Interaction between depth and ocularity features in attentional attraction during visual search

Abstract

An eye of origin singleton, e.g., a single bar shown to the left eye among many identical bars shown to the right eye, can attract attention more strongly than an orientation singleton (Zhaoping, 2008 Journal of Vision 8(5):1, 1-18). More generally, when input strengths of an item to the left and right eyes are C_L and C_R respectively, contrast in ocularity (defined as C_L-C_R) between an item and its neighbors increases this item's saliency (Zhaoping, 2010, Perception 39, ECVP Abstract Supplement, p4). When input items have non-zero disparities, ocularity is generalized to relate different image locations (for each item) in the two eyes. We investigate in more detail saliency by unique ocularity when different items in a display have different depths. Subjects do visual search for a target defined as the one having an unique feature (e.g., orientation) other than ocularity and depth. The target is easier to find when it is also an ocularity singleton (having a unique ocularity among non-targets of uniform ocularity) than the case when all items have the same ocularity. In contrast, the search is more difficult when a non-target is an ocularity singleton. These effects are significant when the ocularity contrast between the ocularity singleton and the other items is sufficient. They suggest that the ocularity singleton attracts attention to itself, thereby facilitating or interfering with the search, consistent with the theory that V1 creates a bottom-up saliency map (Li, 2002, Trends Cog. Sci. 6:9-16). The effects persist even when the ocularity singleton is neither nearest nor farthest in depth among items of inhomogeneous depths. In at least some subjects, the non-target ocularity singleton continues to interfere with the search even when the target is in front of a depth plane containing all non-target items.

The Gatsby Charitable Foundation, and Tsinghua University 985 grant.