Hayo Terband – Modelling processing deficits in developmental speech sound
disorders.
Speech disorders are estimated to form about 75% of all communication disorders in
children. Yet, little is known about the neurological deficits and the linguistic processes
that underlie the wide variety of symptoms that are found in developmental speech
sound disorders. This forms a major bottleneck for diagnosis and treatment. The
fundamental problem in isolating the underlying deficits is the developmental interaction
between the different linguistic levels of processing. For example, poor articulation of
particular speech sounds affects the patient’s perceptual acuity for contrasts involving
these speech sounds. Individual patients vary widely in these developmental interaction
patterns, and the effects of developmental interaction between linguistic levels on
individual development is largely unknown.
This problem can be addressed by using a modelling approach. Based on clinical theories,
specific processing deficits are implemented in a computational model, which lead to
specific predictions regarding a developmental trajectory. These predictions are then
tested against speech data from speech production experiments involving children with
the hypothesised diagnosis.
Previous computational modelling studies have demonstrated that, by manipulating
parameters independently and systematically, this paradigm can provide a unique insight
into the relationship between core deficit, derived or consequential deficits, and adaptive
strategies, and in how all of these express themselves in symptomatology. For example,
results showed drastic differences in the linguistic level of a specific speech-motor
impairment depending on the ability of the system for auditory self-monitoring, while the
clinical expression remained largely the same.
Currently, we are expanding these modelling studies to higher levels of the speech
production process. The results will lead to a better understanding of the mechanisms
involved in speech sound disorders. This knowledge is essential for focused and
purposeful treatment for children that suffer from these disorders.