What a difference a day makes: Change in memory for newly learned word forms over 24 hours

Purpose: This study explored the role of time and retrieval experience in the consolidation of word forms.

Method: Participants were 106 adults trained on 16 novel word-referent pairs, then tested immediately and 24 hr later for recognition and recall of word forms. In the interim, tests were repeated 2 hr or 12 hr after training, or not at all, thus varying the amount and timing of retrieval experience.

Results: Recognition accuracy was stable and speed improved over the 24-hr period. But these manifestations of consolidation did not depend on interim retrieval experience; in fact, the 2-hr interim test interfered with improvements in speed. In contrast, the number of word forms recalled increased only with interim retrieval experiences, and the 12-hr interim test was more advantageous to recall than the 2-hr test.

Conclusions: After a word form is encoded, it can become stronger with time. Retrieval experience can also strengthen the trace, but, if retrieval occurs when the memory is still labile, it can be disruptive. This complex interplay between retrieval experience and time holds implications for measuring learning outcomes and for scheduling practice in classrooms and clinics.