Evidence for Cardiac Phase-Linked Perception of Heartbeats.

Commonly used methods for assessing cardiac interoceptive accuracy have been criticized for assuming that all individuals perceive their heartbeat at the same delay following contraction of the heart, despite evidence for notable variability across individuals. 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. Identification of all heartbeat perceivers is critical for accurate measurement of cardiac interoceptive accuracy; individual differences in which are theorized to play a role in several aspects of higher-order cognition as well as health and wellbeing. In the current study, data from 526 participants who completed the Phase Adjustment Task (PAT) as a measure of cardiac interoceptive accuracy were examined. In this task, participants are asked to adjust a virtual dial until tones appear synchronous with their heartbeats. Data were analyzed using a novel framework that allows differentiation between delay-based and phase-based response patterns. Of 76 interoceptive individuals identified, 21% (N = 16) demonstrated response patterns consistent only 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.