Discretionary task interleaving RUNNING HEAD: DISCRETIONARY TASK INTERLEAVING Discretionary task interleaving: Heuristics for time allocation in cognitive foraging

When participants allocated time across two tasks (in which they generated as many words as possible from a fixed set of letters) they made frequent switches. This allowed them to allocate more time to the more productive task (i.e. the set of letters from which more words could be generated), even though times between the last word and the switch decision (“giving-up times”) were higher in the less-productive task. These findings were reliable across two experiments using Scrabble tasks and one experiment using word-search puzzles. Switch decisions appeared relatively unaffected by the ease of the competing task, or by explicit information about tasks’ potential gain. We proposed that switch decisions reflected a dual orientation to the experimental tasks. First, there was a sensitivity to continuous rate of return – an information foraging orientation which produced a tendency to switch in keeping with Green’s rule (1984), and a tendency to stay longer in more rewarding tasks. Second, there was a tendency to switch tasks after subgoal completion. A model combining these tendencies predicted all the reliable effects in the experimental data.