Just thinking you had a good night’s sleep can improve cognitive skills

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Sleep ‘placebo’ improves brain function, researchers have found

Heather Saul

Thursday, 23 January 2014
Just thinking you had a better night sleep creates a placebo effect that can improve your cognitive abilities, a new study has found.

Researchers at Colorado College found students who were told they had a good night’s sleep, even if they did not, performed better on attention and memory skill tests than those who had been informed they had slept badly.

Research led by Christina Draganich and Colorado College Psychology Professor Kristi Erdal involved 164 students who were told a new technique, which does not actually exist, would be used to measure their sleep pattern from the night before.

Researchers randomly split participants into “above average” quality sleep and “below average” quality sleep groups. Students in both groups were also given a five minute talk on sleep quality and how important it is for cognitive function. They were told the average proportion of REM sleep a night was between 20 and 20 per cent.

Participants were then connected to a machine they were told would measure their brainwave frequency and shown spreadsheets and formulas.

sleep-research-creative

Those in the “above average” sleep quality condition were told by researchers they had spent 28.7 per cent of their total sleep time in REM, whereas those in the “below average” sleep quality condition were informed that they had only spent 16.2 per cent of their time in REM sleep.

The students who were told they got a good night’s sleep performed significantly better in the Paced Auditory Serial Addition Test, a cognitive exercise which measured their ability to listen and process information.

The authors say what the students were told about their sleep is known as “placebo sleep.” The effect of that information was a placebo effect, which has to do with the person’s mindset regarding his or her treatment.

They concluded: “These findings supported the hypothesis that mindset can influence cognitive states in both positive and negative directions, suggesting a means of controlling one’s health and cognition.”

The study Placebo Sleep Affects Cognitive Functioning is published in the Journal of Experimental Psychology: Learning, Memory and Cognition.

Placebo sleep affects cognitive functioning.
Draganich C, Erdal K.

Abstract
The placebo effect is any outcome that is not attributed to a specific treatment but rather to an individual’s mindset (Benson & Friedman, 1996). This phenomenon can extend beyond its typical use in pharmaceutical drugs to involve aspects of everyday life, such as the effect of sleep on cognitive functioning. In 2 studies examining whether perceived sleep quality affects cognitive functioning, 164 participants reported their previous night’s sleep quality. They were then randomly assigned to 1 of 2 sleep quality conditions or 2 control conditions. Those in the “above average” sleep quality condition were informed that they had spent 28.7% of their total sleep time in REM, whereas those in the “below average” sleep quality condition were informed that they had only spent 16.2% of their time in REM sleep. Assigned sleep quality but not self-reported sleep quality significantly predicted participants’ scores on the Paced Auditory Serial Addition Test and Controlled Oral Word Association Task. Assigned sleep quality did not predict participants’ scores on the Digit Span task, as expected, nor did it predict scores on the Symbol Digit Modalities Test, which was unexpected. The control conditions showed that the findings were not due to demand characteristics from the experimental protocol. These findings supported the hypothesis that mindset can influence cognitive states in both positive and negative directions, suggesting a means of controlling one’s health and cognition. (PsycINFO Database Record (c) 2014 APA, all rights reserved).
PMID: 24417326 [PubMed – in process]

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