Developmental coordination disorder (DCD) is a surprisingly common problem; it's thought that 6-8% of school aged children are diagnosable. DCD is a motor disorder, where children have great difficulty in producing skilled actions, especially anything requiring fine motor control. Handwriting, tying your shoelaces, sports of any kind are all huge problems for these children.
One key question about DCD is why does it occur. Part of the problem in answering this is that it is a behavioural diagnosis; you get diagnosed if you have severe motor impairments that aren't a known side effect of something else. Regardless, there are two basic ways in which children might end up with such problems; crudely, they might have difficulties in producing movements, or they might have difficulty learning movements. My colleague and author on this paper, Mark Mon-Williams, uses the analogy that children with DCD may be bad drivers of perfectly working cars or good drivers of malfunctioning cars. It's obviously a little messier than that, but this is the essential idea, and the answer has implications for the kind of interventions you'll try and design.
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