Multiple images captured from a single encounter do not promote face learning.

Viewing multiple images of a newly encountered face improves recognition of that identity in new instances. Studies examining face learning have presented high-variability (HV) images that incorporate changes that occur from moment-to-moment (e.g., head orientation and expression) and over time (e.g., lighting, hairstyle, and health). We examined whether low-variability (LV) images (i.e., images that incorporate only moment-to-moment changes) also promote generalisation of learning such that novel instances are recognised. Participants viewed a single image, six LV images, or six HV images of a target identity before being asked to recognise novel images of that identity in a face matching task (training stimuli remained visible) or a memory task (training stimuli were removed). In Experiment 1 (n = 71), participants indicated which image(s) in 8-image arrays belonged to the target identity. In Experiment 2 (n = 73), participants indicated whether sequentially presented images belonged to the target identity. Relative to the single-image condition, sensitivity to identity improved and response biases were less conservative in the HV condition; we found no evidence of generalisation of learning in the LV condition regardless of testing protocol. Our findings suggest that day-to-day variability in appearance plays an essential role in acquiring expertise with a novel face.

Learning faces from variability: Four- and five-year-olds differ from older children and adults.

Children under 6 years of age have difficulty recognizing a familiar face across changes in appearance and telling the face apart from similar-looking people. Understanding the process by which newly encountered faces become familiar can provide insights into these difficulties. Exposure to the ways in which a person varies in appearance is one mechanism by which adults and older children (≥6 years) learn new faces. We provide the first investigation of whether this mechanism for face learning functions in younger children. Children aged 4 and 5 years were read two storybooks featuring an unfamiliar character. Participants viewed six images of the character in one story and one image of the character in the other story. After each story, children were asked to identify novel images of the character that were intermixed with images of a similar-looking distractor. Like older children, 4- and 5-year-olds were more sensitive to identity in the 6-image condition, but they also adapted a less conservative criterion. Young children identified more images of the character after viewing six images versus one image. However, many also incorrectly identified more images of the distractor after viewing six images versus one image, an effect not previously found for older children and adults. These results suggest that this mechanism for face learning is not fully refined before 6 years of age.

Children's ability to recognize their parent's face improves with age.

Adults are experts at recognizing familiar faces across images that incorporate natural within-person variability in appearance (i.e., ambient images). Little is known about children's ability to do so. In the current study, we investigated whether 4- to 7-year-olds (n = 56) could recognize images of their own parent-a person with whom children have had abundant exposure in a variety of different contexts. Children were asked to identify images of their parent that were intermixed with images of other people. We included images of each parent taken both before and after their child was born to manipulate how close the images were to the child's own experience. When viewing before-birth images, 4- and 5-year-olds were less sensitive to identity than were older children; sensitivity did not differ when viewing images taken after the child was born. These findings suggest that with even the most familiar face, 4- and 5-year-olds have difficulty recognizing instances that go beyond their direct experience. We discuss two factors that may contribute to the prolonged development of familiar face recognition.

Picture this: Photographers no better than controls for recognizing unfamiliar faces.

With the exception of super recognizers and forensic examiners, people make a surprising number of errors when deciding whether photographs of unfamiliar faces belong to the same person or different people. Training protocols designed to improve professionals' (e.g., passport officers) performance often include photography. We evaluated the influence of life-time photography experience on the ability to distinguish matched versus mismatched face pairs. Expert photographers were not more sensitive to identity than hobbyists or novices-despite specializing in human subjects; Hobbyists were more liberal (more same responses) than Experts. We conclude that photography experience is not a route to expertise.

First impressions of child faces: Facial trustworthiness influences adults' interpretations of children's behavior in ambiguous situations.

Despite the profound behavioral consequences that first impressions of trustworthiness have on adult populations, few studies have examined how adults' first impressions of trustworthiness influence behavioral outcomes for children. Using a novel task design, we examined adults' perceptions of children's behavior in ambiguous situations. After a brief presentation of a child's face (high trust or low trust), participants viewed the child's face embedded within an ambiguous scene involving two children (Scene Task) or read a vignette about a misbehavior done by that child (Misbehavior Task). In the Scene Task, participants described what they believed to be happening in each scene; in the Misbehavior Task, participants indicated whether the behavior was done on purpose or by accident. In both tasks, participants also rated the behavior of the target child and indicated whether that child would be a good friend. In Experiment 1, young adults (n = 61) and older adults (n = 57) viewed unaltered face images. In Experiment 2, young adults (N = 59) completed the same tasks while viewing images of child faces morphed toward high-trust and low-trust averages. In both experiments, ambiguous scenes and misbehaviors were interpreted more positively when the target child had a high-trust face versus a low-trust face, with comparable patterns of results for the two age groups. Collectively, our results demonstrate that a child's facial trustworthiness biases how adults interpret children's behavior-a heuristic that may have lasting behavioral consequences for children through a self-fulfilling prophecy.

Visual configural processing in adults born at extremely low birth weight.

Being born at extremely low birth weight (ELBW; ≤1,000 g) is associated with enduring visual impairments. We tested for long-term, higher order visual processing problems in the oldest known prospectively followed cohort of ELBW survivors. Configural processing (spacing among features of an object) was examined in 62 adults born at ELBW (Mage  = 31.9 years) and 82 adults born at normal birth weight (NBW; ≥2,500 g: Mage  = 32.5 years). Pairs of human faces, monkey faces, or houses were presented in a delayed match-to-sample task, where non-matching stimuli differed only in the spacing of their features. Discrimination accuracy for each stimulus type was compared between birth weight groups, adjusting for neurosensory impairment, visual acuity, binocular fusion ability, IQ, and sex. Both groups were better able to discriminate human faces than monkey faces (p < .001). However, the ELBW group discriminated between human faces (p < .001), between monkey faces (p < .001), and to some degree, between houses (p < .06), more poorly than NBW control participants, suggesting a general deficit in perceptual processing. Human face discrimination was related to performance IQ (PIQ) across groups, but especially among ELBW survivors. Coding (a PIQ subtest) also predicted human face discrimination in ELBW survivors, consistent with previously reported links between visuo-perceptive difficulties and regional slowing of cortical activity in individuals born preterm. Correlations with Coding suggested ELBW survivors may have used a feature-matching approach to processing human faces. Future studies could examine brain-based anatomical and functional evidence for altered face processing, as well as the social and memory consequences of face-processing deficits in ELBW survivors.

Interactive situations reveal more about children's emotional knowledge.

Research examining children's emotion judgments has generally used nonsocial tasks that do not resemble children's daily experiences in judging others' emotions. Here, younger children (4- to 6-year-olds) and older children (7- to 9-year-olds) participated in a socially interactive task where an experimenter opened boxes and made an expression (happy, sad, scared, or disgust) based on the object inside. Children guessed which of four objects (a sticker, a broken toy car, a spider, or toy poop) was in the box. Subsequently, children opened a set of boxes and generated facial expressions for the experimenter. Children also labeled the emotion elicited by the objects and static facial expressions. Children's ability to guess which object caused the experimenter's expression increased with age but did not predict their ability to generate a recognizable expression. Children's demonstration of emotion knowledge also varied across tasks, suggesting that when emotion judgment tasks more closely mimic their daily experiences, children demonstrate broader emotion knowledge.

The influence of subtle facial expressions on children's first impressions of trustworthiness and dominance is not adult-like.

Adults' first impressions of others are influenced by subtle facial expressions; happy faces are perceived as high in trustworthiness, whereas angry faces are rated as low in trustworthiness and high in threat and dominance. Little is known about the influence of emotional expressions on children's first impressions. Here we examined the influence of subtle expressions of happiness, anger, and fear on children's implicit judgments of trustworthiness and dominance with the aim of providing novel insights about both the development of first impressions and whether children are able to utilize emotional expressions when making implicit, rather than explicit, judgments of traits. In the context of a computerized storybook, children (4- to 11-year-olds) and adults selected one of two twins (two images of the same identity displaying different emotional expressions) to help them face a challenge; some challenges required a trustworthy partner, and others required a dominant partner. One twin posed a neutral expression, and the other posed a subtle emotional expression of happiness, fear, or anger. Whereas adults were more likely to select a happy partner on trust trials than on dominance trials and were more likely to select an angry partner on dominance trials than on trust trials, we found no evidence that children's choices reflected a combined influence of desirable trait and emotion. Follow-up experiments involving explicit trait judgments, explicit emotion recognition, and implicit first impression judgments in the context of intense emotional expressions provide valuable insights into the slow development of implicit trait judgments based on first impressions.

No experimental evidence for emotion-specific gaze cueing in a threat context.

We examined the utility of a gaze cueing paradigm to examine sensitivity to differences among negatively valenced expressions. Participants judged target stimuli (dangerous or safe), the location of which was cued by the gaze direction of a central face. Dawel et al. reported that gaze cueing effects (faster response times on valid vs. invalid trials) were larger when the central face displayed fear than when it displayed happiness. Our aim was to determine whether this effect was specific to fear, to all threat-related expressions (fear, anger), or to all negatively valenced expressions (fear, anger, sadness, disgust) with the aim of using this protocol to study the development of implicit discrimination of negatively valenced expressions. Across five experiments in which we varied the number of models (1 vs. 4), the number of expressions (2 vs. 5), and the country of residence of participants (Canada vs. Australia) we found no evidence that the magnitude of gaze cueing effects is modulated by expression. We discuss our failure to replicate in the context of the broader literature.

Children's visual attention to emotional expressions varies with stimulus movement.

The majority of studies of emotion perception have relied on static isolated facial expressions. These expressions differ markedly from real-world expressions that include movement and multiple cues (e.g., bodies), leaving our understanding of how expression perception develops incomplete. We examined the looking patterns of younger children (4- and 5-year-olds), older children (8- and 9-year-olds), and adults while watching dynamic video clips or static images of four different emotional expressions: happiness, sadness, anger, and fear. Expressions were presented in three conditions: face only, body only, and whole person (face and body). Children's and adults' looking patterns were affected by whether stimuli were static or dynamic and by which cues were available. Children looked to the head less for static stimuli than for dynamic stimuli, but this difference did not emerge for adults. Children and adults attended to different expression cues when presented with static images. These results demonstrate the need for increased use of dynamic stimuli in developmental studies of expression.

Getting to know you: The development of mechanisms underlying face learning.

Nearly every study investigating the development of face recognition has focused on the ability to tell people apart using one or two tightly controlled images to represent each identity. Such research ignores the challenge of recognizing the same person despite variability in appearance. Whereas natural variation in appearance makes unfamiliar faces difficult to recognize, by 6 years of age people easily recognize multiple images of familiar faces. Two mechanisms are proposed to underlie the process by which adults become familiar with newly encountered faces. We provide the first examination of the development of these mechanisms during childhood (6-11 years). In Experiment 1, we examined children's (6- to 10-year-olds') and adults' ability to engage in ensemble coding-the ability to rapidly extract an average representation of an identity from several instances. In Experiment 2, we examined children's ability to use within-person variability in appearance to recognize novel instances of a newly encountered identity. We created a child-friendly perceptual matching task, and the number of images to which participants were exposed varied across targets. Although children were less accurate than adults overall in Experiment 2, we found no age-related improvement in either ensemble coding or the ability to benefit from exposure to within-person variability in appearance when learning a new face, suggesting that both abilities are developed by 6 years of age. We discuss the implications of these findings for understanding the nature of mechanisms underlying face learning and other developmental processes such as language and music.

Becoming Familiar With a Newly Encountered Face: Evidence of an Own-Race Advantage.

Adults' ability to match identity in images of unfamiliar faces is impaired for other- compared with own-race faces; their ability to match identity in images of familiar faces is independent of face race. Exposure to within-person variability in appearance plays a key role in face learning. Past research suggests that children need exposure to higher levels of variability than adults to learn a new face-a difference that has been attributed to experience. We predicted that adults' limited experience with other-race faces would result in their needing exposure to higher levels of variability when learning other- compared with own-race faces. We introduced adults to four new identities (two own-race; two other-race) in one of the three conditions: a single image, a low-variability video (filmed on 1 day), or a high-variability video (filmed across 3 days). Adults' ability to recognize new instances of learned identities improved in the low-variability condition for own-race faces but only in the high-variability condition for other-race faces. We discuss learning mechanisms that might drive this difference-a difference we attribute to experience.

That's my teacher! Children's ability to recognize personally familiar and unfamiliar faces improves with age.

Most previous research on the development of face recognition has focused on recognition of highly controlled images. One of the biggest challenges of face recognition is to identify an individual across images that capture natural variability in appearance. We created a child-friendly version of Jenkins, White, Van Montford, and Burton's sorting task (Cognition, 2011, Vol. 121, pp. 313-323) to investigate children's recognition of personally familiar and unfamiliar faces. Children between 4 and 12years of age were presented with a familiar/unfamiliar teacher's house and a pile of face photographs (nine pictures each of the teacher and another identity). Each child was asked to put all the pictures of the teacher inside the house while keeping the other identity out. Children over 6years of age showed adult-like familiar face recognition. Unfamiliar face recognition improved across the entire age range, with considerable variability in children's performance. These findings suggest that children's ability to tolerate within-person variability improves with age and support a face-space framework in which faces are represented as regions, the size of which increases with age.

Recognizing "Bella Swan" and "Hermione Granger": No Own-Race Advantage in Recognizing Photos of Famous Faces.

We investigated recognition of familiar and unfamiliar own- and other-race faces across natural variability in appearance. Participants sorted 20 photographs of each of two identities into piles such that each pile contained all photographs of a single identity. The other-race effect was limited to unfamiliar faces. When faces were unfamiliar, participants perceived more identities when sorting other-race faces; when faces were familiar, participants made two piles for both own- and other-race faces. Our work calls for rethinking the concept of the other-race effect.

Judging Normality and Attractiveness in Faces: Direct Evidence of a More Refined Representation for Own-Race, Young Adult Faces.

Young and older adults are more sensitive to deviations from normality in young than older adult faces, suggesting that the dimensions of face space are optimized for young adult faces. Here, we extend these findings to own-race faces and provide converging evidence using an attractiveness rating task. In Experiment 1, Caucasian and Chinese adults were shown own- and other-race face pairs; one member was undistorted and the other had compressed or expanded features. Participants indicated which member of each pair was more normal (a task that requires referencing a norm) and which was more expanded (a task that simply requires discrimination). Participants showed an own-race advantage in the normality task but not the discrimination task. In Experiment 2, participants rated the facial attractiveness of own- and other-race faces (Experiment 2a) or young and older adult faces (Experiment 2b). Between-rater variability in ratings of individual faces was higher for other-race and older adult faces; reduced consensus in attractiveness judgments reflects a less refined face space. Collectively, these results provide direct evidence that the dimensions of face space are optimized for own-race and young adult faces, which may underlie face race- and age-based deficits in recognition.

Attractiveness judgments and discrimination of mommies and grandmas: perceptual tuning for young adult faces.

Adults are more accurate in detecting deviations from normality in young adult faces than in older adult faces despite exhibiting comparable accuracy in discriminating both face ages. This deficit in judging the normality of older faces may be due to reliance on a face space optimized for the dimensions of young adult faces, perhaps because of early and continuous experience with young adult faces. Here we examined the emergence of this young adult face bias by testing 3- and 7-year-old children on a child-friendly version of the task used to test adults. In an attractiveness judgment task, children viewed young and older adult face pairs; each pair consisted of an unaltered face and a distorted face of the same identity. Children pointed to the prettiest face, which served as a measure of their sensitivity to the dimensions on which faces vary relative to a norm. To examine whether biases in the attractiveness task were specific to deficits in referencing a norm or extended to impaired discrimination, we tested children on a simultaneous match-to-sample task with the same stimuli. Both age groups were more accurate in judging the attractiveness of young faces relative to older faces; however, unlike adults, the young adult face bias extended to the match-to-sample task. These results suggest that by 3 years of age, children's perceptual system is more finely tuned for young adult faces than for older adult faces, which may support past findings of superior recognition for young adult faces.

The neural correlates of the face attractiveness aftereffect: a functional near-infrared spectroscopy (fNIRS) study.

Extensive behavioral evidence shows that our internal representation of faces, or face prototype, can be dynamically updated by immediate experience. This is illustrated by the robust attractiveness aftereffect phenomenon whereby originally unattractive faces become attractive after we are exposed to a set of unattractive faces. Although behavioral evidence suggests this effect to have a strong neural basis, limited neuroimaging evidence exists. Here we used functional near-infrared spectroscopy methodology (fNIRS) to bridge this gap. During the pre-adaptation trials, participants judged the attractiveness of three sets of faces: normal/undistorted faces, compressed faces (the internal features and distances between them were compressed), and expanded faces (the internal features and distances between them were stretched). Then, participants were shown extremely compressed faces for 5 min as adaptation stimuli, after which participants judged the same three sets of faces in post-adaptation trials. Behaviorally, after the adaptation trials, participants rated the compressed faces more attractive whereas they judged the other two sets of faces as less attractive, replicating the robust adaptation effect. fNIRS results showed that short-term exposure to compressed faces led to significant decreases in neural activity to all face types, but in a more extended network of cortical regions in the frontal and occipital cortexes for undistorted faces. Taken together, these findings suggest that the face attractiveness aftereffect mainly reflects changes in the neural representation of the face prototype in response to recent exposures to new face exemplars.

Category-specific face prototypes are emerging, but not yet mature, in 5-year-old children.

Adults' expertise in face recognition has been attributed to norm-based coding. Moreover, adults possess separable norms for a variety of face categories (e.g., race, sex, age) that appear to enhance recognition by reducing redundancy in the information shared by faces and ensuring that only relevant dimensions are used to encode faces from a given category. Although 5-year-old children process own-race faces using norm-based coding, little is known about the organization and refinement of their face space. The current study investigated whether 5-year-olds rely on category-specific norms and whether experience facilitates the development of dissociable face prototypes. In Experiment 1, we examined whether Chinese 5-year-olds show race-contingent opposing aftereffects and the extent to which aftereffects transfer across face race among Caucasian and Chinese 5-year-olds. Both participant races showed partial transfer of aftereffects across face race; however, there was no evidence for race-contingent opposing aftereffects. To examine whether experience facilitates the development of category-specific prototypes, we investigated whether race-contingent aftereffects are present among Caucasian 5-year-olds with abundant exposure to Chinese faces (Experiment 2) and then tested separate groups of 5-year-olds with two other categories with which they have considerable experience: sex (male/female faces) and age (adult/child faces) (Experiment 3). Across all three categories, 5-year-olds showed no category-contingent opposing aftereffects. These results demonstrate that 5 years of age is a stage characterized by minimal separation in the norms and associated coding dimensions used for faces from different categories and suggest that refinement of the mechanisms that underlie expert face processing occurs throughout childhood.

Ensemble coding of facial identity is robust, but may not contribute to face learning.

Ensemble coding - the rapid extraction of a perceptual average - has been proposed as a potential mechanism underlying face learning. We tested this proposal across five pre-registered experiments in which four ambient images of an identity were presented in the study phase. In Experiments 1 and 2a-c, participants were asked whether a test image was in the study array; these experiments examined the robustness of ensemble coding. Experiment 1 replicated ensemble coding in an online sample; participants recognize images from the study array and the average of those images. Experiments 2a-c provide evidence that ensemble coding meets several criteria of a possible learning mechanism: It is robust to changes in head orientation (± 60o), survives a short (30s) delay, and persists when images of two identities are interleaved during the study phase. Experiment 3 examined whether ensemble coding is sufficient for face learning (i.e., facilitates recognition of novel images of a target identity). Each study array comprised four ambient images (variability + average), a single image, or an average of four images (average only). Participants were asked whether a novel test image showed the identity from a study array. Performance was best in the four-image condition, with no difference between the single-image and average-only conditions. We conclude that ensemble coding of facial identity is robust but that the perceptual average per se is not sufficient for face learning.

The effect of early visual deprivation on the development of face detection.

The expertise of adults in face perception is facilitated by their ability to rapidly detect that a stimulus is a face. In two experiments, we examined the role of early visual input in the development of face detection by testing patients who had been treated as infants for bilateral congenital cataract. Experiment 1 indicated that, at age 9 to 20, patients' accuracy and response times on a Mooney face detection task were normal. Experiment 2 revealed that the neural mechanisms underlying face detection in a similar group of adult patients are abnormal: the amplitude of both the P100 and N170 event-related potential were larger in patients than in visually normal controls, and the extent of augmentation was related to the duration of deprivation. Thus, early visual experience is necessary for the establishment of normal neural networks for face detection; abnormalities at these early processing stages may contribute to the deficits we previously reported in configural face processing for this patient cohort.