No evidence for adult smartphone use affecting attribution of communicative intention in toddlers: Online imitation study using the Sock Ball Task.

Adults infer others' communicative intentions, or lack thereof, from various types of information. Young children may be initially limited to attributions based on a small set of ostensive signals. It is unknown when richer pragmatic inferences about communicative intentions emerge in development. We sought novel type of evidence for such inferences in 17-to-19-month-olds. We hypothesized that toddlers recognize adults' smartphone use in face-to-face interactions as incongruous with ostension and would rely on this interpretation when inferring the communicative intention of a model in a new imitation task conducted entirely online, dubbed the Sock Ball Task. In Experiment 1 with a between-subject design, we tested the hypothesis by assessing toddlers' (N = 48) imitation of sub-efficient means and the goal-outcome presented by a model, who interrupted her ostensive demonstration either by using a smartphone or by fiddling with her wristwatch, depending on the condition. We expected toddlers to imitate the sub-efficient means more faithfully in the wristwatch condition than in the smartphone condition. But there was no significant effect of condition on imitation of neither means nor goal. Thus, our hypothesis was not borne out by the results. In Experiment 2, using a within-subject design, we first assessed toddlers' (N = 24) performance in a no-demonstration baseline and then again after a no-disruption ostensive demonstration. In all three conditions with ostensive demonstration (Experiment 1: smartphone, wristwatch; Experiment 2: no-disruption), toddlers produced the demonstrated sub-efficient means significantly above the baseline level. In the no-disruption condition, goals were also imitated significantly above the baseline level. We conclude that the Sock Ball Task is a valid research tool for studying toddler imitation of novel means actions with objects. We end by discussing suggestions for improving the task in future studies.

Naïve chicks do not prefer objects with stable body orientation, though they may prefer behavioural variability.

Domestic chicks (Gallus gallus domesticus) have been widely used as a model to study the motion cues that allow visually naïve organisms to detect animate agents shortly after hatching/birth. Our previous work has shown that chicks prefer to approach agents whose main body axis and motion direction are aligned (a feature typical of creatures whose motion is constrained by a bilaterally symmetric body plan). However, it has never been investigated whether chicks are also sensitive to the fact that an agent maintains a stable front-back body orientation in motion (i.e. consistency in which end is leading and which trailing). This is another feature typical of bilateria, which is also associated with the detection of animate agents in humans. The aim of the present study was to fill this gap. Contrary to our initial expectations, after testing 300 chicks across 3 experimental conditions, we found a recurrent preference for the agent which did not maintain a stable front-back body orientation. Since this preference was limited to female chicks, the results are discussed also in relation to sex differences in the social behaviour of this model. Overall, we show for the first time that chicks can discriminate agents based on the stability of their front-back orientation. The unexpected direction of the effect could reflect a preference for agents' whose behaviour is less predictable. Chicks may prefer agents with greater behavioural variability, a trait which has been associated with animate agents, or have a tendency to explore agents performing "odd behaviours".

Facilitation of object encoding in infants by the observation of giving.

We propose that humans are prepared to interpret giving as a diagnostic cue of reciprocal-exchange relations from infancy. A prediction following from this hypothesis is that infants will represent the identity of an object they see being given, because this information is critical for evaluating potential future reciprocation. Across three looking-time experiments we tested whether the observation of a transfer action induces 12-month-olds to encode the identity of a single object handled by an agent. We found that infants encoded the object identity when the agent gave the object (Experiment 1), but not when she took it (Experiment 2), despite being able to represent the goal of both actions (Experiments 1 and 3). Consistent with our hypothesis, these results suggest that the infants' representation of giving comprises information necessary for comparing the value of transferred goods across sharing episodes.

A multi-lab study of bilingual infants: Exploring the preference for infant-directed speech.

From the earliest months of life, infants prefer listening to and learn better from infant-directed speech (IDS) than adult-directed speech (ADS). Yet, IDS differs within communities, across languages, and across cultures, both in form and in prevalence. This large-scale, multi-site study used the diversity of bilingual infant experiences to explore the impact of different types of linguistic experience on infants' IDS preference. As part of the multi-lab ManyBabies 1 project, we compared lab-matched samples of 333 bilingual and 385 monolingual infants' preference for North-American English IDS (cf. ManyBabies Consortium, 2020: ManyBabies 1), tested in 17 labs in 7 countries. Those infants were tested in two age groups: 6-9 months (the younger sample) and 12-15 months (the older sample). We found that bilingual and monolingual infants both preferred IDS to ADS, and did not differ in terms of the overall magnitude of this preference. However, amongst bilingual infants who were acquiring North-American English (NAE) as a native language, greater exposure to NAE was associated with a stronger IDS preference, extending the previous finding from ManyBabies 1 that monolinguals learning NAE as a native language showed a stronger preference than infants unexposed to NAE. Together, our findings indicate that IDS preference likely makes a similar contribution to monolingual and bilingual development, and that infants are exquisitely sensitive to the nature and frequency of different types of language input in their early environments.

The development of gaze following in monolingual and bilingual infants: A multi-laboratory study.

Determining the meanings of words requires language learners to attend to what other people say. However, it behooves a young language learner to simultaneously encode relevant non-verbal cues, for example, by following the direction of their eye gaze. Sensitivity to cues such as eye gaze might be particularly important for bilingual infants, as they encounter less consistency between words and objects than monolingual infants, and do not always have access to the same word-learning heuristics (e.g., mutual exclusivity). In a preregistered study, we tested the hypothesis that bilingual experience would lead to a more pronounced ability to follow another's gaze. We used a gaze-following paradigm developed by Senju and Csibra (Current Biology, 18, 2008, 668) to test a total of 93 6- to 9-month-old and 229 12- to 15-month-old monolingual and bilingual infants, in 11 laboratories located in 8 countries. Monolingual and bilingual infants showed similar gaze-following abilities, and both groups showed age-related improvements in speed, accuracy, frequency, and duration of fixations to congruent objects. Unexpectedly, bilinguals tended to make more frequent fixations to on-screen objects, whether or not they were cued by the actor. These results suggest that gaze sensitivity is a fundamental aspect of development that is robust to variation in language exposure.

Human tool cognition relies on teleology.

Osiurak and Reynaud's account of human tool cognition misses key element: human capacity for functional representations and teleological inferences. I argue that the teleofunctional approach accounts better for some features of human tool cognition and points to a viable candidate for the cognitive "difference-maker" behind human technological success.

A Forward Bias in Human Profile-Oriented Portraits.

The spatial composition of human portraits obeys historically changing cultural norms. We show that it is also affected by cognitive factors that cause greater spontaneous attention to what is in front rather in the back of an agent. Scenes with more space in front of a directed object are both more often produced and judged as more aesthetically pleasant. This leads to the prediction that, in profile-oriented human portraits, compositions with more space in front of depicted agents (a "forward bias") should be over-represented. By analyzing a large dataset (total N of 1,831 paintings by 582 unique identified European painters from the 15th to the 20th century), we found evidence of this forward bias: Painters tended to put more free space in front of, rather than behind, the sitters. Additionally, we found evidence that this forward bias became stronger when cultural norms of spatial composition favoring centering became less stringent.

Acquiring sub-efficient and efficient variants of novel means by integrating information from multiple social models in preschoolers.

Sub-efficient action routines often represent culture-specific conventional forms of actions that belong to the repertoire of cultural knowledge shared by a social group. Children readily acquire such sub-efficient routines from social demonstrations and often preserve them in their action repertoire despite encountering more efficient alternatives. This suggests that they can treat sub-efficient conventional forms and their efficient alternatives in a context-sensitive selective manner. We hypothesized that children may rely on their sensitivity to differentiate speakers of their own language versus a foreign language as an informative cue indicating whether the model belongs to their own cultural community and the action modeled represents shared cultural knowledge. We assessed preschoolers' imitation following two different demonstrations. The first model demonstrated a sub-efficient action sequence, whereas the second model presented a more efficient alternative to obtain the same goal. We varied whether the children had heard the models speak their own language or a foreign language before their nonverbal action demonstrations. We found that 4-year-olds adopted the second model's efficient alternative, but only when she spoke their own language. However, they disregarded the efficient alternative if it was presented by a foreign-language speaker and continued to perform the sub-efficient routine they initially acquired. Therefore, 4-year-olds employed the cue of shared language to optimize acquiring and maintaining culturally shared sub-efficient action routines by selectively updating their action repertoire relying on their language-based evaluation of the demonstrator's culture-specific competence. In contrast, 5- and 6-year-olds adopted the efficient alternative independently of the demonstrator's language. Possible reasons for this developmental trend are discussed.

Minimal Cues of Possession Transfer Compel Infants to Ascribe the Goal of Giving.

Human infants' readiness to interpret impoverished object-transfer events as acts of giving suggests the existence of a dedicated action schema for identifying interactions based on active object transfer. Here we investigated the sensitivity of this giving schema by testing whether 15-month-olds would interpret the displacement of an object as an agent's goal even if it could be dismissed as a side effect of a different goal. Across two looking-time experiments, we showed that, when the displacement only resulted in a change of object location, infants expected the agent to pursue the other goal. However, when the same change of location resulted in a transfer of object possession, infants reliably adopted this outcome as the agent's goal. The interpretive shift that the mere presence of a potential recipient caused is testament to the infants' susceptibility to cues of benefit delivery: an action efficiently causing a transfer of object possession appeared sufficient to induce the interpretation of goal-directed giving even if the transfer was carried out without any interaction between Giver and Givee and was embedded in an event affording an alternative goal interpretation.

Infant gaze following depends on communicative signals: An eye-tracking study of 5- to 7-month-olds in Vanuatu.

Gaze is considered a crucial component of early communication between an infant and her caregiver. When communicatively addressed, infants respond aptly to others' gaze by following its direction. However, experience with face-to-face contact varies across cultures, begging the question whether infants' competencies in receiving others' communicative gaze signals are universal or culturally specific . We used eye-tracking to assess gaze-following responses of 5- to 7-month olds in Vanuatu, where face-to-face parent-infant interactions are less prevalent than in Western populations. We found that-just like Western 6-month-olds studied previously-5- to -7-month-olds living in Vanuatu followed gaze only, when communicatively addressed. That is, if presented gaze shifts were preceded by infant-directed speech, but not if they were preceded by adult-directed speech. These results are consistent with the notion that early infant gaze following is tied to infants' early emerging communicative competencies and rooted in universal mechanisms rather than being dependent on cultural specificities of early socialization.

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 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 2 sources: an in-house set of LTs that included data from individual participants (47 experiments, 1,584 observations), and a representative set of published articles reporting group-level LT statistics (149 experiments from 33 articles). 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.

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 current study tested two hypotheses, derived from these proposals, about the conditions that facilitate the acquisition of enduring functions for novel tools during human infancy. Using a violation-of-expectation paradigm, we show that 13.5-month-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 counterevidence than those acquired from non-infant-directed presentations and, thus, show similarities to generic representations rather than episodic ones. These findings suggest that the acquisition of tool functions during infancy is guided by both teleological action interpretation mechanisms and the expectation that communicative demonstrations reveal enduring dispositional properties of tools.

To what adaptive problems is human teaching a solution?

We welcome Kline's systematic overview of teaching from a functional evolutionary perspective. However, Kline's framework does not provide satisfying characterization of the adaptive problems driving the evolution of teaching through communication found in humans, where the key function is better characterized in terms of licensing inferences to opaque generic content than in terms of overcoming shortages of access and attention.

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 six 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.

Nine-months-old infants do not need to know what the agent prefers in order to reason about its goals: on the role of preference and persistence in infants' goal-attribution.

Human infants readily interpret others' actions as goal-directed and their understanding of previous goals shapes their expectations about an agent's future goal-directed behavior in a changed situation. According to a recent proposal (Luo & Baillargeon, 2005), infants' goal-attributions are not sufficient to support such expectations if the situational change involves broadening the set of choice-options available to the agent, and the agent's preferences among this broadened set are not known. The present study falsifies this claim by showing that 9-month-olds expect the agent to continue acting towards the previous goal even if additional choice-options become available for which there is no preference-related evidence. We conclude that infants do not need to know about the agent's preferences in order to form expectations about its goal-directed actions. Implications for the role of action persistency and action selectivity are discussed.

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 (human-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.