What is a perception bias?

A perception bias is a psychological tendency to lose objectivity in the perception of people and situations. People may believe that they are capable of fairly and accurately evaluating an event, including making judgments about situations, but a number of biases interact with how they perceive events. A classic example arises in eyewitness testimony, which is notoriously unreliable due to perceptual biases that can affect how people remember and talk about the crimes they witness.

The human brain is constantly forced to make quick decisions about situations and people, and has developed various forms of shorthand to quickly arrive at judgments. Some of these contribute to the formation of the perception bias. Cultural and social pressures can increase these biases, coloring the perception even when people think they are being unbiased. These may include the tendency to make assumptions and attributions that are incorrect while believing them to be correct, or believing in logical fallacies.

Psychologists have identified a host of cognitive biases and situations in which they can become active. A very common perception bias is the fundamental attribution error, where people tend to blame circumstances for their own shortcomings, while blaming the failure of others on their personalities. Rather, they believe that their successes are the result of personality, while the successes of others are due to circumstances. This can develop into a situation where a student performs poorly on a test and blames the test environment, while claiming that a student with the same score did not study hard enough.

These biases are often unconscious, which can make them difficult to identify. This can be dangerous in situations where people are expected to behave objectively. Jurors, for example, are heavily influenced by perceptual bias, something lawyers are acutely aware of when preparing to try cases.

Representatives from both sides may try to use perception bias to push their case; a lawyer may appeal to group bias in a defense, for example, appealing to jurors who belong to the same social groups as the defendant. The attorney could represent the defendant as a loyal and loving parent to appeal to other parents on the jury. Meanwhile, the prosecution could take advantage of a bias known as the availability heuristic, in which people base assumptions of probability on the basis of personal or emotional information. You could show a series of violent crime scene images, for example, to prod the jury into an emotional reaction toward the defendant.

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