Publications of Csibra, G.

Longitudinal development of attention and inhibitory control during the first year of life

Executive functions (EFs) are key abilities that allow us to control our thoughts and actions. Research suggests that two EFs, inhibitory control (IC) and working memory (WM), emerge around 9 months. Little is known about IC earlier in infancy and whether basic attentional processes form the “building blocks” of emerging IC. These questions were investigated longitudinally in 104 infants tested behaviorally on two screen-based attention tasks at 4 months, and on IC tasks at 6 and 9 months. Results provided no evidence that basic attention formed precursors for IC. However, there was full support for coherence in IC at 9 months and partial support for stability in IC from 6 months. This suggests that IC emerges earlier than previously assumed.

Statistical treatment of looking-time data

Looking times (LTs) are frequently measured in empirical research on infant cognition. We analyzed the statistical distribution of LTs across participants in order to develop recommendations for their treatment in infancy research. Our analyses focused on a common within-subject experimental design, in which longer looking to novel or unexpected stimuli is predicted. We analyzed data from two sources: an in-house set of LTs that included data from individual participants (47 experiments, 1584 observations), and a representative set of published papers reporting group-level LT statistics (149 experiments from 33 papers). We established that LTs are log-normally distributed across participants, and therefore should always be log-transformed before parametric statistical analyses. We estimated the typical size of significant effects in LT studies, which allowed us to make recommendations about setting sample sizes. We show how our estimate of the distribution of effect sizes of LT studies can be used to design experiments to be analyzed by Bayesian statistics, where the experimenter is required to determine in advance the predicted effect size rather than the sample size. We demonstrate the robustness of this method in both sets of LT experiments.

Seeing behind the surface: Communicative demonstration boosts category disambiguation in 12-month-olds

In their first years, infants acquire an incredible amount of information regarding the objects present in their environment. While often it is not clear what specific information should be prioritized in encoding from the many characteristics of an object, different types of object representations facilitate different types of generalizations. We tested the hypotheses that one-year-old infants distinctively represent familiar objects as exemplars of their kind, and that ostensive communication plays a role in determining kind membership for ambiguous objects. In the training phase of our experiment, infants were exposed to movies displaying an agent sorting objects from two categories (cups and plates) into two locations (left or right). Afterwards, different groups of infants saw either an ostensive or a non-ostensive demonstration performed by the agent revealing that a new object that looked like a plate can be transformed into a cup. A third group of infants experienced no demonstration regarding the new object. During test, infants were presented with the ambiguous object in the plate format, and we measured generalization by coding anticipatory looks to the plate or the cup side. While infants looked equally often towards the two sides when the demonstration was non-ostensive, and more often to the plate side when there was no demonstration, they performed more anticipatory eye movements to the cup side when the demonstration was ostensive. Thus, ostensive demonstration likely highlighted the hidden dispositional properties of the target object as kind-relevant, guiding infants’ categorization of the foldable cup as a cup, despite that it looked like a plate. These results suggest that infants likely encode familiar objects as exemplars of their kind and that ostensive communication can play a crucial role in disambiguating what kind an object belongs to, even when this requires disregarding salient surface features.

Nonverbal generics: Human infants interpret objects as symbols of object kinds

Human infants are involved in communicative interactions with others well before they start to speak or understand language. It is generally thought that this communication is useful for establishing interpersonal relations and supporting joint activities, but, in the absence of symbolic functions that language provides, these early communicative contexts do not allow infants to learn about the world. However, recent studies suggest that when someone demonstrates something using an object as the medium of instruction, infants can conceive the object as an exemplar of the whole class of objects of the same kind. Thus, an object, just like a word, can play the role of a symbol that stands for something else than itself, and infants can learn general knowledge about a kind of object from non-verbal communication about a single item of that kind. This rudimentary symbolic capacity may be one of the roots of the development of symbolic understanding in children.

Infants learn enduring functions of novel tools from action demonstrations

According to recent theoretical proposals, one function of infant goal attribution is to support early social learning of artifact functions from instrumental actions, and one function of infant sensitivity to communication is to support early acquisition of generic knowledge about enduring, kind-relevant properties of the referents. The present study tested two hypotheses, derived from these proposals, about the conditions that facilitate the acquisition of enduring functions for novel tools in human infancy. Using a violation-of-expectation paradigm, we show that 13.5-months-old infants encode arbitrary end-states of action-sequences in relation to the novel tools employed to bring them about. These mappings are not formed if the same end states of action sequences cannot be interpreted as action goals. Moreover, the tool-goal mappings acquired from infant-directed communicative demonstrations are more resilient to counter-evidence than those acquired from non-infant-directed presentations, and thus show similarities to generic rather than episodic representations. These findings suggest that the acquisition of tool functions in infancy is guided by both teleological action interpretation mechanisms and the expectation that communicative demonstrations reveal enduring dispositional properties of tools.

Toddlers favor communicatively presented information over statistical reliability in learning about artifacts

Observed associations between events can be validated by statistical information of reliability or by testament of communicative sources. We tested whether toddlers learn from their own observation of efficiency, assessed by statistical information on reliability of interventions, or from communicatively presented demonstration, when these two potential types of evidence of validity of interventions on a novel artifact are contrasted with each other. Eighteen-month-old infants observed two adults, one operating the artifact by a method that was more efficient (2/3 probability of success) than that of the other (1/3 probability of success). Compared to the Baseline condition, in which communicative signals were not employed, infants tended to choose the less reliable method to operate the artifact when this method was demonstrated in a communicative manner in the Experimental condition. This finding demonstrates that, in certain circumstances, communicative sanctioning of reliability may override statistical evidence for young learners. Such a bias can serve fast and efficient transmission of knowledge between generations.

Concept-based word learning in human infants

It is debated whether infants initially learn object labels by mapping them onto similarity-defining perceptual features or onto concepts of object kinds. We addressed this question by attempting to teach infants words for behaviorally defined action roles. In a series of experiments, we found that 14-month-olds could rapidly learn a label for the role the chaser plays in a chasing scenario, even when the different instances of chasers did not share perceptual features. Furthermore, when infants could choose, they preferred to interpret a novel label as expressing the actor’s role within the observed interaction rather than as being associated with the actor’s appearance. These results demonstrate that infants can learn labels as easily, or even easier, for concepts identified by abstract behavioral characteristics than by perceptual features. Thus, already at early stages of word learning, infants expect that novel words express concepts.

Neural signatures for sustaining object representations attributed to others in preverbal human infants

A major feat of social beings is to encode what their conspecifics see, know or believe. While various nonhuman animals show precursors of these abilities, humans perform uniquely sophisticated inferences about other people’s mental states. However, it is still unclear how these possibly human-specific capacities develop and whether preverbal infants, similarly to adults form representations of other agents’ mental states, specifically metarepresentations. We explored the neuro-cognitive bases of 8-month-olds’ ability to encode the world from another person’s perspective, using gamma-band EEG activity over the temporal lobes, an established neural signature for sustained object representation after occlusion. We observed such gamma-band activity when an object was occluded from the infants’ perspective, as well as when it was occluded only from the other person (Study 1), and also when subsequently the object disappeared but the person falsely believed the object to be present (Study 2). These findings suggest that the cognitive systems involved in representing the world from infants’ own perspective are also recruited for encoding others’ beliefs. Such results point to an early developing, powerful apparatus suitable to deal with multiple concurrent representations; and suggest that infants can have a metarepresentational understanding of other minds even before the onset of language.

Human infants' learning of social structures: The case of dominance hierarchy

This paper investigates whether human infants go beyond learning about individual social partners and their relations, and form hypotheses about how social groups are organized. We test 15-month-olds’ capacity to represent social dominance hierarchies with more than two agents. Infants find it harder to memorise dominance relations presented in an order that hinders the incremental formation of a single structure (Study 1). Thus, infants attempt to build structures incrementally, relation by relation, thereby simplifying the complex problem of recognizing a social structure. Infants also find circular dominance structures harder to process than linear ones (Study 2). These expectations about the shape of structures may facilitate learning. Our results suggest that infants attempt to represent social structures composed of social relations.

Action anticipation in human infants reveals assumptions about anteroposterior body-structure and action

Animal actions are almost universally constrained by the bilateral body-plan. For example, the direction of travel tends to be constrained by the orientation of the animal’s anteroposterior axis. Hence, an animal’s behaviour can reliably guide the identification of its front and back, and its orientation can reliably guide action prediction. We examine the hypothesis that the evolutionarily ancient relation between anteroposterior body-structure and behaviour guides our cognitive processing of agents and their actions. In a series of studies we demonstrate that, after limited exposure, human infants as young as 6 months of age spontaneously encode a novel agent as having a certain axial direction with respect to its actions, and rely on it when anticipating the agent’s further behaviour. We found that such encoding is restricted to objects exhibiting cues of agency, and does not depend on generalization from features of familiar animals. Our research offers a new tool for investigating the perception of animate agency and supports the proposal that the underlying cognitive mechanisms have been shaped by basic biological adaptations in humans.

Are all beliefs equal? Implicit belief attributions recruiting core brain regions of Theory of Mind.

Humans possess efficient mechanisms to behave adaptively in social contexts. They ascribe goals and beliefs to others and use these for behavioural predictions. Researchers argued for two separate mental attribution systems: an implicit and automatic one involved in online interactions, and an explicit one mainly used in offline deliberations. However, the underlying mechanisms of these systems and the types of beliefs represented in the implicit system are still unclear. Using neuroimaging methods, we show that the right temporo-parietal junction and the medial prefrontal cortex, brain regions consistently found to be involved in explicit mental state reasoning, are also recruited by spontaneous belief tracking. While the medial prefrontal cortex was more active when both the participant and another agent believed an object to be at a specific location, the right temporo-parietal junction was selectively activated during tracking the false beliefs of another agent about the presence, but not the absence of objects. While humans can explicitly attribute to a conspecific any possible belief they themselves can entertain, implicit belief tracking seems to be restricted to beliefs with specific contents, a content selectivity that may reflect a crucial functional characteristic and signature property of implicit belief attribution.

Teleological understanding of actions

An observed behavior is interpreted as an action directed to a particular end state if it is judged to be the most efficient means available to the agent for achieving this goal in the given environment. When such an interpretation is established, it creates a teleological representation of the action, which is held together by the principle of efficiency. The paradigmatic situation in which the functioning of teleological interpretation can be tested is when one observes a behavior (e.g., an agent jumps into the air while moving in a certain direction) leading to an end state (e.g., the agent stops next to another object). If, and only if, the behavior (jumping) is justified by environmental factors (by the presence of a barrier over which the jumping occurs) will this behavior be interpreted as a means action to achieve the end state as the goal of the action (to get in contact with the other object). Researchers have published extensive evidence that infants from at least six months of age form this kind of teleological representations of actions. This chapter attempts to clarify commonly raised issues about this theory in a question-and-answer format.

Neural responses to multimodal ostensive signals in 5-month-old infants

Infants' sensitivity to ostensive signals, such as direct eye contact and infant-directed speech, is well documented in the literature. We investigated how infants interpret such signals by assessing common processing mechanisms devoted to them and by measuring neural responses to their compounds. In Experiment 1, we found that ostensive signals from different modalities display overlapping electrophysiological activity in 5-month-old infants, suggesting that these signals share neural processing mechanisms independently of their modality. In Experiment 2, we found that the activation to ostensive signals from different modalities is not additive to each other, but rather reflects the presence of ostension in either stimulus stream. These data support the thesis that ostensive signals obligatorily indicate to young infants that communication is directed to them.

Representation of stable social dominance relations by human infants

What are the origins of humans’ capacity to represent social relations? We approached this question by studying human infants’ understanding of social dominance as a stable relation. We presented infants with interactions between animated agents in conflict situations. Studies 1 and 2 targeted expectations of stability of social dominance. They revealed that 15-montholds (and to a lesser extent 12-month-olds) expect an asymmetric relationship between two agents to remain stable from one conflict to another. To do so, infants need to infer that one of the agents (the dominant) will consistently prevail when her goals conflict with those of the other (the subordinate). Study 3 and 4 targeted the format of infants’ representation of social dominance. In these studies, we found that 12- and 15-month-olds did not extend their expectations of dominance to unobserved relationships, even when they could have been established by transitive inference. This suggests that infants' expectation of stability originates from their representation of social dominance as a relationship between two agents rather than as an individual property. Infants’ demonstrated understanding of social dominance reflects the cognitive underpinning of humans’ capacity to represent social relations, which may be evolutionarily ancient, and may be shared with non-human species.

Natural pedagogy as evolutionary adaptation

We propose that the cognitive mechanisms that enable the transmission of cultural knowledge by communication between individuals constitute a system of 'natural pedagogy' in humans, and represent an evolutionary adaptation along the hominin lineage. We discuss three kinds of arguments that support this hypothesis. First, natural pedagogy is likely to be human-specific: while social learning and communication are both widespread in non-human animals, we know of no example of social learning by communication in any other species apart from humans. Second, natural pedagogy is universal: despite the huge variability in child-rearing practices, all human cultures rely on communication to transmit to novices a variety of different types of cultural knowledge, including information about artefact kinds, conventional behaviours, arbitrary referential symbols, cognitively opaque skills, and know-how embedded in means-end actions. Third, the data available on early hominin technological culture are more compatible with the assumption that natural pedagogy was an independently selected adaptive cognitive system than considering it as a by-product of some other human-specific adaptation, such as language. By providing a qualitatively new type of social learning mechanism, natural pedagogy is not only the product but also one of the sources of the rich cultural heritage of our species.

Automated gaze-contingent objects elicit orientation following in 8-month-old infants

The current study tested whether the purely amodal cue of contingency elicit orientation following behaviour in 8-months-old infants. We presented 8-month-old infants with automated objects without human features that did or did not react contingently to the infants' fixations recorded by an eye-tracker. We found that an object's occasional orientation towards peripheral targets was reciprocated by a congruent visual orientation following response by infants only when it had displayed gaze-contingent interactivity. Our finding demonstrates that infants' gaze following behaviour does not depend on the presence of a human being. The results are consistent with the idea that the detection of contingent reactivity, like other communicative signals, can itself elicit the illusion of being addressed in 8-months-old infants.

Polymorphisms in dopamine system genes are associated with individual differences in attention in infancy

Knowledge about the functional status of the frontal cortex in infancy is limited. This study investigated the effects of polymorphisms in four dopamine system genes on performance in a task developed to assess such functioning, the Freeze-Frame task, at 9 months of age. Polymorphisms in the catechol-Omethyltransferase (COMT) and the dopamine D4 receptor (DRD4) genes are likely to impact directly on the functioning of the frontal cortex, whereas polymorphisms in the dopamine D2 receptor (DRD2) and dopamine transporter (DAT1) genes might influence frontal cortex functioning indirectly via strong frontostriatal connections. A significant effect of the COMT valine158methionine (Val158Met) polymorphism was found. Infants with the Met/Met genotype were significantly less distractible than infants with the Val/Val genotype in Freeze-Frame trials presenting an engaging central stimulus. In addition, there was an interaction with the DAT1 3
variable number of tandem repeats polymorphism; the COMT effect was present only in infants who did not have two copies of the DAT1 10-repeat allele. These findings indicate that dopaminergic polymorphisms affect selective aspects of attention as early as infancy and further validate the Freeze-Frame task as a frontal cortex task.

Absence of spontaneous action anticipation by false belief attribution in children with autism spectrum disorder

Recently, a series of studies demonstrated false belief understanding in young children through completely nonverbal measures. These studies have revealed that children younger than 3 years of age, who consistently fail the standard verbal false belief test, can anticipate others’ actions based on their attributed false beliefs. The current study examined whether children with autism spectrum disorder (ASD), who are known to have difficulties in the verbal false belief test, may also show such action anticipation in a nonverbal false belief test.We presented video stimuli of an actor watching an object being hidden in a box. The object was then displaced while the actor was looking away. We recorded children’s eye movements and coded whether they spontaneously anticipated the actor’s subsequent behavior, which could only have been predicted if they had attributed a false belief to her. Although typically developing children correctly anticipated the action, children with ASD failed to show such action anticipation. The results suggest that children with ASD have an impairment in false belief attribution, which is independent of their verbal ability.

Communicative function demonstration induces kind-based artifact representation in preverbal infants

Human infants grow up in environments populated by artifacts. In order to acquire knowledge about different kinds of human-made objects, children have to be able to focus on the information that is most relevant for sorting artifacts into categories. Traditional theories emphasize the role of superficial, perceptual features in object categorization. In the case of artifacts, however, it is possible that abstract, non-obvious properties, like functions, may form the basis of artifact kind representations from an early age. Using an object individuation paradigm we addressed the question whether non-verbal communicative demonstration of the functional use of artifacts makes young infants represent such objects in terms of their kinds. When two different functions were sequentially demonstrated on two novel objects as they emerged one-by-one from behind a screen, 10-month-old infants inferred the presence of two objects behind the occluder. We further show that both the presence of communicative signals and causal intervention are necessary for 10-month-olds to generate such a numerical expectation. We also found that communicative demonstration of two different functions of a single artifact generated the illusion of the presence of two objects. This suggests that information on artifact function was used as an indicator of kind membership, and infants expected one specific function to define one specific artifact kind. Thus, contrary to previous accounts, preverbal infants' specific sensitivity to object function underlies, guides, and supports their learning about artifacts.

Communicative function demonstration induces kind-based artifact representation in preverbal infants

Recent evidence suggests that preverbal infants’ gaze following can be triggered only if an actor’s head turn is preceded by the expression of communicative intent. Such connectedness between ostensive and referential signals may be uniquely human, enabling infants to effectively respond to referential communication directed to them. In the light of increasing evidence of dogs’ social communicative skills, an intriguing question is whether dogs’ responsiveness to human directional gestures is associated with the situational context in an infant-like manner. Borrowing a method used in infant studies, dogs watched video presentations of a human actor turning toward one of two objects, and their eye-gaze patterns were recorded with an eye tracker. Results show a higher tendency of gaze following in dogs when the human’s head turning was preceded by the expression of communicative intent (direct gaze, addressing). This is the first evidence to show that (1) eye-tracking techniques can be used for studying dogs’ social skills and (2) the exploitation of human gaze cues depends on the communicatively relevant pattern of ostensive and referential signals in dogs. Our findings give further support to the existence of a functionally infant-analog social competence in this species.

Functional understanding facilitates learning about tools in human children

Human children benefit from a possibly unique set of adaptations facilitating the acquisition of knowledge about material culture. They represent artifacts (man-made objects) as tools with specific functions and seek for functional information about novel objects. Even young infants pay attention to functionally relevant features of objects, and learn tool use and infer tool functions from others’ goal-directed actions and demonstrations. Children tend to imitate causally irrelevant elements of tool use demonstrations, which helps them to acquire means actions even before they fully understand their causal role in bringing about the desired goal. Although non-human animals use and make tools, and recognize causally relevant features of objects in a given task, they - unlike human children - do not appear to form enduring functional representations of tools as being for achieving particular goals when they are not in use.

Visual orienting in the early broader autism phenotype: disengagement and facilitation

Recent studies of infant siblings of children diagnosed with autism have allowed for a prospective approach to examine the emergence of symptoms and revealed behavioral differences in the broader autism phenotype within the early years. In the current study we focused on a set of functions associated with visual attention, previously reported to be atypical in autism. We compared performance of a group of 9-10-month-old infant siblings of children with autism to a control group with no family history of autism on the 'gap-overlap task', which measures the cost of disengaging from a central stimulus in order to fixate a peripheral one. Two measures were derived on the basis of infants' saccadic reaction times. The first is the Disengagement effect, which measures the efficiency of disengaging from a central stimulus to orient to a peripheral one. The second was a Facilitation effect, which arises when the infant is cued by a temporal gap preceding the onset of the peripheral stimulus, and would orient faster after its onset. Infant siblings of children with autism showed longer Disengagement latencies as well as less Facilitation relative to the control group. The findings are discussed in relation to how differences in visual attention may relate to characteristics observed in autism and the broader phenotype.

One-year-old infants appreciate the referential nature of deictic gestures and words

One-year-old infants have a small receptive vocabulary and follow deictic gestures, but it is still debated whether they appreciate the referential nature of these signals. Demonstrating understanding of the complementary roles of symbolic (word) and indexical (pointing) reference provides evidence of referential interpretation of communicative signals. We presented 13-month-old infants with video sequences of an actress indicating the position of a hidden object while naming it. The infants looked longer when the named object was revealed not at the location indicated by the actress's gestures, but on the opposite side of the display. This finding suggests that infants expect that concurrently occurring communicative signals co-refer to the same object. Another group of infants, who were shown video sequences in which the naming and the deictic cues were provided concurrently but by two different people, displayed no evidence of expectation of co-reference. These findings suggest that a single communicative source, and not simply co-occurrence, is required for mapping the two signals onto each other. By 13 months of age, infants appreciate the referential nature of words and deictic gestures alike.

Differential sensitivity to human communication in dogs, wolves and human infants

Ten-month-old infants search for a hidden object persistently at its initial hiding place even after observing it being hidden at another location. Recent evidence suggests that communicative cues from the experimenter contribute to the emergence of this perseverative search error. Here we replicate these results with dogs, who also commit more search errors in ostensive-communicative (in 75% of the total trials) than in non-communicative (39%) or non-social (17%) hiding contexts. However, comparative investigations suggest that communicative signals serve different functions for dogs and infants, while human-reared wolves do not show dog-like context-dependent differences of search errors. We propose that shared sensitivity to human communicative signals stems from convergent social evolution of the Homo and the Canis genera.

Sensitivity to communicative relevance tells young children what to imitate

How do children decide which elements of an action demonstration are important to reproduce in the context of an imitation game? We tested whether selective imitation of a demonstrator’s actions may be based on the same search for relevance that drives adult interpretation of ostensive communication. Three groups of 18-month-old infants were shown a toy animal either hopping or sliding (action style) into a toy house (action outcome), but the communicative relevance of the action style differed depending on the group. For the no prior information group, all the information in the demonstration was new and so equally relevant. However, for infants in the ostensive prior information group, the potential action outcome was already communicated to the infant prior to the main demonstration, rendering the action style more relevant. Infants in the ostensive prior information group imitated the action style significantly more than infants in the no prior information group, suggesting that the relevance manipulation modulated their interpretation of the action demonstration. A further condition (non-ostensive prior information) confirmed that this sensitivity to new information is only present when the ‘old ’ information had been communicated, and not when infants discovered this information for themselves. These results indicate that, like adults, human infants expect communication to contain relevant content, and imitate action elements that, relative to their current knowledge state or to the common ground with the demonstrator, is identified as most relevant.

Predictive motor activation during action observation in human infants

Certain regions of the human brain are activated both during action execution and action observation. This so-called ‘mirror neuron system’ has been proposed to enable an observer to understand an action through a process of internal motor simulation. Although there has been much speculation about the existence of such a system from early in life, to date there is little direct evidence that young infants recruit brain areas involved in action production during action observation. To address this question, we identified the individual frequency range in which sensorimotor alpha-band activity was attenuated in nine-month-old infants’ electroencephalographs (EEGs) during elicited reaching for objects, and measured whether activity in this frequency range was also modulated by observing others’ actions. We found that observing a grasping action resulted in motor activation in the infant brain, but that this activity began prior to observation of the action, once it could be anticipated. These results demonstrate not only that infants, like adults, display overlapping neural activity during execution and observation of actions, but that this activation, rather than being directly induced by the visual input, is driven by infants’ understanding of a forthcoming action. These results provide support for theories implicating the motor system in action prediction.

Infants can infer the presence of hidden objects from referential gaze information

Infants' apparent failure in gaze-following tasks is often interpreted as a sign of lack of understanding the referential nature of looking. In the present study, 8- and 12-month-old infants followed the gaze of a model to one of two locations hidden from their view by occluders. When the occluders were removed, an object was revealed either at the location where the model had looked or at the other side. Infants at both ages looked longer at the empty location when it had been indicated by the model's looking behaviour, and this effect held up even when their first look after gaze following was discounted. This result demonstrates that even young infants hold referential expectations when they follow others' gaze and infer the location of hidden objects accordingly.

Electrophysiological evidence of illusory audiovisual speech percept in human infants

How effortlessly and quickly infants acquire their native language remains one of the most intriguing questions of human development. Our study extends this question into the audiovisual domain, taking into consideration visual speech cues, which were recently shown to have more importance for young infants than previously anticipated [Weikum WM, Vouloumanos A, Navarra J, Soto-Faraco, S, Sebastian-Galles N, Werker JF (2007) Science 316:1159]. A particularly interesting phenomenon of audiovisual speech perception is the McGurk effect [McGurk H, MacDonald J (1976) Nature 264:746-748], an illusory speech percept resulting from integration of incongruent auditory and visual speech cues. For some phonemes, the human brain does not detect the mismatch between conflicting auditory and visual cues but automatically assimilates them into the closest legal phoneme, sometimes different from both auditory and visual ones. Measuring event-related brain potentials in 5-month-old infants, we demonstrate differential brain responses when conflicting auditory and visual speech cues can be integrated and when they cannot be fused into a single percept. This finding reveals a surprisingly early ability to perceive speech cross-modally and highlights the role of visual speech experience during early postnatal development in learning of the phonemes and phonotactics of the native language.

Gaze following in human infants depends on communicative signals

Humans are extremely sensitive to ostensive signals, like eye contact or having their name called, that indicate someone's communicative intention toward them [1-3]. Infants also pay attention to these signals [4-6], but it is unknown whether they appreciate their significance in the initiation of communicative acts. In two experiments, we employed video presentation of an actor turning toward one of two objects and recorded infants' gaze-following behavior [7-13] with eye tracking techniques [11, 12]. We found that 6-month-old infants followed the adult's gaze (a potential communicative-referential signal) toward an object only when such an act is preceded by ostensive cues such as direct gaze (experiment 1) and infant-directed speech (experiment 2). Such a link between the presence of ostensive signals and gaze-following suggests that this behavior serves a functional role in assisting infants to effectively respond to referential communication directed to them. Whereas gaze following in many nonhuman species supports social information gathering [14-18], in humans it initially appears to reflect the expectation of a more active, communicative role from the information source.

Communication-induced memory biases in preverbal infants

Human teaching, a highly specialized form of cooperative information transmission, depends not only on the presence of benevolent communicators in the environment, but also on the preparedness of the students to learn from communication when it is addressed to them. We tested whether 9-month-old human infants can distinguish between communicative and noncommunicative social contexts and whether they retain qualitatively different information about novel objects in these contexts. We found that in a communicative context, infants devoted their limited memory resources to encoding the identity of novel objects at the expense of encoding their location, which is preferentially retained in noncommunicative contexts. We propose that infants' sensitivity to, and interpretation of, the social cues distinguishing infant-directed communication events represent important mechanisms of social learning by which others can help determine what information even preverbal human observers retain in memory.

Infants attribute goals even to biomechanically impossible actions

Human infants readily interpret the actions of others in terms of goals, but the origins of this important cognitive skill are keenly debated. We tested whether infants recognize others' actions as goal-directed on the basis of their experience with carrying out and observing goal-directed actions, or whether their perception of a goal-directed action is based on the recognition of a specific event structure. Counterintuitively, but consistent with our prediction, we observed that infants appear to extend goal attribution even to biomechanically impossible actions so long as they are physically efficient, indicating that the notion of 'goal' is unlikely to be derived directly from infants' experience. (C) 2007 Elsevier B.V. All rights reserved.

Infants' perseverative errors are induced by pragmatic misinterpretation.

Having repeatedly retrieved an object from a location, human infants tend to search the same place even when they observe the object being hidden at another location. This perseverative error is usually explained by infants' inability to inhibit a previously rewarded search response or to recall the new location. We show that the tendency to commit this error is substantially reduced (from 81 to 41%) when the object is hidden in front of 10-month-old infants without the experimenter using the communicative cues that normally accompany object hiding in this task. We suggest that this improvement is due to an interpretive bias that normally helps infants learn from demonstrations but misleads them in the context of a hiding game. Our finding provides an alternative theoretical perspective on the nature of infants' perseverative search errors

'Obsessed with goals': Functions and mechanisms of teleological interpretation of actions in humans

Humans show a strong and early inclination to interpret observed behaviours of others as goal-directed actions. We identify two main epistemic functions that this 'teleological obsession' serves: on-line prediction and social learning. We show how teleological action interpretations can serve these functions by drawing on two kinds of inference ('action-to-goal' or 'goal-to-action'), and argue that both types of teleological inference constitute inverse problems that can only be solved by further assumptions. We pinpoint the assumptions that the three currently proposed mechanisms of goal attribution (action-effect associations, simulation procedures, and teleological reasoning) imply, and contrast them with the functions they are supposed to fulfil. We argue that while action-effect associations and simulation procedures are generally well suited to serve on-line action monitoring and prediction, social learning of new means actions and artefact functions requires the inferential productivity of teleological reasoning. (c) 2006 Elsevier B.V. All rights reserved.

Seeing the face through the eyes: A developmental perspective on face expertise

Most people are experts in face recognition. We propose that the special status of this particular body part in telling individuals apart is the result of a developmental process that heavily biases human infants and children to attend towards the eyes of others. We review the evidence supporting this proposal, including neuroimaging results and studies in developmental disorders, like autism. We propose that the most likely explanation of infants’ bias towards eyes is the fact that eye gaze serves important communicative functions in humans.

Neural correlates of the perception of goal-directed action in infants

We investigated the neural correlates of the perception of human goal-directed action by 8-month-old infants. Infants viewed video loops of complete and incomplete actions, which they could discriminate according to our pilot study, while we recorded their electrophysiological brain activity. Analysis of bursts of gamma-band oscillations resulting from passive viewing of these stimuli indicated increased gamma-band activity over left frontal regions when viewing incomplete actions as compared with complete actions. These results suggest that by 8 months infants are sensitive to the disruption of perceived goal-directed actions. (c) 2006 Elsevier B.V. All rights reserved.

Infant pointing: Communication to cooperate or communication to learn?

Tomasello, Carpenter, and Liszkowski (2007) present compelling data to support the view that infant pointing, from the outset, is communicative and deployed in many of the same situations in which adults would ordinarily point for one another, either to share their interest in something, or to informatively help the other person. This commentary concurs with the view that infant pointing is a communicative gesture, but challenges their interpretation of the motives behind pointing in 12-month-olds. An alternative account is proposed, according to which infant pointing is neither declarative nor imperative, but interrogative, and rather than being driven by the motive to share or help, it may serve a powerful cultural learning mechanism by which infants can obtain information from knowledgeable adults.

Investigation of depth dependent changes in cerebral haemodynamics during face perception in infants

Near-infrared spectroscopy has been used to record oxygenation changes in the visual cortex of 4 month old infants. Our in-house topography system, with 30 channels and 3 different source–detector separations, recorded changes in the concentration of oxy-, deoxy- and total haemoglobin (HbO2, HHb and HbT) in response to visual stimuli (face, scrambled visual noise and cartoons as rest). The aim of this work was to demonstrate the capability of the system to spatially localize functional activation and study the possibility of depth discrimination in the haemodynamic response. The group data show both face stimulation and visual noise stimulation induced significant increases in HbO2 from rest, but the increase in HbO2 with face stimulation was not significantly different from that seen with visual noise stimulation. The face stimuli induced increases in HbO2 were spread across a greater area across all depths than visual noise induced changes. In results from a single subject there was a significant increase of HbO2 in the inferior area of the visual cortex in response to both types of stimuli, and a larger number of channels (source–detector pairs) showed HbO2 increase to face stimuli, especially at the greatest depth. Activation maps were obtained using 3D reconstruction methods on multi source–detector separation optical topography data.

Newborns' preference for face-relevant stimuli: Effects of contrast polarity

There is currently no agreement as to how specific or general are the mechanisms underlying newborns' face preferences. We address this issue by manipulating the contrast polarity of schematic and naturalistic face-related images and assessing the preferences of newborns. We find that for both schematic and naturalistic face images, the contrast polarity is important. Newborns did not show a preference for an upright face-related image unless it was composed of darker areas around the eyes and mouth. This result is consistent with either sensitivity to the shadowed areas of a face with overhead (natural) illumination and/or to the detection of eye contact.

The emergence of the social brain network: Evidence from typical and atypical development

Several research groups have identified a network of regions of the adult cortex that are activated during social perception and cognition tasks. In this paper we focus on the development of components of this social brain network during early childhood and test aspects of a particular viewpoint on human functional brain development: "interactive specialization." Specifically, we apply new data analysis techniques to a previously published data set of event-related potential (ERP) studies involving 3-, 4-, and 12-month-old infants viewing faces of different orientation and direction of eye gaze. Using source separation and localization methods, several likely generators of scalp recorded ERP are identified, and we describe how they are modulated by stimulus characteristics. We then review the results of a series of experiments concerned with perceiving and acting on eye gaze, before reporting on a new experiment involving young children with autism. Finally, we discuss predictions based on the atypical emergence of the social brain network.

Mirror neurons and action understanding. Is simulation involved?

The discovery of mirror neurons (MNs) has been hailed as the most important finding of the last decade in neuroscience (Ramachandran, 2000), paving the road for the explanation of diverse phenomena from the evolution of language (Rizzolatti & Arbib, 1998), through imitation (Iacoboni et al., 1999), to intersubjectivity (Gallese, 2003). Here I am concerned with the more modest claim that credits a fundamental role to mirror neurons in understanding observed actions (section 1). In particular, mirror neurons have been argued to support simulation theories of action understanding and mind reading (Gallese & Goldman, 1998; Gallese et al., 2004), an idea that has also been dubbed as the 'direct-matching hypothesis' (Rizzolatti et al., 2001). I shall argue that the evidence published on the response properties of MNs in monkeys is incompatible with these theories of action understanding because (a) MNs' activation reflects not the commencement but the conclusion of action interpretation (section 2), and because (b) MNs do not 'mirror' observed actions with sufficient accuracy for effective simulation (section 3). I shall offer an alternative interpretation, which preserves the MNs' role in action understanding without imposing a simulation function on them (section 4).

Mechanisms of eye gaze perception during infancy

Previous work has shown that infants are sensitive to the direction of gaze of another's face, and that gaze direction can cue attention. The present study replicates and extends results on the ERP correlates of gaze processing in 4-month-olds. In two experiments, we recorded ERPs while 4-month-olds viewed direct and averted gaze within the context of averted and inverted heads. Our results support the previous finding that cortical processing of faces in infants is enhanced when accompanied by direct gaze. However, this effect is only found when eyes are presented within the context of an upright face.