(Ivanhoe Newswire) -- People who have smaller fingers have a finer sense
of touch, which may explain why women tend to have better tactile acuity than
men.
"Neuroscientists have long known that some people have a better sense of touch
than others, but the reasons for this difference have been mysterious," study
author Daniel Goldreich, PhD, of McMaster University in Ontario, was quoted as
saying. "Our discovery reveals that one important factor in the sense of touch
is finger size."
To learn how finger sensitivity varies, the authors measured index fingertip
size in 100 university students. Each student's tactile acuity was then tested
by pressing progressively narrower parallel grooves against a stationary
fingertip -- the tactile equivalent of the optometrist's eye chart. People with
smaller fingers could discern tighter grooves.
"The difference between the sexes appears to be entirely due to the relative
size of the person's fingertips," Ethan Lerner, MD, Ph.D., of Massachusetts
General Hospital, was quoted as saying. "So, a man with fingertips that are
smaller than a woman's will be more sensitive to touch than the woman."
Tinier digits likely have more closely spaced sensory receptors, the authors
concluded. Several types of sensory receptors line the skin's interior and each
detects a specific kind of outside stimulation. Some receptors, named Merkel
cells, respond to static indentations (like pressing parallel grooves), while
others capture vibrations or movement.
Much like pixels on a screen, each skin receptor sends an aspect of the tactile
image to the brain -- more receptors per inch supply a clearer image. The
authors measured the distance between sweat pores in some of the students,
because Merkel cells cluster around the bases of sweat pores. People with
smaller fingers had greater sweat pore density, which means their receptors are
probably more closely spaced.
"Previous studies from other laboratories suggested that individuals of the same
age have about the same number of vibration receptors in their fingertips.
Smaller fingers would then have more closely spaced vibration receptors,"
Goldreich said. "Our results suggest that this same relationship between finger
size and receptor spacing occurs for the Merkel cells."
SOURCE: The Journal of Neuroscience, December 16, 2009
