"We don’t give them any specific instructions with regards to what they should or shouldn’t do while resting,” Dewar says. “But questionnaires completed at the end of our experiments suggest that most people simply let their minds wander In one study, for instance, participants were asked to imagine a past or future event during their break, which appeared to reduce their later recall of the newly learnt material. So it may be safest to avoid any concerted mental effort during our down time. "

Astounding. I assumed that the high performing test subjects would have used some sort of special memorization technique, but in fact doing and thinking nothing actually wins out.