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).
Approach:
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.
Participants:
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.
Pre-test:
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.
Post-test:
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.
Fidelity:
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.
Results:
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
References:
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.
