In
our literature review we want to find out about vocabulary intervention
approaches, so we know what approaches have been used in earlier research and
what works best with regards to improving vocabulary in children with Down
syndrome.
The
second article that we have selected in this series of our literature review
posts is ‘Advancing imitation and
requesting skills in toddlers with Down syndrome’ by Feeley, Jones,
Blackburn, & Bauer (2011). This study was a hit in our literature search, however,
the study will not be included in our review because it did not meet our
inclusion criteria; this is since it is, a.) Not directly a vocabulary
intervention, and b.) Not including a control group/condition. As the study was
a hit in our search we will nonetheless discuss the study in this post, in
relation to variability in intervention content and research quality across the
various hits in our search.
The
reason we are including only studies with control groups/conditions is a really
important one; if children receive an intervention and their performance
improves, but there is no control group or control condition, then it is not
possible to determine whether they improved simply due to attention, time in
general, or any given property of the specific intervention. Also, without
comparing to another population, it is not possible to argue that the
intervention is specifically effective for the population tested, e.g., Down
syndrome. Without a control condition or control group researchers are unable
to empirically test the theory underlying the given intervention.
The
article by Feeley et al. (2011) aimed to investigate the result of an
intervention program developed for children with Down syndrome that focuses on
imitation and requesting. Four toddlers who have Down syndrome participated in
their study. Due to the suggestion of relative strengths in social development
in Down syndrome, based on a review by Fidler et al (2005), social interaction
was used in the intervention by Feeley et al. to encourage and reinforce
requesting and verbal imitation in toddlers with Down syndrome. The
intervention involved providing specific prompts (telling the child to say a
certain sound) to give the child opportunities to verbally imitate or encourage
them to request. Corrective feedback was also given, along with social
reinforcement such as hugging and social praise.
The
sessions were run by the child’s speech therapist and their mother. Each
intervention session lasted around 15 minutes, with 3 sessions per week.
Sessions could involve up to 10 ‘opportunities’ (meaning opportunities to
respond to prompts), but often consisted of between 5 and 7 opportunities. It
was unclear why this variation was present rather than a set number of
opportunities in each session for each child. Verbal imitation and requesting
interventions were done at the same time so that the children could use any
learnt verbal imitation skills when trying to request. For verbal imitation
children were presented with a model of the target sound (spoken by the
interventionist – mother or speech therapist), such as the ‘ahhhh’ sound. In
earlier sessions the sound was exaggerated, the child was also given a physical
prompt (by having gentle pressure on their chin). Over the course of the
sessions the interventionist made less exaggeration of the target sound and put
less pressure on the child’s chin. For the requesting training, the training
followed a sequence, starting with training the use of a gaze shift to request
social interaction with an object (the interventionist would prompt the gaze
shift by, for instance, taking a deep breath or moving into the child’s line of
sight). If the child looked at the object and then to the interventionist they
were subsequently given the object. Training next moved on to the use of gaze
shift and any vocalisation (whereby the interventionist additionally prompted
the child by gently tapping on their mouth). Finally gaze shift was to be accompanied
with an approximation of the appropriate requesting word (e.g., an ‘mmm’ sound
for ‘more’). The interventionist’s prompt was to tell the child to ‘say ‘mmm’
for instance, and the object was placed in a jar such that the child was
requesting for help (e.g., to get the object from out of the jar).
The
children were assessed in terms of whether they reached a mastery criterion,
e.g., 80% independent correct responding (independent correct responding refers
to children’s ability to imitate the sound made by the interventionist without
the need to hear an exaggerated verbal model and/or a physical prompt, and
their ability to make a request without a prompt) in ‘two consecutive sessions
on two days’ (pg. 2418), we assume this means a correct response one day and
again the next day. The authors found that the children were able to acquire
verbal imitation and requesting skills. Each child’s results are reported
separately in terms of how many probe opportunities it took to reach the
mastery criterion. It is difficult to see how many probe opportunities were
needed on average as group level results are not provided.
Maintenance
of skills was assessed via a follow up (3 to 4 weeks after intervention). The
follow up was based on giving the child just one opportunity to respond to a
probe, e.g., prompting the child to ‘say ‘mmm’, and seeing whether the child
responds correctly in that one instance, or e.g., showing the child the object
in the jar such that they are prompted to make a request for help getting the
object out of the jar. The children were probed once for each of the sounds
that they had learnt in the intervention and the most sophisticated form of
requesting they had learnt in the intervention. For three of the four children
follow up was assessed and showed that children continued to show the skills
(i.e., same level of performance) that they showed at the end of the intervention.
Generalisation
was not measured in a systematic way, e.g., a particular set of non-trained
items tested across each child. Rather,
sounds that the interventionists said that they heard spontaneously during
intervention, but that the child could not say at baseline, were tested again
after the intervention. Generalization was assessed for just 2 of the 4
children and showed that they generalized to novel sounds. Given that this was only
2 children it does not tell us about what we should expect in the Down syndrome
population more generally.
The
authors note that they have demonstrated the effectiveness of the intervention,
however we think this is a rather strong statement given the design and the limitations
of the study. Improvement could be due to natural development over time rather
than an effect of the intervention. The authors note the need for replication,
and a replication was in fact subsequently carried out by Bauer and Jones
(2014); we will discuss this study in another post in this series. However, we
would argue that it is much more than replication that is needed here. The
findings do not give us any idea of meaningful group level patterns for those
with Down syndrome. A follow up intervention study would be needed to test the
claims made by Feeley et al, but this should involve a larger sample and a
control comparison in order to tell us something more meaningful about this
intervention, whether it results in any significant effects, and test the
validity of the theory underlying it.
Further,
for the four children in the study it was difficult to compare individual
differences in abilities. In the initial descriptions of the four children
different measures were reported for the respective children. We were unclear
about why the different measures for different children were reported. Other
issues, such as one child missing a part of the intervention due to
interventionist’s time constraints, and one child’s parents introducing a
different intervention for one of the sounds, present a number of confounds in
terms of interpreting the results in this very small scale study.
References:
Fidler, D. J. (2005). The emerging Down syndrome behavioral
phenotype in early childhood: Implications for practice. Infants & Young
Children, 18(2), 86-103.
Feeley, K. M., Jones, E. A., Blackburn, C., & Bauer, S.
(2011). Advancing imitation and requesting skills in toddlers with Down
syndrome. Research in developmental disabilities, 32(6),
2415-2430.
Liz and
Kari-Anne
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