Is early differentiation of human behavior a precursor to the 1-year-old's understanding of intentional action? Comment on Legerstee, Barna, and DiAdamo (2000)

In a recent issue of Developmental Psychology, M. Legerstee, J. Barna, and C. DiAdamo (2000) reported a study showing that 6-month-olds expect people to talk to persons rather than to inanimate objects and to manipulate inanimates rather than persons. They interpreted this ability as a "precursor" to later understanding of intentionality. The present article takes issue with the authors' 2 different levels of interpretation that contradict each other and raise problems in their own right. It is suggested that M. Legerstee et al.'s finding is most parsimoniously explained by associative learning and may not constitute a precursor to later understanding of intentionality in any well-defined sense of the term. The present article argues for the importance of differentiating between associative and inferential processes and reviews evidence that the understanding of goal-directed action around 9 months of age involves principle-based inferences.     

Distinguishing logic from association in the solution of an invisible displacement task by children (Homo sapiens) and dogs (Canis familiaris): using negation of disjunction

Prior research on the ability to solve the Piagetian invisible displacement task has focused on prerequisite representational capacity. This study examines the additional prerequisite of deduction. As in other tasks (e.g., conservation and transitivity), it is difficult to distinguish between behavior that reflects logical inference from behavior that reflects associative generalization. Using the role of negation in logic whereby negative feedback about one belief increases the certainty of another (e.g., a disjunctive syllogism), task-naive dogs (Canis familiaris; n=19) and 4- to 6-year-old children (Homo sapiens; n=24) were given a task wherein a desirable object was shown to have disappeared from a container after it had passed behind 3 separate screens. As predicted, children (as per logic of negated disjunction) tended to increase their speed of checking the 3rd screen after failing to find the object behind the first 2 screens, whereas dogs (as per associative extinction) tended to significantly decrease their speed of checking the 3rd screen after failing to find the object behind the first 2 screens.     

White-matter microstructure and language lateralization in left-handers: A whole-brain MRI analysis

Most people are left-hemisphere dominant for language. However the neuroanatomy of language lateralization is not fully understood. By combining functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI), we studied whether language lateralization is associated with cerebral white-matter (WM) microstructure. Sixteen healthy, left-handed women aged 20–25 were included in the study. Left-handers were targeted in order to increase the chances of involving subjects with atypical language lateralization. Language lateralization was determined by fMRI using a verbal fluency paradigm. Tract-based spatial statistics analysis of DTI data was applied to test for WM microstructural correlates of language lateralization across the whole brain. Fractional anisotropy and mean diffusivity were used as indicators of WM microstructural organization. Right-hemispheric language dominance was associated with reduced microstructural integrity of the left superior longitudinal fasciculus and left-sided parietal lobe WM. In left-handed women, reduced integrity of the left-sided language related tracts may be closely linked to the development of right hemispheric language dominance. Our results may offer new insights into language lateralization and structure–function relationships in human language system.     

Multisensory integration and age-dependent sensitivity to body representation modification induced by the rubber hand illusion

The aim of the present study was to compare junior and senior healthy participants for their multimodal integration capability. The instrument used for the investigation was the rubber hand illusion (RHI) where synchronous and asynchronous multimodal stimulation were applied. The study focused on assessing the rate of integration for visuo-tactile and visuo-proprioceptive stimuli. Methods: From a large sample of right-handed volunteers, 50 senior employees (containing younger and middle age adults) and 51 senior retired (senior adults) participants were recruited. Results: The between-subject analyses revealed that individuals both the junior and the senior participants responded to induction of RHI with vivid ownership and disownership experiences and a higher mislocalization error in the synchronous condition. However, the between-group analysis showed that participants in the senior group reported less vivid ownership and less vivid total RHI experiences scores compared to members of the junior group, but no mislocalization error differences were found between the groups. Conclusion: The results indicated that when visuo-tactile stimuli synchronously presented, the gain in multisensory integration decreased in seniors group. In contrast, in the case of visuo-proprioceptive synchronous presentation, the efficiency of multisensory integration remained unchanged across the lifespan.     

Fourteen‐month‐old infants track the language comprehension of communicative partners

Infants employ sophisticated mechanisms to acquire their first language, including some that rely on taking the perspective of adults as speakers or listeners. When do infants first show awareness of what other people understand? We tested 14‐month‐old infants in two experiments measuring event‐related potentials. In Experiment 1, we established that infants produce the N400 effect, a brain signature of semantic violations, in a live object naming paradigm in the presence of an adult observer. In Experiment 2, we induced false beliefs about the labeled objects in the adult observer to test whether infants keep track of the other person's comprehension. The results revealed that infants reacted to the semantic incongruity heard by the other as if they encountered it themselves: they exhibited an N400‐like response, even though labels were congruous from their perspective. This finding demonstrates that infants track the linguistic understanding of social partners. A video abstract of this article can be viewed at https://youtu.be/pQUv8yFhnbk .     

On Generalization of Definitional Equivalence to Non-Disjoint Languages

For simplicity, most of the literature introduces the concept of definitional equivalence only for disjoint languages. In a recent paper, Barrett and Halvorson introduce a straightforward generalization to non-disjoint languages and they show that their generalization is not equivalent to intertranslatability in general. In this paper, we show that their generalization is not transitive and hence it is not an equivalence relation. Then we introduce another formalization of definitional equivalence due to Andréka and Németi which is equivalent to the Barrett–Halvorson generalization in the case of disjoint languages. We show that the Andréka–Németi generalization is the smallest equivalence relation containing the Barrett–Halvorson generalization and it is equivalent to intertranslatability, which is another definition for definitional equivalence, even for non-disjoint languages. Finally, we investigate which definitions for definitional equivalences remain equivalent when we generalize them for theories in non-disjoint languages.

     

Seventeen-month-olds appeal to false beliefs to interpret others' referential communication

Recent studies have demonstrated infants' pragmatic abilities for resolving the referential ambiguity of non-verbal communicative gestures, and for inferring the intended meaning of a communicator's utterances. These abilities are difficult to reconcile with the view that it is not until around 4 years that children can reason about the internal mental states of others. In the current study, we tested whether 17-month-old infants are able to track the status of a communicator's epistemic state and use this to infer what she intends to refer to. Our results show that manipulating whether or not a communicator has a false belief leads infants to different interpretations of the same communicative act, and demonstrate early mental state attribution in a pragmatic context.     

One‐year‐old infants use teleological representations of actions productively

Two experiments investigated whether infants represent goal‐directed actions of others in a way that allows them to draw inferences to unobserved states of affairs (such as unseen goal states or occluded obstacles). We measured looking times to assess violation of infants' expectations upon perceiving either a change in the actions of computer‐animated figures or in the context of such actions. The first experiment tested whether infants would attribute a goal to an action that they had not seen completed. The second experiment tested whether infants would infer from an observed action the presence of an occluded object that functions as an obstacle. The looking time patterns of 12‐month‐olds indicated that they were able to make both types of inferences, while 9‐month‐olds failed in both tasks. These results demonstrate that, by the end of the first year of life, infants use the principle of rational action not only for the interpretation and prediction of goal‐directed actions, but also for making productive inferences about unseen aspects of their context. We discuss the underlying mechanisms that may be involved in the developmental change from 9 to 12 months of age in the ability to infer hypothetical (unseen) states of affairs in teleological action representations.     

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.