Article analysis: a night of short sleep and word recall

Introduction

Sleep after learning is thought to help the brain hold on to new information. The researchers predicted that people who slept only 4 hours after studying a word list would recall fewer words the next morning than people who slept 8 hours.

Participants

Sixty undergraduate students (ages 18 to 23; 34 women and 26 men) at one university in the United States volunteered for course credit. All reported normal sleep and no sleep disorders. Before taking part, each student read and signed a consent form that described the sleep schedule and stated that they could stop at any time without losing credit. The university’s institutional review board approved the study.

Method

At 9 p.m., every student studied the same list of 40 unrelated nouns for 10 minutes in the sleep laboratory. A computer then randomly assigned each student to one of two conditions. Students in the short-sleep condition were allowed to sleep from 3 a.m. to 7 a.m. (4 hours); students in the full-sleep condition slept from 11 p.m. to 7 a.m. (8 hours). Short-sleep students watched nature documentaries with a research assistant until 3 a.m. At 8 a.m., each student had 3 minutes to write down as many words from the list as they could remember. A research assistant who did not know each student’s condition counted the correctly recalled words.

Results

The full-sleep group recalled an average of 17 words and the short-sleep group an average of 12 words (see the graph). The difference was statistically significant ($p < .05$).

Discussion

The researchers concluded that a short night of sleep after learning reduced recall the next morning. At the end of the session, each student was told the purpose of the study and given information on healthy sleep habits.

Invented study for practice.