Abstract
Visual search efficiency is commonly measured by the relationship between subject response time (RT) and display set size. Basic features are visual features for which a singleton target can be found efficiently (RT independent of set size), a situation commonly referred to as pop-out. However, the seminal work of Duncan and Humphreys (1989) demonstrated that visual search RT is also correlated with the degree of target-distractor similarity. As similarity of the target with its surrounding distractors increases (and thus the target becomes more difficult to distinguish) RT can dramatically increase. Wolfe (1998a) identified this category as hard feature search, but left both an in-depth analysis of the transition from standard feature search to a hard search as well as the efficiency of hard search largely unexplored beyond a small number of orientation trials. As far as we are aware, the interaction of these two independent factors remains relatively unstudied. For colour and size, two basic features identified by Wolfe (1998b), we systematically vary target-distractor similarity and set size to develop a well-characterized psychometric function across both dimensions. This allows us to explore if there is a transition from efficient to inefficient search, or if even hard feature searches are still efficient when performed over a basic feature difference. We find that the relationship between target-distractor similarity and search efficiency is more complicated than a direct transition to inefficient search as the search grows hard.
Meeting abstract presented at VSS 2017