title: Using the axis of elongation to align shapes: developmental changes between 18 and 24 months of age.
abstract: An object's axis of elongation serves as an important frame of reference for forming three-dimensional representations of object shape. By several recent accounts, the formation of these representations is also related to experiences of acting on objects. Four experiments examined 18- to 24-month-olds' (N=103) sensitivity to the elongated axis in action tasks that required extracting, comparing, and physically rotating an object so that its major axis was aligned with that of a visual standard. In Experiments 1 and 2, the older toddlers precisely rotated both simple and complexly shaped three-dimensional objects in insertion tasks where the visual standard was the rectangular contour defining the opening in a box. The younger toddlers performed poorly. Experiments 3 and 4 provide evidence on emerging abilities in extracting and using the most extended axis as a frame of reference for shape comparison. Experiment 3 showed that 18-month-olds could rotate an object to align its major axis with the direction of their own hand motion, and Experiment 4 showed that they could align the major axis of one object with that of another object of the exact same three-dimensional shape. The results are discussed in terms of theories of the development of three-dimensional shape representations, visual object recognition, and the role of action in these developments.
authors.affiliation: Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, USA. Electronic address: smith4@indiana.edu.
authors.forename: Linda B
authors.initials: LB
authors.lastname: Smith
authors.affiliation: Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Sandra
authors.initials: S
authors.lastname: Street
authors.affiliation: Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Susan S
authors.initials: SS
authors.lastname: Jones
authors.affiliation: Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Karin H
authors.initials: KH
authors.lastname: James
mesh_terms: D002657:Child Development; D003210:Concept Formation; D003867:Depth Perception; D004193:Discrimination Learning; D005260:Female; D005795:Generalization, Stimulus; D006801:Humans; D007223:Infant; D008297:Male; D009949:Orientation; D010364:Pattern Recognition, Visual; D011597:Psychomotor Performance; D021641:Recognition, Psychology; D012858:Size Perception
keywords: Infancy; Insertion task; Object manipulation; Perception–action; Shape; Visual object recognition