Ladd, C. E.; Simpson, J. H.

To determine the algorithmic rules and neural circuits controlling selection amongst competing behaviors, we established assays where adult Drosophila melanogaster choose between grooming and feeding, grooming and courting, or feeding and courting. We find that there is not an absolute hierarchy: while flies typically perform grooming first, they can choose to feed if sufficiently starved, or court if an appropriate female is available. Flies alternate between competing behaviors, performing short bouts of each action rather than completely satisfying one drive before transitioning to another. And we do not find evidence for a common genetic or neuronal locus that affects all decisions, suggesting that the fly may select the best course of action by discrete circuits regulating each pairwise comparison. Our results add to a growing body of work on decision-making in Drosophila and provide a foundation for future investigation of the exact neural circuits required to achieve appropriate choices.