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Understanding developmental changes in children's use of specific visual information for recognizing object categories is essential for understanding how experience shapes recognition. Research on the development of face recognition has focused on children's use of low-level information (e.g. orientation sub-bands), or high-level information. In face categorization tasks, adults also exhibit sensitivity to intermediate complexity features that are diagnostic of the presence of a face. Do children also use intermediate complexity features for categorizing faces and objects, and, if so, how does their sensitivity to such features change during childhood? Intermediate-complexity features bridge the gap between low- and high-level processing: they have computational benefits for object detection and segmentation, and are known to drive neural responses in the ventral visual system. Here, we have investigated the developmental trajectory of children's sensitivity to diagnostic category information in intermediate-complexity features. We presented children (5-10 years old) and adults with image fragments of faces (Experiment 1) and cars (Experiment 2) varying in their mutual information, which quantifies a fragment's diagnosticity of a specific category. Our goal was to determine whether children were sensitive to the amount of mutual information in these fragments, and if their information usage is different from adults. We found that despite better overall categorization performance in adults, all children were sensitive to fragment diagnosticity in both categories, suggesting that intermediate representations of appearance are established early in childhood. Moreover, children's usage of mutual information was not limited to face fragments, suggesting the extracting intermediate-complexity features is a process that is not specific only to faces. We discuss the implications of our findings for developmental theories of face and object recognition.

Although adults' ability to recognize materials from complex natural images has been well characterized, we still know very little about the development of material perception. When do children exhibit adult-like abilities to categorize materials? What visual features do they use to do so as a function of age and material category? In the present study, we attempted to address both of these issues in two experiments that we administered to school-age children (5-10 years old) and adults. In both tasks, we asked our participants to categorize natural materials (metal, stone, water, and wood) using original images of these materials as well as synthetic images made with the Portilla-Simoncelli algorithm. By including synthetic images in our stimulus set, we were able to assess both how material categorization develops during childhood and how visual summary statistics are recruited for material perception across age groups. We observed that when asked to provide category labels for individual images (Experiment 1), young children were disproportionately bad at categorizing some materials after they were synthesized, suggesting material-specific changes in information use over the course of development. However, when asked to match real and synthetic images according to material category without labeling (Experiment 2), these effects were weakened. We conclude that while children have adult-like abilities to encode and compare images based on summary statistics, the mapping between summary statistics and category labels undergoes prolonged development during childhood.

Both face shape and pigmentation are diagnostic cues for face identification and categorization. In particular, both shape and pigmentation contribute to observers' categorization of faces by race. Although many theoretical accounts of the behavioral other-race effect either explicitly or implicitly depend on differential use of visual information as a function of category expertise, there is little evidence that observers do in fact differentially rely on distinct visual cues for own- and other-race faces. In the current study, we examined how Asian and Caucasian children (4-6 years of age) and adults use three-dimensional shape and two-dimensional pigmentation to make similarity judgments of White, Black, and Asian faces. Children in this age range are capable of making category judgments about race but also are sufficiently plastic with regard to the behavioral other-race effect that it seems as though their representations of facial appearance across different categories are still emerging. Using a simple match-to-sample similarity task, we found that children tend to use pigmentation to judge facial similarity more than adults and also that own-group versus other-group category membership appears to influence how quickly children learn to use shape information more readily. Therefore, we suggest that children continue to adjust how different visual information is weighted during early and middle childhood and that experience with faces affects the speed at which adult-like weightings are established., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Brief glimpses of nonverbal behavior (or "thin slices") offer ample visual information to make reliable judgments about individuals. Previous work has largely focused on the personality characteristics and traits of individuals; however, the nature of dyadic relationships (strangers, lovers, or friends) can also be determined (Ambady & Gray, Journal of Personality and Social Psychology, 83, 947-961 2002). Judgments from thin slices are known to be accurate, but the motion features supporting accurate performance are unknown. We explored whether personal familiarity was detectable within the context of "thin slices" of genuine interaction, as well as the invariant properties of thin-slice recognition. In two experiments, participants sequentially viewed two 6-s silent videos on each trial of an individual interacting with an unfamiliar partner; the other depicted the same person interacting with a personally familiar partner. All sequences were cropped so that only the target individual was visible. In Experiment 1, participants viewed either the original sequences, reversed sequences, a static-image "slideshow" of the sequence, or a static-image slideshow with blank frames separating the images. In Experiment 2, all participants viewed the original sequences and clips played at either double speed or half speed. Participants' performance was above chance in the forward and reverse conditions, but was significantly better in both the static-image slideshow conditions. When task speed was manipulated, we found a larger performance cost for fast than for slow videos. Detecting personal familiarity via spontaneous natural gestures depends on information in static images more than on face or body movement. Although static images are typically less important for recognizing nonverbal behavior, we argue they may be valuable for making familiarity judgments from thin slices.

Face recognition abilities develop dramatically during the first year of life, but comparatively little is known about the nature of face-specific perceptual development during early childhood. Face-specific effects of image appearance on recognition, including face inversion and contrast negation, are a useful means of understanding the functional properties of face perception developmentally. Here, we examined the generality of the impact of contrast negation on face perception during early childhood using event-related potentials (ERPs). Specifically, we recorded continuous electroencephalography (EEG) while adult participants and children between 4 and 6 years of age viewed human and non-human primate faces presented in either positive or negative contrast. We examined both the P100 and N170 components to determine whether or not sensitivity to contrast polarity was evident in face-sensitive components during early childhood and also whether or not that sensitivity was specific to species category. We found evidence of a species-specific effect of contrast negation at the N170, suggesting that by early childhood some aspects of face-specific processing have been restricted to a relatively narrow class of face stimuli. However, this effect is of the opposite sign relative to adults, suggesting that there is continued maturation of face-specific processing during childhood., (Copyright © 2013 Elsevier Inc. All rights reserved.)

How does the remarkable human ability for face recognition arise over development? Competing theories have proposed either late maturity (beyond 10 years) or early maturity (before 5 years), but have not distinguished between perceptual and memory aspects of face recognition. Here, we demonstrate a perception-memory dissociation. We compare rate of development for (adult, human) faces versus other social stimuli (bodies), other discrete objects (cars), and other categories processed in discrete brain regions (scenes, bodies), from 5 years to adulthood. For perceptual discrimination, performance improved with age at the same rate for faces and all other categories, indicating no domain-specific development. In contrast, face memory increased more strongly than non-face memory, indicating domain-specific development. The results imply that each theory is partly true: the late maturity theory holds for face memory, and the early maturity theory for face perception., (© 2013 John Wiley & Sons Ltd.)

High-level adaptation effects reveal important features of the neural coding of objects and faces. View-adaptation in particular is a highly useful means of characterizing how depth rotation of the face is represented and therefore, how view-invariant recognition of the face may be achieved. In the present study, we used view adaptation to determine the extent to which depth rotations of a face are represented in an image-based or object-based manner. Specifically, we dissociated object-based axes from image-based axes via a 90° planar rotation of the adapting face and observed that participants' responses pre- and post-adaptation are most consistent with an image-based representation of depth rotations of the face. We discuss our data in the context of previous results describing the impact of planar rotation on related aspects of face perception., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

During the first year of life, infants' face recognition abilities are subject to 'perceptual narrowing', the end result of which is that observers lose the ability to distinguish previously discriminable faces (e.g. other-race faces) from one another. Perceptual narrowing has been reported for faces of different species and different races, in developing humans and primates. Though the phenomenon is highly robust and replicable, there have been few efforts to model the emergence of perceptual narrowing as a function of the accumulation of experience with faces during infancy. The goal of the current study is to examine how perceptual narrowing might manifest as statistical estimation in 'face-space', a geometric framework for describing face recognition that has been successfully applied to adult face perception. Here, I use a computer vision algorithm for Bayesian face recognition to study how the acquisition of experience in face-space and the presence of race categories affect performance for own and other-race faces. Perceptual narrowing follows from the establishment of distinct race categories, suggesting that the acquisition of category boundaries for race is a key computational mechanism in developing face expertise., (© 2012 Blackwell Publishing Ltd.)

Face perception is a critical social ability and identifying its neural correlates is important from both basic and applied perspectives. In EEG recordings, faces elicit a distinct electrophysiological signature, the N170, which has a larger amplitude and shorter latency in response to faces compared to other objects. However, determining the face specificity of any neural marker for face perception hinges on finding an appropriate control stimulus. We used a novel stimulus set consisting of 300 images that spanned a continuum between random patches of natural scenes and genuine faces, in order to explore the selectivity of face-sensitive ERP responses with a model-based parametric stimulus set. Critically, our database contained "false alarm" images that were misclassified as face by computational face-detection system and varied in their image-level similarity to real faces. High-density (128-channel) event-related potentials (ERPs) were recorded while 23 adult subjects viewed all 300 images in random order, and determined whether each image was a face or non-face. The goal of our analyses was to determine the extent to which a gradient of sensitivity to face-like structure was evident in the ERP signal. Traditional waveform analyses revealed that the N170 component over occipitotemporal electrodes was larger in amplitude for faces compared to all non-faces, even those that were high in image similarity to faces, suggesting strict selectivity for veridical face stimuli. By contrast, single-trial classification of the entire waveform measured at the same sensors revealed that misclassifications of non-face patterns as faces increased with image-level similarity to faces. These results suggest that individual components may exhibit steep selectivity, but integration of multiple waveform features may afford graded information regarding stimulus appearance., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Newborn infants appear to possess an innate bias that guides preferential orienting to and tracking of human faces. There is, however, no clear agreement as to the underlying mechanism supporting such a preference. In particular, two competing theories (known as the 'structural' and 'sensory' hypotheses) conjecture fundamentally different biasing mechanisms to explain this behavior. The structural hypothesis suggests that a crude '3-dot' representation of face-specific geometry is responsible for the exhibited preference. By contrast, the sensory hypothesis suggests that face preference is the product of several generic visual preferences for qualities like dark/light vertical asymmetry, horizontal symmetry, and high contrast. To complement existing empirical results, the current study describes a computational investigation of how well both proposals actually support face detection in cluttered natural scenes. The results demonstrate that both models are capable of locating faces effectively, but that the model suggested by the 'sensory hypothesis' is more selective than the model suggested by the 'structural hypothesis'.

Adult observers generally find it difficult to recognize and distinguish faces that belong to categories with which they have limited visual experience. One aspect of this phenomenon is commonly known as the "Other-Race Effect" (ORE) since this behavior is typically highly evident in the perception of faces belonging to ethnic or racial groups other than that of the observer. This acquired disadvantage in face recognition likely results from highly specific "tuning" of the underlying representation of facial appearance, leading to efficient processing of commonly seen faces at the expense of poor generalization to other face categories. In the current study we used electrophysiological (event-related potentials or ERPs) and behavioral measures of performance to characterize face processing in racial categories defined by dissociable shape and pigmentation information. Our goal was to examine the specificity of the representation of facial appearance in more detail by investigating how race-specific face shape and pigmentation separately modulated neural responses previously implicated in face processing, the N170 and N250 components. We found that both components were modulated by skin color, independent of face shape, but that only the N250 exhibited sensitivity to face shape. Moreover, the N250 appears to only respond differentially to the skin color of upright faces, showing a lack of color sensitivity for inverted faces., (2009 Elsevier Ltd. All rights reserved.)