Academic journal article Attention, Perception and Psychophysics

Developmental Trends in Interpolation and Its Spatial Constraints: A Comparison of Subjective and Occluded Contours

Academic journal article Attention, Perception and Psychophysics

Developmental Trends in Interpolation and Its Spatial Constraints: A Comparison of Subjective and Occluded Contours

Article excerpt

Published online: 4 March 2015

© The Psychonomic Society, Inc. 2015

Abstract We examined interpolation in 6- and 9-year-old children and in adults, in the two most common forms of fragmentation: subjective and partially occluded contours. Experiment 1 examined the effects on adults' interpolation of contour geometry, specifically, the effect of a scale-dependent factor (i.e., retinal size) and a scale-independent factor (i.e., support ratio). For both subjective and partially occluded contours, interpolation was affected more by support ratio than absolute size. However, subjective contours were less precisely interpolated and their interpolation was affected more by support ratio than was the case for partial occlusion. Experiment 2 used a subset of retinal size and support ratio levels in children and adults. Interpolation of both subjective and occluded contours improved significantly with age, with the two types of contours equally affected by spatial constraints during early childhood. However, while interpolation of occluded contours became more precise with age and less dependent on support ratio by adulthood, interpolation of subjective contours was less improved and became even more tied to support ratio in adulthood. The implications of these differential age-related changes in the spatial constraints on interpolation of the two types of contours for the mechanisms of perceptual completion are discussed.

Keywords Perceptual completion . Subjective contours · Partially occluded contours · Contour interpolation · Support ratio · Development

Continuous objects often project disparate fragments on the retina as a result of occlusion, shadows, or low-reflectance contrast. Yet, in most cases, humans perceive continuous surfaces and coherent objects. A large body of research has been devoted to uncover the visual mechanisms of contour interpolation mediating this perception of continuity. However, fundamental questions, such as the spatial factors limiting interpolation, whether the same process underlies interpolation in different cases of fragmentation, and the developmental stage at which these interpolation processes become adult-like, remain open. To study these questions, we examined interpolation in 6- and 9-year-old children and in adults, in the two most common forms of fragmentation: subjective contours and partially occluded contours.

In the case of partial occlusion, often referred to as amodal completion, interpolation between distant image fragments behind the occluding surface leads to a complete representation of the occluded object (bottom panel in Fig. 1). A complete representation is often achieved without generating any visually experienced structure in the interpolated area (Michotte, Thines, & Crabbe, 1964). In the case of subjective contours, also known as modal completion, completion yields a visual impression of contours or surfaces in locations where there is no local image contrast to support this percept (top panel in Fig. 1).

A major question in the adult literature is whether a single, common interpolation mechanism is employed by the visual system to transcend these two forms of fragmentation. Kellman and Shipley argue that the same interpolation process operates without regard to the final appearance of a subjective or an occluded figure (e.g., Kellman & Shipley, 1991; Yin, Kellman, & Shipley, 1997). By this identity hypothesis,the appearance of the interpolated contour, as subjective or as occluded, relates to the mechanism responsible for assigning relative depth of the completed contours and surfaces. Empirical support for this hypothesis comes from studies showing, for example, that the two types of contours are affected similarly by contour alignment (Shipley & Kellman, 1992), that they demonstrate similar sensitivity to shape changes (Kellman, Yin, & Shipley, 1998; Ringach & Shapley, 1996), and that they are obligatory in that they arise even when they are detrimental to performance (Davis & Driver, 1998; He & Nakayama, 1992; Rensink & Enns, 1998). …

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