Developmental Language Disorder (DLD) affects language learning in an estimated 7% of children. Although much of the research literature has emphasized difficulties learning grammar, children with DLD also have major deficits in vocabulary. In recent work, the investigators have been examining the benefit of retrieval practice to enhance word learning and retention in preschoolers with DLD. The rationale behind this work is grounded in the growing literature in the field of cognitive psychology which shows that repeated practice in retrieving information results in greater long-term retention than continuous study of that information without opportunities for retrieval. In addition, retrieval practice that occurs after a delay-or "spacing" between study of a word and subsequent recall attempts-can lead to stronger effects.
The investigators have explored the benefits of retrieval practice for preschoolers with DLD and with typical language development (TD), showing that recall and retention for novel words (nouns, adjectives, verbs) were greater when learned using repeated spaced retrieval (RSR) than when learned using repeated study only. Despite benefitting from RSR, children with DLD still showed lower levels of recall than children with TD, in particular in novel verb learning.
In the current study, the investigators seek to improve the absolute levels of word form recall for verbs by modifying the method used previously. Sixteen children with DLD will be recruited for this study along with 16 children with TD matched on chronological age. Using a within-subjects design, children will learn eight novel verbs, four at a time. Each set of four will be learned over two consecutive days, with two words in the RSR condition and two words in a repeated study condition. The referents for these novel words will be video-recorded transitive actions performed by actors on objects and presented on a laptop screen.
In the RSR condition, children will initially hear the word paired with a video of a novel action, immediately be asked to recall the word, and then see/hear it again. After three other words are presented, they will be asked to recall the original word again; this "3" spaced retrieval schedule will continue for the rest of the learning session. In the comparison condition, children will simply hear the words paired with a video of the novel action. In this study, during retrieval practice, children will be prompted to respond with a full sentence containing the verb.
Recall of the verbs will be tested after the learning session on the second day and one week later. At one week, children will also complete a syntactic generalization test in which they are prompted to use the novel verb in a type of sentence that is different from the one used during learning. Finally, children will complete a two-alternative recognition test.
The investigators hypothesize that novel verbs that undergo RSR during the learning period will be learned and recalled better than comparable novel verbs that are assigned to the repeated study condition. This RSR advantage will continue to be observed when the children must use the novel verbs with new actors and objects and will be seen as well in the syntactic generalization test when the children must use the novel verbs in a new sentence frame. Introducing novel verbs representing actions that can be performed on varying objects is expected to improve overall learning. In addition, by having the child produce the verbs in the context of a full sentence, the newly learned verbs should become more integrated with other sentence elements (subjects and direct objects), resulting in a richer representation in memory and consequently, greater recall, recognition, and syntactic flexibility than was observed in the previous novel verb study.
