Developmental Science

Previous research, in which static figures were used, showed that the ability to perceive illusory contours emerges around 7 months of age. However, recently, evidence has suggested that 2-3-month-old infants are able to perceive illusory contours when motion information is available . The present study was aimed at investigating whether even newborns might perceive kinetic illusory contours when a motion easily detected by the immature newborn's visual system (i.e. stroboscopic motion) is used. In Experiment 1, using a preference looking technique, newborns' perception of kinetic illusory contours was explored using a Kanizsa figure in a static and in a kinetic display. The results showed that newborns manifest a preference for the illusory contours only in the kinetic, but not in the static, condition. In Experiment 2, using an habituation technique, newborns were habituated to a moving shape that was matched with the background in terms of random-texture-surface; thus the recovery of the shape was possible relying only on kinetic information. The results showed that infants manifested a novelty preference when presented with luminance-defined familiar and novel shapes. Altogether these findings provide evidence that motion enhances (Experiment 1) and sometimes is sufficient (Experiment 2) to induce newborns' perception of illusory contours.

The present study was aimed at investigating whether, because of a differential sensitivity between the upper and the lower visual fields, in a visual preference task newborns would orient more frequently and look longer at patterns with a great number of high–contrast ...

The numerical knowledge of children from low-income backgrounds trails behind that of peers from middle-income backgrounds even before the children enter school. This gap may reflect differing prior experience with informal numerical activities, such as numerical board games. Experiment 1 indicated that the numerical magnitude knowledge of preschoolers from low-income families lagged behind that of peers from more affluent backgrounds. Experiment 2 indicated that playing a simple numerical board game for four 15-minute sessions eliminated the differences in numerical estimation proficiency. Playing games that substituted colors for numbers did not have this effect. Thus, playing numerical board games offers an inexpensive means for reducing the gap in numerical knowledge that separates less and more affluent children when they begin school.

How have connectionist models informed the study of development? This paper considers three contributions from specific models. First, connectionist models have proven useful for exploring nonlinear dynamics and emergent properties, and their role in nonlinear developmental trajectories, critical periods and developmental disorders. Second, connectionist models have informed the study of the representations that lead to behavioral dissociations. Third, connectionist models have provided insight into neural mechanisms, and why different brain regions are specialized for different functions. Connectionist and dynamic systems approaches to development have differed, with connectionist approaches focused on learning processes and representations in cognitive tasks, and dynamic systems approaches focused on mathematical characterizations of physical elements of the system and their interactions with the environment. The two approaches also share much in common, such as their emphasis on continuous, nonlinear processes and their broad application to a range of behaviors.

The aim of this study was to examine the association of breastfeeding practices with the growth trajectories of children's cognitive development. We used data from the Child Development Supplement (CDS) of the Panel Study of Income Dynamics (PSID) with variables on presence and duration of breastfeeding and standardized test scores obtained during three different panel waves (N = 2681). After adjusting for covariates we found that breastfed children had higher test scores but that breastfed and non-breastfed children had similar growth trajectories in test scores over time. The results indicate that breastfeeding has an important association with test scores, and that subsequent schooling and other experiences during adolescence do not eliminate the breastfeeding gap that appears in very early childhood.

A common way of studying developmental disorders is to adopt a static neuropsychological deficit approach, in which the brain is characterized in terms of a normal brain with some parts or`modules' impaired. In this paper we outline a neuroconstructivist approach in which developmental disorders are viewed as alternative developmental trajectories in the emergence of representations within neural networks. As a concrete instantiation of the assumptions underlying this general approach, we present a number of simulations in an artificial neural network model. The representations that emerge under different architectural, input and developmental timing conditions are then analysed within a multidimensional state space. We explore alternative developmental trajectories in these simulations, demonstrating how initial differences in the same parameter can lead to very different outcomes, and conversely how different starting states can sometimes result in similar end states (phenotypes). We conclude that the assumptions of the neuroconstructivist approach are likely to be more appropriate for analysing developmental deviations in complex dynamic neural networks, such as the human brain.

The human aptitude for imitation and social learning underpins our advanced cultural practices. While social learning is a valuable evolutionary survival strategy, blind copying does not necessarily facilitate survival. Copying from the majority allows individuals to make rapid judgments on the value of a trait, based on its frequency. This is known as the majority bias: an individual's tendency to copy the behavior elicited by the largest number of individuals in a population. An alternative approach is to follow those who are the most proficient. While there is evidence that children do show both processes, no study has directly pitted them against each other. To do this, in the current experiment 36 children aged between 4 and 5 years watched live actors demonstrate, as a group or individually, how to open novel puzzle boxes. Children exhibited a bias to the majority when group and individual methods were successful, but favored the individual if the group method was unsuccessful. Affiliating children with the unsuccessful majority group did not impact on this pattern.

Children and adults were tested on a forced-choice face recognition task in which the direction of eye gaze was manipulated over the course of the initial presentation and subsequent test phase of the experiment. To establish the effects of gaze direction on the encoding process, participants were presented with to-be-studied faces displaying either direct or deviated gaze (i.e. encoding manipulation). At test, all the faces depicted persons with their eyes closed. To investigate the effects of gaze direction on the efficiency of the retrieval process, a second condition (i.e. retrieval manipulation) was run in which target faces were presented initially with eyes closed and tested with either direct or deviated gaze. The results revealed the encoding advantages enjoyed by faces with direct gaze was present for both children and adults. Faces with direct gaze were also recognized better than faces with deviated gaze at retrieval, although this effect was most pronounced for adults. Finally, the advantage for direct gaze over deviated gaze at encoding was greater than the advantage for direct gaze over deviated gaze at retrieval. We consider the theoretical implications of these findings.

A previous finding from our group indicated that teacher-rated antisocial behaviour (AB) among 7-year-olds is particularly heritable in the presence of callous-unemotional (CU) traits. Using a sample of 1865 same-sex twin pairs, we employed DeFries-Fulker extremes analysis to investigate whether teacher-rated AB with/without CU traits also shows aetiological differences among 9-year-olds. Furthermore, we assessed whether the differences in the magnitude of heritability would be evident even when hyperactive symptoms were controlled for in the statistical analysis. AB among 9-year-olds was more heritable with than without concomitant CU. The heritability difference was even more pronounced in magnitude when hyperactive symptoms were controlled. CU traits thus appear to index one valid way of sub-typing children with early-onset AB.

Before they enter preschool, children vary greatly in their numerical and mathematical knowledge, and this knowledge predicts their achievement throughout elementary school (e.g. . Therefore, it is critical that we look to the home environment for parental inputs that may lead to these early variations. Recent work has shown that the amount of number talk that parents engage in with their children is robustly related to a critical aspect of mathematical development -cardinal-number knowledge (e.g. knowing that the word 'three' refers to sets of three entities; Levine, Suriyakham, Rowe, Huttenlocher & Gunderson, 2010). The present study characterizes the different types of number talk that parents produce and investigates which types are most predictive of children's later cardinal-number knowledge. We find that parents' number talk involving counting or labeling sets of present, visible objects is related to children's later cardinal-number knowledge, whereas other types of parent number talk are not. In addition, number talk that refers to large sets of present objects (i.e. sets of size 4 to 10 that fall outside children's ability to track individual objects) is more robustly predictive of children's later cardinal-number knowledge than talk about smaller sets. The relation between parents' number talk about large sets of present objects and children's cardinal-number knowledge remains significant even when controlling for factors such as parents' socioeconomic status and other measures of parents' number and non-number talk.

Previous research has shown that the weighting of, or attention to, acoustic cues at the level of the segment changes over the course of development (Nittrouer & Miller, 1997; Nittrouer, Manning & Meyer, 1993). In this paper we examined changes over the course of development in weighting of acoustic cues at the suprasegmental level. Specifically, we tested English-learning 4-month-olds’ performance on a clause segmentation task when each of three acoustic cues to clausal units was neutralized and contrasted it with performance on a Baseline condition where no cues were manipulated. Comparison with the reported performance of 6-month-olds on the same task (Seidl, 2007) reveals that 4-month-olds weight prosodic cues to clausal boundaries differently than 6-month-olds, relying more heavily on all three correlates of clausal boundaries (pause, pitch and vowel duration) than 6-month-olds do, who rely primarily on pitch. We interpret this as evidence that 4-month-olds use a holistic processing strategy, while 6-month-olds may already be able to attend separately to isolated cues in the input stream and may, furthermore, be able to exploit a language-specific cue weighting. Thus, in a way similar to that in other cognitive domains, infants begin as holistic auditory scene processors and are only later able to process individual auditory cues.

The problem of how to distribute available resources among members of a group is a central aspect of social life. Adults react negatively to inequitable distributions and several studies have reported negative reactions to inequity also in non-human primates and dogs. We report ...

How do our mental representations of number change over development? The dominant view holds that children (and adults) possess multiple representations of number, and that age and experience lead to a shift from greater reliance upon logarithmically organized number representations to greater reliance upon more accurate, linear representations. Here we present a new theoretically motivated and empirically supported account of the development of numerical estimation, based on the idea that number-line estimation tasks entail judgments of proportion. We extend existing models of perceptual proportion judgment to the case of abstract numerical magnitude. Two experiments provide support for these models; three likely sources of developmental change in children's estimation performance are identified and discussed. This work demonstrates that proportion-judgment models provide a unified account of estimation patterns that have previously been explained in terms of a developmental shift from logarithmic to linear representations of number.

This article establishes a state-of-the-art review about the contribution of the community factors in the study of developmental trajectories of antisocial and criminal behavior. It aims to clarify and organize what the scientific discourse says about the relationships between community and behavioral trajectories. With this purpose, divided in two directions it presents, analyzes and discusses the most relevant: (1) theoretical perspectives and (2) empirical studies that can be found within the subject of Developmental Criminology. Before that, a brief passage through the theoretical foundations of this theme – historically speaking, they precede Developmental Criminology (DC) but DC actualizes them – towards a wider theoretical comprehension of the origins and conceptual and empirical games at stake in the present. We will jump towards this review with a starting shot built upon the following questions – to be answered along the article: Which community factors have an impact on antisocial development/life paths and how much do they matter? What interactions do they have with other systems of influences? At what periods in individual’s lives (timing) do communities make an impact? Does the weight of its influence vary across developmental stages or age?



Este artigo realiza uma revisão teórica da contribuição dos fatores comunitários para as trajetórias de desenvolvimento antissocial e criminal. Procura esclarecer e organizar o que diz o discurso científico sobre as relações entre comunidade e trajetórias comportamentais. Para isso, apresenta, analisa e discute, por um lado, as perspetivas teóricas e, por outro, os estudos empíricos mais relevantes encontrados na disciplina da Criminologia Desenvolvimental. Antes disso, faz uma breve passagem pelas fundações teóricas do tema que precedem historicamente esta subdisciplina da Criminologia – que vai beber deles – para uma mais abrangente compreensão teórica das origens e jogos conceituais e empíricos que se observam no presente. Saltaremos para este “estado da arte” com um tiro de partida que se formula pelas seguintes perguntas – a que se procura dar resposta ao longo do artigo: quais os fatores comunitários que impactuam nas trajetórias antissociais/percursos de vida e qual o seu peso? Que interações tecem com outros sistemas de causação? Em que períodos da vida dos indivíduos (timing) surtem as comunidades a sua influência? A magnitude do impacto comunitário varia consoante o estágio desenvolvimental ou idade?

Literature on the so-called bilingual advantage is directed towards the investigation of whether the mastering of two languages fosters cognitive skills in the non-verbal domain. The present study aimed to evaluate whether the bilingual advantage in non-verbal skills could be best defined as domain-general or domain-specific, and, in the latter case, at identifying the basic cognitive skills involved. Bilingual and monolingual participants were divided into two different age groups (children, youths) and were tested on a battery of elementary cognitive tasks which included a choice reaction time task, a go/no-go task, two working memory tasks (numbers and symbols) and an anticipation task. Bilingual and monolingual children did not differ from each other except for the anticipation task, where bilinguals were found to be faster and more accurate than monolinguals. These findings suggest that anticipation, which has received little attention to date, is an important cognitive domain which needs to be evaluated to a greater extent both in bilingual and monolingual participants.

Intuitive theories about the malleability of intellectual ability affect our motivation and achievement in life. But how are such theories shaped by the culture in which an individual is raised? We addressed this question by exploring how Indian children's and adults' attitudes toward the Hindu caste systemand its deterministic worldvieware related to differences in their intuitive theories. Strikingly, we found that, beginning at least in middle school and continuing into adulthood, individuals who placed more importance on caste were more likely to adopt deterministic intuitive theories. We also found a developmental change in the scope of this relationship, such that in children, caste attitudes were linked only to abstract beliefs about personal freedom, but that by adulthood, caste attitudes were also linked to beliefs about the potential achievement of members of different castes, personal intellectual ability, and personality attributes. These results are the first to directly relate the societal structure in which a person is raised to the specific intuitive theories they adopt.

Visual-attentional theories of dyslexia predict deficits for dyslexic children not only for the perception of letter strings but also for non-alphanumeric symbol strings. This prediction was tested in a two-alternative forced-choice paradigm with letters, digits, and symbols. Children with dyslexia showed significant deficits for letter and digit strings but not for symbol strings. This finding is difficult to explain for visual-attentional theories of dyslexia which postulate identical deficits for letters, digits and symbols. Moreover, dyslexics showed normal W-shaped serial position functions for letter and digit strings, which suggests that their deficit is not due to an abnormally small attentional window. Finally, the size of the deficit was identical for letters and digits, which suggests that poor letter perception is not just a consequence of the lack of reading. Together then, our results show that symbols that map onto phonological codes are impaired (i.e. letters and digits), whereas symbols that do not map onto phonological codes are not impaired. This dissociation suggests that impaired symbol-sound mapping rather than impaired visual-attentional processing is the key to understanding dyslexia.

In two experiments, children aged 3, 4 and 5 years ( N = 61) were given conflicting information about the names and functions of novel objects by two informants, one a familiar teacher, the other an unfamiliar teacher. On pre-test trials, all three age groups invested more trust in the familiar teacher. They preferred to ask for information and to endorse the information that she supplied. In a subsequent phase, children watched as the two teachers differed in the accuracy with which they named a set of familiar objects. Half the children saw the familiar teacher name the objects accurately and the unfamiliar teacher name them inaccurately. The remaining half saw the reverse arrangement. In post-test trials, the selective trust initially displayed by 3-year-olds was minimally affected by this intervening experience of differential accuracy. By contrast, the selective trust of 4-and 5-year-olds was affected. If the familiar teacher had been the more accurate, selective trust in her was intensified. If, on the other hand, the familiar teacher had been the less accurate, it was undermined, particularly among 5-year-olds. Thus, by 4 years of age, children trust familiar informants but moderate that trust depending on the informants' recent history of accuracy or inaccuracy.

The present study of over 3000 2-year-old twin pairs used a sex-limitation model to examine genetic and environmental origins of sex differences in verbal and non-verbal cognitive ability. Girls scored significantly higher on both measures (p`0.0001), although gender only accounted for approximately 3% of the variance in verbal ability and 1% of the variance in non-verbal cognitive ability. For the verbal measure boys showed greater heritability than girls. Also the twin-pair correlation is significantly lower for opposite-sex twins than for non-identical same-sex twins. This indicates that individual differences in verbal ability include some sex-specific factors. Non-verbal cognitive ability did not differ in aetiology for boys and girls. We conclude that genetic and environmental influences differ for girls and boys for early verbal but not non-verbal development.

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.

There is a`theory of mind' theory of autism. Meltzoff has recently developed a procedure that gives a nonverbal assessment of`theory of mind'. A group of children with autism and a matched control group of normally developing infants were given three of Meltzoff's tasks and three conventional, gestural imitation tasks. The children with autism showed the expected deficits on gestural imitation, but were significantly better than the normally developing infants on the Meltzoff tasks. The implications of these results for a number of theoretical issues are discussed.

There is considerable lack of evidence concerning the linguistic and cognitive skills underpinning abstract vocabulary acquisition. The present study considers the role of emotional valence in providing an embodied learning experience in which to anchor abstract meanings. First, analyses of adult ratings of age-of-acquisition, concreteness and valence demonstrate that abstract words acquired early tend to be emotionally valenced. Second, auditory Lexical Decision accuracies of children aged 6-7, 8-9, and 10-11 years (n = 20 per group) complement these analyses, demonstrating that emotional valence facilitates processing of abstract words, but not concrete. These findings provide the first evidence that young, school-aged children are sensitive to emotional valence and that this facilitates acquisition of abstract words.

Like adults, young infants prefer attractive to unattractive faces (e.g. Langlois, ). We investigated whether or not 6-month-old infants can categorize faces as attractive or unattractive. In Experiment 1, we familiarized infants to unattractive female faces; in Experiment 2, we familiarized infants to attractive female faces and tested both groups of infants on novel faces from the familiar or novel attractiveness category. Results showed that 6-month-olds categorized attractive and unattractive female faces into two different groups of faces. Experiments 3 and 4 confirmed that infants could discriminate among the faces used in Experiments 1 and 2, and therefore categorized the faces based on their similarities in attractiveness rather than because they could not differentiate among the faces. These findings suggest that categorization of facial attractiveness may underlie the development of the 'beauty is good' stereotype.

The present study explores the ability of 3.5-and 4.5-year-olds to use a causal property (making a machine light up and play music) to build categories of objects, and attach a name to them. First, this use is assessed in the presence or absence of simple perceptual information (color and shape) leading to a conflicting categorization. Second, the role of language is evaluated by varying how the experimenter describes the actions of the objects on the machine. Results show that although children of both ages use causal properties to categorize objects in the absence of conflicting perceptual categorization, older children are more likely than younger children to favor the causal over the perceptual categorization when they conflict. An effect of language was also found with the older children, with explicit causal descriptions of the events enhancing causal categorizations. Finally, a memory probe showed that younger children were likely to misremember causal information when it conflicted with perceptual information. These results suggest that perceptual, linguistic and causal information are all correlated for the younger children, whereas these cues are more independent for the older children.

The current experiment examines if and when children consider the possibility of relationships skewing judgments when evaluating judgments in different contexts. Eighty-seven 6-year-olds, 8-year-olds, 10-year-olds, and adults heard stories about judges who made decisions matching or mismatching possible relationship biases (e.g. a judge choosing a friend or an enemy as the winner) in contests with objective or subjective criteria. While even 6-year-olds distinguished between subjective and objective contests, neither children nor adults focused on the objectivity of the contest criteria when evaluating a judge's claims. Instead, by age 8, if not earlier, children focused on relationships, trusting judgments that mismatched someone's relationship biases and discounting judgments that matched someone's relationship biases. The findings also suggested that children are better at recognizing that a judgment may have been biased than predicting that one will be, and that they may understand that negative relationships may skew judgments before positive ones.

It is well known that adults' face recognition is characterized by an 'other-race effect' (ORE; see Meissner & Brigham, 2001), but few studies have investigated this ORE during the development of the face processing system. Here we examined the role of experience with other-race faces during childhood by testing a group of 6- to 14-year-old Asian children adopted between 2 and 26 months in Caucasian families living in Western Europe, as well as a group of age-matched Caucasian children. The latter group showed a strong ORE in favour of own-race faces that was stable from 6 to 14 years of age. The adopted participants did not show a significant reversal of the ORE, unlike a recently reported study (Sangrigoli et al., 2005), but rather comparable results with Asian and Caucasian faces. Their pattern of performance was neither influenced by their age of adoption, nor by the amount of experience they accumulated during childhood with other-race faces. These results indicate that the balance of performance with Asian and Caucasian faces can be modulated, but not completely reversed, in children whose exposure to own- and other-race faces changes drastically during the period of maturation of the face recognition system, depending on the length of exposure to the new face race. Overall, experience appears to be crucial during childhood to shape the face recognition system towards the most predominant morphologies of faces present in the environment.

Hebbian learning is a biologically plausible and ecologically valid learning mechanism. In Hebbian learning, 'units that fire together, wire together'. Such learning may occur at the neural level in terms of long-term potentiation (LTP) and long-term depression (LTD). Many features of Hebbian learning are relevant to developmental theorizing, including its self-organizing nature and its ability to extract statistical regularities from the environment. Hebbian learning mechanisms may also play an important role in critical periods during development, and in a number of other developmental phenomena.

Adults believe that plagiarizing ideas is wrong, which requires an understanding that others can have ideas and that it is wrong to copy them. In order to test when this understanding emerges, we investigated when children begin to think plagiarism is wrong. In Study 1, children aged 7, 9 and 11 years old, as well as adults, disliked someone who plagiarized compared to someone who drew an original drawing or someone who drew an identical picture by chance. Study 2 investigated the same question with younger children, focusing on children aged 3-6 years old. Children aged 5-6 years old evaluated plagiarizers negatively relative to unique drawers, but 3-4-year-olds did not. Study 3 replicated the findings from Study 2 and found that children justify their negative evaluations of plagiarizers by mentioning concerns over copying. These experiments provide evidence that, by age 5 years old, children understand that others have ideas and dislike the copying of these ideas.

In this study we examined the relationship between menarche and interest in infants among adolescent girls, and the effects of early environment, particularly of father absence from home, on both variables. Eighty-three girls ranging in age from between 11 and 14 years served as study participants. Interest in infants was assessed through their preferences for photos and silhouettes of animal and human faces of infants versus adults. Information on menarche and the early family environment was obtained with questionnaires and interviews. Variation in menarcheal status or timing of menarche was associated with some differences in interest in infants. There was little or no evidence, however, that suggested a direct causal relationship between these variables. Instead, both menarche and interest in infants were independently associated with early father absence from home such that father-absent girls exhibited earlier menarche and greater attraction to infant visual stimuli than father-present girls. Our results are consistent with the hypothesis that father absence is associated with a developmental trajectory characterized by earlier readiness for reproduction and parenting.

We review and relate two literatures on the development of attention in children: one concerning flexible attention switching and the other concerning selective attention. The first is a growing literature on preschool children's performances in an attentionswitching task indicating that children become more flexible in their attentional control during the preschool years. The second literature encompasses a large and robust set of phenomena for the same developmental period that indicates a protracted course of development for selective attention in children. We ask whether developmental changes in processes of selective attention may contribute to more flexible attention switching. We consider the two sets of phenomena with respect to this question and propose an empirical agenda for their joint study that may lead ultimately to a unified account of the development of selective attention and attention switching.

We introduce computer-based methodologies for investigating object identification in 3-to 5-year-old children. In two experiments, preschool children and adults indicated when they could identify degraded pictures of common objects as those pictures either gradually improved or degraded in clarity. Clarity transformations were implemented in four ways: blurring, decreasing the picture's physical size, decreasing the pixel signal-to-noise ratio, and cropping. In Experiment 1, all age groups correctly identified objects at a more degraded state when those objects began moderately, as opposed to very, degraded and then clarified. This finding supports the notion that previous perceptual hypotheses interfere with object identification (i.e. the perceptual interference effect). In Experiment 2, children, but not adults, overestimated their ability to recognize objects in a degraded state when the object's identity was given to them beforehand. This suggests that for young children knowledge of the object's true identity cannot be ignored when evaluating their current perceptions. This is the first demonstration of the perceptual interference effect in children. We discuss both methodological and theoretical implications of the findings for research on object perception and theory of mind.

Neuroconstructivism is a theoretical framework focusing on the construction of representations in the developing brain. Cognitive development is explained as emerging from the experience-dependent development of neural structures supporting mental representations. Neural development occurs in the context of multiple interacting constraints acting on different levels, from the individual cell to the external environment of the developing child. Cognitive development can thus be understood as a trajectory originating from the constraints on the underlying neural structures. This perspective offers an integrated view of normal and abnormal development as well as of development and adult processing, and it stands apart from traditional cognitive approaches in taking seriously the constraints on cognition inherent to the substrate that delivers it.

The lexicon of 6-month-olds is comprised of names and body part words. Unlike names, body part words do not often occur in isolation in the input. This presents a puzzle: How have infants been able to pull out these words from the continuous stream of speech at such a young age? We hypothesize that caregivers' interactions directed at and on the infant's body may be at the root of their early acquisition of body part words. An artificial language segmentation study shows that experimenter-provided synchronous tactile cues help 4-month-olds to find words in continuous speech. A follow-up study suggests that this facilitation cannot be reduced to the highly social situation in which the directed interaction occurs. Taken together, these studies suggest that direct caregiver-infant interaction, exemplified in this study by touch cues, may play a key role in infants' ability to find word boundaries, and suggests that early vocabulary items may consist of words often linked with caregiver touches. A video abstract of this article can be viewed at

... In P. Ekman & Coyness in early infancy 191 © Blackwell Publishers Ltd. 2000 ... The regulation of positive affect: gaze aversion during mother±infant interaction. Infant Behaviour and Development, 14 (1), 111±123. Trevarthen, C. (1993). The self born in intersubjectivity. In U. ...

Children's change over time in frequency of finger use on number combinations was examined in relation to their change in accuracy. Performance was tracked longitudinally over 11 time points, from the beginning of kindergarten (mean age = 5.7 years) to the end of second grade (n = 217). Accuracy in number combinations increased steadily during the time period while frequency of finger use declined. Correlations between finger use and accuracy decreased gradually, ranging from 0.60 in kindergarten to −0.15 at the end of second grade. Low-income children showed linear growth in frequency of finger use while middle-income children slowed down by second grade and even started to decline. Although girls and boys showed similar growth patterns in frequency and accuracy, boys used their fingers less often than girls and were more accurate. The findings indicate that finger use is most adaptive when children are first learning number combinations, but this benefit lessens over time.

The acquisition of reading has an extensive impact on the developing brain and leads to enhanced abilities in phonological processing and visual letter perception. Could this expertise also extend to early visual abilities outside the reading domain? Here we studied the performance of illiterate, ex-illiterate and literate adults closely matched in age, socioeconomic and cultural characteristics, on a contour integration task known to depend on early visual processing. Stimuli consisted of a closed eggshaped contour made of disconnected Gabor patches, within a background of randomly oriented Gabor stimuli. Subjects had to decide whether the egg was pointing left or right. Difficulty was varied by jittering the orientation of the Gabor patches forming the contour. Contour integration performance was lower in illiterates than in both ex-illiterate and literate controls. We argue that this difference in contour perception must reflect a genuine difference in visual function. According to this view, the intensive perceptual training that accompanies reading acquisition also improves early visual abilities, suggesting that the impact of literacy on the visual system is more widespread than originally proposed.

Research with adults indicates that confidence in the correctness of an answer decreases as a function of the amount of time it takes to reach that answer, suggesting that people use response latency as a mnemonic cue for subjective confidence. Experiment 1 extended investigation to 2nd, 3rd and 5th graders. When children chose the answer to general knowledge questions, their confidence in the answer was inversely related to choice latency. However, the strength of the relationship increased with grade, suggesting increased reliance with age on the feedback from task performance. The validity of latency as a cue for the accuracy of the answer also increased with age, possibly contributing to the observed age increase in the extent to which confidence judgment discriminated between correct and wrong answers. Whereas these results illustrate the dependence of metacognitive monitoring on the feedback from control operations, Experiments 2 and 3 examined the idea that control-based monitoring affects subsequent control operations. When children were free to choose which answers to volunteer under a payoff schedule that emphasized accuracy, they tended to volunteer high-confidence answers more than low-confidence answers (Experiment 2) and more short-latency answers than long-latency answers (Experiment 3). The latter tendency was again stronger for older than for younger children. The results are discussed in terms of the intricate relationships between monitoring and control processes.

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 lifespan, between 4 and 85 years of age with an implicit probabilistic sequence learning task, and we found that the difference in implicitly learning highvs. 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 two-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.