How we change what others think, feel, believe and do
Perceptual Contrast Effect
When we make decisions, we tend to do it by contrasting between the decision item and reference items. When two things appear close to one another, we will tend to evaluate them against one another more than against a fixed standard.
Sherif, Taub and Hovland (1958) found that when subjects first lifted a heavy weight, they underestimated the weight of lighter weights they were subsequently asked to lift.
When you meet two other people, you are likely to compare each against the other on several dimensions to decide which you prefer. This may include physical beauty, similarity of interests and various personality factors.
A simple physical way of illustrating perceptual contrast is to put one hand into hot water and other into cold water, then move them both to lukewarm water. The cold hand will feel hot and the hot hand will feel cold.
To make something look good, first show something of inferior quality. To get someone to buy something expensive, first show them something even more expensive.
When you make a decision, think about the comparison standards you are using. If it is something you have recently seen, consider whether the person who showed you the first thing is using it for the contrast effect.