Selecting participants for dyslexia studies: Complexities and challenges

The definition of, the nature of, the diagnosis of, and intervention in dyslexia are controversial. There is no consensual definition of dyslexia and although most of the specialized literature states that dyslexia has a neurodevelopmental basis, the debate seems far from exhausted. Also there is no single diagnostic procedure for dyslexia and it is not clear in what aspects interventions for dyslexia differ from those for other reading related (decoding) problems. Such disceprancies raise concerns about the constitution of samples in studies about dyslexia mainly in those studies where groups of participants with different but related reading conditions are included and compared. Reserchers apparently use different methodologies to constitute theirs samples. This makes any comparisions across studies problematic and eventually threatens the generalisability of the findings.