Self-tickle

[TempstofLaughtr]

Knismesis may in fact represent a vestige
Vestigial structure

Vestigiality describes homology character of organisms which have seemingly lost all or most of their original function in a species through evolution....
of the primitive grooming response, in effect; knismesis serves as a “non-self detector” and protects the subject against foreign objects. Perhaps due to the importance of knismesis in protection, this type of tickle is not dependent on the element of surprise
Surprise

Surprise may refer to:...
and it is possible for one to induce self-knismesis, by light touching. One known way is by gently touching the roof of your mouth with a fingertip.

Gargalesis, on the other hand, produces an odd phenomenon, when a person touches “ticklish” body parts on their own bodies, most people measure no tickling sensation. It is thought that the tickling requires a certain amount of surprise, and because tickling one’s self produces no unexpected motion on the skin, the response is not activated. A recent analysis of the “self-tickle” response has been addressed using MRI technology. Blakemore and colleagues have investigated how the brain
Brain

The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as cnidarian and echinoderm have a decentralized nervous system without a brain, while sponges lack any nervous system at all....
distinguishes between sensations we create for ourselves and sensations others create for us. When the subjects used a joystick
Joystick

A joystick is an input device consisting of a stick that pivots on a base and reports its angle or direction to the device it is controlling. Joysticks are often used to control video games, and usually have one or more push-buttons whose state can also be read by the computer....
to control a "tickling robot", they could not make themselves laugh. This suggested that when a person tries to tickle him- or herself, the cerebellum
Cerebellum

The cerebellum is a region of the brain that plays an important role in the integration of perception, coordination and motoneuron control. In order to coordinate motor control, there are many neural pathways linking the cerebellum with the cerebrum motor cortex and the spinocerebellar tract ....
sends to the somatosensory cortex precise information on the position of the tickling target and therefore what sensation to expect. Apparently an unknown cortical
Cerebral cortex

The cerebral cortex is a structure within the brain that plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness....
mechanism then decreases or inhibits the tickling sensation. A small percentage of people however, have found it possible to tickle themselves.

MUCH AGREED! I try tickling myself (no mechanics just natural fingers) sometimes because my bf is out of town and it sometimes works but most times it doesn't. Recently I've been using an electric foot scrubber and oh man let me tell you. WHOA! haha