Examining Eye Movements in Visual Search through Clusters of Objects in a Circular Array.

Participants were asked to search for a complete O in an array consisting of eight clusters of four Landolt Cs (i.e., Os with a gap) arranged in a ring. The size of the gap in the Cs varied from cluster to cluster but was held constant within a cluster. The manual response time data were consistent with a serial self-terminating search. More importantly, eye movement data supported a serial processing model as (a) clusters were fixated serially (either clockwise or counterclockwise) on most trials and (b) fixation times on a cluster reflected processing time on that cluster and were unaffected by the gap size of either the prior or succeeding cluster. Furthermore, the pattern of fixation times on a cluster was similar to the pattern of response times in a secondary task where a single cluster was presented at fixation. These data extend the findings of Williams and Pollatsek (2007) in which search was through a linear sequence of clusters, and indicate that a serial search pattern through clusters of these kinds of objects is not confined to reading-like linear arrays.