The role of lag effect in distributed practice on learning novel vocabulary.

Purpose: The purpose of the current study was to investigate the lag effects in two different versions of distributed practice on learning novel language vocabulary.

Method: Forty-four healthy monolingual English-speaking participants were randomly assigned to two versions of distributed practice. The two versions of distributed practice were created by altering the temporal lag between the practice sessions. Participants in both groups completed a similar practice regimen wherein they practiced 30 French occupations five times each for a total of 150 times. The pre/post-design employed in this experiment involved participants completing baseline, immediate, and delayed retention tests. The outcome measures included a comprehensive multiple-choice test and a written expression task.

Results: The findings from the comprehensive and expressive tasks indicated that the learning performance of participants across both groups was better during the immediate retention test compared to the delayed retention test. With regard to the group, participants assigned to the condensed version of distributed practice demonstrated superior learning of the novel vocabulary over participants assigned to the extended version of distributed practice.

Conclusion: The findings indicate that an increased temporal lag between the practice sessions results in a "non-monotonic function," wherein the learning continues to improve until an optimal lag, after which the learning declines as the lag continues to increase. This line of research will have a substantive impact on service-delivery models in speech-language pathology.