Developmental changes in automatic rule‐learning mechanisms across early childhood

Infants’ ability to learn complex linguistic regularities from early on has been revealed by electrophysiological studies indicating that 3‐month‐olds, but not adults, can automatically detect non‐adjacent dependencies between syllables. While different ERP responses in adults and infants suggest that both linguistic rule learning and its link to basic auditory processing undergo developmental changes, systematic investigations of the developmental trajectories are scarce. In the present study, we assessed 2‐ and 4‐year‐olds’ ERP indicators of pitch discrimination and linguistic rule learning in a syllable‐based oddball design. To test for the relation between auditory discrimination and rule learning, ERP responses to pitch changes were used as predictor for potential linguistic rule‐learning effects. Results revealed that 2‐year‐olds, but not 4‐year‐olds, showed ERP markers of rule learning. Although, 2‐year‐olds’ rule learning was not dependent on differences in pitch perception, 4‐year‐old children demonstrated a dependency, such that those children who showed more pronounced responses to pitch changes still showed an effect of rule learning. These results narrow down the developmental decline of the ability for automatic linguistic rule learning to the age between 2 and 4 years, and, moreover, point towards a strong modification of this change by auditory processes. At an age when the ability of automatic linguistic rule learning phases out, rule learning can still be observed in children with enhanced auditory responses. The observed interrelations are plausible causes for age‐of‐acquisition effects and inter‐individual differences in language learning.     

Infants' goal anticipation during failed and successful reaching actions

The ability to interpret and predict the actions of others is crucial to social interaction and to social, cognitive, and linguistic development. The current study provided a strong test of this predictive ability by assessing (1) whether infants are capable of prospectively processing actions that fail to achieve their intended outcome, and (2) how infants respond to events in which their initial predictions are not confirmed. Using eye tracking, 8‐month‐olds, 10‐month‐olds, and adults watched an actor repeatedly reach over a barrier to either successfully or unsuccessfully retrieve a ball. Ten‐month‐olds and adults produced anticipatory looks to the ball, even when the action was unsuccessful and the actor never achieved his goal. Moreover, they revised their initial predictions in response to accumulating evidence of the actor's failure. Eight‐month‐olds showed anticipatory looking only after seeing the actor successfully grasp and retrieve the ball. Results support a flexible, prospective social information processing ability that emerges during the first year of life.     

Increasing task difficulty enhances effects of intersensory redundancy: testing a new prediction of the Intersensory Redundancy Hypothesis

Prior research has demonstrated intersensory facilitation for perception of amodal properties of events such as tempo and rhythm in early development, supporting predictions of the Intersensory Redundancy Hypothesis (IRH). Specifically, infants discriminate amodal properties in bimodal, redundant stimulation but not in unimodal, nonredundant stimulation in early development, whereas later in development infants can detect amodal properties in both redundant and nonredundant stimulation. The present study tested a new prediction of the IRH: that effects of intersensory redundancy on attention and perceptual processing are most apparent in tasks of high difficulty relative to the skills of the perceiver. We assessed whether by increasing task difficulty, older infants would revert to patterns of intersensory facilitation shown by younger infants. Results confirmed our prediction and demonstrated that in difficult tempo discrimination tasks, 5‐month‐olds perform like 3‐month‐olds, showing intersensory facilitation for tempo discrimination. In contrast, in tasks of low and moderate difficulty, 5‐month‐olds discriminate tempo changes in both redundant audiovisual and nonredundant unimodal visual stimulation. These findings indicate that intersensory facilitation is most apparent for tasks of relatively high difficulty and may therefore persist across the lifespan.     

To generalize or not to generalize: spatial categories are influenced by physical attributes and language

The current work explored the conditions under which infants generalize spatial relationships from one event to another. English‐learning 5‐month‐olds habituated to a tight‐ or loose‐fit covering event dishabituated to a change in fit during a containment test event, but infants habituated to a visually similar occlusion event did not. Thus, infants’ responses appeared to be driven by the physical nature of the fit rather than visual similarity. This response pattern was replicated with Korean‐speaking adults, but English‐speaking adults showed no sensitivity to change in fit for either event. These findings suggest that language development links linguistic forms to universal, pre‐existing representations of meaning, and that linguistic experience can shape sensitivity to distinctions that are marked in one's native language.     

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.     

Development of category formation for faces differing by age in 9‐ to 12‐month‐olds: An effect of experience with infant faces

We examined category formation for faces differing in age in 9‐ and 12‐month‐olds, and the influence of exposure to infant faces on such ability. Infants were familiarized with adult or infant faces, and then tested with a novel exemplar from the familiarized category paired with a novel exemplar from a novel category (Experiment 1). Both age groups formed discrete categories of adult and infant faces, but exposure to infant faces in everyday life did not modulate performance. The same task was conducted with child versus infant faces (Experiment 2). Whereas 9‐month‐olds preferred infant faces after familiarization with child faces, but not child faces after familiarization with infant faces, 12‐month‐olds formed discrete categories of child and infant faces. Moreover, more exposure to infant faces correlated with higher novel category preference scores when infants were familiarized with infant faces in 12‐month‐olds, but not 9‐month‐olds. The 9‐month‐old asymmetry did not reflect spontaneous preference for infant over child faces (Experiment 3). These findings indicate that 9‐ and 12‐month‐olds can form age‐based categories of faces. The ability of 12‐month‐olds to form separate child and infant categories suggests that they have a more exclusive representation of face age, one that may be influenced by prior experience with infant faces.     

Discrimination of Lexical Tones in the First Year of Life

In the current study, we examined the developmental course of the perception of non‐native tonal contrast. We tested 4, 6 and 12‐month‐old Dutch infants on their discrimination of Chinese low‐rising tone and low‐dipping tone using the visual fixation paradigm. The infants were tested in two conditions that differed in terms of degree of variability. The 4‐month‐olds did not show discrimination effect in either condition. The 6‐ and 12‐month‐old infants, however, discriminated the tones in both conditions. The improvement of perception might be the result of cognitive development carried over from learning the native phonology. Infants can become better listeners in general in the first year of life, as well as get cognitively better equipped in dealing with the variable input in speech in general. Copyright © 2015 John Wiley & Sons, Ltd.     

Developmental shift in the discrimination of vowel contrasts in bilingual infants: is the distributional account all there is to it?

A shift from language‐general to language‐specific sound discrimination abilities has been largely attested in different populations of infants during the second half of the first year of life; however, data are still scarce regarding bilingual populations. Previous research with 4‐, 8‐ and 12‐month‐old Catalan‐Spanish bilingual infants had offered evidence of a U‐shaped pattern in their ability to discriminate a language‐specific vowel contrast. This research explores monolingual and bilingual 4‐ and 8‐month‐olds’ capacities to discriminate two common vowel contrasts: /o–u/ and /e–u/. All groups succeeded except 8‐month‐old bilinguals tested on the phonetically close /o–u/ contrast. Discrimination was not facilitated when talker and token variability were reduced. A U‐shaped pattern was again found when data from an additional group of 12‐month‐olds were included. These results confirm bilinguals’ specific developmental pattern of perceptual reorganization for acoustically close vowels and challenge an interpretation merely based on a distributional account.     

Bilingual infants excel at foreign‐language talker recognition

Bilingual and monolingual infants differ in how they process linguistic aspects of the speech signal. But do they also differ in how they process non‐linguistic aspects of speech, such as who is talking? Here, we addressed this question by testing Canadian monolingual and bilingual 9‐month‐olds on their ability to learn to identify native Spanish‐speaking females in a face‐voice matching task. Importantly, neither group was familiar with Spanish prior to participating in the study. In line with our predictions, bilinguals succeeded in learning the face‐voice pairings, whereas monolinguals did not. We consider multiple explanations for this finding, including the possibility that simultaneous bilingualism enhances perceptual attentiveness to talker‐specific speech cues in infancy (even in unfamiliar languages), and that early bilingualism delays perceptual narrowing to language‐specific talker recognition cues. This work represents the first evidence that multilingualism in infancy affects the processing of non‐linguistic aspects of the speech signal, such as talker identity.     

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 ontogeny of relational memory and pattern separation

Episodic memory relies on memory for the relations among multiple elements of an event and the ability to discriminate among similar elements of episodes. The latter phenomenon, termed pattern separation, has been studied mainly in young and older adults with relatively little research on children. Building on prior work with young children, we created an engaging computer‐administered relational memory task assessing what‐where relations. We also modified the Mnemonic Similarity Task used to assess pattern discrimination in young and older adults for use with preschool children. Results showed that 4‐year‐olds performed significantly worse than 6‐year‐olds and adults on both tasks, whereas 6‐year‐olds and adults performed comparably, even though there were no ceiling effects. However, performance on the two tasks did not correlate, suggesting that two distinct mnemonic processes with different developmental trajectories may contribute to age‐related changes in episodic memory.     

Experience with visual barriers and its effects on subsequent gaze‐following in 12‐ to 13‐month‐olds

Thirty 12‐ to 13‐month‐olds were tested to determine whether they could use the self as an analogy for understanding others' looking. Using a procedure similar to Brooks and Meltzoff (2002) , we examined gaze‐following when the adult's view of a target was occluded by a blindfold (blindfold without training). Some infants received experience with the blindfold's sight‐blocking qualities (blindfold with training). The control was a headband condition. Gaze‐following was highest in the headband condition. Gaze‐following in the headband and blindfold without training conditions, but not the blindfold with training conditions, were significantly greater than zero. These results demonstrate that 12‐ to 13‐month‐olds have some understanding of the looking behaviour of others. Only weak support was found for simulation theories of the development of social cognition.     

The shift in infant preferences for vowel duration and pitch contour between 6 and 10 months of age

This study investigates the influence of the acoustic properties of vowels on 6‐ and 10‐month‐old infants’ speech preferences. The shape of the contour (bell or monotonic) and the duration (normal or stretched) of vowels were manipulated in words containing the vowels /i/ and /u/, and presented to infants using a two‐choice preference procedure. Experiment 1 examined contour shape: infants heard either normal‐duration bell‐shaped and monotonic contours, or the same two contours with stretched duration. The results show that 6‐month‐olds preferred bell to monotonic contours, whereas 10‐month‐olds preferred monotonic to bell contours. In Experiment 2, infants heard either normal‐duration and stretched bell contours, or normal‐duration and stretched monotonic contours. As in Experiment 1, infants showed age‐specific preferences, with 6‐month‐olds preferring stretched vowels, and 10‐month‐olds preferring normal‐duration vowels. Infants’ attention to the acoustic qualities of vowels, and to speech in general, undergoes a dramatic transformation in the final months of the first year, a transformation that aligns with the emergence of other developmental milestones in speech perception.     

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.     

Lexical‐processing efficiency leverages novel word learning in infants and toddlers

Children who rapidly recognize and interpret familiar words typically have accelerated lexical growth, providing indirect evidence that lexical processing efficiency (LPE) is related to word‐learning ability. Here we directly tested whether children with better LPE are better able to learn novel words. In Experiment 1, 17‐ and 30‐month‐olds were tested on an LPE task and on a simple word‐learning task. The 17‐month‐olds’ LPE scores predicted word learning in a regression model, and only those with relatively good LPE showed evidence of learning. The 30‐month‐olds learned novel words quite well regardless of LPE, but in a more difficult word‐learning task (Experiment 2), their LPE predicted word‐learning ability. These findings suggest that LPE supports word‐learning processes, especially when learning is difficult.     

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.     

Simulating the role of visual selective attention during the development of perceptual completion

We recently proposed a multi‐channel, image‐filtering model for simulating the development of visual selective attention in young infants (Schlesinger, Amso & Johnson, 2007). The model not only captures the performance of 3‐month‐olds on a visual search task, but also implicates two cortical regions that may play a role in the development of visual selective attention. In the current simulation study, we used the same model to simulate 3‐month‐olds’ performance on a second measure, the perceptual unity task. Two parameters in the model – corresponding to areas in the occipital and parietal cortices – were systematically varied while the gaze patterns produced by the model were recorded and subsequently analyzed. Three key findings emerged from the simulation study. First, the model successfully replicated the performance of 3‐month‐olds on the unity perception task. Second, the model also helps to explain the improved performance of 2‐month‐olds when the size of the occluder in the unity perception task is reduced. Third, in contrast to our previous simulation results, variation in only one of the two cortical regions simulated (i.e. recurrent activity in posterior parietal cortex) resulted in a performance pattern that matched 3‐month‐olds. These findings provide additional support for our hypothesis that the development of perceptual completion in early infancy is promoted by progressive improvements in visual selective attention and oculomotor skill.     

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.     

The effect of eye size on discriminating faces: Can infants recognize facial uncanniness?

Infants' ability to recognize uncanny human faces increases during the first year of life. In turn, their ability to recognize faces of other species declines at almost the same period (perceptual narrowing). In the current study, we aimed to clarify the relationship between the perception of uncanniness of faces and perceptual narrowing in infants and adults. We used the “uncanny valley task,” in which the participants were required to discriminate the faces of humans and monkeys by different eye size. Results showed that 3‐ to 5‐month‐old infants could not discriminate either monkey or human faces by eye size, whereas 6‐ to 8‐month olds could. Adults showed higher discrimination performance for human than monkey faces and perceived the human faces with extremely large or small eyes as exceedingly eerie. Our results suggest that perception of uncanniness of faces is formed after perceptual narrowing.