Time-course contingencies in perceptual organization and identification of fragmented object outlines.

Abstract

To study the dynamic interplay between different component processes involved in the identification of fragmented object outlines, the authors used a discrete-identification paradigm in which the masked presentation duration of fragmented object outlines was repeatedly increased until correct naming occurred. Survival analysis was used to investigate whether and when different types of information-such as contour integration cues (proximity, collinearity, and fragment density), fragment properties (low vs. high curvature), stimulus complexity (global symmetry, number and saliency of the parts), and memory factors (natural vs. artifactual)-influenced the timing of identification. The results show that the importance of these different types of information can change over the time course of object identification, indicating so-called time-course contingencies. Most important, the straight segments of a contour played a larger role for complex outlines with high part saliency during early (bottom-up) grouping processes, whereas the curved segments of object outlines were more important during later (top-down) matching processes for simpler outlines with lower part saliency. This new insight can explain why different studies on shape-based object identification have produced seemingly contradictory results.

Visual complexity exerts opposing effects on object categorization and identification

“…The findings by Gerlach and Toft are compatible with this in that a positive correlation between RT and visual complexity (r = .27) was found in full outline version, whereas a negative correlation (r = −.33) was found in the silhouette version. Similar findings suggesting that visual complexity may impact differentially at different stages in visual object processing have been reported by Wagemans and colleagues with 754 GERLACH AND MARQUES fragmented stimuli (Panis, De Winter, Vandekerckhove, & Wagemans, 2008;Panis & Wagemans, 2009;Torfs, Panis, & Wagemans, 2010).…”

Processing convexity and concavity along a 2-D contour: figure–ground, structural shape, and attention

“…This has been confirmed with the same method on a larger sample of outlines of everyday objects in a study by De Winter and Wagemans (2008). Subsequently, Panis and Wagemans (2009) have tried to resolve these apparent contrasting results by examining the time course of object identification. They concluded that straight edges were more important for complex outlines early in the matching process and that curved edges were more important for simple outlines in later (top-down) matching processes.…”

Now you see it, now you don't: The context dependent nature of category-effects in visual object recognition

“…The same mask was used for the generation of all fragmented stimuli. Hence, no attempt was made to delete specific portions of the stimuli even though studies have shown that recovery of object structure might depend on whether parts, midsegments or vertices are deleted (Biederman, 1987;Panis & Wagemans, 2009). While this procedure does lead to randomness with respect to which segments are deleted, it is equally random for stimuli depicting natural objects and artefacts, and this is of primary importance considering the purpose of the present study.…”