Last month, Stephanie Mazza and colleagues published a paper (1) looking at the interaction of sleep, spacing, and retrieval practice to see if combining these strategies could lead to better learning. Here’s what they did:

All participants learned 16 French-Swahili word pairs, which looked something like this:

Chat-Paka

Bateau-Mashua

First they read all 16 word pairs and then they were given a test where they saw one of the words and had to type in the correct pair:

Chat-______

If they got it wrong, they were shown the correct answer and that item was tested again later. If they got it right, they didn’t see it again. They kept testing until they had gotten all 16 correct.

Participants were then divided into three groups:

Sleep Group: Studied the word pairs at 9 p.m. and came back to take a test at 9 a.m.

No Sleep Group: Studied the word pairs at 9 a.m. and came back to take a test at 9 p.m.

Control Group: Studied the word pairs at 9 p.m. and came back to take a test at 9 a.m (see below for the difference between Control and Sleep groups).

When the Sleep and No Sleep groups came back, they took a test to see how much they remembered and then went through the same procedure as before, being tested on all of the items until they got them all correct. The Control group simply took a test without relearning the items that they missed. Finally, they tested participants after 1 week and 6 months to see how much they remembered.

Participants were also tested on their quality of sleep and both their short-term and long-term memory function and all three groups scored similarly on all measures.

Here is how each group performed over time: