correlated with grey matter volume of the bilateral ventral anterior temporal lobes. Subsequently, we quantified familiarity-specific and name-specific recognition deficits as the sum of the celebrities of which respectively only the name or only the familiarity was accurately recognized. Both indices were associated with grey matter volume of the bilateral anterior temporal cortices. These findings extent previous results by documenting the involvement of the left anterior temporal lobe (ATL) in familiarity detection and the right ATL in name recognition deficits in fronto-temporal lobar degeneration.

Facial expression recognition in people with medicated and unmedicated Parkinson’s disease

Recognition of facial expressions of emotion was investigated in people with medicated and unmedicated Parkinson's disease (PD) and matched controls (unmedicated PD, n=16; medicated PD, n=20; controls, n=40). Participants in the medicated group showed some visual impairment (impaired contrast sensitivity) and performed less well on perception of unfamiliar face identity, but did not show significant deficits in the perception of sex, gaze direction, or familiar identity from the face. For both Parkinson's disease groups, there was evidence of impaired recognition of facial expressions in comparison to controls. These deficits were more consistently noted in the unmedicated group, who were also found to perform worse than the medicated group at recognising disgust from prototypical facial expressions, and at recognising anger and disgust in computer-manipulated images. Although both Parkinson's disease groups showed impairments of facial expression recognition, the consistently worse recognition of disgust in the unmedicated group is consistent with the hypothesis from previous studies that brain regions modulated by dopaminergic neurons are involved in the recognition of disgust.

Recognition of Facial Expressions: Selective Impairment of Specific Emotions in Huntington's Disease

Recognition of facial expressions of basic emotions was investigated in HL and UJ, two people with Huntington's disease who showed little evidence of general cognitive deterioration. No impairments were found in tests of the perception of age, sex, familiar face identity, unfamiliar face identity, and gaze direction, indicating adequate processing of the face as a physical stimulus. Computer-interpolated ("morphed") images of facial expressions of basic emotions were used to demonstrate deficits in the recognition of disgust and fear for UJ. HL also showed a deficit in the recognition of disgust, and was not very adept (but not significantly impaired) at recognising fear. Other basic emotions (happiness, surprise, sadness, anger) were recognised atnormal levels of performance by HL and UJ. These results show that impairments of emotion recognition can be circumscribed; affecting some emotions more than others, and occurring in people who do not show pronounced perceptual or intellectual deterioration. Questionnaires examining self-assessed emotion indicated normal experience of anger by HL and UJ, but possible abnormalities for disgust and fear. The processes involved in recognising other people's emotions may therefore be linked to those involved in experiencing emotion, and the basic emotions of fear and disgust may have separable neural substrates.

Loss of disgust. Perception of faces and emotions in Huntington's disease.

Face perception and emotion recognition were investigated in a group of people with Huntington's disease and matched controls. In conventional tasks intended to explore the perception of age, sex, unfamiliar face identity (Benton test) and gaze direction from the face, the Huntington's disease group showed a borderline impairment of gaze direction perception and were significantly impaired on unfamiliar face matching. With a separate set of tasks using computerinterpolated ('morphed') facial images, people with Huntington's disease were markedly impaired at discriminating anger from fear, but experienced less difficulty with continua varying from male to female, between familiar identities, and from happiness to sadness. In a further test of recognition of facial expressions of basic emotions from the Ekman and Friesen (1976) series, interpolated images were created for six continua that lay around the perimeter of an emotion hexagon (happiness-surprise; surprise-fear; fear-sadness; sadness-disgust; disgust-anger; anger-happiness). In deciding which emotion these morphed images were most like, people with Huntington's disease again showed deficits in the recognition of anger and fear, and an especially severe problem with disgust, which was recognized only at chance level. A follow-up study with tests of facially and vocally expressed emotions confirmed that the recognition of disgust was markedly poor for the Huntington's disease group, still being no better than chance level. Questionnaires were also used to examine self-assessed emotion, but did not show such striking problems. Taken together, these data reveal severe impairments of emotion recognition in Huntington's disease, and show that the recognition of some emotions is more impaired than others. The possibility that certain basic emotions may have dedicated neural substrates needs to be seriously considered: among these, disgust is a prime candidate.

The independence of face identity and facial expression recognition mechanisms: Relationship to sex and cognitive style

Two tasks, one mapping the recognition of unfamiliar face identity and the other the identification of six facial expressions were unilaterally presented to field dependent and field independent individuals of both genders. Regardless of sex, field independent subjects showed faster-response times (RTs) in the left visual field (LVF) for face identity and for the identification of disgust and fear and faster RTs in the RVF for the identification of anger. A trend toward LVF superiority was found over the whole sample for the facial expression task; this effect was still present when the face identity task was partialled out, indicating the independence of the underlying mechanisms.