Some people are ticklish and others (like myself) are not. I have always wondered why that is, so I figured I would take the time to finally look it up and let you guys know too. But first, here is a super cute video of Cookie the penguin being ticked.
Ok, back to work. Upon first doing the research I found that there is very little on the topic of why people are ticklish. More has apparently been done on why people laugh when they are tickled. What I did seem to find, however, is that tickling or being tickled is a form of social bonding. Generally speaking this social bond is amongst individuals you know well. I mean it would be kind of awkward to go up to someone you don't know so well and start tickling them. Would anyone ever randomly tickle Dr. Read? Insert awkward turtle here:
Some people are also more sensitive to touch than others which helps to explain things a bit. The sense of touch has varying levels of sensitivity just as the sense of sound, smell or taste. For some people blasting music is the way they choose to listen to it, but for others this volume may be way too loud. The same goes for the level of spiciness of foods or scent of a flower for instance. Heightened senses exist and the sense of touch is no different. Scientists believe that this is due to our evolutionary history. Hunting and protecting ourselves and family requires these sense to be on and ready for anything.
The areas of the brain that are responsible for the tickle sensation are the primary somatosensory cortex and secondary somatosensory cortex. It has also been found that these areas of the brain are activated upon an anticipated tickle. Scientists feel that this is a response mechanism that we developed to protect ourselves against danger. The brain is able to sense stimuli prior to the body being touched, which coincides with people having "cat-like reflexes."
Well, I started with a cute tickling video so I might as well end with one too :D