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Reactivating Memories during Sleep Can Reduce Bias

Reactivating Memories during Sleep Can Reduce Bias

A provocative new study suggests a type of training delivered while we sleep may be an effective method to eliminate ingrained bias toward race and gender.

Sadly, many social biases may occur without people realizing they are occurring. For example, when playing a videogame with instructions to shoot only people carrying weapons, players were more likely to shoot unarmed targets when they were Black versus White.

Another form of bias is often demonstrated in hiring decisions. For instance, scientists were more likely to hire males than equally qualified female candidates for research positions.

The new research, to be published in the journal Science, builds on recent findings that discovered memories can be selectively reactivated and strengthened during slumber.

As a result, Northwestern University investigators aimed to find out whether learning to alter habitual reactions to other people could be enhanced during sleep.

In prior studies, a type of training called counter-stereotype training resulted in temporary reductions in this unconscious or implicit bias. The new study examined a strategy to bolster the benefits of this kind of training.

Researchers have recently discovered that memory maybe reactivated during sleep. Generally, participants first hear distinctive sounds during a learning session. A short period of sleep came next. After people woke up, what they could remember was changed if learning-related sounds were presented during sleep.

“We call this Targeted Memory Reactivation, because the sounds played during sleep could produce relatively better memory for information cued during sleep compared to information not cued during sleep,” said Ken Paller, senior author of the study and professor of psychology at Northwestern’s Weinberg College of Arts and Sciences.

“For example, we used this procedure to selectively improve spatial memory, such as learning the locations of a set of objects, and skill memory, like learning to play a melody on a keyboard.”

The current study, to be published in the journal Science, was designed to apply the same sort of procedure to counter-stereotype training.

“This type of learning falls into the category of habit learning,” said Paller, who is also director of the Cognitive Neuroscience Program at Northwestern. “So in addition to spatial learning and skill learning, we can include habit learning as another type of learning that depends on memory processing during sleep.”

Participants in the experiment completed two training regimens, one designed to reduce racial bias and the other gender bias.

In the computerized training tasks, faces were paired with words that ran contrary to a stereotype. For example, female faces appeared with words associated with math or science, and Black faces appeared with pleasant words. There were two distinctive sounds during this training, one that came to be strongly associated with the women+science pairs and the other with the Black+pleasant pairs.

Following the training, participants took a nap. While they were in deep sleep and without their knowledge, one of the sounds was played repeatedly, but with the volume set low enough to avoid disturbing sleep.

The sleep procedure produced the selective benefits that the investigators expected. Bias reduction was stronger for the specific type of training reactivated during sleep. This relative advantage remained one week later.

“It is somewhat surprising that the sleep-based intervention could have an impact that was still apparent one week later,” said Xiaoqing Hu, lead author of the study and a Ph.D. student at Northwestern when he began the study.

“The usual expectation is that a brief, one-time intervention is not strong enough to have a lasting influence. It might be better to use repeated sessions and more extensive training. But our results show how learning, even this type of learning, depends on sleep.”

“Producing lasting changes in implicit biases is challenging,” said Galen V. Bodenhausen, professor of psychology at Northwestern’s Weinberg College, who also co-authored the study.

“These biases arise from long-term socialization, and they are frequently reinforced by the mass media.”

He added that further experiments will need to examine whether these procedures can reduce the impact of implicit biases in important decision-making situations. One implication of the study, Paller said, is that it can broaden the discussion of what sorts of efforts can be made to combat social bias in society.

“Biases can operate even when we have the conscious intention to avoid them,” said Bodenhausen. “We can try to correct for our biases after the fact, but our results point to a more encouraging possibility — reducing the bias in the first place.”

The study also has implications for reducing many other kinds of unwanted social biases and stigmas. Researchers believe unlearning implicit bias may be a lot like breaking other bad habits.

Paller noted that the research also has implications for new techniques to combat habits such as smoking, self-centeredness, phobias, or unhealthy eating behaviors.

Source: Northwestern University/EurekAlert!

Reactivating Memories during Sleep Can Reduce Bias

Rick Nauert PhD

Rick Nauert, PhDDr. Rick Nauert has over 25 years experience in clinical, administrative and academic healthcare. He is currently an associate professor for Rocky Mountain University of Health Professionals doctoral program in health promotion and wellness. Dr. Nauert began his career as a clinical physical therapist and served as a regional manager for a publicly traded multidisciplinary rehabilitation agency for 12 years. He has masters degrees in health-fitness management and healthcare administration and a doctoral degree from The University of Texas at Austin focused on health care informatics, health administration, health education and health policy. His research efforts included the area of telehealth with a specialty in disease management.

APA Reference
Nauert PhD, R. (2018). Reactivating Memories during Sleep Can Reduce Bias. Psych Central. Retrieved on September 27, 2020, from
Scientifically Reviewed
Last updated: 8 Aug 2018 (Originally: 29 May 2015)
Last reviewed: By a member of our scientific advisory board on 8 Aug 2018
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