Altered interoceptive beliefs in alexithymia: Dissociating bias and precision using the heart rate discrimination task

Alexithymia has been widely associated with altered interoception, yet empirical findings remain inconsistent, partly because prior research has insufficiently examined the multidimensional components of interoception. This study aimed to provide a more comprehensive understanding of the relationship between alexithymia and interoception by independently examining the associations on interoceptive sensibility and interoceptive belief with alexithymia, while controlling for depression and trait anxiety. 86 undergraduate and graduate students completed questionnaires assessing alexithymia, interoceptive sensibility, depression, anxiety, and autistic traits. Interoceptive belief was measured using the Heart Rate Discrimination task, which provides psychophysical estimates of bias and precision in cardiac interoceptive judgements, alongside an exteroceptive condition. Results showed that alexithymia was selectively related to altered interoceptive belief. Difficulty describing feelings was associated with biased overestimation of cardiac activity, whereas externally oriented thinking was associated with reduced precision, indicating greater uncertainty in interoceptive belief. Path analysis further showed that reduced precision in interoceptive belief uniquely predicted externally oriented thinking, independent of depressive and anxiety symptoms. Interoceptive sensibility was evaluated using the Japanese version of the Multidimensional Assessment on Interoceptive Awareness. Results indicated that higher levels of alexithymia were associated with reduced adaptive interoceptive sensibility across multiple dimensions of bodily awareness. These findings suggest that while diminished interoceptive sensibility characterizes the subjective experience of alexithymia, altered interoceptive belief plays a more proximal role in its cognitive core, highlighting the importance of belief-based mechanisms in emotional inference.