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Contrast principle


Principles > Contrast principle

Principle | How it works | So what



We notice difference between things, not absolute measures.

How it works

When we make judgments, evaluating how good a dress or person is, we don't make absolute judgments. The way we judge pretty much anything is in comparison with something else. When we say someone is smart or talkative, we actually mean they are smarter or more talkative than other people. (Note the '-er' at the end of the adjective and the 'more' -- these are sure signs of contrastive words).

Perceptual contrast

Put your left hand in a bowl of cold water and your right in hot water. Leave them there for a while, then plunge both together into a bowl of lukewarm water. Surprise! The left feels hot whilst the right will feel cold. 

This is the principle of Perceptual Contrast by which our senses work. Put light next to dark and it seems lighter. A stale smell will seem worse after a sweet smell. The same effect also applies to more our complex cognitive constructions.


We are not good at selecting from a large group as there are too many contrasts to make. When faced with many candidates for a job or many possible suits to purchase, we will rapidly simplify the decision by breaking things down to a very short shortlist.

Pair-wise comparison

Although we can select from a group of things, we compare best when we have only two things from which to select. In fact one of the reasons that we do reduce choices to a shortlist is that we have less pairs to compare. Even then, we will break things down further, comparing the top two or three, one again another.


When seeking to separate two things, it is easier to differentiate if there is a higher contrast. We hence polarize, pushing our perceptions more towards extremes in order to say 'this is clearly different from that', rather than 'this is a bit different from that'. Living in a black-and-white world is easier, if less accurate, and many hence choose to take extreme views rather than live with uncertainty.

We polarize by selectively amplifying those aspects that will support our position and downplaying or ignoring those which will not. In this way, we create selective distortion.

We do this in particular when separating ourselves (and our friends) from other people, especially if values are involved, as we seek to ensure we are all good and we can project all bad things onto the other person.

Comparing with prototypes and stereotypes

A prototype is an idealized stereotype, both of which use polarized thinking. Sometime the standard against which we judge other things is a prototype that we have constructed. Thus when house-hunting we will compare each residence against a non-existent prototype which has four bedrooms, a large kitchen and so on.

Prototypes, like Frankenstein's monster, are often made up of all the best bits from a wide range of experiences. Thus our prototype house might have our cousin's kitchen, a friend's bathroom and so on.

Comparing with  what is available

If two women are standing side by side, a man will evaluate one against the other, as the other woman is more immediately available than a recalled prototype.

Women, of course, will do the same. In fact we all will tend to use whatever comparators are most available to us at the time of judgment. In our usual lazy mental manner, we are more likely to use the comparator that is easiest to access than one which may be more appropriate. Thus given an unattractive person and an average-looking person, we will judge the average person to be more attractive than if we saw them alone.

Comparing against other people

When evaluating ourselves, the main comparator is other people. We decide how happy, beautiful and so on we are by comparing ourselves with others. In particular we tend to look to peers and people who are 'like us' to compare ourselves against. Thus rich people compare against other rich people (and often feel quite poor as a result!). People for whom being intelligent is important will compare themselves with other clever folks.

A result of this is that being rich, powerful, clever and so on is no predictor of happiness. We may strive for success, but if we change our comparators along the way, we will not seem to have achieved that much.

So what

Contrast is an important principle by which we make decisions. So to persuade something, we can leverage this by paying attention to these comparisons. 

Sales tricks

Sales people will often use the contrast effect by showing you a poor quality product alongside the one that they want you to buy.

They might also show you a wonderful product that is way beyond your reach. When you compare your ideal purchase with this, you are then likely to re-evaluate it upwards. Then when you look at a range of products, you will chose higher up the scale than you might otherwise have done.

They will also sell you add-ons. For example when you buy an expensive car, the optional extras seem very cheap in comparison.

Control the comparator

The overall trick is in controlling the comparator. Once you have identified the decisions that you want them to make, identify the comparator that they may use and then work to replace it with your comparator.

You can make it more available. You can stretch their envelope by making it better or worse than expected. You can also change the priorities, for example getting them to compare first quality instead of cost.

See also

Perceptual Contrast Effect, Social Comparison Theory

Theories about meaning


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