Is focussed stimulation by parents effective to improve vocabulary in Down syndrome?

The next article that we will discuss in our series of blog posts related to our systematic literature review is entitled ‘Vocabulary intervention for young children with Down syndrome: parent training using focussed stimulation’, by Girolametto, Weitzman and Clements-Baartman (1998).


The study assessed the effect of training parents of children with Down syndrome to use a technique called focussed stimulation, to improve their children’s vocabulary. The idea is that language development is stimulated by the parent ‘modelling language at their child’s level during naturally occurring situations’ (pg. 110), and parents receive training to do this in various ways to target specific language goals. The details of techniques involved in the focussed stimulation approach are outline further on in this post under the intervention details.


There were 12 children included in the study (mean age: 29-46 months), randomly allocated to either the training group or to the control group. The children in the study communicated using single words or signs at the outset.

Children in the experimental group did not receive other therapy programs during the training period. The children in the control group carried on receiving language intervention services during the course of the experimental phase as it was part of their pre-school program. As the authors note, it would be preferable to have a no-treatment control group for comparison.


In a first pre-test session children were videotaped during 15 mins of free play with their mother during which the speech sounds checklist (Girolametto, Pearce, & Weitzman, 1994) was completed by a speech-language pathologist. They also completed various scales to assess vocabulary.

Prior to a second pre-test session 20 target words were selected for each child. The target words were chosen on the basis of being words that the child could comprehend but not produce. The words were those that are acquired by most typically developing children at 24 months of age, and each word started with a phoneme that the child had in their speech sound repertoire (able to make that sound). Finally the words had to be relevant in terms of being functional early in development.

In the second pre-test session, interviews with mothers were carried out to check that children did not already use any of these target words at home, and if they did use a target word already then it was replaced with a different one.


Mother-child free play sessions were again videotaped, assessments taken at pre-test were repeated and children were given naturalistic semi-structured probes, i.e., an object that represented the child’s target words, to assess the child’s expressive use of the 20 target words.

Intervention details:

The Hanen Program (Manolson, 1992; see for more details) was used, this has thorough parent handbooks and videotapes to follow, along with the language stimulation program. The mothers were given the 20 target words and picked 10 that they thought would be most motivating for their child to learn. Parents kept diaries of the children’s word use, and if a child made use of one of the target words spontaneously on 3 occasions, and in 3 different contexts then it was replaced by another word from those remaining on the list.

The program was 13 weeks long; spread across the 13 weeks there were 9 evening sessions to teach parents the techniques (each 2.5 hours long) and four home visits to give parents feedback on their techniques. The authors provide a week by week description of the program content, so that it is clear what was done at each stage. We will not outline each week here as of course the full details can be read in the article but to summarize some key components; parents record and watch back videotapes of interactions with the child, they also watch lectures given by clinicians, including roleplays of how to carry out techniques, and they review techniques based on watching back videotapes, with feedback. The parents are taught to follow the child’s lead. Below are some of the key techniques used across the weeks:

·         Observing waiting and listening

·         Imitation

·         Asking for clarification

·         Commenting

·         Encouraging the child to participate

·         Learning how to ask appropriate questions to encourage turn taking.

·         Using signs to accompany verbal labels

·         Expanding verbal utterance by techniques such as emphasising the word.

·         Adapting songs to facilitate target word learning.

·         Suggestions to increase child’s exposure to books and print.

·         Making book reading interactive.

·         Child centred play – exploratory, creative and flexible.

·         Making use of target words during interaction, but based on the child’s interest, e.g., use the word in the game the child wants to play.

·         Clinician to coach techniques as and when necessary during home visits.



Treatment fidelity was assessed via parental attendance data at the parent training sessions, consumer evaluations, and reports from the home visit by the speech-language pathologist. There was a high level of commitment to the program and parents who missed any session were updated on the next session.


The authors checked that the groups did not differ significantly at pre-test for age, vocabulary size, speech sound inventory, play level, receptive language age, and all outcome measures.

Regarding the mothers there was a significant difference between those in the experimental vs control groups for the rate of talk per minute at post-test. The two groups of mothers did not differ at post-test with regards to the complexity of their language or their mean length of utterance. In the experimental group the mothers used the target words significantly more than the control mothers and used more focussed stimulation of these words.

With regards to the children, the two groups differed significantly at post-test in terms of parental report of the amount of target words produced, with the experimental group using twice as many. The children in the experimental group also used the target words significantly more in free play interactions than did the children in the control group. The frequency of target use was very low in the videotaped interaction for the experimental group (median = 1.5), however this was still greater than the control group since for the control group it was practically non-existent. The two groups did not however differ significantly in their use of target words during the semi-structured probes task.

For the overall vocabulary size estimate there was no significant difference between the two groups of children. From the data reported in the article (medians and ranges) it looks as though the control group actually have much greater gains in overall vocabulary size. It is problematic in terms of showing how very little the effects generalize to vocabulary, and that the control group are doing numerically better here. Of course, the small sample size also comes into play here with the difficulty to interpret, as there are only 6 in each group. The authors note the need for a replication to really make any claims based on these findings for the future, this of course limits the conclusions from the study.

Other limitations:

Although group differences were not significant at pre-test it is worth considering in these types of analyses the influence that even non-significant pre-test differences can have on interpretation of subsequent post-test differences (hence one would usually use a repeated measures design to compare before vs after in each group). Take for example two groups whereby one group starts with a score of 10 and the other a score of 18, if both groups achieved 22 at post-test there would be no difference between their post-test scores, however for the group who began at 10 this is an improvement of 12 compared to just 4 for the other group. Thus, although pre-test differences may not have reached significance, it can be important to consider the relative degree of improvement in the two groups.  This does not apply for the target words in the current study, as, for all children these words were unknown at pre-test, but for variables such as vocabulary size it is a consideration.

As already noted, the study has a very small sample size, which leads to a lack of power. A problem that we have seen in many of the language interventions for those with Down syndrome.

Again, generalisability however was clearly lacking. The authors note that this could be due to the study being too brief, a lack of statistical power, or that perhaps children with Down syndrome do not easily generalise word learning activities to new words. It is of course nothing new to say that we need to look at ways to encourage and promote generalisation, an issue for all interventions regardless of population. Nonetheless, having the tools to directly improve target vocabulary, chosen on the basis of carefully considered criteria, such as functional relevance, is important in itself.

Liz and Kari-Anne


Girolametto, L., Weitzman, E., & Clements-Baartman, J. (1998). Vocabulary intervention for children with Down syndrome: Parent training using focused stimulation. Infant-Toddler Intervention: the Transdisciplinary Journal, 8(2), 109-25.

Girolametto, L., Pearce, P. S., & Weitzman, E. (1994). Speech Sound Checklist. Unpublished manuscript.

Manolson, A. (1992). It takes two to talk: A parent’s guide to helping children communicate. Toronto, ON: The Hanen Centre.

Visiting Bristol

Anne Grethe and Lovise have travelled to Bristol this week to work together with Liz at Bristol University. As we are writing this the trip will sadly soon be over; we are looking back at some productive and enjoyable days, and we have captured some of these moments.

This week we have been working together on finalizing some aspects of the DSL+ intervention design, for instance the main menu designs of the application. We also worked together on the teacher guidance manual that explains to the teachers how to carry out the intervention.

We have also had the chance to collaborate further on papers associated with the project.
It was very motivating to work in a different setting and useful to spend the time together to work on the project.

We have been working hard during this trip but we also found some time to explore the city and enjoy some good food. 

We enjoyed spending the time together and we look forward to future trips.

Lovise, Anne Grethe and Liz

Effectiveness of vocabulary interventions for individuals with Down syndrome, what can we learn, what’s missing, and where next?

During the process of scanning abstracts from our literature search on vocabulary interventions for children with Down syndrome, we are finding patterns with regards to the types of inclusion criteria not tending to be met; preventing us from including various articles in our review on this topic. While at the outset, we had expected to find a relatively small number of hits meeting all our inclusion criteria, we are finding even fewer than expected. The reason for the lack of articles being included is due to various reasons, but in particular to the lack of control groups in many of the studies in this area, and also due to the lack of studies specifically targeting vocabulary in children with Down syndrome. It is also worth noting that the only RCT that we are currently aware of involving vocabulary intervention for children with Down syndrome was itself primarily aiming to improve reading in children with Down syndrome. There is very little research assessing the effectiveness of vocabulary interventions for children with Down syndrome, and research in vocabulary-related areas is often lacking sufficient empirical quality to assess statistically whether the interventions are effective.

If we were to discard various inclusion criteria such that we could have more articles meet our criteria and enough to carry out a meta-analysis, this would reduce the quality and relevance of what goes into the meta-analysis and that in turn would simply be reflected in the quality and clarity of the meta-analysis results, and the conclusions and implications of those overall results. Such results would be of little value to those attempting to assess what is effective for improving vocabulary, and future directions. What we can do at this stage however, is carry out a systematic literature review on the various articles out there to get a grasp on the current state of the intervention literature and what may have theoretical relevance for future intervention approaches, as well as to consider the effectiveness of those very few studies in the area that do meet all or most of the inclusion criteria.  

Of course, interventions tend to be a fairly large investment of time and resources, with pre-tests, post-tests and various treatments. It is also worth keeping in mind the importance of well-researched theory behind the domain being trained, prior to the training itself being carried out. With regards to vocabulary, it is clearly an area that needs to be targeted in Down syndrome. Language generally, is often an area of weakness in individuals with Down syndrome, tending to be reported as delayed and below individuals’ other cognitive abilities.  While vocabulary has often been suggested to be a strength in children with Down syndrome compared to other areas of language that children tend to find particularly difficult e.g., grammar, it is important to note that vocabulary seems to be a bottleneck to develop other language skills, reading skills and social skills. Therefore improving vocabulary is a valuable goal. We also know that children with Down syndrome are likely to have poorer abilities to express vocabulary, relative to stronger vocabulary comprehension. Vocabulary interventions for those with Down syndrome need to use approaches specific to the needs of these children and consider their various strengths and weakness. It is important that children with Down syndrome feel engaged and motivated to participate in interventions that are aimed at them. We can also look to the findings of interventions that appear to work for typically developing children, or other populations, and explore areas related to vocabulary, and consider how these may be relevant or adapted for those with Down syndrome in order to develop an intervention that may succeed in improving vocabulary for them. One possibility that we have yet to explore is that there have been vocabulary interventions carried out that have not been published, e.g. because of null-results. We will attempt to find out about any unpublished cases to provide a full picture of types of vocabulary intervention research being carried out in the Down syndrome population.

With vocabulary such an important component of a child’s development it is an area that is deserving of attention, and we therefore feel positive about developing an RCT intervention in this area. It is apparent that more research is needed, and it is also worth us acknowledging of course that other domains as well as vocabulary are of course likely to be in need of empirical intervention research for those with Down syndrome. This research is needed for us to progress in the quality and success with which we educate children with Down syndrome in various areas.

Liz Smith & Kari-Anne Næss

Vocabulary assessment

I have participated in a guest lecture by Professor Norbert Schmitt from the University of Nottingham (UK), that I found interesting. The lecture was held at the University of Oslo in conjunction with a network meeting of LUNAS (Language Use in Nordic Academic Settings) and was supported by the Nordplus Nordic Languages Programme and the Department of Linguistics and Scandinavian Studies.

Schmitt focused the lecture around four main questions related to assessment of vocabulary:

1)      Why do you want to assess?

2)      What words do you want to assess?

3)      What kind of knowledge do you want to assess?

4)      Which item format do you want to assess?

The lecture was given in a very interactive manner and the participants actively participated to contextualize the talk from different perspectives. Below I will give a very short summary of what I have taken away with me from participating in that lecture.

Under the heading Why do you want to assess/test?, Schmitt mentioned a number of different purposes of assessments. The purpose of the measuring could e.g. be to look at achievement, for motivation, to see what the students already know, to identify shortfalls in lexical knowledge, diagnostic, proficiency, to look at the short term or long term effect of an intervention etc. This means that the purpose therefore differs according to context but whether it is related to practice or research the purpose may not only be related to vocabulary knowledge but also the language use. Therefore not only a vocabulary score should be considered but rather what the vocabulary score means. 

Determining What words do you want to assess depends on the purpose of the assessment but Schmitt also clearly highlighted that word frequency may be the best tool to decide on which words to assess (e.g. the COCA corpus; He realized this is not a perfect tool for selecting relevant words to include but suggested it to be the most relevant. For younger children, however, a written corpus will make no sense and the corpus should rather be based on talks occurring between teacher/pre-school teacher and their students/children, and talks between parents and their children, as these may then be preferable.

What kind of knowledge  should be assessed depends on the purpose of the assessment. Schmitt referred to Nation ‘s word knowledge aspects (2001) and the component form, meaning and use which originally may have been adapted from Bloom and Lahey (1978).

Which item format to assess is also related to the purpose of the assessment. It could be e.g. multiple choice item format, matching vocabulary, recall item format by context or by definition. Schmitt’s examples were taken from work with second language learners and students, no examples from young children were given. However, a work in progress by Benjamin Kremmel looking at the relationship between clinical test results and the results from interview/talk with the informants may possibly give the same result across age?

Kremmel found ca 20% overestimation of the vocabulary scores when multiple choices and matching were compared to the interview.  While recall definition and recall context result in an underestimation of scores by approximately 15-19%. Low frequency words result in guessing and both overestimating and underestimating occurs. This means that considering how to report results from vocabulary assessments is very important. Instead of reporting that an individual  knows words or has learnt words (which may include derivations and collocation), and assuming that the words are known and used regardless of contexts, we rather should refer to the specific context in our reporting of the results.

Finally, Schmitt also referred to an article he had written together with Zimmermann (2002) focusing on word families versus lemmas. In their study they found that we cannot make the assumption that word families are known by students (e.g. noun, verb, adjective and adverb/persistence, persist, persistent, persistently). The students had higher scores on recognition compared to expression of items but different word forms were directly accessible for the students in general. Therefore Schmitt suggested lemmas to be an actual compromise between word families and individual words.

I think Schmitt gave a good and very engaging talk about a very interesting topic. However, I found that a very important question was missing in his talk, namely - who would you like to assess? Typically there is little focus on the group under investigation but to reveal assessment results of high quality the group under investigation should also be considered.


Bloom, L. & Lahey, M. (1978). Language development and language disorders. New York:
John Wiley & Sons.

Nation, I.S. P. (2001). Learning vocabulary in another language. Cambridge UK: CambridgeUniversity Press.

 Schmitt, N.  & Zimmermann, C. B. (2002). Derivative Word Forms: What Do Learners Know?TESOL Quarterly, 36(2), 145–171. doi: 10.2307/3588328

A really interesting web page when working on vocabulary can be found here:

 -Kari-Anne B. Næss-

Does dose frequency play a role in the effectiveness of early vocabulary interventions?

The third article discussed in our series of posts on vocabulary interventions is entitled “Effects of Dose Frequency of early communication intervention in young children with and without Down syndrome” by Yoder, Woynaroski, Fey, & Warren (2014). In this article Yoder et al (2014) report a reanalysis of data from a previous intervention study that was carried out by their research Group (Fey et al., 2013).

Intervention dose frequency

The study assessed whether the frequency of intervention sessions received (dose frequency) affected the outcomes of an intervention, aiming to improve spoken vocabulary. Participants were 35 children with Down syndrome aged between 18-27 months and a control group of children who did not have Down syndrome, but had intellectual disabilities (n = 28). Approximately half of the children from each population were allocated to a high frequency dose group, while the other half were allocated to a low frequency dose group.  Each intervention session was 60 minutes long; the high frequency dose group received five hours of intervention sessions per week, while the low frequency dose group received a one hour intervention session per week. This was over a 9 month treatment.

Yoder et al (2014) direct the reader to the article by Fey et al (2013) for explanation of the intervention. The intervention used milieu communication teaching (MCT). However, Fey et al report only the essential details of the MCT training, directing the reader to Fey et al (2006) and Warren et al (2006) for descriptions of MCT, thus to get a full picture of the intervention when reading the article by Yoder et al it is necessary to refer back to various other articles. The three main intervention components in MCT are; Responsivity education, Prelinguistic Milieu Teaching, and Milieu Teaching. The essential details provided by Fey et al (2013) regarding each MCT component are summarized below:

Responsivity education (RE) sessions; these were weekly and aimed to (a) increase caregivers’ responsiveness to the child’s play actions and attempts to communicate such as imitating the child’s acts and vocalizations or commenting on them, (b) putting the child’s nonverbal communication into words, (c) add more meaning to the child’s topic, the example they give is: child says, “ball,” and the parent responds, “You can bounce it”; or (d) repeat what the child said but with added structure and meaning, such as when the child says ‘A ball’ the parent then says ‘Yeah, it is a ball’.

Prelinguistic milieu teaching (PMT): The aim of PMT is to ‘increase the frequency, clarity and complexity of the child’s nonverbal communication acts’ (pg. 683, Fey et al., 2013), to give the child a solid foundation of nonverbal communication skills to build upon during linguistic development. In PMT the clinician seeks to produce one ‘teaching episode’ each minute. It was hard to fully grasp the key content described by Fey et al (2013); it appears that there are various goals set for each child, such as gestures, and the task is to create opportunities for children to use these communication acts. The sessions do not appear to be systematic, based on the descriptions given by Fey et al (2013).


Milieu teaching (MT): MT is received after PMT. The aim of MT sessions is to increase frequency and/or complexity of verbal communication acts, again aiming for one ‘teaching episode’ each minute. Depending on the child’s current level of vocabulary they had either 5-10 ‘lexical targets’ i.e., words focused on, during the MT sessions, or for children with more advanced vocabularies the goal was to work on ‘multiword semantic relations’; again these essential details of the procedure were not completely transparent from the descriptions by Fey et al (2013). For those readers seeking more thorough details of the procedure we suggest looking back to Fey et al (2006) and/or Warren et al (2006), however, in this blog post we would rather like to focus on the frequency dose.

In addition to MCT most of the participants were receiving treatment by a speech and language therapist.

Results reported by Fey et al (2013) in the original article:

The results of this intervention were first reported by Fey et al (2013); they used growth curve modelling (i.e., to plot the average growth in spoken vocabulary performance across the children over time). They found that children improved significantly over time during the intervention. However, quite surprisingly, children’s growth was not associated with dose frequency. Thus, those receiving more sessions did not have greater outcomes (larger increases in performance over time). Dose frequency had no differential effect on spoken vocabulary as a function of presence or absence of Down syndrome (DS) either. The authors did however find that children who engaged in more functional play with objects (measured via the Developmental Play Assessment, Lifter, 2000) did experience greater gains in vocabulary as a result of high dose frequency compared to low dose frequency MCT. The moderating effect of functional play levels could reflect the child’s engagement in the study sessions, i.e., if they are more engaged then the higher frequency of MCT sessions is effective.

Reanalysis of results, by Yoder et al (2014)

In the article by Yoder et al they re-analysed this same data from the intervention, with the aim to evaluate whether a different (more complex) type of analysis may yield different results. In this re-analysis they again created a growth curve for vocabulary development, however this time in a way that accounts for periods of deceleration (slower growth) and acceleration in growth (faster growth) over time, rather than assuming stable (linear) increases in vocabulary growth over time (for more details of this approach see ‘Statistical Analysis Plan’ in Yoder et al., 2014). They also analyzed those with Down syndrome separately to those without Down syndrome, rather than pooled across both groups. When reanalyzing the data in this way, they detected some additional findings that were not detected in the original analysis by Fey et al (2013). Specifically, they found for those with Down syndrome, receiving a higher frequency dose was beneficial (relative to the low frequency dose), resulting in them producing more words post-treatment. However, for the group without Down syndrome this was not the case. The effect of object play did remain across both groups, with those children who engage in more functional play showing greater gains as a result of a higher dose relative to the lower frequency dose intervention.

Session frequency and session content

The authors conclude that increasing intensity of milieu communication teaching (MCT) by dosage (more sessions) does not necessarily result in improvements in the effect of that treatment for all children. These findings suggest rather, that the extra sessions of MCT have to be planned in such a way that the child is engaged in the sessions. We can take this into consideration when thinking about how each session during any intervention is helping the child to learn, build upon and consolidate knowledge. Various factors could interact with dose frequency. The content of the sessions in a high dose condition could involve different levels of variability, content shown in a different context or format, repetitions of previous sessions for consolidation, or coverage of new additional content. Levels of interaction in the sessions is also important to consider, for instance with respect to how motivated and engaged the child is during the sessions.

The finding that specific groups were affected differently based on the Yoder et al (2014) analyses highlights the relevance of designing interventions for specific populations based on their specific group profiles, while allowing for flexibility to meet individual differences in needs and preferences. The finding of dose frequency effects in those with Down syndrome but not in the control group, may reflect an importance of repetition for children with Down syndrome. Though, it may also be important to consider the relatively small sample size in these split analyses and the effect this may have on results. It would of course be useful to assess dose frequency with other types of interventions, where measures are taken to further promote task engagement in all sessions, and more children are included in the sample.

The study has a particular focus on individual factors and the Down syndrome etiology, aspects such as children’s language profile and their potential tendency for task resistance are especially mentioned as potential factors that may explain variability in response to intervention.

We would suggest that factors non-specific to the Down syndrome etiology, such as children’s socioeconomic status (SES) may also be an important variable with respect to their treatment outcomes and this could interact with effects of intensity such as dose frequency. SES has often been shown to relate to children’s learning outcomes, particularly with regards to language ability (Hart & Risley, 1995, Hoff, 2003; 2013; Hoff-Ginsberg, 1998)

To summarize, increased dose frequency does not improve MCT treatment outcomes for all children. However, engagement appears to be an important moderating factor, indicating that when children are potentially more engaged in sessions, the outcomes may be more successful. For those with Down syndrome, higher dose frequency of MCT was beneficial. The article by Yoder et al highlights that how growth is modelled (e.g., with a simple vs a complex model, and across vs within etiological subgroups) may impact whether a significant treatment effect is detected.



Fey, M. E., Yoder, P. J., Warren, S. F., Bredin-Oja, S. (2013). Is more better? Milieu communication teaching in toddlers with intellectual disabilities. Journal of Speech Language and Hearing Research, 56(2), 679-693.

Fey, M. E., Warren, S. F., Brady, N. C., Finestack, L. H., Bredin-Oja, S. L., Fairchild, M., Yoder, P. (2006). Early effects of responsivity education/prelinguistic milieu teaching for children with developmental delays and their parents. Journal of Speech, Language, and Hearing Research, 49, 526–547.

Hart, B. & Risley, T. R. (1995). Meaningful differences in the everyday experiences of young American children. Baltimore: Paul H. Brookes.

Hoff, E. (2003). The Specificity of Environmental Influence: Socioeconomic Status Affects Early Vocabulary Development Via Maternal Speech. Child Development, Volume 74, Number 5, Pages 1368–1378

Hoff, E. (2013). Interpreting the language trajectories of children from low-SES and language minority homes: Implications for closing achievement gaps. Developmental Psychology, 49, 4–14.

Hoff-Ginsberg, E. (1998). The relation of birth order and socioeconomic status to children's language experience and language development. Applied Psycholinguistics, 19, 603–630.

Lifter K. Linking assessment to intervention for children with developmental disabilities or at-risk for developmental delay: The developmental play assessment (DPA) instrument. In: Gitlin-Weiner K, Sandgrund A, Schafer C, editors. Play diagnosis and assessment. 2nd ed. Wiley; New York, NY: 2000. pp. 228–261.

Warren, S. F., Bredin-Oja, S. L., Fairchild, M., Finestack, L. H., Fey, M. E., Brady, N. C. (2006). Responsivity education/prelinguistic milieu teaching. In: McCauley RJ, Fey ME, editors. Treatment of language disorders in children. Brookes; Baltimore, pp. 47–75.

Yoder, P., Woynaroski, T., Fey, M., & Warren, S. (2014). Effects of dose frequency of early communication intervention in young children with and without Down syndrome. American journal on intellectual and developmental disabilities, 119(1), 17-32.


-Liz Smith and Kari-Anne B. Næss -

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