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.
Despite the growing evidence that repeated spaced retrieval (RSR) results in greater word learning for preschoolers with DLD, much remains to be learned. One important question concerns the absolute level of learning achieved through RSR. These investigators have found that, in the more optimal condition of RSR, these children's ability to recall new word forms (i.e., recall the phonetic form of the word such as /pobɪk/) is still low, despite being higher than recall in the comparison conditions. The main obstacle appeared to be initial word form encoding during the learning period. Longer-term retention was less of a problem, i.e., those words children could recall immediately after the learning period were also recalled one week later. In the current study, the investigators seek to improve word form recall through modifications that may improve this initial encoding. The principal means by which this study will attempt to improve encoding and, as a result, subsequent recall, is through an adaptive retrieval schedule, described below.
Sixteen children with DLD will be recruited for this study along with 16 children with typical language development (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 one block of four in the standard RSR condition and the other block in the adaptive RSR condition. The referents for these novel words will be photos of unfamiliar plants and animals, presented on a laptop screen. Recall of word forms and meanings will be tested 5 minutes after the learning session on the second day, and again one week later. After the one-week recall testing, a picture-pointing recognition task will also be completed.
In both conditions, children will initially hear the word paired with a photo (Study trial: This is a nepp. It's a nepp. A nepp likes rain.), immediately be asked to recall the word (Retrieval trial: What's this called?), and then see/hear it again (Study trial: This is a nepp. It's a nepp. A nepp likes rain.). After three other words are presented, the children will be asked to recall the original word (nepp) again (What's this called? What does it like?); this retrieval trial is followed by a study or "feedback" trial (This is a nepp. It's a nepp. A nepp likes rain.). The "3" spaced retrieval schedule will continue for the rest of the learning session. The difference between conditions is this: in the adaptive condition, if the child is unsuccessful in retrieving the word form, whether on the initial trial or on one of the "3" spaced trials, the subsequent study/feedback trial will be followed by an additional immediate retrieval trial for that word. If, on the other hand the child retrieves the word form successfully, the next retrieval - study sequence will appear after three intervening words. In the standard condition, an unsuccessful recall attempt will be followed by a study trial but there will be no additional immediate retrieval opportunity. Note that while children will also be asked to retrieve the word meaning (what it likes), unsuccessful recall of this information will not trigger an additional immediate retrieval opportunity. This is based on previous findings showing that the real difficulty for children with DLD is recalling the phonetic form of words, rather than meaning information.
The investigators predict that the strategic placement of additional immediate retrieval trials after incorrect spaced retrieval trials in the adaptive condition will increase the likelihood of the child's success on the next spaced retrieval trial. Findings show that spaced retrieval needs to be successful in order to build strength and promote long-term retention. With the boost to encoding provided by the immediate retrieval trial for words the child is having difficulty remembering, the word form may be more firmly encoded and more likely to be recalled on the spaced retrieval trials. This should lead to higher absolute levels of word learning in the adaptive condition compared to the standard condition.
