What is a Contrast Effect?

Mary McMahon
Mary McMahon

The contrast effect is a phenomenon where people perceive greater or lesser differences than are actually present as a result of prior or simultaneous exposure to something with similar base characteristics, but different key qualities. In a simple example of how the contrast effect works with vision, a researcher can present a subject with a dark square and a light square, each enclosing a smaller square. Even if the smaller squares are actually the same color, the contrast effect will lead the viewer to think the square against the dark background is lighter than the one against the light background.

Visual perception may be skewed by the contrast effect.
Visual perception may be skewed by the contrast effect.

Visual perception is not the only thing the contrast effect can skew. This can also occur with human cognition, in an example of a cognitive bias. A teaching assistant might grade a mediocre essay more harshly after reading a very good writing sample, for example. People can utilize this effect in sales. A coffin salesperson can show people the same medium-range coffin in the midst of low-end products and high-end products, and they will perceive it differently depending on the surrounding comparison samples. This may encourage people to spend more than they would otherwise.

A teacher who grades a mediocre essay more harshly after reading an exceptional essay is experiencing cognitive bias.
A teacher who grades a mediocre essay more harshly after reading an exceptional essay is experiencing cognitive bias.

In the positive contrast effect, people will perceive something as better than it is as a result of exposure to a worse comparison sample, while in the negative version, people will think something is worse because they have a better comparison sample. This cognitive bias is extremely difficult to overcome, as it is naturally engrained in the brain and the way people think about and perceive the world around them.

Awareness of the contrast effect can lead people to try and take steps to compensate for it. In grading, for instance, people have a rubric they can use to create a more objective standard, and a teaching assistant may take a random sample of papers with various grades and ask another assistant to look them over and make sure the grades are fair. Concerns about visual contrast are especially important with signs and graphic design, where colors can appear abnormal depending on their surroundings and how people handle them.

Like other cognitive biases, the contrast effect can explain some seemingly contradictory human behaviors, and it is an important part of human psychology. People may engage in activities against their own best interests as a result of these biases, and could also do things that seem out of character, like spending more on a purchase than originally planned because of clever sales tactics exploiting known psychological vulnerabilities.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


I really love those eye tricks where they do things like this. There are a lot of very good sites online where you can find them.

I've also heard you can use this trick to help you eat less. If you put food on a smaller plate, it looks like there is more food by comparison and you actually feel fuller after eating it. If you put the same amount of food on a huge plate and you can see all the empty plate there, it looks like less food and you won't feel as full after.


@croydon - It's not all bad though. You can use that kind of contrast effect to get people to work harder. For example, I'm a writer and I try to make sure that if I'm editing my own work, that I'm also reading a book that I consider to be very good.

It tends to make me harder on my own work, which is really good. If I was reading something light and fluffy, I might see my work as better in comparison and not be so hard on it. And my work would ultimately suffer.


This kind of cognitive bias is so important to watch for in teaching, particularly, because it can lead to kids being treated unfairly and in a way that leads them to do worse and worse in their grades. It's a well documented fact that if a teacher thinks a child isn't smart, the child's grades gradually get worse to reflect this belief (and the opposite is also true).

So, if you've got a teacher who is comparing the whole class to a few bright students, they are all going to suffer.

As long as the teacher is aware that this is a possibility and tries to adjust for it, the kids will be OK.

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