Language, Reading, and Motor Control: Get Rhythm!

Biological Foundations of Language already included a discussion of the role of temporal structural regularities and rhythm as organizing principle in language (see chapter 3 in Lenneberg 1967). In this article, we rely on Lenneberg’s biological notion of language and related ideas like rhythmicity and temporal structural regularities in order to show that individuals with developmental dyslexia (DD) are less efficient than control individuals in using structural regularities during handwriting and some language activities. Consequently, they cannot fully exploit (temporal) structural representations to process oral language, to execute handwriting movement and to read, although they have developed compensatory mechanisms to understand language, perform motor activities, and read. This proposal is based on findings collected in a varieties of studies conducted in our lab. First, we show that children with DD, who do not fail standardized language tests, but do not process oral language in the same ways as age-matched peers, as evident through ERP measures. They are also less efficient than control peers in morphologically manipulating non-words. Second, we show that children with DD are impaired in complying with two rhythmic principles governing handwriting considered in its motor dimension (not spelling), although they do not meet the criteria for disgraphia. Thus, children with DD have subtle oral language problems and motor disorders, beyond clear reading difficulties. Although we are aware of the great genetic and phenotypic heterogeneity of dyslexia and language disorders, we would like to conjecture that there might be a common source to language, motor and reading difficulties. This lies in the efficient use of the temporal structural regularities underlying these three behaviors. The possibility of a common source does not preclude the existence of different phenotypic manifestations, as the way to compensate for the difficulties may vary across individuals.