Time Limits During Visual Foraging Reveal Flexible Working Memory Templates

During difficult foraging tasks, humans rarely switch between target categories, but switch frequently during easier foraging. Does this reflect fundamental limits on visual working memory (VWM) capacity or simply strategic choice due to effort? Our participants performed time-limited or unlimited foraging tasks where they tapped stimuli from 2 target categories while avoiding items from 2 distractor categories. These time limits should have no effect if capacity imposes limits on VWM representations but more flexible VWM could allow observers to use VWM according to task demands in each case. We found that with time limits, participants switched more frequently and switch-costs became much smaller than during unlimited foraging. Observers can therefore switch between complex (conjunction) target categories when needed. We propose that while maintaining many complex templates in working memory is effortful and observers avoid this, they can do so if this fits task demands, showing the flexibility of working memory representations used for visual exploration. This is in contrast with recent proposals, and we discuss the implications of these findings for theoretical accounts of working memory. Public Significance Statement When we search for 2 things at once, are 2 search templates simultaneously activated, or do we switch rapidly between the 2 templates, in essence only searching for 1 item at any given moment? Our results suggest that while we may avoid keeping 2 search templates active in visual working memory due to the effort involved, we are able to do so when the task demands require this or reward it for a short period of time. The fact that participants seem to be able to change their foraging patterns according to task demands suggests that visual working representations used for attentional guidance are flexible, but not fixed at 1 feature as some current theories suggest. This finding has important consequences for theoretical conceptions of visual working memory.