Exogenous Orientation of Attention to the Center of Mass in a Visual Search Task

Abstract

Anne Treisman’s scientific career included broad-ranging contributions that advanced our understanding of the attentional mechanisms that people rely on to make sense of the world. In this paper, we describe results from a visual-search paradigm first developed by Grabowecky and Treisman (Grabowecky, 1992). Their design exploited known feature-search asymmetries (Treisman & Gormican, 1988) to investigate the role of a center of mass (CoM) mechanism in determining the initial locus of visual-spatial attention in visual search. The original experiment supported the hypothesis that CoM influences initial orienting of visual-spatial attention, as targets near the CoM of a multi-element array were detected more quickly than targets distant from the CoM. These findings were replicated in a follow-up experiment using a different feature-search asymmetry, with eye-tracking added to verify central fixation. We also investigated whether CoM had any influence on pop-out search, and found no evidence that it does. Surprisingly, the effect of position of the search array on the CoM suggested that CoM may be computed independently for elements contained within each visual hemifield. Whereas our work on CoM with Treisman was initiated within an earlier theoretical context, the present results are also compatible with contemporary theoretical advances; both the early results and the new results can be integrated within current ways of thinking about attention and pre-attentive mechanisms.