The relative importance to man and animals
It is difficult to grade the senses in relative importance to mankind. Opinions vary particularly between sight and hearing. A person blind from birth has no concept of vision, so presumably does not `miss’ sight. It is different for a person who goes blind because suddenly, or gradually, so much is lost; personal independence to a large degree, driving a car, reading and watching television, enjoyment of all forms of visual beauty. Some of these deprivations can be partially overcome. The loss of sight tends to train a more acute hearing. People will always help the blind in practical ways, and there are many modern aids for the visually handicapped, ranging from braille and books on tape to all kinds of domestic appliances designed for the sightless. Musical appreciation and music making are also open to the blind. Many blind people would grade vision as less important than hearing, since, given help and their own determination, they can live a relatively full life. The obvious drawback to deafness lies in loss of communication, though today there are some marvelous machines which allow the sufferer to learn speech through varied frequencies of vibration. The traditional method of lip-reading supplements this, so that conversation and teaching can be carried out. The social disadvantage of deafness is that of the impatience of others. Deafness is not at once obvious and so may be mistaken for stupidity. In the modern world deafness can also be dangerous; traffic-sense, particularly in children, depends largely on hearing. Touch, taste and smell are all sources of pleasure, the two latter being important in the enjoyment of food, but they are all relatively dispensable. Their absence can, however be dangerous; the loss of nerve endings can lead to severe domestic burns and abrasions, while taste and smell can detect lethal gases and poisonous substances.
From the human point of view most people would grade the importance of the senses in the order given in the question. This is not necessarily so in the animal world. Smell or ‘scent’ is of crucial importance to many animals, which rely on it to detect enemies and to find quarry. Thus it becomes far more highly developed than in humans, since survival may depend on it. For the same reason hearing is of nearly the same importance. The hearing range of animals is much wider than that of humans. Dogs can hear supersonic sounds and react to them at great distances. Many animals have very limited vision, simply because vision is relatively unimportant. Touch and taste are also of less importance to animals than to humans, though, as with humans, these two senses, combined with smell, have a protective role in warning them off obnoxious and poisonous organic and inorganic substances.
Nobody can ask an animal to grade the importance of the senses, but it seems to be, smell, hearing, sight, touch and taste in that order.
