Sensation and perception.

Essay by chattering_loryA-, April 2003

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Sensation and Perception

Evaluate These Statements

1.Colour television could produce better quality colour if they used more than three primary colours. (false)

When we are watching television, light rays of different wavelengths enter our eyes. Among the three primary colours of red, green and blue, the mixture of lights occurs in our eyes. It is an additive mixture instead of a subtractive mixture. The three kinds of wavelengths are combined in different proportions to produce almost any colour of lights. So light of other colours is useless to combine more colours.

According to the Trichomatic theory, there are three kinds of receptors, short receptors, medium receptors and long receptors, on our retina which are stimulated by the three primary colours, red, green and blue respectively. The quality of the colour is coded by the pattern of activity of the three receptors rather than by specific receptors for each colour.

So the receptors would function in the same way with or without a new primary colour presented.

2.What we perceive to exist is what actually exists. (debatable)

Perception involves both bottom-up process and top-down process.

For example, for pattern recognition, according to the Template theory, the Prototype-Matching Theory and the Pendemonium Theory, which are related to data-driven processing, we recognize patterns relying on basic, simple, physical features. We see what falls on our retina. Features detection comes first, matching follows and then recognition is done.

However, perception is also a conceptually-driven process. We use our concepts such as knowledge, context, schema and past experience to shape our perceptions. We set up a hypothesis first, then we actively search for evidence to support it. For instance, when we see a moving object in a field, we may perceive that it is a cow even though we cannot see it...