There are senses which we use to explore the world immediately around us – just outside our bodies and also on or within our bodies. Somatosenses respond to: pressure temperature vibration information signalling dangers to our bodies (e.g. cuts and abrasions, corrosive chemicals, extreme heat, electrical discharges) possible problems inside our bodies
Exploring through touch
Our skin contains nerve endings which can detect sources of energy. Some parts of our bodies, such as our fingers, have a higher density of nerve endings than other parts, and so fingers and hands are used in active exploration of the world immediately around us. Mostly, this is to corroborate information that is also provided by other senses, such as vision; but of course we can still touch things without seeing them. I recently played a game with some friends in New York, where there is a park with small statues of weird objects. We closed our eyes, were led to a statue, and had to tell what it was. Through active exploration lasting many minutes, we were able to give a pretty precise description of the object, but it was still a big surprise to actually see it when we opened our eyes. This experiment shows that the sense of touch can be used to give a pretty good image of what an object is, but the information takes time to build up. Also, for the process to work efficiently, we need a memory for things that we have experienced before – in this case, a tactile memory. Sensing pain and discomfort The same nerve endings that respond to mechanical pressure and allow this kind of tactile exploration also respond to temperature and any substances or events that cause damage to the skin, such as cuts, abrasions, corrosive chemicals or electric shock. The sensation of pain associated with such events usually initiates a response of rapid withdrawal from the thing causing the pain. There are similar nerve endings inside our bodies, which enable us to sense various kinds of ‘warning signals’ from within. An example of this is that dreadful ‘morning-after’ syndrome, comprising headache, stomach ache and all the other cues that try to persuade us to change our lifestyle before we damage ourselves too much!