Zero-Shot Generalization of Prospective Planning in Macaques

Achieving a goal in natural environments often requires a sequence of actions whose consequences extend beyond their immediate outcomes. Because actions within a sequence can hinder or facilitate subsequent actions, successful behavior often demands prospective planning: selecting current actions based on their consequences for future actions. Although prospective planning is well documented in humans, its generalization to unfamiliar problems in nonhuman animals remains poorly understood. Here, we developed maze-navigation tasks in which macaque monkeys moved a token toward a goal while navigating around obstacles. Monkeys selected routes based on the positions of downstream obstacles, and their choices could not be explained by simple whole-maze visual summaries. In previously unseen, complex branching mazes, monkeys avoided deceptive dead ends--routes that initially approached the goal but ultimately failed--even when those dead ends extended several maze segments downstream. Prospective route selection was evident from the first encounters with multistep mazes and generalized to previously unencountered arrangements of familiar obstacles. These findings demonstrate zero-shot generalization of prospective planning: macaques applied a prospective strategy to unfamiliar multistep problems without learning the appropriate action sequences through repeated experience.