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Sensing Contrast

Explanations > Perception > The Progression of Perception > Contrast

Description | Example | Discussion | So what?

Description

When we look, listen, smell, taste or touch, contrast is the first thing we seek in order to understand what we are sensing. If we can find contrast, then we can find some thing.

Faced with a blank wall, our eyes desperately hunt for something to latch onto. Contrast is about change. It is about difference. It is the transition from nothing to something, from light to dark, from one thing to another.

Contrast can be sharp, such as in a step change from black to white or silence to loud noise. It can also be gradual, such as in a slow gradient from white through every shade of gray.

Example

Notice how your eye homes in on even this faint area:

Discussion

Contrast is at the root of all perception. If we do not detect change then we perceive nothing. There is an apocryphal tale of a frog, placed in a gently warmed pan of water that eventually gets boiled alive. Yet if the frog is dropped in hot water it will leap out. When the frog cannot contrast the temperature increments, it does not realize it is getting hotter until it is too late.

Without contrast our senses wander, seeking anything of contrast to latch onto. Without contrast, such as in a dark night, we may hallucinate, creating our own perceptual contrasts. Put a person in sensory deprivation tank and they will soon start seeing and hearing things (and the longer they are there, the more real these imaginings become). Perhaps this related to imagination and dreaming. In the dark of nights or daytime musing, our mind needs to perceive something, so it just makes things up.

Visually, contrast is detected in a static image by the differing signals from the optical nerves in our eyes. We will detect a tiny white light in a dark room (though the overload on our optic nerves of all white makes a black dot white harder to see).

Contrast is also detected over time as we compare succeeding mental images. In nature, this is a critical ability for predators who look for movement before static image contrast. The natural camouflage that their prey have evolved weakens the contrast between them and their backgrounds. Yet this advantage is lost when they move, which is why many have learned to freeze all motion.

So what?

So

See also