Ren Palmer

Despite concerns regarding its validity, the two-alternative forced choice heartbeat detection task (2AFC-HDT) is a frequently used measure of cardiac interoceptive accuracy. In this task participants must decide whether a series of tones occur synchronously with their heartbeats. One series of tones is predefined by the researcher as synchronous with heartbeats, and one series predefined as asynchronous. The 2AFC-HDT may result in individuals judged to be not interoceptive when they are, either if participants perceive their heartbeats as occurring synchronously with tones predefined as asynchronous rather than synchronous with their heartbeats, or if they do not perceive either set of tones as synchronous. Currently, there is little data on the proportion of participants this may affect. We addressed this using data from the Phase Adjustment Task (PAT) – a measure of cardiac interoceptive accuracy that determines if, and when in the cardiac cycle, a participant can perceive their heartbeat. The timing of heartbeat perception in 43 interoceptive participants was compared to the timing of synchronous and asynchronous tones used in the 2AFC-HDT assuming temporal precision of 50, 100, and 150ms. Results suggest that between 53.5%-97.7% of delay-based interoceptive individuals perceive heartbeats at a delay that does not correspond to the typical asynchronous or synchronous delays used to present tones on the 2AFC-HDT. These issues suggest that the 2AFC-HDT (or other measures that make assumptions about perceived timing of heartbeats) should not be used to measure cardiac interoceptive accuracy, or cardiac interoceptive insight (also known as awareness or metacognition).  

Interoceptive accuracy, the ability to correctly perceive internal body signals such as heartbeats, has been empirically and theoretically linked to stress. However, issues with the measurement of both interoceptive accuracy and stress have led to lack of clarity regarding this relationship. This systematic review and meta-analysis aimed to clarify whether interoceptive accuracy is associated with different facets of stress, including - physical, cognitive and self-reported stressors and the physiological stress response. A systematic search identified 2014 abstracts. Twenty-eight authors were contacted to request data for eligible studies, which yielded a final sample of 20 studies. Results revealed a positive association between heartbeat counting task (HCT) performance and acute physical stressors, and a negative association between HCT performance and physiological stress responses. No significant relationships were observed between stress and interoceptive accuracy assessed by the heartbeat discrimination task. While these findings offer tentative support for stress–interoceptive accuracy associations, they must be interpreted with caution given substantial heterogeneity in stress measures, limited use of interoception tasks beyond the HCT, and ongoing concerns regarding task validity. Implications for future research and methodological recommendations are discussed.

Interoception is broadly defined as the processing of internal bodily states at multiple conscious and preconscious levels (Brewer et al., 2021). Because of the breadth of this construct, many measures exist to probe individual differences in interoception (Desmedt et al., 2023; Khalsa et al., 2018). Measures of interoception can be separated into different domains (e.g., cardiac, respiratory, gastric) and dimensions (e.g., accuracy, attention). Some of the most assessed domains of interoception, and associated measures, are reviewed below. We focus on interoceptive accuracy, as well as self-reported, implicit and neural measures of interoception, however, it should be noted that there are many other dimensions (Khalsa et al., 2018). Specific considerations for the measurement of stress alongside interoception are provided.