Mice learn multi-step routes by memorizing subgoal locations

The behavioral strategies that mammals use to learn multi-step routes in natural settings are unknown. Here we show that mice spontaneously adopt a subgoal memory strategy. We first investigated how mice navigate to shelter in response to threats when the direct path is blocked. Initially, they fled toward the shelter and negotiated obstacles using sensory cues. Within twenty minutes, they adopted a subgoal strategy, initiating escapes by running directly to the obstacle’s edge. Mice continued to target this subgoal location after the obstacle was removed, indicating use of spatial memory. However, standard models of spatial learning – egocentric-movement repetition and internal-map building – did not explain how subgoal memories formed. Instead, mice used a hybrid approach: memorizing salient locations encountered during spontaneous ‘practice runs’. This strategy was also used during geometrically identical reward-seeking behavior. These results suggest that subgoal memorization is a fundamental strategy by which rodents learn efficient multi-step routes in new environments.