Retrieval-Based Word Learning in Developmental Language Disorder
Phase: NA
Conditions: Developmental Language Disorder, Specific Language Impairment, Language Development
Sponsor: Purdue University

Official Title: Retrieval-Based Word Learning in Developmental Language Disorder 
Grant #: R01DC014708 
NCT#: NCT05325333 
Date: March 1, 2022 
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Purpose 
Word learning is one of the principal weaknesses in children with developmental language disorder 
(DLD). Our previous work has shown that special benefits accrue when these children must 
frequently recall newly introduced words during the course of learning, however their absolute 
levels of learning are still low compared to typically developing peers. In this study, we seek to 
increase the children's absolute levels of learning by adjusting retrieval schedules such that they 
might improve the initial encoding of new word forms. We include typically developing peers as a 
comparison group. 
 
Participant selection 
 
Preschool children with DLD are recruited through local speech-language pathologists and 
preschool teachers. Children with typical language development are recruited through 
advertisements in parent newsletters, preschools, and community events.  
For interested families, a phone interview is used to screen for the following eligibility requirements: 
1) current age between 4;0 and 5;11 (years; months) 
2) monolingual English speaker; or bilingual speaker with significant English exposure 
from birth. 
3) no significant neurological condition or neurodevelopmental disorder (e.g, ASD). 
Informed consent is obtained at the first session and eligibility testing is then completed. To be 
eligible, the child must:  
1) pass a pure tone hearing screening in both ears at 20 dB at 500, 1000, 2000, and 4000 
Hz  

2) score above 75 on a test of non-verbal intelligence  (Kaufman Assessment Battery for 
Children – Second Edition). 
3) complete the Structured Photographic Expressive Language Test – Preschool 2 and 
receive a standard score in the following range:  
a. To be included in the DLD group, children had a standard score below 87. This 
cutoff score has been found to show good sensitivity and specificity 
(Greenslade et al., 2009). 
b. To be included in the TD group, children had a standard score above 87. 
 
All children also complete the Peabody Picture Vocabulary Test – Fifth Edition. Parents complete a 
questionnaire that includes mother’s total years of education. The PPVT standard scores and years 
of maternal education are both used as covariates in all statistical analyses. 
 
For eligible children, 6 sessions are scheduled to complete the study.   
Word learning procedure 
The principal means by which we hoped to improve encoding and, as a result, subsequent recall, is 
to create a more gradual spacing of retrieval trials as the learning period proceeds. 
In the current study, we compare our “standard” procedure to a gradual or “expanding” retrieval 
schedule.  In both conditions, children first hear each word and what it likes, and then are 
immediately asked to recall this information. After these trials, the schedule for the two conditions 
diverge.  For subsequent recall in the “standard” condition, three other words intervene between 
the last time the child heard the word and the time when the child is asked to recall it. In contrast, 
in the “expanding” condition, the spacing between study and subsequent retrieval of the word is 
initially narrow -- one intervening word - and expands more gradually to three intervening words. 
The words in the two learning conditions - standard retrieval and expanding retrieval - are presented 
sequentially in separate sets. The sets are counterbalanced in order. Each set involved two learning 
sessions held on consecutive days with a recall test administered five minutes after the second 
learning session, followed by another recall test one week later. The second set begins the next 
week, following the same scheme as the first set. 
Four novel word “forms” are learned in each set. Colored photographs appearing on a laptop 
screen are the visual referents for these words. We also associate each word with something the 
referent "likes" (although what it likes was not shown on the photograph). This serves as the 
"meaning" of the word. During each study trial, the novel word is mentioned three times and its 
meaning is mentioned once, as in: "This is a /nɛp/. It's a /nɛp/. A /nɛp/ likes rain". For conditions that 
included retrieval trials, the child sees the picture and is asked, "What's this called? What do we 
call this?" and then "And what does this one like? What does it like?" Audio stimuli is pre-recorded 
and presented along with the visual stimuli (scanned photographs) on the laptop.   
The novel words are monosyllabic (consonant-vowel-consonant) and are matched across 
conditions according to phonotactic probability and neighborhood density (based on Storkel & 
Hoover, 2010). 

The two learning sessions within each set are identical. For the set constituting the standard 
condition, each novel word is presented initially in a study trial, followed by an immediate retrieval 
trial, followed by another study trial. We refer to such retrieval trials as "0" retrieval trials, reflecting 
the fact that there are zero words intervening between a word's study trial and its retrieval trial. After 
each novel word has had a 0 trial, all subsequent retrieval trials occur after three other words have 
intervened since the last time the word appeared in a study trial. Such trials are followed by a study 
trial for the same word. We refer to these retrieval trials as "3" retrieval trials, again, reflecting the 
number of intervening words used. The retrieval schedule for each day for the words in the standard 
condition is 0-3-3-3-3. However, after the second 3 trial of the four words, we insert one study trial 
for each word. This study trial is intended as a "refresher" under the assumption that some words 
will not yet be recalled at that point. The insertion of these study trials does not change the 3 
spacing between a word's retrieval trial and its previous study trial. The next day has the 0-3-3-3-3 
schedule with a “refresher” study trial after the second 3 trial. 
For the set constituting the expanding retrieval condition, each word first occurs in a study trial, 
followed by an immediate retrieval trial, and then another study trial. The next two retrieval trials 
occur after only one other novel word has intervened since the word's most recent study trial. These 
retrieval trials were followed by a study trial. We refer to these retrieval trials as "1" retrieval trials, 
as there is one intervening word. The two remaining retrieval trials for words in this condition are 3 
retrieval trials, with each retrieval trial followed by a study trial for the same word. The schedule for 
each day, then, is 0-1-1-3-3. After the second 1 retrieval trial for the four words in the set, a study 
trial is presented for each word as a "refresher," as was done for the words in the standard 
condition. 
With this design, the two learning conditions provide the same number of exposures to the word 
forms and meanings, and the same number of retrieval opportunities throughout the two-day 
learning period. The two conditions differ only in the retrieval schedule - 0-3-3-3-3 versus 0-1-1-3-3. 
See https://pubs.asha.org/doi/full/10.1044/2024_JSLHR-23-00528 Appendix A and B for an 
illustration of the details of words and learning schedules. 
Outcome measures 
 
Primary outcome measures:  
 
Form Recall and Meaning Recall test at 5 minutes. For each set, after the child has 
completed the learning session of the second day, a five-minute break is given. Then a recall 
test of each word form and meaning is administered. Two items for each word form and 
meaning are used, with the second item for each word presented only after all four words 
had been tested once. Prompts used for the recall items are identical to those used in the 
retrieval trials (“What’s this called?”; “What does this one like?”).  
 
Form Recall and Meaning Recall at one week. The Form and Meaning recall test is re-
administered one week after the first day of learning. 
 
Form Recognition at one week.  Immediately following the one-week Form and Meaning 
Recall test, a picture-pointing recognition test is administered. The photo of each novel 

word referent is shown along with the referents of the other three referents (in an array of 
four photos) and the child was asked, "Show me the e.g., /nɛp/."   
 
Secondary outcome measures:  
 
Peabody Picture Vocabulary Test – Fifth Edition is completed. Standard scores are obtained 
and used as a covariate in all statistical analyses. 
 
Parents complete a questionnaire that includes mother’s total years of education. Years of 
maternal education is used as a covariate in all statistical analyses. 
 
Scoring 
Word Form Recall measure: Eight items were used for the word form recall test for each set.  
Several steps are used in the scoring of children’s word productions: 
1) Productions of real words alternatives to the novel word (e.g., “cactus”) are scored as 
incorrect.  
2) Productions that appear to be attempts at the novel word but are not accurate are 
submitted to the scoring system of Edwards et al. (2004). Each consonant is awarded one 
point each for correct place, manner, and voicing. For vowels, one point is given for each of 
length, height, and backness. An additional point is credited for correct syllable shape 
(CVC).  Given that all novel words had the syllable shape CVC, all fully adult-like 
pronunciations earned 10 points. For any non-adult-like production to be scored as correct, 
the production is required to have a higher point total than the total that would be given if 
the child is instead trying to produce one of the other novel words. 
 
Meaning Recall measure: Eight items were used for the meaning recall test. 
Scoring of the children’s responses on the meaning recall test as correct or incorrect is 
straightforward, as pronunciation, even when non-adult-like, is not a factor in distinguishing 
among the possible meanings (e.g., grass, butterflies, rain, sun).  
 
Form Recognition measure: Eight items were used for the form recognition test. 
The child’s picture pointing response is recorded at the time of test. The score for the 
recognition test was the number of items in which the child pointed to the correct 
photograph in the four-photograph array.   
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Data analysis plan 
The first set of analyses examined the children’s longer-term recall and recognition. 
Specifically, children’s responses on the word form recall test, the meaning recall test, and the 
recognition test were evaluated using a series of mixed-effects models, with and without the 
covariates of PPVT-5 standard score and maternal education in years. The outcome was the 
number of correctly recalled items in a set of 8 items (as 2 items were used for each of 4 novel 
words). Diagnostic group (DLD, TD) was a between-participant variable; within-participant variables 
were learning condition (01133, 03333), and time (5-minute, 1-week, for the word form and 
meaning tests only). Random slopes for learning condition and time were included in the models 
when they were not close to zero. As a result, the random slope for the learning condition variable 
was included in the word form recall and meaning recall models and the random slope for time was 
included in the meaning recall model.  
Main effects models and full factorial models that included all possible two-way and three-
way interactions were tested hierarchically.  
Effect sizes are reported as partially standardized beta coefficients (bstd), which are 
comparable to a Cohen’s d except they represent conditional standardized mean differences, 
conditioned on other variables in the model. Restricted maximum likelihood (REML) estimation was 
used. Bootstrapped standard errors with 1,000 replicates were used to account for non-normal 
error terms in the meaning recall and recognition models. Stata version 17.0 was used for mixed 
effects model analyses (StataCorp, 2019).  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
 
Collapsing across sets, each measure has a range of 0-8 in each of the two conditions. 
 
We hypothesized that the use of “1” retrieval trials prior to proceeding the 3 retrieval trials would 
increase the children's ability to encode the novel word forms and meanings. Accordingly, we 
expected that recall and recognition scores would be higher for words in the expanding 0-1-1-3-3 
condition than in the standard 0-3-3-3-3 condition. This was a rather stringent test given that our 
previous work has shown that the standard condition was more successful than comparison 
conditions that did not involve spacing. Nevertheless, it was necessary to attempt to improve on 
the standard condition given, using this retrieval schedule, children were unable to learn more than 
approximately half of the words employed. 
We expected that the expanding condition would lead to better results than the standard condition 
for both the children with DLD and the children with TD. In our earlier work, group differences were 
often seen favoring the TD children for the standard condition but the difference was smaller than 
the group differences seen for the comparison conditions. The current study involve two conditions 
that each involved spaced retrieval, with only the particular retrieval schedule distinguishing the 
two. We expected that the expanding condition would show narrower differences between the two 
groups of children than the standard condition.