Speaker: Professor Árni Kristjánsson (School of Health Sciences, University of Iceland)
Topic: A new foraging task reveals individual differences in visual attention abilities.
Details: Visual foraging with multiple targets of different types is often a more realistic model of attentional function than single-target visual searches since our goals are not necessarily narrowly focused on a single target, with searches ending when it is found. I will discuss a new visual foraging task on mobile touchpad devices (iPads) where observers cancel a series of targets among distractors by tapping them until all are gone. During feature-based foraging observers cancel green and red disks among yellow and blue distractors (or vice versa). During conjunction-based foraging they cancel red disks and green squares among green disks and red squares (or vice versa). For feature-based foraging, typical strategies deviated only slightly from random, indicating that observers can simultaneously maintain two or more color templates. For conjunction-based foraging, the typical pattern was dramatically different: most observers focused on one target-type, finishing most or all of those before switching to the other target type. But a notable subset of observers switched repeatedly between target types during conjunction foraging. Importantly, they to do this without sacrificing speed or accuracy, a finding which is at odds with many models of visual search. The rest of the observers perform what might be termed two sequential subset searches. This dramatic difference between conjunction and feature-based foraging is shown here for the first time, and is unexpected under many current models of attention. New extensive tests reveal we find that this subset of individuals who can use similar strategies for both tasks is about 15-20% of observer. I will discuss further tests of the task, including tests of “gaze foraging” and the potential implications of these findings for theories of visual attention.