Does Going to Bed Sooner Help Preschoolers Remember?
Four-year-olds built toys with a grown-up, then slept. Did an earlier bedtime protect the memory, and why do kids claim they did the grown-up's steps?
In one paragraph
Researchers asked whether falling asleep sooner after learning helps four-year-olds remember, and whether it changes who they think did what. 76 children built toys with an experimenter, by taking turns or by watching, at different times of day. Turn-taking made children more likely to claim the adult's steps as their own. But the wait until sleep, sleep length and sleep quality did not predict memory two weeks later. Sleep timing was only observed, and the task was easy.
How did researchers test sleep and memory in four-year-olds?
A team in Germany invited 76 children, around four years old, to a child lab. Each child built four custom toys with an experimenter, such as a gong and a marble run, following six picture steps per toy. For two toys the child and adult took turns, one step each. For the other two, one person built the whole toy while the other watched.
After a short break, the children rebuilt the toys from memory and then looked at 24 photos of the steps, saying who had done each one. About two weeks later they came back and did both tasks again.
To vary how long children stayed awake after learning, visits were spread across the day rather than bedtimes being set. A wrist-worn activity tracker, called an actigraph, and a parent diary recorded when each child fell asleep that night. The predictions were registered before the study began.
Did falling asleep sooner improve what the children remembered?
No. The time between the learning session and falling asleep that night did not predict how well children rebuilt the toys two weeks later, nor how their mistakes about who did what changed. In exploratory checks, how long and how efficiently the children slept that night did not predict memory either.
The collaboration result did hold up. On the first day, children wrongly claimed 43.68% of the adult's steps as their own but gave away only 28.47% of their own steps. This tendency, known as the "I-did-it" bias, was stronger after taking turns than after watching. Two weeks later both kinds of error had grown and the gap was no longer significant.
Rebuilding was better right after the session than two weeks later, and taking turns did not improve it.
Why might sleep not have helped in this study?
Many studies show that sleep soon after learning helps young children keep what they learned, so this null result is best read as a boundary rather than a reversal. The authors offer three explanations.
First, by about four years old, the brain's short-term memory store may be big enough to hold a morning's learning until bedtime, so timing matters less than for younger children. Second, a sleep benefit might appear the next day and fade over a two-week delay. Third, the rebuilding task was easy, and when nearly everyone scores near the top there is little room for sleep to make a difference.
The team tested the third idea with a harder measure, getting the steps in the right order. Scores were lower, but sleep timing still did not predict them, so task ease is probably not the whole story.
What are the limits of this preschool sleep study?
Read before you quote it
Sleep timing was not assigned. It depended on when families booked their visit, so other differences between children could travel along with it. The same toys were used at both visits, so rebuilding them on the first day may have worked as practice.
The activity trackers cannot tell sleep stages apart, so the study says nothing about deep sleep specifically, and eight children napped before their night sleep. Only one age group was tested, and most parents had a university degree.
The study does not show that sleep is unimportant for young children's memory. It also cannot say whether there was a short-lived benefit the day after learning, because memory was only tested right away and about two weeks later.
- It does not show that sleep is unimportant for young children's memory.
- It does not test whether a short-term sleep benefit existed the day after learning.
- Sleep timing was not assigned but varied naturally with the visit time, so it is observational.
- Children performed near ceiling on rebuilding, especially on the first day, which can hide sleep effects.
- The same toys were tested at both visits, so rebuilding them on day one may have acted as practice.
- Actigraphy cannot tell sleep stages apart, and 8 children napped before their night sleep.
- Only one age group was studied, from a mostly university-educated German sample.
Takeaways
- saysBuilding toys by taking turns made four-year-olds more likely to claim the adult's steps as their own.
- saysHow soon they fell asleep that night didn't predict their memory or the bias two weeks later.
- saysEasy tasks, a long delay and sleep that was only observed may explain the null result.
- explainsDuring sleep, the brain is thought to move fresh memories from a small short-term store into long-term storage.
- interpretsA fair reading is that the result marks where a sleep effect stops showing, not that bedtime is irrelevant for children.
Ask the paper
In PaperSays you can ask this paper anything, by text or by saying “Hey Aiden”. Three questions listeners asked:
Does going to bed sooner after learning help four-year-olds remember?
In this study, no: the wait until sleep did not predict memory two weeks later. Hear the full answer in the app →
What is the "I-did-it" bias in children?
Claiming a partner's actions as your own after doing a task together, stronger after taking turns. Ask in the app →
Why might the study have missed a sleep effect?
The task was easy, the delay was two weeks and sleep timing was observed rather than controlled. Ask in the app →
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