Stimulus trace in the mentally retarded: defect or developmental lag?

In order to determine whether the central organismic variable of stimulus trace theory, i.e., neural integrity (ni), was more closely related to MA or IQ, comparisons were made between digit span performance of groups who were matched on either MA or CA but who differed in IQ. Differences were found between normal, borderline, and retarded IQ groups matched on CA, but not between those matched on MA. It was concluded that ni was related to MA but not to IQ and that as a consequence stimulus trace theory was best regarded as a developmental rather than a defect approach to mental retardation. The differential implications and research strategies of developmental and defect approaches were discussed as was the significance of the finding of no differences in variability of digit span performance between normal and retarded children.