From Our 2009 Archives

More to Fingerprints Than Catching Crooks

Study Shows Fingerprints Help Humans Process Touch

By Bill Hendrick
WebMD Health News

Reviewed By Louise Chang, MD

Jan. 30, 2009 -- Fingerprints didn't evolve to help cops catch crooks, but the intricate swirls on our fingers likely developed as filters to help us process information we get from touch, a new study shows.

An article in the Jan. 29 edition of Sciencexpress says fingerprints send signals to our brains about textures and can detect features as fine as a human hair.

Such an ability would have been important to the survival of our human ancestors, and not just because the textures help us grip objects, according to French researchers led by Julien Schiebert of the CNRS Ecole Normale Superieure research center in Paris.

The researchers set out to investigate how vibrations caused by fingerprint patterns translate into real feelings.

They developed a mechanical sensor covered with a stretchy elastic cap that could be either smooth or ridged, the way fingertips are.

"When the fingerprinted sensor was rubbed across a variety of patterned surfaces, the vibrations that developed had a frequency that certain endings in the skin, called 'Pacinian corpuscles,' are able to detect," according to a Sciencexpress news release. "The fingerprinted surface, but not the smooth one, enabled the nervous system to detect the signal."

The French scientists developed sensors to detect vibrations like those created when fingertips move over a fine surface, or one with texture.

Devices that mimicked fingertip skin covered the sensors. One phony fingertip had ridges similar in distribution and size to those of humans, while another was left completely smooth.

Vibrations detected by sensors of both showed different properties, leading the researchers to hypothesize that fingerprints make our touch-sensing system more efficient. Fingerprints send vibrations that provide clues about what's being touched regardless of the direction the finger is moved, they report.

"The hand is an important means for human interaction with the physical environment," the researchers write in the journal article. "Many of the tasks that the hand can undertake -- such as precision grasping and manipulation of objects, detection of individual defects on smooth surfaces, discrimination of textures -- depend on the exquisite tactile sensitivity of the fingertips."

The perception of coarse textures relies on variations of lines and fingertip textures, according to the researchers. Therefore, they write, fingertip patterns reinforce friction and improve our ability to securely grasp objects.

The findings may prove helpful, according to the study, in designing realistic mechanisms that could be used in "humanoid" robots.

SOURCES: News release, Sciencexpress. Schiebert, J. Sciencexpress, Jan. 29, 2009.

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