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An important problem faced by children is discriminating between entities capable of goal-directed action, i.e. intentional agents, and non-agents. In the case of discriminating between living and dead animals, including humans, this problem is particularly difficult, because of the large number of perceptual cues that living and dead animals share. However, there are potential costs of failing to discriminate between living and dead animals, including unnecessary vigilance and lost opportunities from failing to realize that an animal, such as an animal killed for food, is dead. This might have led to the evolution of mechanisms specifically for distinguishing between living and dead animals in terms of their ability to act. Here we test this hypothesis by examining patterns of inferences about sleeping and dead organisms by Shuar and German children between 3 and 5-years old. The results show that by age 4, causal cues to death block agency attributions to animals and people, whereas cues to sleep do not. The developmental trajectory of this pattern of inferences is identical across cultures, consistent with the hypothesis of a living/dead discrimination mechanism as a reliably developing part of core cognitive architecture.

Young children learn selectively from reliable over unreliable sources. However, the cognitive underpinnings of their selectivity (attentional biases or trait ascriptions) and its early ontogeny are unclear. Thus, across three studies (N = 139, monolingual German speakers, 67 female), selective-trust tasks were adapted to test both preschoolers (5-year-olds) and toddlers (24-month-olds), using eye-tracking and interactive measures. These data show that preschoolers' selectivity is not based on attentional biases, but on person-specific trait ascriptions. In contrast, toddlers showed no selective trust, even in the eye-tracking tasks. They succeeded, however, in eye-tracking tasks with the same word-learning demands, if no ascriptions of reliability were required. Thus, these findings suggest that preschoolers, but not toddlers, use trait-like ascriptions of reliability to guide their selective learning., (© 2024 The Authors. Child Development published by Wiley Periodicals LLC on behalf of Society for Research in Child Development.)

Upon hearing a novel label, listeners tend to assume that it refers to a novel, rather than a familiar object. While this disambiguation or mutual exclusivity (ME) effect has been robustly shown across development, it is unclear what it involves. Do listeners use their pragmatic and lexical knowledge to exclude the familiar object and thus select the novel one? Or is the effect, at least in early childhood, simply based on an attraction to novelty and a direct mapping of the novel label to a novel object? In a preregistered online study with 2- to 3-year-olds ( n = 75) and adults ( n = 112), we examined (a) whether relative object novelty alone (without pragmatic or lexical information) could account for participants' disambiguation and (b) whether participants' decision processes involved reasoning by exclusion. Participants encountered either a known and an unknown object (classic ME condition) or two unknown objects, one completely novel and one preexposed (novelty condition) as potential referents of a novel label. Reasoning by exclusion was assessed by children's looking patterns and adults' explanations. In the classic ME condition, children and adults significantly chose the novel object and both used reasoning by exclusion. In contrast, in the novelty condition, children and adults chose randomly. Across conditions, a retention test revealed that adults remembered their prior selections, while children's performance was fragile. These results suggest that referent disambiguation is not based on relative object novelty alone. Instead, to resolve referential ambiguity, both young children and adults seem to make use of pragmatic and/or lexical sources of information and to engage in reasoning by exclusion strategies. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

How do children succeed in learning a word? Research has shown robustly that, in ambiguous labeling situations, young children assume novel labels to refer to unfamiliar rather than familiar objects. However, ongoing debates center on the underlying mechanism: Is this behavior based on lexical constraints, guided by pragmatic reasoning, or simply driven by children's attraction to novelty? Additionally, recent research has questioned whether children's disambiguation leads to long-term learning or rather indicates an attentional shift in the moment of the conversation. Thus, we conducted a pre-registered online study with 2- and 3-year-olds and adults. Participants were presented with unknown objects as potential referents for a novel word. Across conditions, we manipulated whether the only difference between both objects was their relative novelty to the participant or whether, in addition, participants were provided with pragmatic information that indicated which object the speaker referred to. We tested participants' immediate referent selection and their retention after 5 min. Results revealed that when given common ground information both age groups inferred the correct referent with high success and enhanced behavioral certainty. Without this information, object novelty alone did not guide their selection. After 5 min, adults remembered their previous selections above chance in both conditions, while children only showed reliable learning in the pragmatic condition. The pattern of results indicates how pragmatics may aid referent disambiguation and learning in both adults and young children. From early ontogeny on, children's social-cognitive understanding may guide their communicative interactions and support their language acquisition. RESEARCH HIGHLIGHTS: We tested how 2-3-year-olds and adults resolve referential ambiguity without any lexical cues. In the pragmatic context both age groups disambiguated novel word-object-mappings, while object novelty alone did not guide their referent selection. In the pragmatic context, children also showed increased certainty in disambiguation and retained new word-object-mappings over time. These findings contribute to the ongoing debate on whether children learn words on the basis of domain-specific constraints, lower-level associative mechanisms, or pragmatic inferences., (© 2023 The Authors. Developmental Science published by John Wiley & Sons Ltd.)

The current study set out to examine the underlying physiological mechanisms of and the emotional response associated with word learning success in young 3-year-old predominantly white children. In particular, we examined whether children's physiological arousal following a word learning task predicts their word learning success and whether successful learning in turn predicts children's subsequent positive emotions. We presented children (n = 50) with a cross-situational word learning task and measured their pupillary arousal following completion of the task, as well as changes to their upper body posture following completion of the task, as indices of children's emotions following task completion. Children who showed greater physiological arousal following the novel word recognition task (n = 40) showed improved subsequent word recognition performance. We found that children showed more elevated posture after completing a familiar word learning task compared to completing a novel word learning task (n = 33) but results on children's individual learning success and postural elevation were mixed. We discuss the findings with regards to children's affective involvement in word learning., (© 2023. The Author(s).)

The current study investigates infants' and toddlers' understanding of teasing interactions and its effect on subsequent social interactions. Teasing is a special kind of social interaction due to its dual nature: It consists of a slightly provocative contingent action accompanied by positive ostensive emotional cues. Teasing thus presents an especially interesting test case to inform us about young children's abilities to deal with complex social intentions. In a first experiment, we looked at 9-, 12-, and 18-month-old infants' ability to understand and differentiate a teasing intention from a trying intention and a refuse intention. We found that by 12 months of age, infants react differently (gaze, reach) and by 18 months they smile more in reaction to the Tease condition. In the second experiment, we tested 13-, 20- and 30-month-old children in closely matched purely playful and teasing situations. We also investigated potential social effects of teasing interactions on a subsequent affiliation sequence. Twenty- and 30-month-old children smile more in the Teasing than in the Play condition. For the 30-month-old toddlers, additionally, number of laughs is much higher in the Tease than in the Play condition. No effect on affiliation could be found. Thus, from very early in development, infants and toddlers are able to differentiate teasing from superficially similar but serious behavior and from around 18 months of age they enjoy it more. Infants and toddlers are able to process a complex social intention like teasing. Findings are discussed regarding infant and toddler intention understanding abilities., (Copyright © 2022. Published by Elsevier B.V.)

When dogs interact with humans, they often show appropriate reactions to human intentional action. But it is unclear from these everyday observations whether the dogs simply respond to the action outcomes or whether they are able to discriminate between different categories of actions. Are dogs able to distinguish intentional human actions from unintentional ones, even when the action outcomes are the same? We tested dogs' ability to discriminate these action categories by adapting the so-called "Unwilling vs. Unable" paradigm. This paradigm compares subjects' reactions to intentional and unintentional human behaviour. All dogs received three conditions: In the unwilling-condition, an experimenter intentionally withheld a reward from them. In the two unable-conditions, she unintentionally withheld the reward, either because she was clumsy or because she was physically prevented from giving the reward to the dog. Dogs clearly distinguished in their spontaneous behaviour between unwilling- and unable-conditions. This indicates that dogs indeed distinguish intentional actions from unintentional behaviour. We critically discuss our findings with regard to dogs' understanding of human intentional action., (© 2021. The Author(s).)

Caregivers typically use an exaggerated speech register known as infant-directed speech (IDS) in communication with infants. Infants prefer IDS over adult-directed speech (ADS) and IDS is functionally relevant in infant-directed communication. We examined interactions among maternal IDS quality, infants' preference for IDS over ADS, and the functional relevance of IDS at 6 and 13 months. While 6-month-olds showed a preference for IDS over ADS, 13-month-olds did not. Differences in gaze following behavior triggered by speech register (IDS vs. ADS) were found in both age groups. The degree of infants' preference for IDS (relative to ADS) was linked to the quality of maternal IDS infants were exposed to. No such relationship was found between gaze following behavior and maternal IDS quality and infants' IDS preference. The results speak to a dynamic interaction between infants' preference for different kinds of social signals and the social cues available to them., (© 2020 The Authors. Infancy published by Wiley Periodicals LLC on behalf of International Congress of Infant Studies.)

Young children learn selectively from others based on the speakers' prior accuracy. This indicates that they recognize the models' (in)competence and use it to predict who will provide the most accurate and useful information in the future. Here, we investigated whether 5-year-old children are also able to use speaker reliability retrospectively, once they have more information regarding their competence. They first experienced two previously unknown speakers who provided conflicting information about the referent of a novel label, with each speaker using the same novel label to refer exclusively to a different novel object. Following this, children learned about the speakers' differing labelling accuracy. Subsequently, children selectively endorsed the object-label link initially provided by the speaker who turned out to be reliable significantly above chance. Crucially, more than half of these children justified their object selection with reference to speaker reliability, indicating the ability to explicitly reason about their selective trust in others based on the informants' individual competences. Findings further corroborate the notion that young children are able to use advanced, metacognitive strategies (trait reasoning) to learn selectively. By contrast, since learning preceded reliability exposure and gaze data showed no preferential looking toward the more reliable speaker, findings cannot be accounted for by attentional bias accounts of selective social learning., Competing Interests: We declare we have no competing interests., (© 2020 The Authors.)

Imitation is a powerful and ubiquitous social learning strategy, fundamental for the development of individual skills and cultural traditions. Recent research on the cognitive foundations and development of imitation, though, presents a surprising picture: Although even infants imitate in selective, efficient, and rational ways, children and adults engage in overimitation. Rather than imitating selectively and efficiently, they sometimes faithfully reproduce causally irrelevant actions as much as relevant ones. In this article, we suggest a new perspective on this phenomenon by integrating established findings on children's more general capacities for rational action parsing with newer findings on overimitation. We suggest that overimitation is a consequence of children's growing capacities to understand causal and social constraints in relation to goals and that it rests on the human capacity to represent observed actions simultaneously on different levels of goal hierarchies.

Recent research has amply documented that even preschoolers learn selectively from others, preferring, for example, reliable over unreliable and competent over incompetent models. It remains unclear, however, what the cognitive foundations of such selective learning are, in particular, whether it builds on rational inferences or on less sophisticated processes. The current study, therefore, was designed to test directly the possibility that children are in principle capable of selective learning based on rational inference, yet revert to simpler strategies such as global impression formation under certain circumstances. Preschoolers (N = 75) were shown pairs of models that either differed in their degree of competence within one domain (strong vs. weak or knowledgeable vs. ignorant) or were both highly competent, but in different domains (e.g., strong vs. knowledgeable model). In the test trials, children chose between the models for strength- or knowledge-related tasks. The results suggest that, in fact, children are capable of rational inference-based selective trust: when both models were highly competent, children preferred the model with the competence most predictive and relevant for a given task. However, when choosing between two models that differed in competence on one dimension, children reverted to halo-style wide generalizations and preferred the competent models for both relevant and irrelevant tasks. These findings suggest that the rational strategies for selective learning, that children master in principle, can get masked by various performance factors., (© 2017 John Wiley & Sons Ltd.)

Cooperation is essential for human society, and children engage in cooperation from early on. It is unclear, however, how children select their partners for cooperation. We know that children choose selectively whom to learn from (e.g. preferring reliable over unreliable models) on a rational basis. The present study investigated whether children (and adults) also choose their cooperative partners selectively and what model characteristics they regard as important for cooperative partners and for informants about novel words. Three- and four-year-old children (N = 64) and adults (N = 14) saw contrasting pairs of models differing either in physical strength or in accuracy (in labeling known objects). Participants then performed different tasks (cooperative problem solving and word learning) requiring the choice of a partner or informant. Both children and adults chose their cooperative partners selectively. Moreover they showed the same pattern of selective model choice, regarding a wide range of model characteristics as important for cooperation (preferring both the strong and the accurate model for a strength-requiring cooperation tasks), but only prior knowledge as important for word learning (preferring the knowledgeable but not the strong model for word learning tasks). Young children's selective model choice thus reveals an early rational competence: They infer characteristics from past behavior and flexibly consider what characteristics are relevant for certain tasks.

Children's strong tendency to over-imitate - i.e., to reproduce causally irrelevant actions - presents a well-documented, yet puzzling, phenomenon. On first sight this instrumentally inefficient behavior seems maladaptive and different accounts have been put forward to explain it. Causal accounts claim that children are misled by an adult's demonstration, mistake the superfluous actions as causally necessary, and therefore imitate them. Other accounts emphasize cognitive-motivational aspects underlying over-imitation, e.g. social motivations to affiliate with the model, or to adhere to normative conventions. Since all accounts predict the occurrence of over-imitation under typical conditions, different parameters and circumstances have to be considered to distinguish between them. Thus, we investigated children's over-imitation and their spontaneous verbal reactions to a puppet's behavior, in contexts in which a causally irrelevant action either led to the destruction of a valuable object belonging to the experimenter, or not. In addition, children saw the full action sequence being demonstrated either with an instrumental or a conventional focus. Causal accounts predict no flexibility across these contexts, because over-imitation is said to occur automatically. Normative accounts claim that different normative considerations affect children's behavior and action parsing, and therefore predict different response patterns across conditions. We found that over-imitation was less frequent in costly and instrumental conditions. Children criticized the puppet for omitting irrelevant actions more often in the non-costly condition, but criticized her more often for performing irrelevant actions in the costly condition, often expressing their moral concern. The results support the rational normative action interpretation account of over-imitation., (Copyright © 2015 Elsevier B.V. All rights reserved.)

In recent years, ample research has shown that preschoolers choose selectively who to learn from, preferring, for example, to learn novel words from a previously accurate over a previously inaccurate model. But this research has not yet resolved what cognitive foundations such selectivity builds upon. The present article reports 2 studies that investigate whether preschoolers' selective trust is based on global impression formation (halo effects), on the close matching of past and future behavior or on trait-based inferences, and moreover whether the cognitive strategies used are the same for both positive and negative information (high and low competent models). Four- and 5-year-old children (N = 96) were presented with 2 high-competence models (strong vs. knowledgeable; Study 1) or 2 low-competence ones (weak vs. unknowledgeable; Study 2). In 5 subsequent task groups, which required strength and knowledge to different degrees, children were asked to choose between the 2 models. Children in both studies chose models selectively in accordance with their corresponding attributes, preferring the strong (or avoiding the weak) model for strength-related tasks and preferring the knowledgeable (or avoiding the unknowledgeable) model for knowledge-related tasks. This pattern of selective model choice held only for those children who correctly identified the attributes of both models (strong, smart), as indicated by their answers to trait questions at the end of the session. This suggests that trait reasoning plays a crucial role in young children's selective social learning., ((c) 2015 APA, all rights reserved).)

Adults' intentionality judgments regarding an action are influenced by their moral evaluation of this action. This is clearly indicated in the so-called side-effect effect: when told about an action (e.g. implementing a business plan) with an intended primary effect (e.g. raise profits) and a foreseen side effect (e.g. harming/helping the environment), subjects tend to interpret the bringing about of the side effect more often as intentional when it is negative (harming the environment) than when it is positive (helping the environment). From a cognitive point of view, it is unclear whether the side-effect effect is driven by the moral status of the side effects specifically, or rather more generally by its normative status. And from a developmental point of view, little is known about the ontogenetic origins of the effect. The present study therefore explored the cognitive foundations and the ontogenetic origins of the side-effect effect by testing 4-to 5-year-old children with scenarios in which a side effect was in accordance with/violated a norm. Crucially, the status of the norm was varied to be conventional or moral. Children rated the bringing about of side-effects as more intentional when it broke a norm than when it accorded with a norm irrespective of the type of norm. The side-effect effect is thus an early-developing, more general and pervasive phenomenon, not restricted to morally relevant side effects.

Recent research has documented the robust tendency of children to "over-imitate," that is, to copy causally irrelevant action elements in goal-directed action sequences. Different explanations for over-imitation have been proposed. Causal accounts claim that children mistakenly perceive such action elements as causally relevant and, therefore, imitate them. Affiliation accounts claim that children over-imitate to affiliate with the model. Normative accounts claim that children conceive of causally irrelevant actions as essential parts of an overarching conventional activity. These different accounts generally hold the same predictions regarding children's imitative response. However, it is possible to distinguish between them when one considers additional parameters. The normative account predicts wide-ranging flexibility with regard to action interpretation and the occurrence of over-imitation. First, it predicts spontaneous protest against norm violators who omit the causally irrelevant actions. Second, children should perform the causally irrelevant actions less frequently, and criticize others less frequently for omitting them, when the actions take place in a different context from the one of the initial demonstration. Such flexibility is not predicted by causal accounts and is predicted for only a limited range of contexts by affiliation accounts. Study 1 investigated children's own imitative response and found less over-imitation when children acted in a different context from when they acted in the same context as the initial demonstration. In Study 2, children criticized a puppet less frequently for omitting irrelevant actions when the puppet acted in a different context. The results support the notion that over-imitation is not an automatic and inflexible phenomenon., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Much is known about young children's use of deictic gestures such as pointing. Much less is known about their use of other types of communicative gestures, especially iconic or symbolic gestures. In particular, it is unknown whether children can create iconic gestures on the spot to inform others. Study 1 provided 27-month-olds with the opportunity to inform a novice how to perform a task. The majority of children created appropriate iconic gestures, and they did so significantly more than in a control condition in which the need to inform someone was removed. In Study 2, some of the 21-month-olds tested also created novel iconic gestures but to a lesser extent. Results are discussed in relation to children's symbolic, linguistic, and social-cognitive development., (PsycINFO Database Record (c) 2014 APA, all rights reserved.)

Much recent research has shown that the capacity for mental time travel and temporal reasoning emerges during the preschool years. Nothing is known so far, however, about young children's grasp of the normative dimension of future-directed thought and speech. The present study is the first to show that children from age 4 understand the normative outreach of such future-directed speech acts: subjects at time 1 witnessed a speaker make future-directed speech acts about/towards an actor A, either in imperative mode ("A, do X!") or as a prediction ("the actor A will do X"). When at time 2 the actor A performed an action that did not match the content of the speech act at time 1, children identified the speaker as the source of a mistake in the prediction case, and the actor as the source of the mistake in the imperative case and leveled criticism accordingly. These findings add to our knowledge about the emergence and development of temporal cognition in revealing an early sensitivity to the normative aspects of future-orientation.

Recent research has documented that children readily engage in overimitation, that is, the reproduction of causally irrelevant elements within a bigger action sequence. Different explanations have been put forward. Affiliation accounts claim that children overimitate to affiliate with the model. Causal confusion accounts claim that children mistakenly perceive causally irrelevant elements as causally relevant and, thus, imitate them. Normativity accounts claim that overimitation arises when children view causally irrelevant elements as an essential part of an overarching conventional activity. To test among these accounts, we had children watch a model produce some effect by performing a sequence of causally irrelevant and relevant acts, with the latter resulting in some effect. In two conditions, the model presented the action sequence as focused either more on the method or more on the goal, with the normativity account predicting that children should interpret the causally irrelevant element as essential more often in the method condition than in the goal condition. Three measures were used: (a) children's own overimitation, (b) their spontaneous responses to a puppet engaging in or refraining from overimitation, and (c) their explicit judgments about the puppet's behavior. Results revealed that overimitation was frequent in both conditions. In addition, however, children protested against the puppet only when she did not overimitate, they did so more in the method condition than in the goal condition, and they explicitly judged omission of the irrelevant actions to be a mistake in the method condition. These results are not readily compatible with affiliation and causal confusion accounts, and they speak in favor of normativity accounts., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Despite its importance in the development of children's skills of social cognition and communication, very little is known about the ontogenetic origins of the pointing gesture. We report a training study in which mothers gave children one month of extra daily experience with pointing as compared with a control group who had extra experience with musical activities. One hundred and two infants of 9, 10, or 11 months of age were seen at the beginning, middle, and end of this one-month period and tested for declarative pointing and gaze following. Infants'ability to point with the index finger at the end of the study was not affected by the training but was instead predicted by infants' prior ability to follow the gaze direction of an adult. The frequency with which infants pointed indexically was also affected by infant gaze following ability and, in addition, by maternal pointing frequency in free play, but not by training. In contrast, infants' ability to monitor their partner's gaze when pointing, and the frequency with which they did so, was affected by both training and maternal pointing frequency in free play. These results suggest that prior social cognitive advances, rather than adult socialization of pointing per se, determine the developmental onset of indexical pointing, but socialization processes such as imitation and adult shaping subsequently affect both infants' ability to monitor their interlocutor's gaze while they point and how frequently infants choose to point., (© 2012 Blackwell Publishing Ltd.)

This study explored whether infants aged 12 months already recognize the communicative function of pointing gestures. Infants participated in a task requiring them to comprehend an adult's informative pointing gesture to the location of a hidden toy. They mostly succeeded in this task, which required them to infer that the adult was attempting to direct their attention to a location for a reason - because she wanted them to know that a toy was hidden there. Many of the infants also reversed roles and produced appropriate pointing gestures for the adult in this same game, and indeed there was a correlation such that comprehenders were for the most part producers. These findings indicate that by 12 months of age infants are beginning to show a bidirectional understanding of communicative pointing., (©2011 The British Psychological Society.)

The hepatocellular carcinoma (HCC) is one of the most common malignant tumors and carries a poor survival rate. The management of patients at risk for developing HCC remains challenging. Increased understanding of cancer biology and technological advances have enabled identification of a multitude of pathological, genetic, and molecular events that drive hepatocarcinogenesis leading to discovery of numerous potential biomarkers in this disease. They are currently being aggressively evaluated to establish their value in early diagnosis, optimization of therapy, reducing the emergence of new tumors, and preventing the recurrence after surgical resection or liver transplantation. These markers not only help in prediction of prognosis or recurrence but may also assist in deciding appropriate modality of therapy and may represent novel potential targets for therapeutic interventions. In this paper, a summary of most relevant available data from published papers reporting various tissue and serum biomarkers involved in hepatocellular carcinoma was presented.

The influence of culture on cognitive development is well established for school age and older children. But almost nothing is known about how different parenting and socialization practices in different cultures affect infants' and young children's earliest emerging cognitive and social-cognitive skills. In the current monograph, we report a series of eight studies in which we systematically assessed the social-cognitive skills of 1- to 3-year-old children in three diverse cultural settings. One group of children was from a Western, middle-class cultural setting in rural Canada and the other two groups were from traditional, small-scale cultural settings in rural Peru and India.In a first group of studies, we assessed 1-year-old children's most basic social-cognitive skills for understanding the intentions and attention of others: imitation, helping, gaze following, and communicative pointing.Children's performance in these tasks was mostly similar across cultural settings. In a second group of studies, we assessed 1-year-old children's skills in participating in interactive episodes of collaboration and joint attention.Again in these studies the general finding was one of cross-cultural similarity. In a final pair of studies, we assessed 2- to 3-year-old children's skills within two symbolic systems (pretense and pictorial). Here we found that the Canadian children who had much more experience with such symbols showed skills at an earlier age.Our overall conclusion is that young children in all cultural settings get sufficient amounts of the right kinds of social experience to develop their most basic social-cognitive skills for interacting with others and participating in culture at around the same age. In contrast, children's acquisition of more culturally specific skills for use in practices involving artifacts and symbols is more dependent on specific learning experiences.

Infants intentionally communicate with others from before their 1st birthday. But there is some question about how they understand the communicative process. Do they understand that for their request to work the recipient must both understand the request and be cooperatively disposed to fulfill it? On the basis of the study by Shwe and Markman (1997), we developed a new paradigm that tested whether and how 18-, 24-, and 30-month-old children repair a failed request. Children at all ages repaired their requests in the case of a misunderstanding even if they had obtained the requested object already. They also repaired differently depending on the precise reason for the communicative failure (e.g., misunderstanding the referent versus the communicative intent) and did not repair in the case of correct understanding, even if they did not get the requested object. Thus, from very early in their communicative careers, young children operate with a basic understanding of the mental and cooperative nature of human communication.

We investigated whether 1-year-old infants use their shared experience with an adult to determine the meaning of a pointing gesture. In the first study, after two adults had each shared a different activity with the infant, one of the adults pointed to a target object. Eighteen- but not 14-month-olds responded appropriately to the pointing gesture based on the particular activity they had previously shared with that particular adult. In the second study, 14-month-olds were successful in a simpler procedure in which the pointing adult either had or had not shared a relevant activity with the infant prior to the pointing. Infants just beginning to learn language thus already show a complex understanding of the pragmatics of cooperative communication in which shared experience with particular individuals plays a crucial role.

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.

We propose that the crucial difference between human cognition and that of other species is the ability to participate with others in collaborative activities with shared goals and intentions: shared intentionality. Participation in such activities requires not only especially powerful forms of intention reading and cultural learning, but also a unique motivation to share psychological states with others and unique forms of cognitive representation for doing so. The result of participating in these activities is species-unique forms of cultural cognition and evolution, enabling everything from the creation and use of linguistic symbols to the construction of social norms and individual beliefs to the establishment of social institutions. In support of this proposal we argue and present evidence that great apes (and some children with autism) understand the basics of intentional action, but they still do not participate in activities involving joint intentions and attention (shared intentionality). Human children's skills of shared intentionality develop gradually during the first 14 months of life as two ontogenetic pathways intertwine: (1) the general ape line of understanding others as animate, goal-directed, and intentional agents; and (2) a species-unique motivation to share emotions, experience, and activities with other persons. The developmental outcome is children's ability to construct dialogic cognitive representations, which enable them to participate in earnest in the collectivity that is human cognition.

Infants experienced a female adult handling them toys. Sometimes, however, the transaction failed, either because the adult was in various ways unwilling to give the toy (e.g., she teased the child with it or played with it herself) or else because she was unable to give it (e.g., she accidentally dropped it). Infants at 9, 12, and 18 months of age reacted with more impatience (e.g., reaching, looking away) when the adult was unwilling to give them the toy than when she was simply unable to give it. Six-month-olds, in contrast, showed no evidence of this differentiation. Because infants' behavioral responses were appropriately adapted to different kinds of intentional actions, and because the adult's actions sometimes produced results that did not match her goal (when having accidents or failed attempts), these findings provide especially rich evidence that infants first begin to understand goal-directed action at around 9 months of age., (Copyright 2005 APA, all rights reserved.)