ABSTRACT
This chapter examines the research evidence pertaining to some of the possible causal factors in reading disability (RD). It draws upon research from an intrinsic perspective, and from an extrinsic perspective. These bodies of research show that both intrinsic biological differences and environmental factors play a role in the causation of RD. Research on possible structural differences in the brains of individuals with RD has employed two major methods: postmortem studies and neuroimaging techniques. Methodological shortcomings characterize much of the research on biological differences in RD. The studies on structural differences in the brain have also come under heavy criticism for problems such as failure to appraise handedness in subjects, failure to describe subjects adequately, and questionable classification of some subjects as having RD.
