We Have More Than Five Senses

Every year in January, the Edge Foundation asks noted intellectuals from around the world to answer an "annual question." This year's—"What one scientific concept would improve everybody's cognitive toolkit?"—yielded a host of expectedly fascinating answers (David Pizarro's "Everyday Apophenia" stands out).

Our favorite response, however, belongs to Barry Smith, director of the Institute of Philosophy at the University of London. According to Smith, humans have way more than five senses, and we need to start recognizing that.

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For far too long we have laboured under a faulty conception of the senses. Ask anyone you know how many senses we have and they will probably say five; unless they start talking to you about a sixth sense. But why pick five? What of the sense of balance provided by the vestibular system, telling you whether you are going up or down in a lift, forwards or backwards on a train, or side to side on a boat? What about proprioception that gives you a firm sense of where your limbs are when you close your eyes? What about feeling pain, hot and cold? Are these just part of touch, like feeling velvet or silk? And why think of sensory experiences like seeing, hearing, tasting, touching and smelling as being produced by a single sense?

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Besides an inaccurate view of our number of senses, Smith also argues that people's unwillingness to think of our senses as a concert piece stunts our understanding of them. Consider his take on our sense of taste:

What we call taste is one of the most fascinating case studies for how inaccurate our view of our senses is: it is not produced by the tongue alone but is always an amalgam of taste, touch and smell. Touch contributes to sauces tasting creamy, and other foods tasting chewy, crisp, or stale. The only difference between potato chips, which "taste" fresh or stale, is a difference in texture. The largest part of what we call "taste" is in fact smell in the form of retronasal olfaction, which is why people who lose their ability to smell say they can no longer taste anything.

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If this sounds like hooey, Smith says to think of how, even at the same temperature, a jalapeño will feel hot in the mouth while a mentholated food will feel cool. This, he says, is due to an "irritation of the trigeminal nerve in the face," proof positive that taste and touch are inextricably linked.

photo (cc) via Flickr user woodleywonderworks