Voluntary visual search is modulated by the cardiac cycle

Abstract

Perception and reasoning vary according to fluctuating inner bodily stimuli such as heartbeat. This has been shown by locking the presentation of sensory events to distinct phases of the cardiac cycle. However, we argue that task-relevant information is not usually encountered in a phase-locked manner nor passively accessed, but actively sampled at one’s pace. Moreover, we propose that this sampling may be influenced by integrating cardiac signals. We test this by coregistration of eye movements and heartbeat signals while participants freely compared differences between two arrays. Across two experimental samples and three different analyses, we found a significant coupling of saccades and subsequent fixations with the heartbeat. More eye movements were generated during the early phase of the cardiac cycle compared to the later diastole phase; opposite pattern found for fixations. These results provide new evidence for a mechanism by which humans sample the world according to oscillatory bodily states.