The staircase-heartbeat discrimination task (S-HDT).

Cardiac interoceptive accuracy has received significant attention in the growing field of interoception. Despite this, there are clear, and openly discussed limitations to the tasks commonly used to assess this dimension, including questionable construct validity, unjustified assumptions, and that, depending on the task, few participants exceed chance performance. To address this, we propose a novel version of the heartbeat discrimination task. The Staircase-Heartbeat Discrimination Task (S-HDT) addresses the aforementioned limitations and facilitates a more nuanced understanding of individual differences in cardiac interoceptive accuracy. Herein we (i) detail the experimental null, (ii) demonstrate the recoverability of known point of subjective simultaneity and accuracy values by passing simulated data through our analysis pipeline and (iii) highlight the feasibility and tolerability of this task in a young adult sample (n = 42; mean age = 22.57 +/- 4.55; 64.28 % women). In our sample, we show the S-HDT has greater sensitivity and specificity than the original HDT, and enables the prediction of accuracy as well as individuals point of subjective simultaneity. With a running time of ∼30 min, fully automated, open source, and freely available code (via GitHub), this task is accessible to further our understanding of cardiac interoception across multiple interoceptive domains.