Does spacing retrieval practice lead to a benefit in word learning before and after sleep? A developmental perspective

Understanding how to promote word learning across development is a crucial research area, as vocabulary size can predict academic and employment success. Spaced (relative to massed) retrieval practice (i.e., practising retrieval in sessions separated by hours or days) has been argued to benefit the long-term retention of novel vocabulary in adults and children. However, the effects of spaced retrieval practice are similar to sleep effects and the effects of repeated retrieval practice with feedback. Few studies have examined spaced retrieval practice in the absence of sleep between retrieval attempts or without feedback. This thesis addresses these areas by examining word learning performance up to 7 days after within-day spaced or massed retrieval practice with or without feedback and with or without a retrieval opportunity 24 hours after initial training in adult and child populations. We found a benefit in word learning performance from massed retrieval practice in adults and children on the first day of testing. Further, while within-day spaced retrieval practice protected memories from forgetting one week later, novel words were not better retained after within-day spaced retrieval practice in adult or child populations. We also conducted a direct comparative analysis of the adult and child data where we found that within-day spaced retrieval practice or a post-sleep retrieval opportunity generally slowed forgetting in adults, but children continued to improve their performance. However, developmental differences in the effects from within-day spaced retrieval practice only emerged if a post-sleep retrieval opportunity was provided. These results will be considered in the context of retrieval effort, contextual variability, and reconsolidation theories. Overall, this thesis provides critical evidence that a spacing benefit does not always emerge and that a post-sleep retrieval opportunity slows the forgetting of novel words one week later in adults but encourages continued improvements in children.