As human beings we are aware of just five senses – vision, hearing, touch, taste and smell, which we have looked at in some detail in the previous chapters. Are there any others? As we noted in Chapter 9 we do have a subsidiary olfactory sense, the vomeronasal organ, known to be sensitive to pheromones in other mammals. There is still argument about whether human beings do indeed detect pheromones, but the evidence is mounting that we do (§9.3.9). Thus, as we come to the end of the book, we look at other senses which human beings either do not have or senses which have atrophied to the extent that they are no longer accessible to consciousness.

But are there other senses of which we are not aware? If we leave out paranormal phenomena, the only possibility might be some sort of innate navigational system. But in other animals there are documented electrical, magnetic and infrared image sensors. Compared to the other senses discussed previously, these are far less studied. Thus the information estimates in this chapter are considerably less accurate and more speculative than before.

Electrical sense

If you have the misfortune to be chased by a shark, don't bleed! Sharks have an exceptionally acute sense of smell. But even if, wrapped up tight in a wet suit, from whence you omit no detectable odour, the worst may still not be over. Sharks have an electrical sense, able to pick up the electrical signals from animal neural and other activity (Kalmijn, 1971). It gets worse if you bleed – injuries release electrolytes into the water enhancing the electrical activity and the shark uses its electrical sense to home in on the victim at close range (Fields, 2007b).