More is not always better: The testing effect on retention of emergent Korean vocabulary

Traditionally, testing is seen as a tool for assessing learning. However, research suggests it also enhances retention. Despite abundant research on the testing effect, its specific role in foreign language vocabulary learning remains unclear, particularly its effect on retention of emergent untrained verbal relations. To address this gap, the current study compared the retention outcomes of free-operant (fluency practice) and restricted-operant (accuracy practice) test trials with two English-speaking adults learning Korean vocabulary. Dependent variables included retention accuracy and response rates for emergent and directly trained vocabulary over a six-month period. Results from the first experiment revealed no functional relation between testing type and retention. However, the second experiment demonstrated that retention improved to criterion levels when practice tests with corrective feedback were spaced weekly. These results suggest that increasing the dosage of practice tests had a minimal impact, while spacing practice sessions enhanced the retention of both directly trained and emergent vocabulary. The findings provide important considerations for foreign-language vocabulary learning.