Modeling affective touch pleasantness across skin types at the individual level reveals a reliable and stable basic...

Area of Science:

• Neuroscience
• Psychology
• Somatosensation

Background:

• Tactile pleasantness is linked to C-tactile afferent activation at specific velocities.
• Group-level data show an inverted-U relationship between touch velocity and pleasantness.
• Individual-level variations and stability across skin types remain largely unexplored.

Purpose of the Study:

• To investigate the individual-level prevalence, reliability, and stability of the velocity-dependent pleasantness function.
• To examine how skin type (hairy vs. nonhairy) influences this relationship.
• To explore correlations between individual differences (interoceptive accuracy, depression) and the observed tactile pleasantness function.

Main Methods:

• Tested 7 velocities (0.3–27 cm/s) using a soft brush on hairy and nonhairy skin in 123 participants.
• Employed a negative quadratic model to describe the pleasantness-velocity relationship at the individual level.
• Conducted multiple experiments to assess stability across body sites, sessions, and repetitions.

Main Results:

• A negative quadratic model best described individual tactile pleasantness in the majority of participants (62.6–67.1%).
• This quadratic relationship was stable across different body sites, experimental sessions, and touch repetitions.
• Higher interoceptive accuracy correlated with a better model fit, while self-reported depression related to curve steepness.

Conclusions:

• Individual tactile pleasantness perception exhibits a characteristic, stable, and velocity-dependent function across skin types.
• This function demonstrates trait-like characteristics, suggesting individual consistency.
• Affective touch perception may serve as a potential behavioral biomarker for mental health conditions.