PERCEPTION

In a single day, the body’s network of sensory cells sends millions of messages to the brain. Perception is the extraordinary subtle process by which we select and interpret information from those messages.

We know the world around us through our senses. We see the colours of the rainbow, hear the voices of other people, smell burning toast, taste chocolate cake, feel the pressure of a handshake and the stabbing pain of a torn muscle. Our sensations and how we perceive them are made possible through specialized sensory cells in the body, which convert various kinds of energy - light energy, sound energy and so on - into electrical impulses travelling along nerve pathways to the brain. Special areas of the brain then interpret this stream of impulses, and we see, hear, smell, taste, feel.

SENSING AND PERCEIVING

There is a distinction between sensing and perceiving. The sensing process is the collection and transmission of signals to the brain about shape, colour, temperature, noise level, flavour and so on. Perception is the selection and interpretation of vast quantities of information. Some of it is ignored, some of it is noticed depending on our individual personalities and the effect the information has on us at that moment. What each of us sees, hears, touches, tastes, smells and feel is influenced by memory, imagination, experience, learning and expectation, and even our mood. No two people ever perceive the same thing in exactly the same way, because no two people are identical in every detail of their personalities and their lives. We react differently, even in similar situations and circumstances because we are different.

APPEARANCE AND REALITY

Since each of us interprets and makes use of sensory information differently, how can we be sure that what we call reality or the ‘real world’ exists apart from ourselves, and it is not just an illusion of our senses? Can anything be known about the physical world in the way that we know two and two make four?

What the senses are and how they work are subjects covered by human biology; what knowledge is and how we acquire it are the province of philosophy. The bridge between biology and philosophy is provided by perception, the point where the ‘human factor’ enters in. It is how we begin to ‘make sense’ of what our sense tell us.

To some extent, certainly, reality is in the eye, the ear or some other sensory area of the beholder. A group of people describing a scene that is familiar to all of them will each emphasize and also overlook - different details, usually without even realizing that they are doing so, and with no intention to mislead. Painters can deal with the same subject in such different ways that it is sometimes hard to remember that they are, in the strictly sensory meaning of the word, ‘seeing’ the same thing.

In our everyday lives, we generally assume that we all mean more or less the same thing by the same word. If someone says, in greeting, ‘Warm day’, whoever hears the remark knows well enough what it means without first enquiring what range of temperature is covered by; ‘warm’ and whether there is total agreement on where the upper and lower limits of the range lie! But a discussion about a particular colour soon shows that the working agreement on the meaning of words is not much help when any degree of precision is needed, and that one person’s blue is another person’s violet. The mechanism of a healthy eye makes it possible to recognize a particular colour, and when we use the name of the colour, we may all be referring to a perception other hand, we may be using the same word for different perceptions. Science can tell us how we see, but not what we see. Our separate perceptions are like the pieces of a huge jigsaw puzzle: if they fit smoothly together, we like to think that they form a true picture of the world, recognizable to all of us. When there are pieces that will not fit, we can either turn a blind eye to them, or we can simply assume that there are many realities, not just this one.