Sleep can help repair prejudices

Learning new stuff takes sleep. Robbed of the restorative balm of slumber, research shows that the human brain will quickly lose its ability to make and hold on to new memories, and learning takes a dive.

A new study, however, finds that sleep is also crucial to unlearning stuff that we may have committed to memory without a proper quality-control check.

Implicit biases — those stereotypes about gender, race, age and ethnicity that you might never own up to but which nevertheless colour your reactions to people and situations — are laid down early, and they are surprisingly hard to break.

In a study published Thursday in Science, psychologists from Northwestern University note that although a systematic retraining session can begin to undo implicit biases, its effect is fragile and fleeting. With just a nudge — a news report, a personal interaction that supports a long-held implicit bias or just the passage of time — the effects of training aimed at countering such unconscious prejudice disappear.

The new research finds, however, that adding sleep to the mix — and subtly reinforcing the retraining during subsequent sleep — helped stamp out implicit bias robustly and enduringly in experimental subjects. When participants slept soundly after viewing a series of images designed to counter implicit bias, and got a subtle reminder of that learning during their sleep, their implicit biases were more clearly unlearned. And those prejudices stay unlearned for longer, the study found.

The results suggest that harnessing sleep to the task — and reinforcing such learning with associated sounds, smells or sensations during sleep — might ease the challenge of changing hearts and minds.

“Perhaps novel sleep manipulations could be adapted to aid people in changing various unwanted or maladaptive habits, such as smoking, unhealthy eating, catastrophizing, or selfishness,” the authors write.