Categorization,categorical perception,and asymmetry in infants’ representation of face race

The present study examined whether 6‐ and 9‐month‐old Caucasian infants could categorize faces according to race. In Experiment 1, infants were familiarized with different female faces from a common ethnic background (i.e. either Caucasian or Asian) and then tested with female faces from a novel race category. Nine‐month‐olds were able to form discrete categories of Caucasian and Asian faces. However, 6‐month‐olds did not form discrete categories of faces based on race. In Experiment 2, a second group of 6‐ and 9‐month‐olds was tested to determine whether they could discriminate between different faces from the same race category. Results showed that both age groups could only discriminate between different faces from the own‐race category of Caucasian faces. The findings of the two experiments taken together suggest that 9‐month‐olds formed a category of Caucasian faces that are further differentiated at the individual level. In contrast, although they could form a category of Asian faces, they could not discriminate between such other‐race faces. This asymmetry in category formation at 9 months (i.e. categorization of own‐race faces vs. categorical perception of other‐race faces) suggests that differential experience with own‐ and other‐race faces plays an important role in infants’ acquisition of face processing abilities.     

Asymmetrical responding to male versus female other-race categories in 9- to 12-month-old infants

Faces can be categorized along various dimensions including gender or race, an ability developing in infancy. Infant categorization studies have focused on facial attributes in isolation, but the interaction between these attributes remains poorly understood. Experiment 1 examined gender categorization of other-race faces in 9- and 12-month-old White infants. Nine- and 12-month-olds were familiarized with Asian male or female faces, and tested with a novel exemplar from the familiarized category paired with a novel exemplar from a novel category. Both age groups showed novel category preferences for novel Asian female faces after familiarization with Asian male faces, but showed no novel category preference for novel Asian male faces after familiarization with Asian female faces. This categorization asymmetry was not due to a spontaneous preference hindering novel category reaction (Experiment 2), and both age groups displayed difficulty discriminating among male, but not female, other-race faces (Experiment 3). These results indicate that category formation for male other-race faces is mediated by categorical perception. Overall, the findings suggest that even by 12 months of age, infants are not fully able to form gender category representations of other-race faces, responding categorically to male, but not female, other-race faces.     

Perceptual narrowing towards adult faces is a cross‐cultural phenomenon in infancy: a behavioral and near‐infrared spectroscopy study with Japanese infants

Recent data showed that, in Caucasian infants, perceptual narrowing occurs for own‐race adult faces between 3 and 9 months of age, possibly as a consequence of the extensive amount of social and perceptual experience accumulated with caregivers and/or other adult individuals of the same race of the caregiver. The neural correlates of this developmental process remain unexplored, and it is currently unknown whether perceptual tuning towards adult faces can be extended to other cultures. To this end, in the current study we tested the ability of 3‐ and 9‐month‐old Japanese infants to discriminate among adult and infant Asian faces in a visual familiarization task (Experiment 1), and compared 9‐month‐olds’ cerebral hemodynamic responses to adult and infant faces as measured by near‐infrared spectroscopy (NIRS) (Experiment 2). Results showed that 3‐month‐olds exhibit above‐chance discrimination of adult and infant faces, whereas 9‐month‐olds discriminate adult faces but not infant faces (Experiment 1). Moreover, adult faces, but not infant faces, induced significant increases in hemodynamic responses in the right temporal areas of 9‐month‐old infants. Overall, our data suggest that perceptual narrowing towards adult faces is a cross‐cultural phenomenon occurring between 3 and 9 months of age, and translates by 9 months of age into a right‐hemispheric specialization in the processing of adult faces.     

Narrowing in categorical responding to other‐race face classes by infants

Infants can form object categories based on perceptual cues, but their ability to form categories based on differential experience is less clear. Here we examined whether infants filter through perceptual differences among faces from different other‐race classes and represent them as a single other‐race class different only from own‐race faces. We used a familiarization/novelty‐preference procedure to investigate category formation for two other‐race face classes (Black vs. Asian) by White 6‐ and 9‐month‐olds. The data indicated that while White 6‐month‐olds categorically represented the distinction between Black and Asian faces, White 9‐month‐olds formed a broad other‐race category inclusive of Black and Asian faces, but exclusive of own‐race White faces. The findings provide evidence that narrowing can occur for mental processes other than discrimination: category formation is also affected. The results suggest that frequency of experience with own‐race versus other‐race classes of faces may propel infants to contrast own‐race faces with other‐race faces, but not different classes of other‐race faces with each other.     

Learning unfamiliar faces in infants: The advantage of the regular sequence presentation and the three‐quarter view superiority

We investigated the effect of the regular sequence of different views and the three‐quarter view effect on the learning of unfamiliar faces by infants. 3–8‐month‐old infants were familiarized with unfamiliar female faces in either the regular condition (presenting 11 different face views from the frontal view to the left‐side profile view in regular order) or the random condition (presenting the same 11 different face views in random order). Following the familiarization, infants were tested with a pair of a familiarized and a novel female face either in a three‐quarter (Experiment 1) or in a profile view (Experiment 2). Results showed that only 6–8‐month‐old infants could identify a familiarized face in the regular condition when they were tested in three‐quarter views. In contrast, 6–8‐month‐old infants showed no significant novelty preference in profile views. The results suggest that the regular sequence of different face views promotes the learning of unfamiliar faces by infants over 6 months old. Moreover, our findings imply that the three‐quarter view effect appears in infants.     

Development of Recognition of Face Parts from Unfamiliar Faces

The present study examined developmental changes in the ability to recognize face parts. In Experiment 1, participants were familiarized with whole faces and given a recognition test with old and new eyes, noses, mouths, inner faces, outer faces, or whole faces. Adults were above chance in their recognition of the eye and mouth regions. However, children did not naturally encode and recognize face parts independently of the entire face. In addition, all age groups showed comparable inner and outer face recognition, except for 8‐ to 9‐year‐olds who showed a recognition advantage for outer faces. In Experiment 2, when participants were familiarized with eyes, noses, or mouths and tested with eyes, noses, or mouths, respectively, all ages showed above‐chance recognition of eyes and mouths. Thirteen‐ to 14‐year‐olds were adult‐like in their recognition of the eye region, but mouth recognition continued to develop beyond 14 years of age. Nose recognition was above chance among 13‐ to 14‐year‐olds, but recognition scores remained low even in adulthood. The present findings reveal unique developmental trajectories in the use of isolated facial regions in face recognition and suggest that featural cues (as a class) have a different ontogenetic course relative to holistic and configural cues. Copyright © 2012 John Wiley & Sons, Ltd.     

Neural markers of subordinate‐level categorization in 6‐ to 7‐month‐old infants

Subordinate‐level category‐learning processes in infants were investigated with ERP and looking‐time measures. ERPs were recorded while 6‐ to 7‐month‐olds were presented with Saint Bernard images during familiarization, followed by novel Saint Bernards interspersed with Beagles during test. In addition, infant looking times were measured during a paired‐preference test (novel Saint Bernard vs. novel Beagle) conducted at the conclusion of ERP recording. Slow wave activity corresponded with learning a familiarized category at the subordinate and basic levels, whereas Negative central (Nc) and P400 components were linked with novel category preference. The results provide the first evidence identifying the neural markers of subordinate‐level categorization observed in looking‐time tasks conducted with infants. Moreover, when considered in conjunction with prior research investigating the neural markers of basic‐level categorization in infants, the findings indicate that (1) slow wave and Nc components of infant ERP waveforms are general markers for processes of category learning on the one hand and novel category preference on the other, (2) novel category preference for a contrast category at the basic and subordinate levels have the Nc component in common, but novel category preference at the subordinate level is accompanied by an additional P400 component, a finding in keeping with the notion that subordinate‐level categorization is governed by mechanisms supplementary to those underlying basic‐level categorization, and (3) slow wave activity associated with subordinate‐level learning followed that associated with basic‐level learning by approximately 200 ms, a result in accord with a coarse‐to‐fine scheme for the emergence of category partitioning.     

Joint attention and object learning in 5‐ and 7‐month‐old infants

We examined the effects of joint attention for object learning in 5‐ and 7‐month‐old infants. Infants interacted with an adult social partner who taught them about a novel toy in two conditions. In the Joint Attention condition, the adult spoke about the toy while alternating gaze between the infant and the toy, while in the Object Only condition, the adult looked to the toy and to a spot on the ceiling, but never at the infant. In the test trials following each social interaction, we presented infants with the ‘familiarization’ toy and a novel toy, and monitored looking times to each object. We found that 7‐month‐olds looked significantly longer to the novel toy following the Joint Attention relative to the Object Only condition, while 5‐month‐old infants did not show a significant difference across conditions. We interpret these results to suggest that joint attention facilitated 7‐month‐old infants' encoding of information about the familiarization object. Implications for the ontogeny of infant learning in joint attention contexts are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Older but not younger infants associate own‐race faces with happy music and other‐race faces with sad music

We used a novel intermodal association task to examine whether infants associate own‐ and other‐race faces with music of different emotional valences. Three‐ to 9‐month‐olds saw a series of neutral own‐ or other‐race faces paired with happy or sad musical excerpts. Three‐ to 6‐month‐olds did not show any specific association between face race and music. At 9 months, however, infants looked longer at own‐race faces paired with happy music than at own‐race faces paired with sad music. Nine‐month‐olds also looked longer at other‐race faces paired with sad music than at other‐race faces paired with happy music. These results indicate that infants with nearly exclusive own‐race face experience develop associations between face race and music emotional valence in the first year of life. The potential implications of such associations for developing racial biases in early childhood are discussed.     

Overcoming the other‐race effect in infancy with multisensory redundancy: 10–12‐month‐olds discriminate dynamic other‐race faces producing speech

We tested 4–6‐ and 10–12‐month‐old infants to investigate whether the often‐reported decline in infant sensitivity to other‐race faces may reflect responsiveness to static or dynamic/silent faces rather than a general process of perceptual narrowing. Across three experiments, we tested discrimination of either dynamic own‐race or other‐race faces which were either accompanied by a speech syllable, no sound, or a non‐speech sound. Results indicated that 4–6‐ and 10–12‐month‐old infants discriminated own‐race as well as other‐race faces accompanied by a speech syllable, that only the 10–12‐month‐olds discriminated silent own‐race faces, and that 4–6‐month‐old infants discriminated own‐race and other‐race faces accompanied by a non‐speech sound but that 10–12‐month‐old infants only discriminated own‐race faces accompanied by a non‐speech sound. Overall, the results suggest that the ORE reported to date reflects infant responsiveness to static or dynamic/silent faces rather than a general process of perceptual narrowing.     

The movement of internal facial features elicits 7 to 8‐month‐old infants' preference for face patterns

A preference for static face patterns is observed in newborns and disappears around 3 months after birth. A previous study has demonstrated that 5‐month‐old infants prefer schematic faces only when the internal features are moving, suggesting that face‐specific movement enhances infants' preference. The present study investigates the facilitative effect of the movement of internal facial features on infants' preference. To examine infants' preference, we used animated face patterns consisting of a head‐shaped contour and three disk blobs. The inner blobs expanded and contracted to represent the opening and closing of the eyes and mouth, and were constrained to open and close only in a biologically possible vertical direction resembling the facial muscle structure. We compared infants' preferential looking time for this vertically moving (VM) face pattern with their looking time for a horizontally moving (HM) face pattern in which blobs transformed at the same speed in a biologically impossible, horizontal direction. In Experiment 1, 7 to 8‐month‐olds preferred the VM to the HM, but 5 to 6‐month‐olds did not. However, the preference was diminished in both cases when the moving face patterns were presented without contour (Experiment 2). Our results suggest that internal facial features with vertical movements promote face preference in 7 to 8‐month‐olds. Copyright © 2011 John Wiley & Sons, Ltd.     

Evidence of rapid correlation‐based perceptual category learning by 4‐month‐olds

Young infants are very sensitive to feature distribution information in the environment. However, existing work suggests that they do not make use of correlation information to form certain perceptual categories until at least 7 months of age. We suggest that the failure to use correlation information is a by‐product of familiarization procedures that encourage infants to over encode individual exemplars rather than relations across exemplars. By changing the exemplar presentation regime to one in which exemplars are rapidly (2 s durations) and repeatedly presented we find that 4‐month‐olds can form perceptual categories on the basis of feature correlation information. In addition, this ability emerges rapidly between 114 and 134 days. We argue that the ability to process correlation information is present very early on but that the demonstration of that ability in categorization tasks is mediated by the demands of the task the infant is tested with. Copyright © 2005 John Wiley & Sons, Ltd.     

Asymmetric interference in 3‐ to 4‐month‐olds' sequential category learning

Three‐ to 4‐month‐old infants show asymmetric exclusivity in the acquisition of cat and dog perceptual categories. The cat perceptual category excludes dog exemplars, but the dog perceptual category does not exclude cat exemplars. We describe a connectionist autoencoder model of perceptual categorization that shows the same asymmetries as infants. The model predicts the presence of asymmetric retroactive interference when infants acquire cat and dog categories sequentially. A subsequent experiment conducted with 3‐ to 4‐month‐olds verifies the predicted pattern of looking time behaviors. We argue that bottom‐up, associative learning systems with distributed representations are appropriate for modeling the operation of short‐term visual memory in early perceptual category learning.     

Two rooms,two representations? Episodic‐like memory in toddlers and preschoolers

Episodic memory involves binding together what‐where‐when associations. In three experiments, we tested the development of memory for such contextual associations in a naturalistic setting. Children searched for toys in two rooms with two different experimenters; each room contained two identical sets of four containers, but arranged differently. A distinct toy was hidden in a distinct container in each room. In Experiment 1, which involved children between 15 and 26 months who were prompted with a very explicit cue (a part of the hidden toy), we found a marked shift in performance with age: while 15‐ to 20‐month‐olds concentrated their searches on the two containers that sometimes contained toys, they did not distinguish between them according to context, but 21–26‐month‐olds did. However, surprisingly, without toy cues, even the youngest children showed a fragile ability to disambiguate the two containers by room context. In Experiment 2, we tested 34‐ to 40‐month‐olds and 64‐ to 72‐month‐olds without toy cues. The 5‐year‐olds were nearly perfect, and the 3‐year‐olds showed a significant preference for the correct container given only the context. In Experiment 3, we filled in the age range, and also investigated the effects of the use of labels (i.e. names of experimenters and rooms) and of familiarization time, in groups of 34‐ to 40‐month‐olds, 42‐ to 48‐month‐olds, and 50‐ to 56‐month‐olds. Neither labels nor familiarization time had an effect. Across experiments, there was regular age‐related improvement in context‐based memory. Overall, the results suggest that children's episodic memory may undergo an early qualitative change, yet to be precisely characterized, and that continuing increments in the use of contextual cues occur throughout the preschool period. A video abstract of this article can be viewed at https://www.youtube.com/watch?v=DkwEFw0UEz4&list=PLwxXcOKHPC0llAPVcJyW4EtzlA934A2Rz&index=1     

The effects of adults' affective expression and direction of visual gaze on 12‐month‐olds' visual preferences for an object following a 5‐minute, 1‐day,or 1‐month delay

Between 12‐ and 14 months of age infants begin to use another's direction of gaze and affective expression in learning about various objects and events. What is not well understood is how long infants' behaviour towards a previously unfamiliar object continues to be influenced following their participation in circumstances of social referencing. In this experiment, we examined infants' sensitivity to an adult's direction of gaze and their visual preference for one of two objects following a 5‐min, 1‐day, or 1‐month delay. Ninety‐six 12‐month‐olds participated. For half of the infants during habituation (i.e., familiarization), the adults' direction of gaze was directed towards an unfamiliar object (look condition). For the remaining half of the infants during habituation, the adults' direction of gaze was directed away from the unfamiliar object (look‐away condition). All infants were habituated to two events. One event consisted of an adult looking towards (look condition) or away from (look‐away condition) an object while facially and vocally conveying a positive affective expression. The second event consisted of the same adult looking towards or away from a different object while conveying a disgusted affective expression. Following the habituation phase and a 5‐min, 1‐day, or 1‐month delay, infants' visual preference was assessed. During the visual preference phase, infants saw the two objects side by side where the adult conveying the affective expression was not visible. Results of the visual preference phase indicate that infants in the look condition showed a significant preference for object previously paired with the positive affect following a 5‐min and 1‐day delay. No significant visual preference was found in the look condition following a 1‐month delay. No significant preferences were found at any retention interval in the look‐away condition. Results are discussed in terms of early learning, social referencing, and early memory.     

Infant gaze following depends on communicative signals: An eye‐tracking study of 5‐ to 7‐month‐olds in Vanuatu

Gaze is considered a crucial component of early communication between an infant and her caregiver. When communicatively addressed, infants respond aptly to others’ gaze by following its direction. However, experience with face‐to‐face contact varies across cultures, begging the question whether infants’ competencies in receiving others’ communicative gaze signals are universal or culturally specific . We used eye‐tracking to assess gaze‐following responses of 5‐ to 7‐month olds in Vanuatu, where face‐to‐face parent–infant interactions are less prevalent than in Western populations. We found that—just like Western 6‐month‐olds studied previously—5‐ to ‐7‐month‐olds living in Vanuatu followed gaze only, when communicatively addressed. That is, if presented gaze shifts were preceded by infant‐directed speech, but not if they were preceded by adult‐directed speech. These results are consistent with the notion that early infant gaze following is tied to infants’ early emerging communicative competencies and rooted in universal mechanisms rather than being dependent on cultural specificities of early socialization.     

Development of chromatic induction in infancy

The perception of colour in an embedded field is affected by the surround colour. This phenomenon is known as chromatic induction. In the present study we investigated whether the colour perception by infants aged 5–7 months could be affected by the surround colour. In Experiments 1 and 2 each stimulus was composed of an array of six squares in tandem. The colour appearance of the array in the familiarization stimulus was established by chromatic induction. In Experiment 1 we used familiarization stimuli that were perceived as two‐colour array with a two‐colour surround. In Experiment 2 we used a familiarization stimulus that was perceived as a uniform‐colour array with a two‐colour surround. In the test phase, the uniform‐colour array and the two‐colour array were presented on a white uniform‐colour surround in both experiments. The results showed that in Experiment 1 the 5‐ and 7‐month‐old infants had novelty preference for the uniform‐colour test array. This suggested that the infants' colour perception could be affected by surround colour. The results of Experiment 2 showed that the 7‐month‐olds showed a novelty preference for the two‐colour test array, but the 5‐month‐olds showed no novelty preference. This suggested that 7‐month‐olds' colour perception could be affected by surround colour, but that of 5‐month‐olds could not. We discuss the contradiction of the results between Experiments 1 and 2. Copyright © 2007 John Wiley & Sons, Ltd.     

Differential effects of happy,neutral, and sad still‐faces on 2‐, 4‐ and 6‐month‐old infants

The role of facial expression in the determination of infants' reaction to the sudden still‐face of a social partner was investigated. In a within subject design, 2, 4 and 6‐month‐old infants were tested in periods of normal interaction interspersed with periods of prolonged still‐face episodes in which the female adult social partner adopted either a happy, neutral, or sad static facial expression while maintaining eye contact with the infant. Proportion of infants' smiling and gazing at the social partner as indices of reaction from the various still‐face episodes reveal that, in comparison with same age control groups, four and six‐month‐old infants did not demonstrate any differential responses depending on either happy, neutral, and sad still‐faced expression. In contrast, two‐month olds demonstrated some evidence of a reduced still‐face effect in the happy still‐face condition. These results point to early developmental changes in the mechanisms underlying the still‐face phenomenon. We propose that by 4 months, and not prior, the reaction to still‐face episodes are essentially based on the detection of social contingencies. Copyright © 2002 John Wiley & Sons, Ltd.     

The role of the physical context in supporting young children's use of spatiotemporal organization in recall

Four experiments were conducted to investigate the role of the physical context in supporting 3‐ to 5‐year‐olds' use of spatiotemporal organization in recall. Children were familiarized with several target items and their corresponding landmarks arranged along a path in a model park. After familiarization, an experimenter removed the target items from the park. In Experiment 1, 3‐ and 4‐year‐olds recalled the missing items with the park either in view or out of view. When the park model was in view, 4‐ year‐olds used the order of the items along the path to structure their recall. In Experiment 2, 4‐ and 5‐year‐olds recalled the missing items with the landmarks arranged either in the same order as in familiarization or in a new order. Children used the order of landmarks along the path at test to structure their recall, even though the order of landmarks changed from familiarization to test. Experiment 3 was identical to Experiment 2, except that the path was removed from the park. Five‐year‐olds used the order of landmarks along the path at test to structure their recall when the order of landmarks remained the same from familiarization to test, but had much more difficulty doing so when the order of landmarks changed from familiarization to test. Using a more difficult task, Experiment 4 revealed that spatiotemporal organization was positively related to amount recalled. Together, these findings suggest that the structure of the physical environment plays an important role in supporting young children's use of spatiotemporal organization in recall.     

Pupillometry reveals communication‐induced object expectations in 12‐ but not 8‐month‐old infants

Several interaction‐based and looking‐time studies suggest that 1‐year‐old infants understand the referential nature of deictic gestures. However, these studies have not unequivocally established that referential gestures induce object expectations in infants prior to encountering a referent object, and have thus remained amenable to simpler attentional highlighting interpretations. The current study tested whether nonlinguistic referential communication induces object expectations in infants by using a novel pupil dilation paradigm. In Experiment 1, 12‐month‐olds watched videos of a protagonist who either pointed communicatively toward an occluder in front of her or remained still. At test, the occluder opened to reveal one of two outcomes: an empty surface or a toy. Results showed that infants’ pupils were larger for the unexpected outcome of an empty surface following a point compared to the control condition (an empty surface following no point). These differences were not caused by differences in looking times or directions. In Experiment 2, an attention‐directing nonsocial control cue replaced the referential communication. The cue did direct 12‐month‐olds’ attention to the occluder, but it did not induce an object expectation. In Experiment 3, we tested 8‐month‐olds in the setting of Experiment 1. In contrast to 12‐month‐olds, 8‐month‐olds did not reveal object expectations following communication. Findings demonstrate that communicative pointing acts induce object expectations at 12 months of age, but not at 8 months of age, and that these expectations are specific to a referential‐communicative as opposed to an attention‐directing nonsocial cue.