Boosting long-term memory via wakeful rest: intentional retrieval is not necessary, consolidation is sufficient

People perform better on tests of delayed free recall if learning is followed immediately by a short wakeful rest than by a
short period of sensory stimulation. Animal and human work suggests that wakeful resting provides optimal conditions for
the consolidation of recently acquired memories. However, an alternative account cannot be ruled out, namely that wakeful
resting provides optimal conditions for intentional rehearsal of recently acquired memories, thus driving superior memory.
Here we utilised non-recallable words to examine whether wakeful rest boosts long-term memory, even when new
memories could not be rehearsed intentionally during the wakeful rest delay. The probing of non-recallable words requires
a recognition paradigm. Therefore, we first established, via Experiment 1, that the rest-induced boost in memory observed
via free recall can be replicated in a recognition paradigm, using concrete nouns. In Experiment 2, participants heard 30
non-recallable non-words, presented as ‘foreign names in a bridge club abroad’ and then either rested wakefully or played a
visual spot-the-difference game for 10 minutes. Retention was probed via recognition at two time points, 15 minutes and 7
days after presentation. As in Experiment 1, wakeful rest boosted recognition significantly, and this boost was maintained
for at least 7 days. Our results indicate that the enhancement of memory via wakeful rest is not dependent upon intentional
rehearsal of learned material during the rest period. We thus conclude that consolidation is sufficient for this rest-induced
memory boost to emerge. We propose that wakeful resting allows for superior memory consolidation, resulting in stronger
and/or more veridical representations of experienced events which can be detected via tests of free recall and recognition.