Cardiorespiratory cycles couple with saccadic eye movements during active visual sampling

Bodily rhythms, including respiration and cardiac activity, influence perception and action. However, most evidence comes from passive paradigms in which participants have limited control over how sensory information is acquired. Here, we investigated whether saccadic eye movements are coupled to cardiorespiratory cycles and whether this coupling differs between active visual search and visual tracking. Fifty-five adults completed a task in which a Gabor patch was concealed by an image and revealed through a viewing window that either followed their own gaze (active search) or replayed another participant’s gaze trajectory (visual tracking). We recorded eye movements, electrocardiography, and respiration, and assessed interoceptive sensibility using the Three-domain Interoceptive Sensations Questionnaire (THISQ). Compared with visual tracking, active search elicited higher heart rate, reduced heart rate variability (HRV), faster breathing, and greater pupil dilation, alongside larger saccades and longer fixations. Across both conditions, saccades were preferentially initiated during mid-to-late exhalation. Saccade timing was also non-uniformly distributed across the cardiac cycle, revealing two subgroups with distinct phase preferences for systole or diastole. Neither coupling strength nor preferred phase differed significantly between conditions. Cardiorespiratory deceleration around trial onset further suggested that participants may have adjusted their bodily rhythms to task structure in both conditions. Interoceptive sensibility was not associated with coupling strength. Together, these findings indicate that saccadic eye movements are temporally coupled to both respiratory and cardiac cycles, with consistent respiratory phase preferences but substantial individual variability in cardiac phase preferences.