Face Discrimination Abilities Research Articles

Healthy aging impairs face discrimination ability.

Face images enable individual identities to be discriminated from one another. We aimed to quantify age-related changes in different aspects of face identity discrimination. Face discrimination sensitivity was measured with a memory-free “odd-one-out” task. Five age groups (N = 15) of healthy adults with normal vision were tested: 20, 50-59, 60-69, 70-79, and 80-89. Sensitivity was measured for full-face images (all features visible), external features (head-shape, hairline), internal features (nose, mouth, eyes, and eyebrows) and closed-contour shapes (control object). Sensitivity to full-faces continuously declined by approximately 13% per decade, after 50 years of age. When age-related differences in visual acuity were controlled, the effect of age on face discrimination sensitivity remained. Sensitivity to face features also deteriorated with age. Although the effect for external features was similar to full-faces, the rate of decline was considerably steeper (approximately 3.7 times) for internal, relative to external, features. In contrast, there was no effect of age on sensitivity to shapes. All age groups demonstrated the same overall pattern of sensitivity to different types of face information. Healthy aging was associated with a continuous decline in sensitivity to both full-faces and face features, although encoding of internal features was disproportionately impaired. This age-related deficit was independent of differences in low-level vision. That sensitivity to shapes was unaffected by age suggests these results cannot be explained by general cognitive decline or lower-level visual deficits. Instead, healthy aging is associated with a specific decline in the mechanisms that underlie face discrimination.

ENHANCED PERIPHERAL FACE PROCESSING IN DEAF INDIVIDUALS.

Studies of compensatory changes in visual functions in response to auditory loss have shown that enhancements tend to be restricted to the processing of specific visual features, such as motion in the periphery. Previous studies have also shown that deaf individuals can show greater face processing abilities in the central visual field. Enhancements in the processing of peripheral stimuli are thought to arise from a lack of auditory input and a subsequent increase in the allocation of attentional resources to peripheral locations, while enhancements in face processing abilities are thought to be driven by experience with ASL and not necessarily hearing loss. This combined with the fact that face processing abilities typically decline with eccentricity suggests that face processing enhancements may not extend to the periphery for deaf individuals. Using a face matching task, we examined whether deaf individuals' enhanced ability to discriminate between faces extends to the peripheral visual field. Deaf participants were more accurate than hearing participants in discriminating faces presented both centrally and in the periphery. Our results support earlier findings that deaf individuals possess enhanced face discrimination abilities in the central visual field and further extend them by showing that these enhancements also occur in the periphery for more complex stimuli.

Enhanced Peripheral Face Processing in Deaf Individuals †

Studies of compensatory changes in visual functions in response to auditory loss have shown that enhancements tend to be restricted to the processing of specific visual features, such as motion in the periphery. Previous studies have also shown that deaf individuals can show greater face processing abilities in the central visual field. Enhancements in the processing of peripheral stimuli are thought to arise from a lack of auditory input and subsequent increase in the allocation of attentional resources to peripheral locations, while enhancements in face processing abilities are thought to be driven by experience with American sign language and not necessarily hearing loss. This combined with the fact that face processing abilities typically decline with eccentricity suggests that face processing enhancements may not extend to the periphery for deaf individuals. Using a face matching task, the authors examined whether deaf individuals’ enhanced ability to discriminate between faces extends to the peripheral visual field. Deaf participants were more accurate than hearing participants in discriminating faces presented both centrally and in the periphery. Their results support earlier findings that deaf individuals possess enhanced face discrimination abilities in the central visual field and further extend them by showing that these enhancements also occur in the periphery for more complex stimuli.

Infants' Gaze Patterns for Same-Race and Other-Race Faces, and the Other-Race Effect.

The other-race effect (ORE) can be described as difficulties in discriminating between faces of ethnicities other than one’s own, and can already be observed at approximately 9 months of age. Recent studies also showed that infants visually explore same-and other-race faces differently. However, it is still unclear whether infants’ looking behavior for same- and other-race faces is related to their face discrimination abilities. To investigate this question we conducted a habituation–dishabituation experiment to examine Caucasian 9-month-old infants’ gaze behavior, and their discrimination of same- and other-race faces, using eye-tracking measurements. We found that infants looked longer at the eyes of same-race faces over the course of habituation, as compared to other-race faces. After habituation, infants demonstrated a clear other-race effect by successfully discriminating between same-race faces, but not other-race faces. Importantly, the infants’ ability to discriminate between same-race faces significantly correlated with their fixation time towards the eyes of same-race faces during habituation. Thus, our findings suggest that for infants old enough to begin exhibiting the ORE, gaze behavior during habituation is related to their ability to differentiate among same-race faces, compared to other-race faces.

High test-retest reliability of a neural index of rapid automatic discrimination of unfamiliar individual faces

ABSTRACTAn important aspect of human individual face recognition is the ability to discriminate unfamiliar individual. Since many general processes contribute to explicit behavioural performance in individual face discrimination tasks, isolating a measure of unfamiliar individual face discrimination ability in humans is challenging. In recent years, a fast periodic visual stimulation approach (FPVS) has provided objective (frequency-locked) implicit electrophysiological indices of individual face discrimination that are highly sensitive at the individual level within a few minutes of testing. Here we evaluate the test-retest reliability of this response across scalp electroencephalographic (EEG) recording sessions separated by more than two months, in the same 30 individuals. We found no test-retest difference overall across sessions in terms of amplitude and spatial distribution of the EEG individual face discrimination response. Moreover, with only 4 stimulation sequences corresponding to 4 min of recordings per session, the individual face discrimination response was highly reliable in terms of amplitude, spatial distribution, and shape. Together with previous observations, these results strengthen the diagnostic value of FPVS-EEG as an objective and rapid flag for specific difficulties at individual face recognition in the human population.

The role of response inconsistency in older adults' face discrimination ability

The role of response inconsistency in older adults' face discrimination ability

Sibling experience modulates perceptual narrowing toward adult faces in the first year of life.

During the first year of life face discrimination abilities narrow toward adult human faces of the most frequently encountered ethnic group/s. Earlier studies showed that perceptual learning under laboratory-training protocols can modulate this narrowing process. Here we investigated whether natural experience acquired in everyday settings with an older sibling's face can shape the trajectory of perceptual narrowing towards adult faces. Using an infant-controlled habituation procedure we measured discrimination of adult (Experiment 1) and child faces (Experiment 2) in 3- and 9- month-old infants with and without a child sibling. Discrimination of adult faces was observed for infants at both ages, although accompanied by posthabituation preferences in opposite directions, whereas at both ages the discrimination of child faces critically depended on sibling experience. These results provide the first evidence that natural experience acquired with siblings affects the tuning properties of infant face representation.

Meta-analytic review of the development of face discrimination in infancy: Face race, face gender, infant age, and methodology moderate face discrimination.

Infants show facility for discriminating between individual faces within hours of birth. Over the first year of life, infants' face discrimination shows continued improvement with familiar face types, such as own-race faces, but not with unfamiliar face types, like other-race faces. The goal of this meta-analytic review is to provide an effect size for infants' face discrimination ability overall, with own-race faces, and with other-race faces within the first year of life, how this differs with age, and how it is influenced by task methodology. Inclusion criteria were (a) infant participants aged 0 to 12 months, (b) completing a human own- or other-race face discrimination task, (c) with discrimination being determined by infant looking. Our analysis included 30 works (165 samples, 1,926 participants participated in 2,623 tasks). The effect size for infants' face discrimination was small, 6.53% greater than chance (i.e., equal looking to the novel and familiar). There was a significant difference in discrimination by race, overall (own-race, 8.18%; other-race, 3.18%) and between ages (own-race: 0- to 4.5-month-olds, 7.32%; 5- to 7.5-month-olds, 9.17%; and 8- to 12-month-olds, 7.68%; other-race: 0- to 4.5-month-olds, 6.12%; 5- to 7.5-month-olds, 3.70%; and 8- to 12-month-olds, 2.79%). Multilevel linear (mixed-effects) models were used to predict face discrimination; infants' capacity to discriminate faces is sensitive to face characteristics including race, gender, and emotion as well as the methods used, including task timing, coding method, and visual angle. (PsycINFO Database Record

The Caledonian face test: A new test of face discrimination

This study aimed to develop a clinical test of face perception which is applicable to a wide range of patients and can capture normal variability. The Caledonian face test utilises synthetic faces which combine simplicity with sufficient realism to permit individual identification. Face discrimination thresholds (i.e. minimum difference between faces required for accurate discrimination) were determined in an “odd-one-out” task. The difference between faces was controlled by an adaptive QUEST procedure. A broad range of face discrimination sensitivity was determined from a group (N=52) of young adults (mean 5.75%; SD 1.18; range 3.33–8.84%). The test is fast (3–4min), repeatable (test–re-test r2=0.795) and demonstrates a significant inversion effect. The potential to identify impairments of face discrimination was evaluated by testing LM who reported a lifelong difficulty with face perception. While LM’s impairment for two established face tests was close to the criterion for significance (Z-scores of −2.20 and −2.27) for the Caledonian face test, her Z-score was −7.26, implying a more than threefold higher sensitivity. The new face test provides a quantifiable and repeatable assessment of face discrimination ability. The enhanced sensitivity suggests that the Caledonian face test may be capable of detecting more subtle impairments of face perception than available tests.

Gender differences in crowd perception.

In this study, we investigated whether the first impression of a crowd of faces—crowd perception—is influenced by social background and cognitive processing. Specifically, we explored whether males and females, two groups that are distinct biologically and socially, differ in their ability to extract ensemble characteristics from crowds of faces that were comprised of different identities. Participants were presented with crowds of similar faces and were instructed to scroll through a morphed continuum of faces until they found a face that was representative of the average identity of each crowd. Consistent with previous research, females were more precise in single face perception. Furthermore, the results showed that females were generally more accurate in estimating the average identity of a crowd. However, the correlation between single face discrimination and crowd averaging differed between males and females. Specifically, male subjects' ensemble integration slightly compensated for their poor single face perception; their performance on the crowd perception task was not as poor as would be expected from their single face discrimination ability. Overall, the results suggest that group perception is not an isolated or uniform cognitive mechanism, but rather one that interacts with biological and social processes.

Starting School Improves Preschoolers' Ability to Discriminate Child Faces

Children take many years to become as skilled as adults in differentiating among faces and there is debate about the role of face experience in improving their skills. Here we tested whether the increase in exposure to the faces of children associated with entering school leads to improved face discrimination for this face category. To do so, we compared the face discrimination abilities of 3- to 4-year-old children who began attending school for the first time with those of age-matched controls not yet in school. Both groups completed a 2-alternative forced-choice matching task with adult and child faces, presented both in an upright and inverted orientation, at Time 1 (within the first month of entering school for the school group) and at Time 2 (5 months later). Between Time 1 and Time 2, both groups improved in discriminating between adult faces, but only the preschoolers improved for child faces. These effects were not modulated by inversion. Overall, these results suggest that, during the preschool years, a natural increase in exposure to the faces of 1 face category leads to improved discrimination of novel exemplars of this face category.

Development of face discrimination abilities, and relationship to magnocellular pathway development, between childhood and adulthood

The current study tested the development of face and object processing in young children (mean age = 5.24 years), adolescents (mean age = 15.8 years), and adults (mean age = 21.1 years) using stimuli that were equated for low-level visual characteristics (luminance, contrast, and spatial frequency make-up) and methods that equate for difficulty across ages. We also tested sensitivity to luminance and chromatic contrast (i.e., thought to be mediated primarily by the subcortical Magnocellular (M) and Parvocellular (P) pathways, respectively) to determine whether age-related improvements in face or object discrimination were driven by age-related changes in the M and/or P pathways. Results showed a selective age-related improvement in face sensitivity and a relationship between age-related increases in face sensitivity and luminance contrast sensitivity. These results add to the mounting evidence that the M pathway may influence face processing.

A quantitative link between face discrimination deficits and neuronal selectivity for faces in autism

Individuals with Autism Spectrum Disorder (ASD) appear to show a general face discrimination deficit across a range of tasks including social–emotional judgments as well as identification and discrimination. However, functional magnetic resonance imaging (fMRI) studies probing the neural bases of these behavioral differences have produced conflicting results: while some studies have reported reduced or no activity to faces in ASD in the Fusiform Face Area (FFA), a key region in human face processing, others have suggested more typical activation levels, possibly reflecting limitations of conventional fMRI techniques to characterize neuron-level processing. Here, we test the hypotheses that face discrimination abilities are highly heterogeneous in ASD and are mediated by FFA neurons, with differences in face discrimination abilities being quantitatively linked to variations in the estimated selectivity of face neurons in the FFA. Behavioral results revealed a wide distribution of face discrimination performance in ASD, ranging from typical performance to chance level performance. Despite this heterogeneity in perceptual abilities, individual face discrimination performance was well predicted by neural selectivity to faces in the FFA, estimated via both a novel analysis of local voxel-wise correlations, and the more commonly used fMRI rapid adaptation technique. Thus, face processing in ASD appears to rely on the FFA as in typical individuals, differing quantitatively but not qualitatively. These results for the first time mechanistically link variations in the ASD phenotype to specific differences in the typical face processing circuit, identifying promising targets for interventions.

The effects of visual degradation on face discrimination

People with reduced visual acuity (VA) and/or contrast sensitivity have difficulty recognizing faces and facial expressions. We have quantified these difficulties, using a synthetic face discrimination task employing both normal and artificially degraded vision. VA and contrast thresholds were measured using an optimised staircase procedure [Freiburg acuity Test (FrACT)] in 25 young adults (aged 18-24 years) with corrected visual acuity of 0.0 logMAR or better and with four levels of vision degraded with Bangerter occlusion foils. For face discrimination, male face images were synthesised from 37 cardinal points (position of eyes, width of nose, head shape etc) derived from frontal face photographs and manipulated by altering the points as a fraction of the mean head radius. Face discrimination thresholds (% difference) were measured from a simultaneous four-alternative forced choice of 'odd one out' from three identical faces and one that differed. Psychometric functions were measured for four participants with normal and degraded vision. Subsequently, the difference between faces was fixed at twice the discrimination thresholds and the size of the faces manipulated using the FrACT threshold procedure in 25 participants. Data were converted to equivalent face discrimination distances for realistic face dimensions. With normal vision, face discrimination thresholds ranged from 2.7% to 5.6%; these increased systematically and were more variable with visual degradation. When manipulating face size, face discrimination distance was highly correlated with both acuity and contrast sensitivity (r(2) = 0.77 and 0.80 respectively, p < 0.01). The mean distance with normal vision was 15.3 m (14.5-16.2 ± S.E.M.). With vision degraded to 0.6 logMAR (6/24 Snellen, contrast threshold 15%) the mean face discrimination distance was reduced to 3.9 m (3.7-4.1, ±S.E.M.). Poor face discrimination has a profound impact on real-life social communication. Here we report that artificial visual degradation also adversely impacts a synthetic face recognition task. As a rule of thumb, reduction in VA of 0.3 logMAR (halving the decimal VA) reduces the face recognition distance by a factor of 0.6 times. The FrACT-based face discrimination task provides an efficient new tool to quantify and monitor face discrimination ability.

A Test of Face Discrimination Ability in Aging and Vision Loss

The ability to recognize faces is fundamental to social interactions but has not been studied extensively in visual disorders such as age-related macular degeneration (AMD). We report here the development of a face discrimination test, in which both response times (RTs) and accuracies are measured. Results are compared for young and older control subjects and older adults with AMD to determine the factors underlying performance on this test. Subjects were 14 older controls, 11 young adult controls, and 34 individuals with binocular AMD. In the face discrimination test, colored reference photographs of eight people were presented continuously (male faces in the first half of the test, female faces in the second). On each trial, subjects reported which reference face matched the test face (shown with different poses and/or expressions). In addition, the older controls then identified the expression on the test face. The older controls showed generally small numbers of errors (0 to 9%) on the face identifications but more errors on expression identifications (up to 22%). They tended to show shorter RTs (but no changes in accuracy) with repeated presentations of the same face. The young controls responded more quickly, and they made almost no mistakes. Although performance varied, as a group, those with AMD were slower and showed more errors in identification than the older controls did. Across all subjects, both visual acuity and contrast sensitivity contributed significantly to the variances in RTs and accuracy. The group of older controls had poorer and more variable RTs and accuracies than the young controls. Difficulties in face matching, in terms of both accuracy and RT, were observed for subjects with AMD. Performance accuracy and RTs for this new test depended on both visual acuity and contrast sensitivity.

Early Experience Predicts Later Plasticity for Face Processing

Research has shown that experience acquired in infancy dramatically affects face-discrimination abilities. Yet much less is known about whether face processing retains any flexibility after the 1st year of life. Here, we show that early experience with an individual infant face can modulate the recognition performance of 3-year-old children and the perceptual processes they use to recognize infant faces (Experiment 1). Similar experience acquired in adulthood does not produce measurable effects (Experiment 2). We also show that the effects of early-acquired experience with an infant face become dormant during development in the absence of continued experience (Experiment 3) and can be reactivated in adulthood by reexposure to the original experience (Experiment 2). Overall, the results indicate that early experience can preserve the face-processing system from the loss of plasticity that would otherwise take place between childhood and adulthood.

Understanding the developmental origins of primate face recognition: Theoretical commentary on Martin-Malivel and Okada (2007).

J. Martin-Malivel and K. Okada (2007, this issue) reported that chimpanzees raised with extensive social contact with humans show face discrimination abilities for human faces that exceed those for conspecific faces. Martin-Malivel and Okada have placed this finding in the theoretical context of the relative role of experience and innate face representations. The present article discusses the logic of the various styles of studies relevant to this question--considering primates without prior visual experience, sensitive periods, perceptual narrowing, childhood development, other-species effects, other-race effects, social quality of experience with nonconspecifics, and perceived social group membership--and also reviews the key current data. A case is made that there is still a long way to go in understanding whether there is an innate representation of conspecific faces, how tightly tuned any such representation is to conspecific morphology, and how experience obtained during different age brackets (e.g., infancy versus adulthood) affects discrimination and interacts with any innate representation.

Developmental prosopagnosia and the Benton Facial Recognition Test.

The Benton Facial Recognition Test is used for clinical and research purposes, but evidence suggests that it is possible to pass the test with impaired face discrimination abilities. The authors tested 11 patients with developmental prosopagnosia using this test, and a majority scored in the normal range. Consequently, scores in the normal range should be interpreted cautiously, and testing should always be supplemented by other face tests.

Enhanced Facial Diserimination: Effects of Experience With American Sign Language

On-line comprehension of American Sign Language (ASL) requires rapid discrimination of linguistic facial expressions. We hypothesized that ASL signers' experience discriminating linguistic facial expressions might lead to enhanced performance for discriminating among different faces. Five experiments are reported that investigate signers' and non-signers' ability to discriminate human faces photographed under different conditions of orientation and lighting (the Benton Test of Facial Recognition). The results showed that deaf signers performed significantly better than hearing non-signers. Hearing native signers (born to deaf parents) also performed better than hearing nonsigners, suggesting that the enhanced performance of deaf signers is linked to experience with ASL rather than to auditory deprivation. Deaf signers who acquired ASL in early adulthood did not differ from native signers, which suggests that there is no 'critical period' during which signers must be exposed to ASL in order to exhibit enhanced face discrimination abilities. When the faces were inverted, signing and nonsigning groups did not differ in performance. This pattern of results suggests that experience with sign language affects mechanisms specific to face processing and does not produce a general enhancement of visual discrimination. Finally, a similar pattern of results was found with signing and nonsigning children, 6-9 years old. Overall, the results suggest that the brain mechanisms responsible for face processing are somewhat plastic and can be affected by experience. We discuss implications of these results for the relation between language and cognition.