Individual differences in physiological adaptation correlate with cardioceptive precision in the heart rate discrimination task

Interoception, the process through which the organism senses internal bodily signals is most commonly studied across the cardiac domain, yet the physiological basis of cardioception remains only partially understood. Moreover, most research has assessed cardiac interoception at rest, neglecting its dynamic nature. In this study we used the Heart Rate Discrimination (HRD) task to examine individual differences in cardiac physiology associated with interoceptive precision, particularly through ethanol-induced physiological modulation.In a double-blind within-subjects design, 36 participants completed the HRD at baseline, consumed an alcohol or placebo beverage, followed by a post-beverage HRD instance. Cardiac indices, (high-frequency and 0.1 Hz heart rate variability, HRV), heart rate baroreflex sensitivity (HR-BRS), and mean heart rate, were recorded before and after beverage administration.Preregistered baseline analyses showed no associations between baseline cardiac physiology and HRD precision. Exploratory analyses revealed selective baseline relationships for other HRD metrics: HF HRV correlated negatively with metacognitive sensitivity, while interoceptive threshold correlated negatively with mean heart rate and positively with HR-BRS. Crucially, preregistered mixed models showed that within-subject increases in 0.1 Hz HRV over time predicted greater interoceptive precision across both alcohol and placebo sessions. Results indicate that physiological adaptation, rather than resting cardiac state, shapes interoceptive precision. Increases in 0.1 Hz HRV were associated with reduced uncertainty in cardioceptive decisions, while bias and metacognitive components related to distinct physiological markers. Together, these findings suggest that the temporal structure of afferent cardiac signals is a key determinant of interoceptive precision, underscoring the importance of studying interoception under changing physiological states.