Contrast Bias

by Craig Shrives

What Is Contrast Bias?

The Quick Answer

In Critical Thinking, contrast bias is allowing one comparison to outrank other comparisons that ought to be made.
Contrast bias, also known as the anchoring and adjustment bias, is a cognitive bias that occurs when individuals overemphasize the differences between two or more objects, events, or stimuli, rather than evaluating them independently. It involves the tendency to judge or perceive something based on its relative contrast to a preceding or simultaneous stimulus.

Here's a short example to illustrate contrast bias:
Imagine you are shopping for a new car. You visit a dealership and test-drive a basic model with standard features. Afterward, the salesperson shows you a higher-end model with additional luxurious features. Due to contrast bias, you might perceive the higher-end model as significantly better than the basic model, even if the additional features are not essential to your needs. The contrast between the two models influences your perception of their value and desirability.
Contrast bias can also be observed in various contexts, such as pricing decisions, product comparisons, or performance evaluations. For instance, when presented with two similar products at different price points, individuals may perceive the more expensive product as higher in quality and value due to the contrast with the cheaper alternative.

This bias occurs because our judgments and perceptions are influenced by the context in which they are presented. We tend to evaluate and compare objects or events based on their relative differences rather than their absolute qualities. As a result, our assessments can be skewed by the contrast effect, leading to biased judgments.

Being aware of contrast bias can help individuals make more objective evaluations and decisions. By consciously considering the absolute qualities and merits of each object or event independently, rather than solely focusing on their relative differences, individuals can reduce the impact of contrast bias and arrive at more accurate assessments.
What is contrast bias?

Easy Definition of Contrast Bias

When ranking things, be sure to consider the whole group. You shouldn't rank something based on just one comparison.

Academic Definition of Contrast Bias

Contrast bias is promoting or demoting something in a large grouping after a single comparison with one of its peers.

An Example of Contrast Bias

Gather your least attractive mates together and go on the pull

contrast bias handsome Average-looking people seem more attractive when alongside those who are less easy on the eye. Imagine an average-looking man was being scored for his looks. When judged independently, he might score 5/10. But, when judged alongside a less attractive person, his score would increase if the judge were suffering from contrast bias. And, it's likely the judge would be.

Contrast bias is extremely common. In a bias-free world, the man would score 5/10 regardless of those around him. But we know it's not. So, if you're looking for love, it really is in your best interest to arrange a night out with a group of your not-so-aesthetically-pleasing friends. In effect, the average level of attractiveness of your group of friends is established as an anchor (see Anchoring Bias) against which observers make a relative judgement.

A Practical Application for Contrast Bias

Create a product that no one will buy and your sales will rocket

I love this sales technique. In his book Predictably Irrational, Dan Ariely offers a great example of how The Economist created an advert to force readers to make a comparison that influenced their buying decisions. At the start, The Economist presented the following advert: Subscription....................$59
(On-line access to all articles for one year)

Print and Web Subscription.....................$125
(1-year subscription to the printed edition and full on-line access)

This advert saw 68% of buyers go for the $59 product and 32% go for the $125 one. Not happy with how their advert was performing, they then presented the advert below. It's the same advert but with a "decoy" added. Subscription....................$59
(On-line access to all articles for 1 year)

Print Subscription...................................$125
(1-year subscription to the printed edition)

Print and Web Subscription.....................$125
(1-year subscription to the printed edition and full on-line access)

What they'd done is force the reader to make a comparison between the first $125 product and the second $125 product. Clearly, the second one was a much better offer. In the minds of the readers, that comparison trumped the real comparison they should have been making, i.e., the one with the $59 product. The sales then went:
  • 16% for the $59 product
  • 0% for the first $125 product (obviously)
  • 84% for the second $125 product
In other words, the decoy (the one in the middle) had caused a rise from 32% to 84% for the $125 product.

You can use this technique too. If you're selling two things and want people to buy your more expensive one, create a decoy that costs the same (or about the same) as your most expensive product but is obviously far poorer value for money. This will force people to make a comparison between your decoy and the most expensive product. That comparison will knock out the real comparison they should make between your cheapest and most expensive products.

Summary of Contrast Bias

If you think someone is ranking something wrongly after making a largely irrelevant comparison, tell them they are suffering from contrast bias.

Critical Thinking Test

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