We often talk that we have five senses as a universal truth. In reality, there may be more or less – it depends on the way you look at the question. Christian Jarrett explains the controversy. All of us know that there are some myths about the brain, such as the idea we only use 10% of our grey matter, but it is notorious, especially among neuroscientists. These myths constantly arise (look at the idea of the Lucy movie this summer). Besides, there are other misconceptions, one of these is the idea that the human brain is served by five senses. This belief is so ingrained that even the scientifically literate will treat it as taken-for-granted common knowledge. The principle of five basic human senses is often traced back to Aristotle’s De Anima (On the Soul), in which he devotes a separate chapter to vision, hearing, touch, smell and taste. Today, the five senses are considered such an elementary truth that it is sometimes used as a point of consensus before writers embark on more mysterious or contentious topics. “What do we actually mean by reality?” asked the author of a recent article in New Scientist magazine. “A straightforward answer is that it means everything that appears to our five senses.” If only it were that simple. Simply defining what we mean by a “sense” leads you down a slippery slope into philosophy. One, somewhat vague, definition might argue that a human sense is simply a unique way for the brain to receive information about the world and the body. If that is the case, then we can claim with confidence that there are certainly more than five human senses. Actually, there is no single, logical way to define the senses. In some ways, it might make little sense to draw divisions between them at all – considering that they often seem to blend together; the colour of food – and even the sounds of a restaurant – can influence taste, for instance. Understanding these relationships is important when studying conditions like synaesthesia and could even shed light on consciousness itself. But whichever way you look at it, five is a pretty arbitrary and meaningless number – a glaring “myth” of the brain that needs further recognition. Indeed, once you start thinking about all the different kinds of information reaching the human brain, you might even find that you develop a brand new sense – a radar-like sensitivity to some of the other misconceptions regarding the way the brain experiences the world. You might have once called it a “sixth sense” – but you know better now, don’t you?
