Eighteen-month-old human infants show intensive development in comprehension of different types of pointing gestures

This study explored children’s development in comprehending four types of pointing gestures with different familiarity. Our aim was to highlight human infants’ pointing comprehension abilities under the same conditions used for various animal species. Sixteen children were tested longitudinally in a two-choice task from 1 year of age. At the age of 12 and 14 months, infants did not exceed chance level with either of the gestures used. Infants were successful with distal pointing and long cross-pointing at the age of 16 months. By the age of 18 months, infants showed a high success rate with the less familiar gestures (forward cross-pointing and far pointing) as well. Their skills at this older age show close similarity with those demonstrated previously by dogs when using exactly the same testing procedures. Our longitudinal studies also revealed that in a few infants, the ability to comprehend pointing gestures is already apparent before 16 months of age. In general, we found large individual variation. This has been described for a variety of cognitive skills in human development and seems to be typical for pointing comprehension as well.     

Ontogenetic Emergence of Cognitive Reference Comprehension

Prelinguistic cognitive reference comprehension is foundational to language acquisition and higher cognitive functions. However, its ontogenetic origins in the first year of life are currently not well understood. The current study pitted cognitivist against social interactionist views. We worked with infants monthly from 10 to 13 months of age and observed their behavioral search during a reference comprehension task. Our goal was to first establish the age at which infants begin to cognitively expect an occluded object in one of two locations following a communicative pointing cue. We then tested whether infants' cognitive referential expectations would prospectively predict social interaction skills and experiences (as assessed by spontaneous infant and parent pointing) or, conversely, be predicted by social interaction skills and experiences. Results revealed a linear increase in cognitive reference comprehension, with clear above chance performance, individual stability in month-to-month correlations, and a synchronous correlation to referential pointing all emerging at 12 months but not earlier. Regarding developmental predictions, infants' cognitive referential expectations were not predictive of social interaction skills and experiences; on the contrary, they were predicted by social interaction skills and experiences. Findings suggest that a nonverbal cognitive understanding of reference to occluded entities is neither early emerging, hard wired, nor causal to infants' or caregivers' referential pointing. Instead, this foundational skill is predicted by earlier social interaction. Findings are consistent with the view that cognitive reference comprehension develops via a social construction process in the first year of life.     

Ethnic differences in mother-infant language and gestural communications are associated with specific skills in infants

We examined gestural and verbal interactions in 226 mother-infant pairs from Mexican, Dominican, and African American backgrounds when infants were 14 months and 2 years of age, and related these interactions to infants' emerging skills. At both ages, dyads were video-recorded as they shared a wordless number book, a wordless emotion book, and beads and string. We coded mothers' and infants' gestures and language/vocalizations. Each maternal utterance was coded as referential (e.g. 'That's a bead') or regulatory (e.g. 'Put it there'). Mothers reported on infants' gestural, receptive, and productive vocabularies at 14 months, and infants were assessed on receptive language, expressive language, and action sequencing and imitation at 2 years of age. Mothers of the three ethnicities differed in their gesturing, distributions of the two types of language, and coupling of language and gestures. Mothers' ethnicity, language, and gestures were differentially associated with infants' 2-year skills. Mother-infant communicative interactions are foundational to infant learning and development, and ethnic differences in modes of early communication portend divergent pathways in the development of specific skills.     

Infants' symbolic comprehension of actions modeled with toy replicas

While very young children's understanding of objects as symbols for other entities has been the focus of much investigation, very little is known concerning the emergence of comprehension for symbolic relations among actions modeled with toy replicas and their real counterparts. We used videotaped depictions of real actions in a preferential looking task to assess toddlers' ability to comprehend such connections for action categories aligned with familiar object concepts. Across two experiments, 16- and 18-month-olds provided no evidence of understanding such relations, even when action categories were highlighted with verbal prompts. Among 24- and 26-month-olds, comprehension of relations between certain actions modeled with toys and videos of their real-world counterparts began to emerge, independent of expressive vocabulary size. Implications of our results for theoretical conclusions drawn from use of the generalized imitation procedure to study early conceptual development are discussed.     

Precursors of a theory of mind: A longitudinal study

The study examined whether the pointing gesture and intentional understanding abilities at 12 and 15 months of age predict the later understanding of perception and intention, as well as the ability to explain others' actions in a psychological way at 39 months of age. Thirty‐five infants (18 girls) were administered pointing and intention‐understanding tasks at the age of 12 and 15 months. Children were again evaluated at the age of 39 months with perception and intention tasks, and a psychological explanation task. Results showed that only 12‐month‐olds' comprehension of the pointing gesture with an imperative motive contributed to the prediction of later understanding of perception and mentalistic explanations of actions. Moreover, the ability of 12‐ and 15‐month‐olds to understand intentions contributed to the prediction of later preschool understanding of perceptions and intentions. These results indicate that a developmental trajectory in children's understanding of mental states from infancy to childhood is present, but depends on the level of engagement and communication that are required to perform these tasks.     

Early communicative gestures and play as predictors of language development in children born with and without family risk for dyslexia

The present study investigated early communicative gestures, play, and language skills in children born with family risk for dyslexia (FR) and a control group of children without this inheritable risk at ages 12, 15, 18, and 24 months. Participants were drawn from the Tromsø Longitudinal study of Dyslexia (TLD) which follows children's cognitive and language development from age 12 months through Grade 2 in order to identify early markers of developmental dyslexia. Results showed that symbolic play and parent reported play at age 12 months and communicative gestures at age 15 months explained 61% of the variance in productive language at 24 months in the FR group. These early nonlinguistic measures seem to be potentially interesting markers of later language development in children born at risk for dyslexia.     

Spanish-speaking caregivers’ use of referential labels with toddlers is a better predictor of later vocabulary than their use of referential gestures

Variation in how frequently caregivers engage with their children is associated with variation in children's later language outcomes. One explanation for this link is that caregivers use both verbal behaviors, such as labels, and non-verbal behaviors, such as gestures, to help children establish reference to objects or events in the world. However, few studies have directly explored whether language outcomes are more strongly associated with referential behaviors that are expressed verbally, such as labels, or non-verbally, such as gestures, or whether both are equally predictive. Here, we observed caregivers from 42 Spanish-speaking families in the US engage with their 18-month-old children during 5-min lab-based, play sessions. Children's language processing speed and vocabulary size were assessed when children were 25 months. Bayesian model comparisons assessed the extent to which the frequencies of caregivers’ referential labels, referential gestures, or labels and gestures together, were more strongly associated with children's language outcomes than a model with caregiver total words, or overall talkativeness. The best-fitting models showed that children who heard more referential labels at 18 months were faster in language processing and had larger vocabularies at 25 months. Models including gestures, or labels and gestures together, showed weaker fits to the data. Caregivers’ total words predicted children's language processing speed, but predicted vocabulary size less well. These results suggest that the frequency with which caregivers of 18-month-old children use referential labels, more so than referential gestures, is a critical feature of caregiver verbal engagement that contributes to language processing development and vocabulary growth.

Research Highlights

• We examined the frequency of referential communicative behaviors, via labels and/or gestures, produced by caregivers during a 5-min play interaction with their 18-month-old children.
• We assessed predictive relations between labels, gestures, their combination, as well as total words spoken, and children's processing speed and vocabulary growth at 25 months.
• Bayesian model comparisons showed that caregivers’ referential labels at 18 months best predicted both 25-month vocabulary measures, although total words also predicted later processing speed.
• Frequent use of referential labels by caregivers, more so than referential gestures, is a critical feature of communicative behavior that supports children's later vocabulary learning.

     

Toddlers' responsive imitation predicts preschool-age conscience

Imitation has long been considered a mechanism for the development of conscience. Despite the central role of imitation in theories of moral internalization, the prediction from imitation to moral behavior has not been tested using an individual differences approach. In a longitudinal design, we examined whether individual differences in toddlers' responsive imitation predict preschool-age conscience. Mothers modeled actions for their children to imitate, and both matching behavior and motivation were observed at 14 and 22 months of age. We also measured preschool conscience by observing children's internalized conduct and guilt at ages 33 and 45 months. Imitation measures consistently predicted conscience variables. These relations were strengthened by aggregation across measures and times of assessment. Motivation and matching behavior each contributed independent variance in predicting preschool-age conscience. Results are consistent with the claim that responsive imitation reflects a general receptive stance to parents' guidance, and with both neopsychoanalytic and social cognitive views of imitation's importance in early moral development.     

Motor Imitation in Young Children with Autism: What's the Object?

Two studies investigated the nature of motor imitation in young children with autism. Study 1 compared different types of motor imitation in 18 autistic children, 18 children with developmental delay, and 18 normally developing children. Results revealed weaker imitation skills for the autistic group, though all groups demonstrated a similar pattern of performance across different imitation domains. Imitation of body movements was more difficult than imitation of actions with objects, and imitation of nonmeaningful actions was more difficult than imitation of meaningful actions. Study 2 investigated concurrent and predictive relations between imitation and other developmental skills within a sample of 26 two-year-old children with autism. Results suggested that imitation of body movements and imitation of actions with objects represent independent dimensions. Imitation of body movements was concurrently and predictively associated with expressive language skills, and imitation of actions with objects was concurrently associated with play skills. Improvements in both motor imitation domains occurred over a 1-year period.     

Imitation from 12 to 24 months in autism and typical development: a longitudinal Rasch analysis

The development of imitation during the second year of life plays an important role in domains of sociocognitive development such as language and social learning. Deficits in imitation ability in persons with autism spectrum disorder (ASD) from toddlerhood into adulthood have also been repeatedly documented, raising the possibility that early disruptions in imitation contribute to the onset of ASD and the deficits in language and social interaction that define the disorder. This study prospectively examined the development of imitation between 12 and 24 months of age in 154 infants at familial risk for ASD and 78 typically developing infants who were all later assessed at 36 months for ASD or other developmental delays. The study established a developmental measure of imitation ability and examined group differences over time, using an analytic Rasch measurement model. Results revealed a unidimensional latent construct of imitation and verified a reliable sequence of imitation skills that was invariant over time for all outcome groups. Results also showed that all groups displayed similar significant linear increases in imitation ability between 12 and 24 months and that these increases were related to individual growth in both expressive language and ratings of social engagement but not in fine motor development. The group of children who developed ASD by age 3 years exhibited delayed imitation development compared with the low-risk typical outcome group across all time-points, but were indistinguishable from other high-risk infants who showed other cognitive delays not related to ASD.     

Exploring the Relation Between Memory, Gestural Communication, and the Emergence of Language in Infancy: A Longitudinal Study

The relationship between recall memory, visual recognition memory, social communication, and the emergence of language skills was measured in a longitudinal study. Thirty typically developing Swedish children were tested at 6, 9 and 14 months. The result showed that, in combination, visual recognition memory at 6 months, deferred imitation at 9 months and turn-taking skills at 14 months could explain 41% of the variance in the infants' production of communicative gestures as measured by a Swedish variant of the MacArthur Communicative Development Inventories (CDI). In this statistical model, deferred imitation stood out as the strongest predictor.     

Olive baboons communicate intentionally by pointing

A pointing gesture creates a referential triangle that incorporates distant objects into the relationship between the signaller and the gesture’s recipient. Pointing was long assumed to be specific to our species. However, recent reports have shown that pointing emerges spontaneously in captive chimpanzees and can be learned by monkeys. Studies have demonstrated that both human children and great apes use manual gestures (e.g. pointing), and visual and vocal signals, to communicate intentionally about out-of-reach objects. Our study looked at how monkeys understand and use their learned pointing behaviour, asking whether it is a conditioned, reinforcement-dependent response or whether monkeys understand it to be a mechanism for manipulating the attention of a partner (e.g. a human). We tested nine baboons that had been trained to exhibit pointing, using operant conditioning. More specifically, we investigated their ability to communicate intentionally about the location of an unreachable food reward in three contexts that differed according to the human partner’s attentional state. In each context, we quantified the frequency of communicative behaviour (auditory and visual signals), including gestures and gaze alternations between the distal food and the human partner. We found that the baboons were able to modulate their manual and visual communicative signals as a function of the experimenter’s attentional state. These findings indicate that monkeys can intentionally produce pointing gestures and understand that a human recipient must be looking at the pointing gesture for them to perform their attention-directing actions. The referential and intentional nature of baboons’ communicative signalling is discussed.     

Individual differences in the linguistic competence of referential and expressive subjects

The aim of this work was to examine individual differences in referential and expressive style through a longitudinal study. The composition of the first 50 words, communicative gestures, the conversational style of dyads and the percentage of vocabulary produced from 12 to 24 month-olds were analyzed. The vocabulary was collected through interviews to parents and sessions of mother-infant interaction in the laboratory. Significant differences in the proportion of common nouns and frozen phrases between referential and expressive children in the frequency of communicative gestures and style conversation were found. Thus, referential children and their mothers used more pointing gestures than the expressive children and their mothers. Additionally, mothers of referential children used completing more frequently.     

Individual differences in social, cognitive, and morphological aspects of infant pointing

Little is known about the origins of the pointing gesture. We sought to gain insight into its emergence by investigating individual differences in the pointing of 12-month-old infants in two ways. First, we looked at differences in the communicative and interactional uses of pointing and asked how different hand shapes relate to point frequency, accompanying vocalizations, and mothers’ pointing. Second, we looked at differences in social-cognitive skills of point comprehension and imitation and tested whether these were related to infants’ own pointing. Infants’ and mothers’ spontaneous pointing correlated with one another, as did infants’ point production and comprehension. In particular, infants’ index-finger pointing had a profile different from simple whole-hand pointing. It was more frequent, it was more often accompanied by vocalizations, and it correlated more strongly with comprehension of pointing (especially to occluded referents). We conclude that whole-hand and index-finger pointing differ qualitatively and suggest that it is index-finger pointing that first embodies infants’ understanding of communicative intentions.     

Atypical development of language and social communication in toddlers with Williams syndrome

Williams syndrome (WS) is a genetic disorder which results in an uneven cognitive profile. Despite superior language compared to other syndromes in the phenotypic outcome, toddlers with WS are as delayed in their language onset and early linguistic development as are toddlers with other syndromes. The cause of this delay in WS is as yet unknown. In a series of experiments, we examined whether atypical socio‐interactive precursors to language could contribute to the explanation of the late language onset and atypical developmental pathways observed in WS. Experiment 1 showed that despite superficially good social skills, toddlers with WS were only proficient at dyadic interaction. They were impaired in triadic interaction, essential for the referential uses of language, and showed none of the correlations between socio‐interactive markers and language seen in the typical controls. Experiment 2 focused on the comprehension and production of referential pointing. Again, the WS group was impaired, despite vocabulary levels higher than those of typically developing controls. Finally, Experiment 3 examined fine motor skills. The WS lack of pointing could not be explained in terms of motor impairments, since the WS toddlers were proficient at fine motor control, such as the pincer grip. Overall, our data indicate that the early stages of WS language follow an atypical pathway. The findings challenge the frequent claims in the literature that individuals with Williams syndrome have preserved linguistic and social skills.     

The Development of Internal State Language during the Third Year of Life: A Longitudinal Parent Report Study

Children's talk about the mind has been scarcely studied in non‐English speakers. For this reason, this longitudinal study documents age‐related changes in German‐speaking children's internal state language. At 24, 30 and 36 months, children were administered general language tests and their internal state vocabulary levels were obtained via parental report. The developmental transition from a vocabulary rich in physiological, perceptual and desire terms to a vocabulary rich in a wider range of mental concepts confirmed previous research with French‐speaking and English‐speaking children and research in children's internal state comprehension. Further, children's category scores proved to be developmentally stable. Finally, with increasing age, children's category scores became more specifically related to each other, independent of general language skills. The results are discussed in regard to the universality of children's talk about the mind. Copyright © 2012 John Wiley & Sons, Ltd.     

Exploitation of pointing as a referential gesture in young children, but not adolescent chimpanzees

The ability of adolescent chimpanzees and 2- and 3-year-old children to use pointing gestures to locate hidden surprises was examined in two experiments. The results revealed that although young 2-year-old children appeared to have no difficulty extracting referential information from a pointing gesture (independent of gaze or distance cues) and spontaneously using it to search in specific locations, adolescent chimpanzees appeared to rely on cueconfiguration and distance-based rules. Thus, although these chimpanzees were trained to respond appropriately to the pointing gestures of a human by searching in a particular location, this ability did not easily generalize to situations in which the distance between the pointing hand and the location were more distal. Furthermore, even those chimpanzees that were able to generalize in this fashion appeared to use distance-based cues, not ones based on an appreciation of the internal attentional focus or mental referent of the experimenter as indicated by his pointing gesture.     

DO INFANTS SHOW GENERALIZED IMITATION OF GESTURES?

Two experiments were conducted to investigate generalized imitation of manual gestures in 1- to 2-year-old infants. In Experiment 1, 6 infants were first trained four baseline matching relations (e.g., when instructed "Do this", to raise their arms after they saw the experimenter do so). Next, four novel gestures that the infants did not match in probe trials were selected as target behaviors during generalized imitation Test 1; models of these gestures were presented on unreinforced matching trials interspersed with intermittently reinforced baseline matching trials. None of the infants matched the target behaviors. To ensure that these behaviors were in the infants' motor skills repertoires, the infants were next trained to produce them, at least once, under stimulus control that did not include an antecedent model of the target behavior. In repeat generalized imitation trials (Test 2), the infants again failed to match the target behaviors. Five infants (3 from Experiment 1) participated in Experiment 2, which was identical to Experiment 1 except that, following generalized imitation Test 1, the motor-skills training was implemented to a higher criterion (21 responses per target behavior), and in a multiple-baseline, across-target-behaviors procedure. In the final generalized imitation test, 1 infant matched one, and another infant matched two target behaviors; the remaining 17 target behaviors still were not matched. The results did not provide convincing evidence of generalized imitation, even though baseline matching was well maintained and the target behaviors were in the infants' motor skills repertoires, raising the question of what are the conditions that reliably give rise to generalized imitation.     

One-year-olds comprehend the communicative intentions behind gestures in a hiding game

This study explored infants' ability to infer communicative intent as expressed in non-linguistic gestures. Sixty children aged 14, 18 and 24 months participated. In the context of a hiding game, an adult indicated for the child the location of a hidden toy by giving a communicative cue: either pointing or ostensive gazing toward the container containing the toy. To succeed in this task children had to do more than just follow the point or gaze to the target container. They also had to infer that the adult's behaviour was relevant to the situation at hand - she wanted to inform them that the toy was inside the container toward which she gestured. Children at all three ages successfully used both types of cues. We conclude that infants as young as 14 months of age can, in some situations, interpret an adult behaviour as a relevant communicative act done for them.     

Infants' Understanding of Looking,Pointing, and Reaching as Cues to Goal-Directed Action

Phillips, Wellman, and Spelke (2002) provided experimental evidence indicating that by the age of 12 months infants use information about an adult's gaze-direction and emotional expression to predict action. We investigate the generality of this ability, using Phillips et al.'s paradigm across different referential gestures. If infants have a rich concept of people as intentional agents, they should encode the person-goal relation and predict action from a variety of referential gestures (such as looking and pointing), as well as from (goal-directed) reaching and grasping actions. Results of Studies 1 and 2 (within-subjects design) and Study 3 (between-subjects design) converge in indicating that Phillips et al.'s basic finding generalizes to reach-and-gaze as cue condition. In Study 3b generalization was demonstrated for point-and-gaze as cue condition. Whereas these findings suggest a general understanding of referential intent at 12 months, a control experiment (Study 4) showed that infants' action expectations could be reversed following a psychologically inconsistent habituation phase (actor points at Object A and subsequently picks up Object B) in the point-and-gaze condition, although no such reversal was obtained in the reach-and-gaze condition. These findings indicate that 1-year-old infants have well-established expectations about action goals signaled by an actor's gaze-direction and reaching and grasping movements but that an understanding of pointing as a cue to action intentions may develop later and follow a different route of acquisition.