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Business News/ Opinion / The (new) power of sleep
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The (new) power of sleep

Sleep improves memory and learning. It could also reduce our biases

Photo: iStockPhoto Premium
Photo: iStockPhoto

We are largely—if vaguely—aware of the benefits of a good night’s sleep. For most people anything beyond seven or nine hours keeps you fresh, cheery and alert. The long-term paybacks emerge, many studies show, in terms of a better and longer life.

An extra hour of sleep—of course, the quality of your sleep also matters—may not keep disease at bay, but inadequate sleep is linked to a variety of ailments, from heart attacks to obesity. Your immunity can improve, so can your memory and your sex life.

As science improves its knowledge of the human brain, a surprising new consequence of a good night’s sleep has emerged. A study published on Thursday in the journal Science says that sleep can modify deeply rooted attitudes, such as racial and gender bias—not the removal of prejudice itself, but a lightening of preconceived notions, lead researcher Xioqing Hu told me.

“One direct implication of the study (Unlearning implicit social biases during sleep) is that it opens doors for novel interventions to reduce social biases such as racial prejudice and gender stereotypes," Hu, a postdoctoral fellow at the University of Texas-Austin, US, said in an email interview. “Even the best intentioned of us have pre-existing biases but that doesn’t mean we can’t change." A related study, titled Exploiting sleep to modify bad attitudes, by researchers at the University of Tübingen, Germany, also released on Thursday in Science, indicates the progress in and potential of this line of research.

Scientists know that sleep enhances the formation of memory, rejuvenating gentle neuronal activity, first apparent when a person is awake. In other words, as you sleep, memories and learning grow stronger. Going to sleep shortly after learning new material is most beneficial for recall, a 2012 study found. This is because the brain and the body do not shut down when you sleep. Apart from biological maintenance, the brain works on what you knew and what you know.

Past experiments have shown that this process can apply to subjects who are provided reminders of past experiences. It was one such study that inspired Hu to carry out his own. “Inspired by such studies, I started to think about how to employ sleep to help people reduce social biases," said Hu. With colleagues from Northwestern University, Princeton University and his own university, he has now shown that these techniques work as well on beliefs formed at childhood.

“We show that biases are amenable," said Hu. “However, a good night’s sleep is not enough to change prejudice or stereotypes. What the study showed is actually that sleep and counter-bias memory reactivation led to bias change."

While the researchers studied race and gender biases, would the conclusions hold true for religious biases as well? I asked Hu, specifically with the subcontinent in mind (although racial and gender biases are a big problem as well).

“That would be a great empirical question!" he said. “I do think that our paradigm can be generalized to study the reduction of other types of bias, such as people’s stigma to mental illness. In our findings, we found a similar pattern of bias reduction across racial bias and gender stereotyping."

There is hope, Hu said, that such intervention can work well in reducing religious bias, but he offered a caveat. “One may argue that religious belief lies in one’s core value system, (so) intervention targeting at reducing such bias may be less effective," he said.

Here’s how Hu’s experiment panned out. Participants were first given what is called “counter-stereotype training", meant to reduce their pre-existing stereotypes. Faces were paired with words corresponding to a specific stereotype. For example, they showed participants female faces with words related to mathematics and science; black faces with “pleasant words". Conventional biases do not associate women with mathematics and science and black people with being amiable and friendly.

Participants then took a nap and after they entered deep sleep, the researchers, without waking them, played one of the sounds repeatedly. “When we sleep our brains are still processing sensory information," said Hu. So, these sound cues reactivate the effect of the positive words they heard when awake, the “counter-stereotype training".

“For the bias associated with the sounds that are played during sleep, there is less stereotyping after the nap and when we tested again one week later," said Hu.

The study also found that the longer subjects spent in rapid-eye-movement (REM) sleep—which occurs more than an hour after falling asleep, the period of dreams—and deep sleep (called slow-wave sleep, or SWS), the stronger the bias reduction. This finding, said Hu, is consistent with the hypothesis that REM sleep and SWS are involved with improved learning and stronger memories.

It’s now been about a century since science first discovered that sleep helps people remember. It would be nice if they learned to remember things that made them better people.

Samar Halarnkar is editor of IndiaSpend.org, a data-driven, public-interest journalism, non-profit organisation. He also writes the column Our Daily Bread in Mint Lounge.

Comments are welcome at frontiermail@livemint.com. To read Samar Halarnkar’s previous columns, go to www.livemint.com/frontiermail

Follow Mint Opinion on Twitter at https://twitter.com/Mint_Opinion

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Published: 28 May 2015, 04:00 PM IST
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