Prevalence and Cognitive Profiles of Children With Comorbid Literacy and Motor Disorders

Abstract

There is a high prevalence of comorbidity between neurodevelopmental disorders. Contemporary research of these comorbidities has led to the development of multifactorial theories of causation, including the multiple deficit model (MDM). While several combinations of disorders have been investigated, the nature of association between literacy and motor disorders remains poorly understood. Comorbid literacy and motor disorders were the focus of the two present studies. In Study 1, we examined the prevalence of comorbid literacy and motor difficulties relative to isolated literacy and motor difficulties in a community sample (N = 605). The prevalence of comorbidity was five times greater than expected by chance alone, implying some relationship between difficulties. In Study 2, we examined the cognitive profiles of children with literacy and motor disorders amongst a subsample of children from Study 1 (N = 153). Children with literacy disorder had deficits in phonological processing, selective attention, and memory whilst children with motor disorder had deficits in visuospatial processing and memory, suggesting the disorders should be considered to have both independent and shared (memory) cognitive risk factors. Children with comorbid literacy and motor disorder demonstrated an additive combination of these deficits. Together, these findings are consistent with predictions from the MDM.

How Do Spelling, Handwriting Speed, and Handwriting Quality Develop During Primary School? Cross-Classified Growth Curve Analysis of Children's Writing Development

“…The few studies focusing on legibility used criteria that are commonly related to letter formation and to spatial organization within and between words (e.g., unusual letter shapes, size fluctuation, bad letter alignment, abnormal space between letters; Graham et al, 2006;Caravolas et al, 2020). Such criteria allow identifying children who have graphomotor difficulties, leading to illegible handwriting like in the case of developmental coordination disorder or, to a lesser extent, dyslexia (Prunty and Barnett, 2017;Di Brina et al, 2018;Downing and Caravolas, 2020). However, handwriting has never been investigated with such precise legibility criteria in typically developing children, to measure the quality of their handwriting.…”

Second Graders’ Grapho-Motor Skill Learning and Verbal Learning: The Effects of Socio-Educational Factors

“…Moreover, ILT studies showed different abilities as well as transfer gains in children with developmental coordination disorder (DCD; Adi-Japha and Brestel, 2020), commonly associated with difficulties in mastering handwriting (Farmer et al, 2016). It should be noted that due to the high comorbidity of reading and spelling difficulties and DCD (Downing and Caravolas, 2020), the research questions of the current study may be also relevant to children with DCD.…”

“…In the current study, we will focus on this population. Motor difficulties are common among children with reading and spelling difficulties, with a third or more of the children showing reading and spelling difficulties being diagnosed with motor difficulties (for a recent review, see Downing and Caravolas, 2020). Studies on motor skill learning among children with reading and spelling difficulties focus almost exclusively on the initial training session, implying intact performance in longer training sessions (for a recent review, see He and Tong, 2017).…”

“…Children with reading and spelling difficulties were shown to have motor difficulties. Several hypotheses were made regarding the source of comorbidity between reading and spelling difficulty and lower motor skills, all relate to the multifactorial nature of development with complex interactions within the environmental and the biological/genetic substrate and between these substrates (Downing and Caravolas, 2020). The effect of reading and spelling difficulties on training gains was shown to depend on training length (He and Tong, 2017).…”

“…Verbal difficulties are characteristic of children with reading and spelling difficulties (Downing and Caravolas, 2020), however verbal learning relate more to memory for words than to other verbal skills (e.g., phonology). In this context, only weak association was reported between reading difficulties and verbal short-term/working memory (Landerl et al, 2013).…”