Placebo sleep affects cognitive functioning.
Level 2 - randomized trial
Randomized laboratory experiment (graded by design analogy for non-clinical research).
PubMed 24417326 · doi:10.1037/a0035546
What was done
Across two experimental studies, 164 participants reported their previous night's sleep quality and were then randomly assigned to receive sham sleep quality feedback or to one of two control conditions. Participants in the "above average" condition were informed they had spent 28.7% of total sleep time in REM, while those in the "below average" condition were told they spent 16.2% in REM. Cognitive performance was evaluated using the Paced Auditory Serial Addition Test (PASAT), Controlled Oral Word Association Task (COWAT), Digit Span task, and Symbol Digit Modalities Test (SDMT).
What was found
Assigned sham sleep quality significantly predicted scores on the PASAT and COWAT, whereas self-reported sleep quality did not. Assigned sleep quality did not predict scores on the Digit Span task or the Symbol Digit Modalities Test. The abstract reports the manipulation percentages (28.7% vs. 16.2% REM) but provides no numerical cognitive test scores, effect sizes, or p-values.
Why it matters
This study demonstrates that mindset can influence cognitive performance, showing that subjective beliefs about prior sleep quality can modulate subsequent cognitive function independently of actual perceived sleep.
Limits
The abstract reports no numeric test scores, effect sizes, or confidence intervals. The effect was task-specific and did not impact the Digit Span task or Symbol Digit Modalities Test. The total sample of 164 participants was distributed across two studies and four conditions, and no participant demographic details or objective baseline sleep data were reported.
Cited by
- partial Providing individuals with false positive sleep tracker scores improves their cognitive and physical performance the next day, while false negative sleep scores impair performance (sham sleep feedback effect).