For many, tickling may seem like the most useless of bodily functions. It serves no obvious purpose, except to entertain some and petrify others.
While not everyone is ticklish, and the places on the body that are most sensitive often vary, there does seem to be some common ground.
Think about it: what areas of the body are most often ticklish to everyone? The neck and the ribs. As noted by psychiatrist Donald Black of the University of Iowa, these particular areas are not only associated with tickling, but are also the most vulnerable in combat.
Tickling is a practice seen predominantly in children, and so Black suggested that tickling is an evolutionary technique that teaches children to protect their weakest parts during tickle fights in preparation for genuine combat. However, this theory does not explain why areas such as the feet are also highly ticklish.
Instead, neuroscientist Robert R. Provine of the University of Maryland suggests that the purpose of tickling is to build interpersonal relationships. The laughter babies produce within the first few months of their life in response to tickling is one of the first forms of communication that occurs between infant and caregiver. Parents become conditioned to associate tickling their baby with laughter, and only continue to do so when they get a positive response. This causes a bond to form between the caregiver and child, as they both leave the interaction feeling satisfied from the response from the other. This theory also explains why we laugh when tickled, and why we can’t tickle ourselves (as cited in Wolchover, 2013).
However, Provine does not explain why many find tickling so unpleasant, as surely if it were meant to form positive associations between people then we would enjoy it a little more?
There has been research to suggest that the purpose of tickling has nothing to do with forming bonds through positive reinforcement. Psychologists at the University of San Diego, California found that, contrary to popular belief, the laughter response to tickling has nothing to do with human contact. In this experiment, 34 students (20 male and 14 female) with their ages ranging from 18-28 were asked to sit in a chair in front of a “tickle machine” and were told that they would be tickled twice – once by the experimenter and once by the machine. The participants wore earplugs and a blindfold to block out their senses, after being told that they needed to pay close attention to the tickling. This, however was all lies. In actuality, the tickle machine did nothing at all. Instead, the researcher tickled the participant both times in order to simulate the normal physical stimulation while leaving the participant with the impression that they were being tickled by a machine (Harris & Christenfeld, 1999).
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If tickling’s only purpose were to develop interpersonal relationships between humans, then when the participants were supposedly being tickled by the machine they would not of had a response. However, the results of this study showed that the subjects smiled, laughed, and wiggled, both times when they were being tickled. This suggests that tickling’s purpose is not to aid attachment between child and caregiver, and that instead we laugh just because the sensation makes us do so.
What, then, is the true purpose of tickling? Is it just an evolutionary mistake, or something else that these psychologists are missing entirely? What do you think?
Harris, C. R., & Christenfeld, N. (1999). Can a machine tickle? Psychonomic Bulletin & Review, 6(3), 504-510. doi:10.3758/BF03210841
UCSD psychologists tackle ticklish subject. (1997, January 31). Retrieved from http://www.newswise.com/articles/ucsd-psychologists-tackle-ticklish-subject
Wolchover, N. (2013, August 12). FYI: what is the evolutionary purpose of tickling? Retrieved from http://www.popsci.com/science/article/2010-12/fyi-what-evolutionary-purpose-tickling
Edited by: Zoe