Eye movements during search and detection in comparative visual search

Motivated by the fact that previous visual memory paradigms have imposed encoding and retrieval constraints, the present article presents two experiments that address how observers allocate eye movements in memory and comparison processes in the absence of constraints. A comparative visual search design (Pomplun, Sichelschmidt, et al., 2001) was utilized in which observers searched for a difference between two images presented side by side. Robust time course effects were obtained, whereby search was characterized by brief fixations and a high proportion of comparative saccades. Then, upon target detection, fixations were extended, more comparative saccades were elicited, and the search focus was narrowed. The saliency and presence of differences did not guide attention, and detection was contingent upon direct fixation of the targets. The results indicate that, when full control is given, observers adopt a strategy that cuts down on memory usage in favor of restricted encoding and active scanning.