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Science and an Afternoon Nap: How consolidating learning can combat implicit biases

Lynn Hull
Apr 18, 2016

Although many people value equality and tolerance, we are repeatedly exposed to social biases though our daily media consumption and other interactions. Those can lead us to have negative, unconscious reactions in opposition to our values. What if science and an afternoon nap could help?

Researchers at Northwestern University published their work on training to reduce implicit racial and gender bias. The study measured participants’ biases using two versions of the Implicit Association Test. In a gender-focused version, participants saw mens’ or womens’ faces paired with either an art or science word. They indicated which combinations they preferred. The more often they preferred a woman’s face along with an art word, the more gender bias. The second version focused on racial biases: white or black faces were shown along with positive or negative words. Participants showed implicit social biases for both gender and race.

With implicit social biases confirmed, the researchers had participants engage in training designed to reduce those biases. During the training session participants had to identify counter-stereotype word/face pairs mixed with stereotypical pairs. When they made the correct response they heard two unusual sounds, one for counter-gender-bias responses and one for counter-racial-bias responses. This training established a strong association between the sound and the unbiased pairs.

After the training, participants took the Implicit Association Test again, and their biases were significantly reduced. But how long would this training last? Previous research has shown that this type of improvement is relatively fragile and short lived, possibly because of the onslaught of biased information people are exposed to throughout the day. The researchers hypothesized that these training sessions might need to go through memory consolidation to take a firmer foothold in the mind. Memory consolidation is the reinforcement process that allows a newly-formed memory to become more permanent in the mind. It is reinforced by sleep, which physically strengthens memories on a protein and cellular level. In order to test the hypothesis that memory consolidation would help reinforce learned improvement in social biases, the researchers invited the participants to take a 90 minute nap in their lab. While sleeping they were repeatedly played either the counter-gender bias sound or the counter-racial bias sound that they heard during their training session.

After the nap participants showed a significant reduction in implicit bias compared to pre-nap testing, but only for the counter-bias they’d heard the sound for. People not exposed to the training sounds during their nap had no difference in their scores after waking up. One week later, the reduction in biases was maintained for people who heard the sound, but the others returned to their baseline levels from before the training session.

The researchers concluded that, while this type of learning reinforcement needs further investigation, it may prove useful is aiding people to change a variety of unwanted or maladaptive habits including unhealthy eating and selfishness. That further investigation will include using methods other than the IAT to measure bias. With only this study, the possibility remains that participants were learning to perform “better” on this specific task, rather than actually reducing their biases.

If you are interested in finding out what implicit biases you may have, you can participate in an online Implicit Associate Test hosted at Harvard. Like GI Joe says, “Knowing is half the battle!”


Image Courtesy of Lance Anderson/

Lynn Hull

Lynn C. Hull, Ph.D. is an Alumni AAAS Science & Technology Fellow who is currently working with the FDA's Center for Tobacco Products. She blogs about innovations in the medical research field. Lynn is interested in drug abuse and addiction research as well as policy dealing with medical access.



This blog does not necessarily reflect the views of AAAS, its Council, Board of Directors, officers, or members. AAAS is not responsible for the accuracy of this material. AAAS has made this material available as a public service, but this does not constitute endorsement by the association.

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