Abstract
Interoceptive accuracy plays a central role in theories of emotion, and atypical interoceptive accuracy is increasingly recognized as a feature in the pathophysiology of multiple clinical and subclinical conditions. However, existing methods for assessing interoceptive accuracy have limitations that may constrain research progress. This study presents the first electrocardiogram‐based implementation of the phase adjustment task (PAT‐ECG), a rigorous measure of cardiac interoceptive accuracy, and provides the materials and experimental code for its use. Similar to existing PAT implementations, the task presents tones at each participant's heart rate and requires them to adjust the phase of the tone to synchronize it with their heartbeats. Crucially, this implementation replaces the photoplethysmographic signal used in previous implementations with ECG, enabling superior temporal resolution and more precise triggering via the R‐wave peak. We additionally introduce a novel phase‐delay timing procedure during task execution and explore new data‐analytic approaches. Data from 91 participants are used to demonstrate the task, and eight options for classifying individuals as interoceptive or non‐interoceptive are evaluated. Seventeen percent of participants were classified as interoceptive at rest via PAT‐ECG. Findings extend evidence for distinct variable‐period and fixed‐period interoceptive pathways. Weighting trials by confidence ratings further influenced interoceptive accuracy scores. The original PAT represented a significant advancement in cardiac interoceptive accuracy assessment; this open‐access ECG‐based implementation extends PAT methodological precision, providing an even more rigorous assessment tool for further advancing interoception theories and research. Accurate measurement remains a central challenge in interoception research. This study advances the field by introducing the first electrocardiogram‐based phase adjustment task (PAT‐ECG), offering superior precision to existing PAT implementations alongside novel implementation and analytic options. Findings extend evidence for distinct interoceptive pathways and highlight how analytic choices shape classification outcomes. PAT‐ECG is provided as an open‐source tool to support the next generation of rigorous and precise interoception research.