In the heart of time: investigating the link between cardiac activity and interoception in explicit and implicit timing

Recent research suggests that our sense of time is influenced by interoceptive abilities. Efficient access to bodily signals, measured objectively (interoceptive accuracy) and subjectively (interoceptive sensibility), may contribute to more accurate time perception. However, the link between cardiac activity, interoceptive abilities, and time perception is still unclear, particularly in distinguishing implicit and explicit timing. We explored this relationship in two studies. Interoceptive accuracy was assessed using a heartbeat counting task (HCT). Interoceptive sensibility was measured using the Body Perception Questionnaire and subjective confidence ratings (0-9 scale) provided during the HCT. Resting heart rate variability (HRV) served as an index of cardiac vagal control. In Study 1, participants (N = 31, M = 23.1 years, SD = 3.23) completed an implicit timing task (foreperiod) and an explicit timing task (time bisection). In Study 2, participants (N = 51, M = 22.6 years, SD = 1.52) performed an explicit timing task (self-paced finger-tapping). Results showed that better interoceptive accuracy was associated with faster response speed in the foreperiod task, suggesting improved motor readiness. In contrast, greater subjective confidence in heartbeat detection corresponded to poorer performance in the time bisection task (Study 1), indicating over-reliance on inaccurate interoceptive signals. Higher vagal tone (indexed by heightened HRV high frequency power) was associated with a faster tapping rhythm (Study 2). These findings highlight the distinct roles of cardiac interoception and activity in explicit and implicit timing, emphasizing their nuanced contributions to time perception.