Vision and proprioception make equal contributions to path integration in a novel homing task.

Navigation is a vital cognitive function for animals to find resources and avoid danger, and navigational processes are theorized to be a critical evolutionary foundation of episodic memory. Path integration, the continuous updating of position and orientation during self-motion, is a major contributor to spatial navigation. However, the most common paradigm for testing path integration-triangle completion-includes potential sources of error that cannot be disentangled. Here, we introduce a novel loop closure paradigm to test path integration, including the relative contributions of visual and body-based cues to performance. Contrary to triangle completion, we found that vestibular information alone led to chance performance, while visual optic flow and proprioception made relatively equal and independent contributions. The integration of these two cues was previously unknown, and we found that the two cues were not integrated in a Bayesian ideal manner. Our novel paradigm demonstrates the importance of both vision and proprioception to human path integration and provides the first test of optic flow and proprioception Bayesian cue combination for homing behavior. These findings open up new avenues to study navigation.