The developing infant learns about the physical and the social world by engaging with objects and with people. In the study reported here, we investigated the relationship between infants’ interactions with the physical and the social world. Three-month-old infants were trained for 2 weeks and experienced either actively manipulating objects themselves or passively having objects touched to their hands. Following active or passive experiences, spontaneous orienting towards faces and objects was compared between the trained groups and untrained 3- and 5-month-olds. It is known that the onset of reaching behavior increases infants’ interest in objects. However, we report that active, self-produced reaching experiences also increase infants’ spontaneous orienting towards faces, while passive experiences do not affect orienting behavior. Regression analyses provide evidence for a link between manual engagement and the development of orienting towards faces. Implications of orienting towards faces for the development of triadic interactions, joint attention, and social cognition in general are discussed.
In both children and adults there is large variability in reading skill, with approximately 5–10% of individuals characterized as having reading disability; these individuals struggle to learn to read despite adequate intelligence and opportunity. Although it is well established that a substantial portion of this variability is attributed to the genetic differences between individuals, specifics of the connections between reading and the genome are not understood. This article presents data that suggest that variation in the COMT gene, which has previously been associated with variation in higher-order cognition, is associated with reading and reading-related skills, both at the level of brain and behavior. In particular, we found that the COMT Val/Met polymorphism at rs4680, which results in the substitution of the ancestral Valine (Val) by Methionine (Met), was associated with better performance on a number of critical reading measures and with patterns of functional neural activation that have been linked to better readers. We argue that this polymorphism, known for its broad effects on cognition, may modulate (likely through frontal lobe function) reading skill.
Cortical function and related cognitive, language, and communication skills are genetically influenced. The auditory brainstem response to speech is linked to language skill, reading ability, cognitive skills, and speech-in-noise perception; however, the impact of shared genetic and environmental factors on the response has not been assessed. We assessed auditory brainstem responses to speech presented in quiet and background noise from 1) 23 pairs of same sex, same learning diagnosis siblings (Siblings), 2) 23 unrelated children matched on age, sex, IQ, and reading ability to one of the siblings (Reading-Matched), and 3) 22 pairs of unrelated children matched on age and sex but not on reading ability to the same sibling (Age/Sex-Matched). By quantifying response similarity as the intersubject response-to-response correlation for sibling pairs, reading-matched pairs, and age- and sex-matched pairs, we found that siblings had more similar responses than age- and sex-matched pairs and reading-matched pairs. Similarity of responses between siblings was as high as the similarity of responses collected from an individual over the course of the recording session. Responses from unrelated children matched on reading were more similar than responses from unrelated children matched only on age and sex, supporting previous data linking variations in auditory brainstem activity with variations in reading ability. These results suggest that auditory brainstem function can be influenced by siblingship and auditory-based communication skills such as reading, motivating the use of speech-evoked auditory brainstem responses for assessing risk of reading and communication impairments in family members.
auditory brainstem; speech; genetics; environment; siblings; reading
Infants can use statistical regularities to form rudimentary word categories (e.g. noun, verb), and to learn the meanings common to words from those categories. Using an artificial language methodology, we probed the mechanisms by which two types of statistical cues (distributional and phonological regularities) affect word learning. Because linking distributional cues vs. phonological information to semantics make different computational demands on learners, we also tested whether their use is related to language proficiency. We found that 22-month-old infants with smaller vocabularies generalized using phonological cues; however, infants with larger vocabularies showed the opposite pattern of results, generalizing based on distributional cues. These findings suggest that both phonological and distributional cues marking word categories promote early word learning. Moreover, while correlations between these cues are important to forming word categories, we found infants’ weighting of these cues in subsequent word-learning tasks changes over the course of early language development.
A commonly shared assumption in the field of visual-word recognition is that retinotopic representations are rapidly converted into abstract representations. Here we examine the role of visual form vs. abstract representations during the early stages of word processing –as measured by masked priming– in young children (3rd and 6th graders) and adult readers. To maximize the chances of detecting an effect of visual form, we employed a language with a very intricate orthography, Arabic. If visual form plays a role in the early moments of processing, greater benefit would be expected from related primes that have the same visual form (in terms of the ligation pattern between a word’s letters) as the target word (e.g., - [ktzb-ktAb] –note that the three initial letters are connected in prime and target) than for those that do not ( [ktxb-ktAb]). Results showed that the magnitude of priming effect relative to an unrelated condition (e.g., ) was remarkably similar for both types of primes. Thus, despite the visual complexity of Arabic orthography, there is fast access to the abstract letter representations not only in adult readers by also in developing readers.
word_recognition; reading_development; masked_priming
Performing action has been found to have a greater impact on learning than observing action. Here we ask whether a particular type of action—the gestures that accompany talk—affect learning in a comparable way. We gave 158 6-year-old children instruction in a mental transformation task. Half the children were asked to produce a Move gesture relevant to the task; half were asked to produce a Point gesture. The children also observed the experimenter producing either a Move or Point gesture. Children who produced a Move gesture improved more than children who observed the Move gesture. Neither producing nor observing the Point gesture facilitated learning. Doing gesture promotes learning better than seeing gesture, as long as the gesture conveys information that could help solve the task.
We know early experience plays a crucial role in the development of face processing, but we know little about how infants learn to distinguish faces from different races, especially for non-Caucasian populations. Moreover, it is unknown whether differential processing of different race faces observed in typically-studied monoracial infants extends to biracial infants as well. Thus, we investigated 3-month-old Caucasian, Asian and biracial (Caucasian-Asian) infants’ ability to distinguish Caucasian and Asian faces. Infants completed two within-subject, infant-controlled habituation sequences and test trials as an eye tracker recorded looking times and scanning patterns. Examination of individual differences revealed significant positive correlations between own-race novelty preference and scanning frequency between eye and mouth regions of own-race habituation stimuli for Caucasian and Asian infants, suggesting that facility in own-race face discrimination stems from active inspection of internal facial features in these groups. Biracial infants, however, showed the opposite effect: An “own-race” novelty preference was associated with reduced scanning between eye and mouth regions of “own-race” habituation stimuli, suggesting that biracial infants use a distinct approach to processing frequently encountered faces. Future directions for investigating face processing development in biracial populations are discussed.
infants; face perception; other race effect; intergroup processes
Recent evidence suggests those with autism may be generally impaired in visual motion perception. To examine this, we investigated both coherent and biological motion processing in adolescents with autism employing both psychophysical and fMRI methods. Those with autism performed as well as matched controls during coherent motion perception but had significantly higher thresholds for biological motion perception. The autism group showed reduced posterior Superior Temporal Sulcus (pSTS), parietal and frontal activity during a biological motion task while showing similar levels of activity in MT+/V5 during both coherent and biological motion trials. Activity in MT+/V5 was predictive of individual coherent motion thresholds in both groups. Activity in dorsolateral prefrontal cortex (DLPFC) and pSTS was predictive of biological motion thresholds in control participants but not in those with autism. Notably, however, activity in DLPFC was negatively related to autism symptom severity. These results suggest that impairments in higher-order social or attentional networks may underlie visual motion deficits observed in autism.
Theories of language acquisition have highlighted the importance of adult speakers as active participants in children’s language learning. However, in many communities children are reported to be directly engaged by their caregivers only rarely (Lieven, 1994). This observation raises the possibility that these children learn language from observing, rather than participating in, communicative exchanges. In this paper, we quantify naturally occurring language input in one community where directed interaction with children has been reported to be rare (Yucatec Mayan). We compare this input to the input heard by children growing up in large families in the United States, and we consider how directed and overheard input relate to Mayan children’s later vocabulary. In Study 1, we demonstrate that 1-year-old Mayan children do indeed hear a smaller proportion of total input in directed speech than children from the US. In Study 2, we show that for Mayan (but not US) children, there are great increases in the proportion of directed input that children receive between 13 and 35 months. In Study 3, we explore the validity of using videotaped data in a Mayan village. In Study 4, we demonstrate that word types directed to Mayan children from adults at 24 months (but not word types overheard by children or word types directed from other children) predict later vocabulary. These findings suggest that adult talk directed to children is important for early word learning, even in communities where much of children’s early language input comes from overheard speech.
As with all culturally relevant human behaviours, words are meaningful because they are shared by the members of a community. This research investigates whether 9-month-old infants understand this fundamental fact about language. Experiment 1 examined whether infants who are trained on, and subsequently habituated to, a new word-referent link expect the link to be consistent across a second speaker. Experiment 2 examined whether 9-month-old infants distinguish between behaviours that are shared across individuals (i.e., words) from those that are not (i.e., object preferences). The present findings indicate that infants as young as 9 months of age expect new word-referent links, but not object preferences, to be consistent across individuals. Thus, by 9 months, infants have identified at least one of the aspects of human behaviour that is shared across individuals within a community. The implications for children’s acquisition of language and culture are discussed.
shared knowledge; conventionality; culture; pedagogy; infant cognition; action perception; language development
Theory of mind requires belief- and desire-understanding. Event-related brain potential (ERP) research on belief- and desire-reasoning in adults found mid-frontal activations for both desires and beliefs, and selective right-posterior activations only for beliefs. Developmentally, children understand desires before beliefs; thus, a critical question concerns whether neural specialization for belief-reasoning exists in childhood or develops later. Neural activity was recorded as 7- and 8-year-olds (N = 18) performed the same diverse-desires, diverse-beliefs, and physical control tasks used in a previous adult ERP study. Like adults, mid-frontal scalp activations were found for belief- and desire-reasoning. Moreover, analyses using correct trials alone yielded selective right-posterior activations for belief-reasoning. Results suggest developmental links between increasingly accurate understanding of complex mental states and neural specialization supporting this understanding.
The current study presents a series of computational simulations that demonstrate how the neural coding of numerical magnitude may influence number cognition and development. This includes behavioral phenomena cataloged in cognitive literature such as the development of numerical estimation and operational momentum. Though neural research has begun to describe neural coding of number, it is unclear how specific characteristics of the neural coding may relate to the expansive list of behavioral phenomena in the development of number cognition. The following study considers several possibilities.
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.
Very little is known about the neural underpinnings of language learning across the lifespan and how these might be modified by maturational and experiential factors. Building on behavioral research highlighting the importance of early word segmentation (i.e. the detection of word boundaries in continuous speech) for subsequent language learning, here we characterize developmental changes in brain activity as this process occurs online, using data collected in a mixed cross-sectional and longitudinal design. One hundred and fifty-six participants, ranging from age 5 to adulthood, underwent functional magnetic resonance imaging (fMRI) while listening to three novel streams of continuous speech, which contained either strong statistical regularities, strong statistical regularities and speech cues, or weak statistical regularities providing minimal cues to word boundaries. All age groups displayed significant signal increases over time in temporal cortices for the streams with high statistical regularities; however, we observed a significant right-to-left shift in the laterality of these learning-related increases with age. Interestingly, only the 5- to 10-year-old children displayed significant signal increases for the stream with low statistical regularities, suggesting an age-related decrease in sensitivity to more subtle statistical cues. Further, in a sample of 78 10-year-olds, we examined the impact of proficiency in a second language and level of pubertal development on learning-related signal increases, showing that the brain regions involved in language learning are influenced by both experiential and maturational factors.
Infants begin to segment novel words from speech by 7.5 months, demonstrating an ability to track, encode and retrieve words in the context of larger units. Although it is presumed that word recognition at this stage is a prerequisite to constructing a vocabulary, the continuity between these stages of development has not yet been empirically demonstrated. The goal of the present study is to investigate whether infant word segmentation skills are indeed related to later lexical development. Two word segmentation tasks, varying in complexity, were administered in infancy and related to childhood outcome measures. Outcome measures consisted of age-normed productive vocabulary percentiles and a measure of cognitive development. Results demonstrated a strong degree of association between infant word segmentation abilities at 7 months and productive vocabulary size at 24 months. In addition, outcome groups, as defined by median vocabulary size and growth trajectories at 24 months, showed distinct word segmentation abilities as infants. These findings provide the first prospective evidence supporting the predictive validity of infant word segmentation tasks and suggest that they are indeed associated with mature word knowledge.
Across all languages studied to date, audiovisual speech exhibits a consistent rhythmic structure. This rhythm is critical to speech perception. Some have suggested that the speech rhythm evolved de novo in humans. An alternative account—the one we explored here—is that the rhythm of speech evolved through the modification of rhythmic facial expressions. We tested this idea by investigating the structure and development of macaque monkey lipsmacks and found that their developmental trajectory is strikingly similar to the one that leads from human infant babbling to adult speech. Specifically, we show that: 1) younger monkeys produce slower, more variable mouth movements and as they get older, these movements become faster and less variable; and 2) this developmental pattern does not occur for another cyclical mouth movement—chewing. These patterns parallel human developmental patterns for speech and chewing. They suggest that, in both species, the two types of rhythmic mouth movements use different underlying neural circuits that develop in different ways. Ultimately, both lipsmacking and speech converge on a ~5 Hz rhythm that represents the frequency that characterizes the speech rhythm of human adults. We conclude that monkey lipsmacking and human speech share a homologous developmental mechanism, lending strong empirical support for the idea that the human speech rhythm evolved from the rhythmic facial expressions of our primate ancestors.
evolution of speech; language evolution; facial expression; audiovisual speech; primate communication; insula; chewing; mother-infant
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.
Implicit skill learning underlies obtaining not only motor, but also cognitive and social skills through the life of an individual. Yet, the ontogenetic changes in humans’ implicit learning abilities have not yet been characterized, and, thus, their role in acquiring new knowledge efficiently during development is unknown. We investigated such learning across the life span, between 4–85 years of age with an implicit probabilistic sequence learning task, and we found that the difference in implicitly learning high vs. low probability events - measured by raw reaction time (RT) - exhibited a rapid decrement around age of 12. Accuracy and z-transformed data showed partially different developmental curves suggesting a re-evaluation of analysis methods in developmental research. The decrement in raw RT differences supports an extension of the traditional 2-stage lifespan skill acquisition model: in addition to a decline above the age 60 reported in earlier studies, sensitivity to raw probabilities and, therefore, acquiring new skills is significantly more effective until early adolescence than later in life. These results suggest that due to developmental changes in early adolescence, implicit skill learning processes undergo a marked shift in weighting raw probabilities vs. more complex interpretations of events, which, with appropriate timing, prove to be an optimal strategy for human skill learning.
skill learning; implicit sequence learning; automaticity; Alternating Serial Reaction Time Task (ASRT); development; aging; critical period
A critical challenge for visual perception is to represent objects as the same persisting individuals over time and motion. Across several areas of cognitive science, researchers have identified cohesion as among the most important theoretical principles of object persistence: An object must maintain a single bounded contour over time. Drawing inspiration from recent work in adult visual cognition, the present study tested the power of cohesion as a constraint as it operates early in development. In particular, we tested whether the most minimal cohesion violation – a single object splitting into two – would destroy infants’ ability to represent a quantity of objects over occlusion. In a forced-choice crawling paradigm, 10- and 12-month-old infants witnessed crackers being sequentially placed into containers, and typically crawled toward the container with the greater cracker quantity. When one of the crackers was visibly split in half, however, infants failed to represent the relative quantities, despite controls for the overall quantities and the motions involved. This result helps to characterize the fidelity and specificity of cohesion as a fundamental principle of object persistence, suggesting that even the simplest possible cohesion violation can dramatically impair infants’ object representations and influence their overt behavior.
Visual working memory (VWM) capacity has been studied extensively in adults, and methodological advances have enabled researchers to probe capacity limits in infancy using a preferential looking paradigm. Evidence suggests that capacity increases rapidly between 6 and 10 months of age. To understand how the VWM system develops, we must understand the relationship between the looking behavior used to study VWM and underlying cognitive processes. We present a dynamic neural field model that captures both real-time and developmental processes underlying performance. Three simulation experiments show how looking is linked to VWM processes during infancy and how developmental changes in performance could arise through increasing neural connectivity. These results provide insight into the sources of capacity limits and VWM development more generally.
In altricial species, like the human, the caregiver, very often the mother, is one of the most potent stimuli during development. The distinction between mothers and other adults is learned early in life and results in numerous behaviors in the child, most notably mother-approach and stranger-wariness. The current study examined the influence of the maternal stimulus on amygdala activity and related circuitry in twenty-five developing children (n=13) and adolescents (n=12), and how this circuitry was associated with attachment-related behaviors. Results indicated that maternal stimuli were especially effective in recruiting activity in the left dorsal amygdala, and activity in this amygdala region showed increased functional connectivity with evaluative and motor regions during viewing of maternal stimuli. Increases in this left dorsal amygdala activity and related amygdala-cortical functional connectivity were associated with increased mother-approach behaviors as measured by in-scanner behavioral responding and out-of-scanner child-report. Moreover, age-related changes in amygdala activity to non-mothers statistically mediated the developmentally typical decline in stranger wariness seen across this period. These results suggest that mother-induced behaviors are enacted by maternal influence on amygdala-cortical circuitry during childhood and adolescence.
Predicting the actions of others is critical to smooth social interactions. Prior work suggests both understanding and anticipation of goal-directed actions appears early in development. In this study, on-line goal prediction was tested explicitly using an adaptation of Woodward’s (1998) paradigm for an eye-tracking task. Twenty 11-month-olds were familiarized to movie clips of a hand reaching to grasp 1 of 2 objects. Then object locations were swapped, and the hand made an incomplete reach between the objects. Here, infants reliably made their first look from the hand to the familiarized goal object, now in a new location. A separate control condition of 20 infants familiarized to the same movements of an unfamiliar claw revealed the opposite pattern: reliable prediction to the familiarized location, rather than the familiarized object. This study suggests by 11-months infants actively use goal analysis to generate on-line predictions of an agent’s next action.