Saturday, June 29, 2013

Foot tickling: Pain or Pleasure?

Tickling has long been a source of fascination: Socrates, Aristotle, Bacon and Darwin have all had views on its purpose and effects. Darwin claimed that in order for laughter to be elicited, there must be an element of surprise, a pleasant hedonic state. In essence he argued that the tickle was a physical joke. Tickling may not be a laughing matter and recent research indicates although tickling may trigger smiling and giggling it has as much to do with amusement as crying while cutting onions has with sadness.

The tickling process starts simply enough, when receptors transmit the skin sensation along pathways to the brain. Just what the brain does with it remains unclear, although research is helping to identify some of the brain areas involved. Psychologists have found significant differences when tickling was compared to emotional reactions and to humour. Tickling appears to be a physiological function and involuntary way of toughening up vulnerable parts of the body. This would support the evolutionary necessity of rough-and-tumble play in developing children.

One hypothesis is tickling evolved to encourage humans to instinctively protect soft body areas from attack. This would explain why we try to fend off the tickler, whilst appearing to enjoy it. Those who were ticklish had an evolutionary advantage because they were practiced at defending vulnerable areas and laughing gave them more advantage because it encouraged their tormentors to continue. Tickling theorists have established there are two types of tickle, and whether it makes you laugh or not depends on the type of tickle.

Knismesis tickling is a light or feather touch, an annoying sensation or movement across the skin.

Gargalesis is the heavy or laughter-associated tickling. The idea that reactions to tickling are a sign of amusement is based on the assumption that the smiling that occurs during tickling is the same as that during humour. Scientists were keen to explore whether garagalesis tickling was a reaction or reflex or a behaviour. In the research, volunteers were filmed while they were tickled from behind by a researcher for ten seconds. They were also filmed reacting to jokes recorded by comedians and while they put their hand in icy water for as long as they could. At the end of the experiment they answered questions about how they felt in the different conditions. The researchers then looked at the films to assess negative and positive facial expressions.

In particular they looked for the so-called “Duchenne smile” which involves both the smile and a creasing of the skin around the eyes, and which is a response to humour. If volunteers were enjoying the tickle, they would show signs of a Duchenne smile. The results indicate, that when tickled, people did show some Duchenne smiles but they also showed facial expressions associated with pain, including wrinkling of the nose and raising the upper lip. While they were being tickled, they also showed more emotions – pain and smiling compared to when they were listening to the comedian. That, say the researchers, implies that smiling is an automatic response to a stimulus rather than a sign of emotion. The findings suggest ticklish smiling need have no closer a connection to mirth and merriment than crying when cutting onions has to sorrow and sadness. However the exact process that underlies the tickling phenomenon remains an open question.

Knowing the pathways which are involved in tickling helps researchers understand just how the brain works. Information about how the brain is able to separate tickle from self-tickle, for example, may be of use to schizophrenia researchers. Schizophrenics can have difficulty distinguishing external events from self-generated ones, believing, say, that they are being touched when they are not. People with schizophrenia can tickle themselves because the produce realistic hallucinations. They can experience self-tickling with the same intensity as if it were produced by someone else.

Tickling has been used as a torture for centuries and people are warned against heavy foot tickling when engaged in foreplay. Tickling assaults today are more common than reported.

Anatomically the sensory supply to the foot and genitalia sit adjacent in the brain and the theory is neural print through might cause cross association in some people. Hence tickling the feet would be the equivalent to 'tickling their fancy.' Most certainly the nerve supply to the foot passes through the pelvic region and this again may have some peripheral association. Traumatic episodes, such as a ticking assault, could forge behavioural associations where tickling and micturation or sexual arousal including ejaculation, may be linked. Although there are other competing theories behaviouralists believe this is how foot fetishism and shoe restifism arise. It is the nature versus nurture debate.

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