The distribution of attention within objects in multiple-object scenes: Prioritization by spatial probabilities and a center bias

Abstract

This research was supported by Grant 4-69018-05-496 from the Kentucky jurisdiction of the National Science Foundation's Experimental Program to Stimulate Competitive Research. Parts of this research were presented at the annual meetings of the Vision Sciences Society (Sarasota, Florida, May 2006) and the Psychonomic Society (Long Beach, California, November 2007). I thank Maureen Doyle for her great help in developing the computer program. For assistance with data collection and useful conversations, I thank Allison Adams, Amy Baker, Jamie Cole, Joshua Edwards, Philip Oliver, Christa Patterson, Amanda Pieratt, Nick Rudd, Jessica Stephens, Amy Vaughn, and Cassie Watkins. I also thank Brian Scholl for helpful conversation and Gilbert Remillard for valuable advice and discussions. This study investigates how the attentional distribution within objects is affected by spatial probabilities, bias toward objects' centers (Alvarez & Scholl, 2005), and object motion. In a multiple-object tracking task, observers tracked line objects while simultaneously detecting probes appearing on the objects. Experiments 1 and 2 manipulated the probabilities of probes appearing at the centers and ends of objects. Overall, probe detection was better at centers than at ends, but it was also affected by probe location probabilities; when probe locations were 100% certain, the center advantage was eliminated. Experiment 3 manipulated rotational, translational, and size-change components of object motion. The center advantage still occurred with stationary objects, and its magnitude was not affected by different motion types. These results indicate that attention is biased toward the centers of objects in multiple-object scenes, both for stationary and moving objects. They also imply that attentional prioritizations based on spatial probabilities can accompany moving objects. Copyright 2008 Psychonomic Society, Inc.