Evidence for Cardiac Phase-Linked Perception of Heartbeats

Commonly used methods for assessing cardiac interoceptive accuracy have been criticised for assuming that all individuals perceive their heartbeat at the same delay following contraction of the heart. However, it remains unclear whether some individuals perceive their heartbeat at a particular phase of their cardiac cycle – that is, at a relative point in the cycle that may vary in absolute timing depending on heart rate - rather than at a specific delay. In the current study, data from 531 participants who had completed the Phase Adjustment Task (PAT) as a measure of cardiac interoceptive accuracy were analysed. In this task, participants are asked to adjust a virtual dial until tones appear synchronous with their heartbeats. Data were analysed using a novel framework that allows differentiation between delay-based and phase-based response patterns. 17% of interoceptive individuals demonstrated response patterns consistent with phase-based responding. These novel findings challenge current assumptions regarding individual differences in the perception of heartbeats, and suggest that many commonly used measures may underestimate the true proportion of heartbeat perceivers.