Taking time to feel our body: Steady increases in heartbeat perception accuracy and decreases in alexithymia over 9 months of contemplative mental training.

The ability to accurately perceive signals from the body has been shown to be important for physical and psychological health as well as understanding one's emotions. Despite the importance of this skill, often indexed by heartbeat perception accuracy (HBPa), little is known about its malleability. Here, we investigated whether contemplative mental practice can increase HBPa. In the context of a 9-month mental training study, the ReSource Project, two matched cohorts (n = 77 and n = 79) underwent three training modules of 3 months' duration that targeted attentional and interoceptive abilities (Presence module), socio-affective (Affect module), and socio-cognitive (Perspective module) abilities. A third cohort (n = 78) underwent 3 months of practice (Affect module) and a retest control group (n = 84) did not undergo any training. HBPa was measured with a heartbeat tracking task before and after each training module. Emotional awareness was measured by the Toronto Alexithymia Scale (TAS). Participants with TAS scores > 60 at screening were excluded. HBPa was found to increase steadily over the training, with significant and small- to medium-sized effects emerging after 6 months (Cohen's d = .173) and 9 months (d = .273) of mental training. Changes in HBPa were concomitant with and predictive of changes in emotional awareness. Our results suggest that HBPa can indeed be trained through intensive contemplative practice. The effect takes longer than the 8 weeks of typical mindfulness courses to reach meaningful magnitude. These increments in interoceptive accuracy and the related improvements in emotional awareness point to opportunities for improving physical and psychological health through contemplative mental training.