The Concept and Development of General Intellectual Ability

This chapter will argue that an understanding of the nature of general intelligence and how it influences cognitive development is vital to an understanding of the majority of developmental disorders. There are two main reasons for this: one is empirical and the other theoretical. The empirical reason, while dull, is very important. Most developmental disorders are diagnosed with reference to a discrepancy in levels of performance from that predicted by the general intellectual functioning of the child. This discrepancy criterion may be obscuring our understanding of these disorders for reasons that I will explain below (Dyck et al., 2004). The theoretical reason is anything but dull. If it is true, as I will argue in this chapter, that understanding developmental disorders requires models that explicitly represent the influence of general intelligence on specific cognitive functions, then this will necessitate a major shift in approach from most who currently investigate a particular disorder, A benefit of grasping this particular nettle, however, is that the comorbidity of developmental disorders, something that is the bane of those researchers who like things neat and tidy, might be put in its proper context