Cognitive, perceptual and motor bases for the acquisition of tool use in infants

Abstract : Tool use is the ability to act on an object with another object. In human infants, this ability develops toward the end of the second year of life. Despite a recent resurgence of interest in the study of tool-use learning in infancy, very little is known about the developmental steps in this learning or the underlying mechanisms. The present thesis presents a series of investigations on the age and conditions under which infants learn to use a tool to retrieve an out-of-reach object.In a first cross-sectional study (Paper 1), based on a preliminary study on 5 infants followed longitudinally from 12 to 20 months of age (Appendices 2 and 3), infants aged 14 to 22 months were tested on a task involving the use of a rake-like tool to retrieve an out-of-reach toy. Infants' performance across variations in the spatial relationship between the rake and the toy was explored. The results showed that infants as young as 14 months of age succeeded spontaneously when the toy was initially placed against the rake or at least lay in the shortest trajectory between the rake and the infant. When the toy was placed at some distance from the rake, outside its shortest trajectory, infants only succeeded spontaneously at the task around 18 to 22 months of age. Likewise, when an adult demonstrated how to use the rake in the same spatial conditions, infants showed sensitivity to the demonstration only starting at 18 months of age. In a follow up of this study, a finer analysis of the data was conducted, which yielded insight on the age at which infants start to plan their action when using a tool (Paper 2). This analysis showed that before 18 months of age, infants were mostly influenced by their manual preference toward the right hand when grasping the tool. In contrast, starting 18 months, infants were more likely to vary the hand they used for grasping according to the toy's position in relation to the tool (right or left). These results show that infants who are in the phase of acquiring tool use are better able to anticipate the action than younger infants.One observation from these first cross-sectional and longitudinal studies was of particular interest. When the toy was attached to the rake, all infants were spontaneously able to successfully retrieve the toy starting at 12 months of age. This suggests that at this age, infants have already acquired the notion of composite objects. In a complementary study, a significant change was observed between 6 and 9 months of age in the understanding of the notion of spatial connectedness between objects. Starting at 8 months of age, infants befan to show visual anticipation toward the distal part of the composite object when grasping its proximal part. Thus, 8-month-old infants use the notion of connectedness when acting on composite objects. This is in line with results from previous studies showing that around 10-12 months infants pull a string to which an out-of-reach object is attached before trying to grasp the object. However, in a pilot study where 16-month-old infants were presented a choice of several strings, only one of which was connected to the out-of-reach object, infants did not systematically choose the connected string. This led us to an investigation of why, at 16 months, infants do not use the notion of connectedness between objects in order to solve this task (Paper 3). To do so a study was conducted comparing infants' performance on the multiple strings task (action condition) with their looking behaviours at the same multiple-string scene when an adult solved the task in front of them (vision condition). The results showed that only infants who succeeded at the task themselves were able to visually anticipate which string the adult had to pull in order to retrieve the object. Additionally, the results showed that lack of inhibitory control partly explains infants' failure at the task....
Keywords : Psychology
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Lauriane Rat-Fischer. Cognitive, perceptual and motor bases for the acquisition of tool use in infants. Psychology. Université René Descartes - Paris V, 2013. English. ⟨NNT : 2013PA05H110⟩. ⟨tel-01262156⟩

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