Seal It With a Sleep: The Role of Sleep in Reducing Bias

Seal It With a Sleep-Everyone knows sleep is good for us. It’s a time to refresh and recharge, for our bodies to heal and our minds to rest after a busy day. We’ve known for a while that sleep helps with memory consolidation (Walker & Stickgold, 2004); that is, sleep helps the brain organize what it’s learned so it can be better remembered and used in the future. New evidence suggests that sleep can also “seal in” lessons the waking brain learns around reducing racial bias and stereotyping.

In a series of experiments at Northwestern, researchers had people participate in computer-based training designed to reduce implicit biases, those deeply-held stereotypes that even non-prejudiced people tend to know well. While they completed the training, they listened to sounds. Then, the participants slept in the lab. Some of them heard the same sounds playing during sleep that they did during the training, while others did not. One week after spending the night in the lab, the people who had heard the noise while they slept showed weaker implicit bias when they repeated the training (Hu et al., 2015). That is, they better learned to separate the stereotypes from the people. The study suggests a few interesting things about sleep:

  • Good sleep doesn’t just seal in what we’ve learned during the day; our brains are still taking in some level of information that can help make that learning even stronger.
  • The environment where we sleep can help support more than a good night’s rest. An extension of these findings to everyday life might be to listen to specific white noise while studying something, then play the same white noise to sleep that night. It could reinforce daytime learning.

The researchers also point out that similar procedures might be able to help people break other ingrained habits, such as cigarette smoking. In fact, this could be an interesting extension of hypnosis, which some people find useful for quitting tobacco. Hypnosis usually happens while someone is awake, but why not softly play the anti-smoking mantras used during sleep to seal the deal?

I’ll look forward to seeing where this line of research goes. In the meantime, sweet dreams.


Hu, X., et al. (2015). Unlearning implicit social biases during sleep. Science, 384 (6238), 1013-1015. doi: 10.1126/science.aaa3841

Walker, M. P., & Stickgold, R. (2004). Sleep-dependent learning and memory consolidation. Neuron, 44 (1), 121-133. doi: 10.1016/j.neuron.2004.08.031