Tactile distance anisotropy on the tongue.

This article focuses on investigating tactile distance anisotropy—the perceptual bias where tactile distances oriented across body part width are perceived as larger than those oriented along body part length—on the tongue, comparing it to the well-established anisotropy on the hand dorsum. Using a forced-choice judgment task with tactile stimuli, the study found clear anisotropy on both the tongue and hand, with no significant difference in magnitude between the two. These results extend previous findings of tactile distance anisotropy across various body parts to include the tongue, suggesting that such perceptual distortions are widespread and likely arise from central somatosensory processing rather than peripheral innervation differences. Exploratory analyses found no significant correlations between anisotropy on the tongue and traits related to avoidant restrictive food intake disorder (ARFID), hunger levels, or age. The study highlights the need for further research on tactile perception of the tongue in clinical populations and its potential links to swallowing disorders.