I love getting my joke of the day. Today’s jokes were on true hospital discharge charts. “Patient has two teenage children but no other abnormalities!” and Discharge status: Alive but without my permission!” I mention this because science has found that the parts of the frontal lobe of the brain stimulated by tickling are the same parts of the brain involved in 1-emotions produced by a funny situation, 2-cognitive activity (the “getting it” part of a joke, and 3-motor function (moving the muscles of the face) to smile.
Laughter and tickling are actually complex interactions between signals from nerve fibers associated with both pain and touch, and the brain. There are two types of tickling. The scientific terms are knismesis and gargalesis. Knismesis is the light feather like touch that doesn’t cause laughter but mild pleasure and sometimes an itching sensation (your body knows when a bug is crawling on it). It’s gargalesis, the heavier touch, that works on humans and primates to cause laughter.
The tricky part about tickling and the subsequent laughter is the inability to tickle oneself. Reach down and tickle your feet. Nothing! Ever hear a funny joke for the fourth time? Nothing! At best a polite smile. The information being sent to your brain is the same, but why the difference in reaction? In order to laugh after a joke or tickling the brain needs to be stimulated by the combination of tension and surprise. There’s evidence that when a person tries to tickle themselves the cerebellums sends to the somatosensory cortex information and what sensation to expect. The cortical mechanism that decreases and inhibits the tickling and laughing sensation is still unknown.
Not everyone laughs when tickled. Tickling by strangers is considered hostile, inappropriate, and sometimes sexually aggressive. There needs to be a relationship between tickler and the one being tickled. The study of laughter and its health benefits has become a subject of serious scientific inquiry. It has it’s own name: gelotology. Laughter increases blood pressure, heart rate, changes breathing patterns, reduces certain neurochemicals, and provides a boost to the immune system Another field of research called psychoneuroimmunology studies the interaction between the immune system and the brain. Laughter has been shown to change the autonomic nervous system and alter stress and neurotransmitter levels. Laughter has also been shown to cause reductions in levels of cortisol, growth hormone, and catecholamines. The tickling and subsequent laughing between parents and children, siblings, and lovers help establish intimacy, cement social bonding and decrease aggression.