Stereotypes can have an unconscious effect on our behaviour – that is, the stereotypes that we maintain may affect our behaviour without us ever being aware that they are doing so.

One example has been the cases of the shooting of young black males by police in the US, although the men are unarmed. Why do police make this mistake so often? The researchers were inspired by the case of Amidou Diallo, an unarmed African immigrant. He was shot by four police in New York after pulling out his wallet.

Psychologists argue that stereotypes lead to automatic behaviours – and in this case, a fatal behaviour.

One of the tests that has been designed to determine the unconscious influence of stereotyping is the IAT – the Implicit Association Test.  The test is described below in the procedure, but you may want to take a version of the test very similar to the procedure below before you read the study.  Go to this page and choose “Weapons IAT.”

Payne et al used a sample of 32 non-Black undergraduates – including 25 women and 7 men. The participants were given the IAT with two black male and two white male faces; four photographs of hand tools (2 types of pliers, wrench, drill) and four photographs of guns.

The participants first did a practice round with 48 trials just identifying tools vs. weapons, without the faces.  This was to make sure that the participants were familiar with the keyboard and how to take the test, as well as able to identify the different images.  Error rates were nearly zero.

In the next round, the participants were told that the test tested their speed and accuracy. They were told that they would see a face briefly flashed on the monitor, followed by a second image. They were instructed to indicate whether the second image was a weapon or a tool by pressing keys on the computer. They were given 500 milliseconds to respond before they were locked out of the screen. Each participant carried out 192 trials.

The rate of errors was 29%; the participants misidentified tools more often than misidentifying weapons.  In addition, participants were more likely to incorrectly identify a tool as a gun when the target was primed with a Black face, compared to a White face. The race of the prime did not affect the likelihood of misperceiving the gun as a tool.

A pilot study was done with the same procedure, but without the time pressure; the error rate was only 6% with no clear evidence of the effect of the stereotype. It appears that time pressure – a form of high cognitive load – played a key role in why the stereotype had such an effect.

The study is highly artificial and has low ecological validity.  It is not clear if this reflects what actually happens in the field.

The study has high internal validity and may be replicated to determine the reliability of the results.

The participants carried out many trials.  It is possible that fatigue effects are responsible for the results.  But this is why it is important to compare this data to the pilot study, in which such effects did not play a significant role.