Many children with developmental language disorder (DLD) have higher-order cognitive deficits (i.e., executive
function, problem solving, and planning) in addition to language impairment. Establishing the relation between
language and cognition is important for our understanding of the nature of DLD and for developing approaches
to improve cognition, which is crucial because higher-order cognitive skills predict later academic and career
success. One possibility is that children with DLD have cognitive deficits because they are less successful
relative to peers with typical language in utilizing self-directed speech (SDS; i.e., speech to oneself) to regulate
their behaviors and thoughts. For example, children with DLD may be less likely to articulate steps while
problem solving or verbally rehearse task rules. As such, language impairment may play a causal role in
higher-order cognitive deficits in DLD via impaired SDS. Sociocultural models suggest that SDS begins as
external regulatory speech from caregivers that children internalize to develop SDS. In this model, expressive
language impairment would negatively affect a child’s ability to produce SDS, and receptive language
impairments would reduce a child’s ability to understand caregivers’ external regulatory speech, which is
central to SDS development. Few studies have examined SDS in DLD, but previous research indicates that
children with DLD have immature SDS relative to typically developing peers. However, there is also promising
evidence that SDS can be trained in children with DLD. Although children with DLD show immature SDS
relative to typical peers, longitudinal research in this area is lacking, making it difficult to determine the
developmental trajectory and discern why children with DLD lag behind typical peers. The first goal of this
research is to document the longitudinal development of SDS in preschoolers with and without DLD in order to
compare the groups in their SDS and planning abilities and to assess the relation between these variables over
time. This goal will be achieved in Study 1 in which preschoolers with and without DLD will complete the Tower
of Hanoi planning task four times over one year. The second goal is to elucidate the effects of SDS on planning
performance in preschoolers with and without DLD. This will be addressed in Study 2 in which preschoolers
with DLD and typical language will complete Tower of Hanoi four times in different experimental conditions that
manipulate (i.e., prevent or encourage) SDS production. If task performance differs across the conditions, it
suggests that planning is affected by increasing or decreasing SDS, supporting a causal relationship between
SDS and cognitive performance. The third goal is to test the predictions of the sociocultural model with respect
to the effects of expressive versus receptive-expressive language deficits on SDS. This goal will be addressed
with data from children with DLD from Studies 1 and 2 by comparing SDS development between children with
expressive language impairment versus those with receptive-expressive impairment. Sociocultural models of
SDS would predict an asymmetry with larger SDS deficits associated with receptive-expressive impairment.
