Of all features that distinguish man from animals, the most striking and the most complex is his ability to make sense to himself and to others of the world around him. He perceives, learns, thinks, remembers, and communicates in language and symbol to others. The general term used for the study of these abilities is cognition.
Through the senses we receive information about the world around us. We have at least eleven senses, but the five main ones are taste, touch, smell, hearing and sight. Each of these senses supplies a different quality of information about environment, but they normally work in harmony to give us a complex multi-dimensional impression of the world. The brain is the control centre and the nerves resemble message lines, transmitting information from our senses to our brain.
So far we have named the five basic senses but these are not the only means that man has for receiving information. The sense of touch, for example, can be divided into four separate sub-senses of pressure, pain, warmth and cold. Each has its characteristic receptors and there are varying concentrations of receptors in the body. The ends of the fingers have a large number of pressure receptors, but the back of the hand has very few.
Each sense organ responds to energy (the ear to sound energy, the eye to light waves, etc.) which it transforms into nerve impulses. These nerve impulses are sent along nerve fibres in the nervous system to the brain. The nervous system is an intricate set of fibres. There are different pathways for different types of messages. The sensory (afferent) nerve cells and fibres pick up their information from the sense organs and transmit the messages to the spinal cord, which acts as the trunk line for messages to the brain. Messages coming down from the brain are called motor (efferent) impulses and are directed to the muscles which go into action in response to these messages.
Although scientists have been able to discover this specialization of different nerve fibres, they have still a great deal to learn about the nature of nerve 'messages' and how they are coded and dealt with by the brain.
Various areas of the brain specialize in the receipt and translation of the nerve impulses arriving from particular sense organs. The back portion of the cerebrum receives the nerve impulses from the eyes. The top portion takes in the touch senses, and so on.
Apparently, the brain receives and sorts the messages and those that are of little or no use to the person are filtered out. The multitude of noises sounds, smells, which are always around us, are banished, preventing our internal message centres from being clogged up with irrelevant or distracting information. The messages that are useful or important are sorted and translated.
Imagine yourself driving a car, when suddenly the traffic lights turn red. The red traffic light will be transmitted through the eye, stimulating nerve impulses to the brain. A return message from the brain makes you stop the car. Other light stimuli, such as the colour of the sky, other cars, people will be also transmitted through your sense of sight, but the brain will filter them out as being irrelevant to your needs at the moment. It is not known how much of this information is stored away in the brain as a permanent record but it is certain that the brain has an enormous capacity for storage. With about ten thousand million interconnected cells the brain can receive, sort and analyze an enormous amount of material for future reference.
The brain, in short, can be thought of as a complicated control and storage system which depends primarily on sensation for its information
(L.S. Skurnik, F. George. Psychology for Everyman. Penguin Books, 1972. P. 13-18).
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