Sleep therapy could be an effective tool for fighting race and gender bias in our society.

Past research has shown temporary reductions in unconscious or implicit bias as a result of what is called "counter-stereotype training," Northwestern University reported. This new research looked for ways to boost the benefits of the equality-based brain training.

In the method, patients are exposed to distinctive sounds followed by a short period of sleep. What the participants could remember was found to be influenced if the learning-related sounds were also played 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 researchers investigate whether the habit-changing method could also reduce biases. Participants were given computerized training tasks in which faces were paired with words that were the opposite of the visual stereotype. For example, women's faces were paired with words such as "science." A distinctive sound was played when these contrasting stereotypes were shown, and this sound was also played quietly while they slept without their knowledge. They found that through this method bias could be reduced, and the effects were still present 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."

The findings were published in a recent edition of the journal Science