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A perception bias is a psychological tendency to lose objectivity in perception of people and situations. People may believe they are able to evaluate an event fairly and accurately, including making judgments about situations, but a number of biases interact with the way they perceive events. One classic example comes up in eyewitness testimony, which is notoriously unreliable because of perception biases that can affect the way people remember and talk about the crimes they witness.
The human brain is constantly forced to make rapid decisions about situations and people, and has developed a number of forms of shorthand to quickly arrive at judgments. Some of these contribute to the formation of perception bias. Cultural and social pressures can add to these biases, coloring perception even when people think they are being impartial. These can include tendency to make assumptions and attributions that are incorrect while believing they are right, or believing in logical fallacies.
Psychologists have identified a large number of cognitive biases and situations where they can become active. One very common perception bias is the fundamental attribution error, where people tend to blame circumstances for their own failings, while blaming the failure of others on their personalities. Conversely, they believe their successes are the result of personality, while successes on the part of others are because of circumstances. This can play out in a situation like a student doing poorly on a test and blaming the testing environment, while claiming that a student with the same score didn’t study hard enough.
These biases are usually unconscious, which can make them hard for people to identify. This can be dangerous in situations where people are expected to behave objectively. Members of a jury, for instance, are heavily influenced by perception bias, something attorneys are well aware of when they prepare to try cases.
Representatives of both sides may attempt to utilize perception bias to push their case; an attorney might appeal to ingroup bias in a defense, for example, appealing to members of the jury who belong to the same social groups as the defendant. The attorney might depict the defendant as a loyal and loving father to appeal to other fathers on the jury. Meanwhile, the prosecution could take advantage of a bias known as the availability heuristic, where people base assumptions of probability on the basis of personal or emotional information. It could show a series of violent images from the crime scene, for instance, to push the jury into an emotional reaction to the defendant.