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 the current study, the investigators aim to increase accuracy levels by embedding the same words and retrieval schedules used in earlier studies into story contexts. Artist-illustrated stories incorporate illustrations of the unfamiliar plants and animals that served as referents of novel nouns in an earlier study. 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 nouns, four embedded in each story. Along with each word form, children will learn a "meaning", that is, an additional piece of semantic information about the referent.
For words in the RSR condition, each novel word and meaning, paired with its referent, will be presented as part of the story. Immediately after hearing it, children will be asked to recall both form and meaning, and then will hear those repeated. All subsequent retrieval trials will occur after three other words have intervened since the last time the word appeared in a study trial. Novel words assigned to the comparison condition will simply be heard paired with their referent during the story at the same frequency as words in the RSR condition. Children will not be asked to recall the words in the comparison condition during the learning period. Stories will be presented twice on each of the learning days. As written, the stories are a reasonable length and pace, but by repeating the story, children will hear the words the same number of times overall as in the investigator's previous studies, allowing evaluation of the benefits of the story format. Recall of the word forms and meanings will be tested after the story book reading on the second day and one week later. One week later, the recall test will be re-administered and children will complete a three-alternative recognition test.
The investigators hypothesize that children will show greater recall for word forms in the RSR condition than those in the repeated study condition; past studies have not consistently shown an advantage for recall of "meaning" or for recognition. It is also expected that children with TD will remember more words overall than children with DLD. To the degree that the story format is more engaging for children, overall recall will be enhanced for both groups. Assuming that the results are replicated, it is hoped that the children's book reading format will prove amenable for use by teachers and speech-language pathologists who work with children with DLD.
