Enumerating and Discovering Highly Discriminative Tasks for Probing Diverse Foraging Strategies

Foraging, an indispensable behavior for survival, consists of long sequences of searches, encounters, and decisions. To forage successfully, animals are thought to leverage the statistical regularities and dynamical rules of their habitats to maximize long-term utility. Since animals encounter different habitats that demand different decision rules, it is important to infer the behavioral strategies that are most relevant to a particular species. One approach is to observe an animal in its natural habitat, but this comes with technical and conceptual challenges of recording and manipulating behavior in naturalistic settings. To circumvent this without compromising the richness of environmental features that evoke an animal’s foraging strategy, we sought to manipulate a vast set of such features in a controlled lab setting. To this end, we designed a two-choice foraging task with complex contingencies in reward delivery (controlled by up to 13 past decisions). By enumerating different reward-delivery rules, we simulated half a million different task conditions—each resembling a slightly different environment and varying in their putative relevance to the animal. As a proof of principle, we tested these tasks on fruit flies. We selected tasks that best discriminate between two classes of strategies: one that requires “one-shot memory” (like Boolean logic), and one that does not. Even though flies’ decisions are highly stochastic from trial to trial, we identify flies that use one-shot memory to perform well, a finding that cannot be explained by rare sampling events from any “memoryless” strategies. This finding suggests that flies can exploit short-timescale decision rules in a manner that differs from longer-timescale adaptive behaviors mediated by synaptic plasticity. Our framework is agnostic to specific model systems and can flexibly perform inferences in different hypothesized strategy spaces. This will allow us to compare foraging strategies across species and studying their dependence on underlying environmental structure.</p