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Our visual system develops in a world of three-dimensional objects, where children often control the dynamic visual experience they experience. Our previous experimental work was the first to analyse in detail what object views are selected in children’s unconstrained manipulation of physical objects. The key finding was the distribution of dwell time across all possible viewpoints; preferred viewpoints are around on-axis views, where the principal axis of elongation is either perpendicular or parallel to the line of sight and flat surfaces are presented approximately perpendicular to the line of sight – so called planar views. The planar bias is statistically above a random exploration baseline at the earliest age tested (12-18 months) and undergoes large changes until at least 30 to 36 months. The planar bias is also characteristic of mature viewing and was found to promote more efficient visual object learning. Its functional role is, however, unknown. Here we present a morphological shape analysis of the object views selected by a large cross-sectional sample of children, while they manipulated objects (N = 54, 12-36 months). We followed an image-based (pixel-based) approach; we coded the 3D object orientation and used it to create computer-generated images of the object and extracted standard shape measures. We investigated if basic shape measures differed between planar and non-planar views. In particular we computed surface area and aspect ratio. In addition, and for a smaller subset of 30-36 month olds (N = 8, 14400 frames) we computed the number of pixels that do not overlap between consecutive frames (a measure of image variability), as a proportion of the maximum object surface area. There were two key results: (1) on average, planar views have lower surface area and lower aspect ratio (i.e. they are more elongated) than non-planar views; (2) on average, consecutive frames of planar views have a lower proportion number of pixels that do not overlap between frames than non planar views. The results suggest that elongation is a characteristic aspect of preferred viewpoints, not solely of the 3D orientation of the main axis but also of the viewed surface. Also, planar views correspond to more stable periods of the object manipulation. This suggests that sampling planar views corresponds to moments of focused attention to a particular view where perhaps learning of a static view is occurring. We will discuss these results in the context of contemporary theories of visual object recognition development., Fundação para a Ciência e a Tecnologia (FCT)

Poster apresentado em "Leuven Christmas Applied Vision Association (AVA) Conference", em Leuven, Bélgica, 2014., As we turn our bodies, as we hold and move objects close to us and act on them, we generate dynamic views. Recent studies have examined the viewpoints that infants select during free play and found large developmental changes in dwell time distribution, namely an increasing preference for orienting objects on or around planar views – i.e. main axis is parallel (foreshortened) or perpendicular to the line of sight, and flat surfaces are perpendicular. This bias is characteristic of mature viewing and was found to promote more efficient learning. The functional role of this bias is poorly understood. We investigated two properties that seem relevant: (1) main axis expansion/foreshortening, and (2) instability – related to dynamic viewing, where rotations around planar views typically yield larger visual changes. In two experiments (E1: N=21, 18-24 months; E2: N = 54, 12-36 months), children inspected objects in a free play task and we measured 3D orientation; the main measures were the angle between the main axis of elongation and the line of sight, and its angular velocity and acceleration. There were two key results: (1) main axis is typically maintained in view (infrequent foreshortening) – this suggests that elongation is a distinctive property of preferred views; (2) planar views correspond to more stable periods of the object manipulation – this suggests that sampling planar views corresponds to moments of focused attention to a particular view and perhaps learning of a static view is occurring, leaving open the question of how view transitions are integrated over time., Fundação para a Ciência e a Tecnologia (FCT)

Three experiments examine 18- to 24-month-old (N = 78) toddlers’ ability to spatially orient objects by their major axes for insertion into a slot. This is a simplified version of the posting task which is commonly used to measure dorsal stream functioning. The experiments identify marked developmental changes in children’s ability to pre-orient objects for insertion, with 18-month-olds failing completely and 24-month-olds succeeding easily. In marked contrast, 18-month-olds pre-orient their empty hands for insertion into the same slots. This developmental dissociation between aligning hands and aligning objects to slots suggests that the key developmental change is in action with the goal of object-to-object alignment versus action on an object.