Interoception is the sensing of internal bodily signals. Individuals vary in their ability to perceive, as conscious sensations, signals like the beating of the heart. Tests of such interoceptive ability are, however, constrained in nature and reliability. Performance of the heartbeat tracking task, a widely used test of cardiac interoception, often corresponds well with individual differences in emotion and cognition, yet is susceptible to reporting bias and influenced by higher order

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... , e.g. of expected heart rate. The present study introduces a new way of assessing cardiac interoceptive ability, focusing on sensitivity to short-term, naturalistic changes in frequency of heartbeats. Results indicate an overall tendency to report fewer heartbeats during accelerations in heart rate. This finding may be driven in part by respiration, with a reduction in heartbeat salience during inspiratory periods when heart rate typically increases. Within-participant performance was also marked by a high degree of variability relative to the heartbeat counting task. Rather than a veridical monitoring of subtle variations in physiology, cardiac interoceptive ability appears to involve interpolation, wherein interoceptive decisions are informed by a dynamic working estimate from, the integration of afferent signalling with higher order predictions.