Abstract
The model of association field proposed that local elements are integrated into global contours if they satisfy the joint constraints of local alignment and spatial position along first-order curves (e.g., collinear contours). However, it is difficult to interpret the surprisingly good detection performance when the elements of the contour align perpendicular to its underlying path (i.e., orthogonal contours) with the model. This raised the debates on whether orthogonal contours share the same integration mechanism with collinear ones. We addressed this issue, in particular, by investigating the role of conscious awareness in the processing of collinear and orthogonal contours. In Experiment 1, we combined an attentional cuing paradigm with a modified version of inattentional blindness paradigm to examine the processing of collinear and orthogonal circular contours under conscious and unconscious conditions. We found that collinear contours induced a positive cueing effect at both unconscious (p<0.01) and conscious (p<0.01) conditions, while orthogonal contours summoned attention only under conscious condition (p<0.05). In Experiment 2, we tested whether collinear and orthogonal contours presented under continuous flash suppression have prioritized access to awareness relative to the Gabor field without a contour (random field, baseline condition). We found that the collinear contours broke from suppression more quickly than the random field (p<0.001). However, no such effect was observed for orthogonal contours (p=0.55). These results demonstrate that collinear contours can be processed without conscious awareness, supporting the idea that its integration implements through lateral interactions within the primary visual cortex. On the other hand, the integration of orthogonal contours requires conscious awareness with at least higher visual cortex involved. Taken together, different fates of collinear and orthogonal contours at unconscious level provide strong evidence that the integration of orthogonal contours is mediated by a different mechanism than collinear contours.
Meeting abstract presented at VSS 2014