Interpersonal stroking touch is targeted to C tactile afferent activation

Area of Science:

• Neuroscience
• Psychology
• Somatic Sensory Science

Background:

• C tactile fibers are specialized nerve fibers in non-glabrous skin.
• These fibers respond optimally to light, gentle stroking at velocities of 1–10 cm/s.
• C tactile fibers contribute to pleasant sensations during social touch and caressing.

Purpose of the Study:

• To investigate whether humans spontaneously apply touch velocities that optimally activate C tactile fibers.
• To compare stroking velocities across different social touch contexts.

Main Methods:

• Three studies were conducted involving participants stroking an artificial arm, a partner, or a baby.
• Stroking velocity was objectively measured in all conditions.
• Participant demographics (age, sex) were recorded.

Main Results:

• Stroking velocities were significantly slower when participants touched a partner or baby compared to an artificial arm.
• All participants stroking a partner or baby utilized velocities within the optimal range for activating C tactile fibers.
• The findings indicate a difference in spontaneous stroking speeds based on the recipient of the touch.

Conclusions:

• Human social stroking, particularly in intimate contexts, appears to be naturally optimized for C tactile fiber stimulation.
• This optimization likely contributes to the pleasant affective experience of social touch.
• The study provides evidence for the role of C tactile afferents in mediating the rewarding aspects of human social interaction.