Kate Crookes

Early maturity of face recognition: No childhood development of holistic processing, novel face encoding, or face-space

Historically, it was believed the perceptual mechanisms involved in individuating faces developed only very slowly over the course of childhood, and that adult levels of expertise were not reached until well into adolescence. Over the last 10 years, there has been some erosion of this view by demonstrations that all adult-like behavioural properties are qualitatively present in young children and infants. Determining the age of maturity, however, requires quantitative comparison across age groups, a task made difficult by the need to disentangle development in face perception from development in all the other cognitive factors that affect task performance. Here, we argue that full quantitative maturity is reached early, by 5-7 years at the latest and possibly earlier. This is based on a comprehensive literature review of results in the 5-years-to-adult age range, with particular focus on the results of the few previous studies that are methodologically suitable for quantitative comparison of face effects across age, plus three new experiments testing development of holistic/configural processing (faces versus objects, disproportionate inversion effect), ability to encode novel faces (assessed via implicit memory) and face-space (own-age bias).

A critical review of the development of face recognition: Experience is less important than previously believed

Historically, it has been argued that face individuation develops very slowly, not reaching adult levels until adolescence, with experience being the driving force behind this protracted improvement. Here, we challenge this view based on extensive review of behavioural and neural findings. Results demonstrate qualitative presence of all key phenomena related to face individuation (encoding of novel faces, holistic processing effects, face-space effects, face-selective responses in neuroimaging) at the earliest ages tested, typically 3–5 years of age and in many cases even infancy. Results further argue for quantitative maturity by early childhood, based on an increasing number of behavioural studies that have avoided the common methodological problem of restriction of range, as well as event-related potential (ERP), but not functional magnetic resonance imaging (fMRI) studies. We raise a new possibility that could account for the discrepant fMRI findings—namely, the use of adult-sized head coils on child-sized heads. We review genetic and innate contributions to face individuation (twin studies, neonates, visually deprived monkeys, critical periods, perceptual narrowing). We conclude that the role of experience in the development of the mechanisms of face identification has been overestimated. The emerging picture is that the mechanisms supporting face individuation are mature early, consistent with the social needs of children for reliable person identification in everyday life, and are also driven to an important extent by our evolutionary history.

Distinguishing Norm-Based From Exemplar-Based Coding of Identity in Children: Evidence From Face Identity Aftereffects

Childrens performance on face identification tests improves dramatically between age 4 and adolescence, yet the source of this improvement is controversial. We used face identity aftereffects to examine whether changes in the organization of face-space during childhood could be a source of this improvement. Specifically we tested whether 7- to 9-year-old children, like adults, show patterns of aftereffects predicted by coding facial identity relative to a norm or the patterns predicted by exemplar-based coding. Consistent with use of norm-based coding childrens aftereffects were larger (a) for opposite than non-opposite adapt-test pairs equated for perceptual similarity, and (b) for adaptors far from the average than for adaptors closer to the average. In addition, face identity aftereffects were present by age 5, suggesting adult-like face-space properties by 5, though we did not conduct specific tests to distinguish norm-based from exemplar-based coding in this age group. We conclude that childrens poor face identification skills cannot be attributed to a failure to use norm-based coding.

The other-race effect: Holistic coding differences and beyond

We evaluate claims that the other-race effect in face memory reflects stronger holistic coding of own-race than other-race faces. Considering evidence from a range of paradigms, including the inversion effect, part–whole effect, composite effect, and the scrambled/blurred task, we find considerable inconsistency, both between paradigms and between participant ethnicities. At the same time, however, studies that isolate configural and component feature processing consistently show better featural, as well as better configural, processing of own-race faces, for both Caucasian and Asian participants. These results raise the possibility that the key feature of own-race face processing is not stronger holistic processing per se, but rather more effective processing of all types of face information (featural as well as holistic).

Importance of the Inverted Control in Measuring Holistic Face Processing with the Composite Effect and Part-Whole Effect

Holistic coding for faces is shown in several illusions that demonstrate integration of the percept across the entire face. The illusions occur upright but, crucially, not inverted. Converting the illusions into experimental tasks that measure their strength – and thus index degree of holistic coding – is often considered straightforward yet in fact relies on a hidden assumption, namely that there is no contribution to the experimental measure from secondary cognitive factors. For the composite effect, a relevant secondary factor is size of the “spotlight” of visuospatial attention. The composite task assumes this spotlight can be easily restricted to the target half (e.g., top-half) of the compound face stimulus. Yet, if this assumption were not true then a large spotlight, in the absence of holistic perception, could produce a false composite effect, present even for inverted faces and contributing partially to the score for upright faces. We review evidence that various factors can influence spotlight size: race/culture (Asians often prefer a more global distribution of attention than Caucasians); sex (females can be more global); appearance of the join or gap between face halves; and location of the eyes, which typically attract attention. Results from five experiments then show inverted faces can sometimes produce large false composite effects, and imply that whether this happens or not depends on complex interactions between causal factors. We also report, for both identity and expression, that only top-half face targets (containing eyes) produce valid composite measures. A sixth experiment demonstrates an example of a false inverted part-whole effect, where encoding-specificity is the secondary cognitive factor. We conclude the inverted face control should be tested in all composite and part-whole studies, and an effect for upright faces should be interpreted as a pure measure of holistic processing only when the experimental design produces no effect inverted.

The Composite Task Reveals Stronger Holistic Processing in Children than Adults for Child Faces

Background While own-age faces have been reported to be better recognized than other-age faces, the underlying cause of this phenomenon remains unclear. One potential cause is holistic face processing, a special kind of perceptual and cognitive processing reserved for perceiving upright faces. Previous studies have indeed found that adults show stronger holistic processing when looking at adult faces compared to child faces, but whether a similar own-age bias exists in children remains to be shown. Methodology/Principal Findings Here we used the composite face task – a standard test of holistic face processing – to investigate if, for child faces, holistic processing is stronger for children than adults. Results showed child participants (8–13 years) had a larger composite effect than adult participants (22–65 years). Conclusions/Significance Our finding suggests that differences in strength of holistic processing may underlie the own-age bias on recognition memory. We discuss the origin of own-age biases in terms of relative experience, face-space tuning, and social categorization.

How well do computer-generated faces tap face expertise?

The use of computer-generated (CG) stimuli in face processing research is proliferating due to the ease with which faces can be generated, standardised and manipulated. However there has been surprisingly little research into whether CG faces are processed in the same way as photographs of real faces. The present study assessed how well CG faces tap face identity expertise by investigating whether two indicators of face expertise are reduced for CG faces when compared to face photographs. These indicators were accuracy for identification of own-race faces and the other-race effect (ORE)–the well-established finding that own-race faces are recognised more accurately than other-race faces. In Experiment 1 Caucasian and Asian participants completed a recognition memory task for own- and other-race real and CG faces. Overall accuracy for own-race faces was dramatically reduced for CG compared to real faces and the ORE was significantly and substantially attenuated for CG faces. Experiment 2 investigated perceptual discrimination for own- and other-race real and CG faces with Caucasian and Asian participants. Here again, accuracy for own-race faces was significantly reduced for CG compared to real faces. However the ORE was not affected by format. Together these results signal that CG faces of the type tested here do not fully tap face expertise. Technological advancement may, in the future, produce CG faces that are equivalent to real photographs. Until then caution is advised when interpreting results obtained using CG faces.

Holistic processing for other-race faces in Chinese participants occurs for upright but not inverted faces

Recent evidence suggests stronger holistic processing for own-race faces may underlie the own-race advantage in face memory. In previous studies Caucasian participants have demonstrated larger holistic processing effects for Caucasian over Asian faces. However, Asian participants have consistently shown similar sized effects for both Asian and Caucasian faces. We investigated two proposed explanations for the holistic processing of other-race faces by Asian participants: (1) greater other-race exposure, (2) a general global processing bias. Holistic processing was tested using the part-whole task. Participants were living in predominantly own-race environments and other-race contact was evaluated. Despite reporting significantly greater contact with own-race than other-race people, Chinese participants displayed strong holistic processing for both Asian and Caucasian upright faces. In addition, Chinese participants showed no evidence of holistic processing for inverted faces arguing against a general global processing bias explanation. Caucasian participants, in line with previous studies, displayed stronger holistic processing for Caucasian than Asian upright faces. For inverted faces there were no race-of-face differences. These results are used to suggest that Asians may make more general use of face-specific mechanisms than Caucasians.

Face inversion disproportionately disrupts sensitivity to vertical over horizontal changes in eye position.

Presenting a face inverted (upside down) disrupts perceptual sensitivity to the spacing between the features. Recently, it has been shown that this disruption is greater for vertical than horizontal changes in eye position. One explanation for this effect proposed that inversion disrupts the processing of long-range (e.g., eye-to-mouth distance) more than local (e.g., interocular distance) spatial relations. Here we investigated the spacing inversion effect for horizontal and vertical changes that could involve long- and short-range spatial relations. Our results replicated the finding of larger inversion effects for vertical than for horizontal changes, and found it was observed regardless of the spatial distance. These results argue against a long-range versus short-range spatial relations explanation of the horizontal versus vertical difference in the size of the spacing inversion effect for eye position. We support the view that inversion effects are relatively small when spacing changes occur within the eye region, but are larger when they occur outside of this region in the absence of focal attention.

Face-blind for other-race faces: Individual differences in other-race recognition impairments.

We report the existence of a previously undescribed group of people, namely individuals who are so poor at recognition of other-race faces that they meet criteria for clinical-level impairment (i.e., they are “face-blind” for other-race faces). Testing 550 participants, and using the well-validated Cambridge Face Memory Test for diagnosing face blindness, results show the rate of other-race face blindness to be nontrivial, specifically 8.1% of Caucasians and Asians raised in majority own-race countries. Results also show risk factors for other-race face blindness to include: a lack of interracial contact; and being at the lower end of the normal range of general face recognition ability (i.e., even for own-race faces); but not applying less individuating effort to other-race than own-race faces. Findings provide a potential resolution of contradictory evidence concerning the importance of the other-race effect (ORE), by explaining how it is possible for the mean ORE to be modest in size (suggesting a genuine but minor problem), and simultaneously for individuals to suffer major functional consequences in the real world (e.g., eyewitness misidentification of other-race offenders leading to wrongful imprisonment). Findings imply that, in legal settings, evaluating an eyewitness’s chance of having made an other-race misidentification requires information about the underlying face recognition abilities of the individual witness. Additionally, analogy with prosopagnosia (inability to recognize even own-race faces) suggests everyday social interactions with other-race people, such as those between colleagues in the workplace, will be seriously impacted by the ORE in some people.