WAIS-R subtest pattern clusters in closed-head-injured and healthy samples

Cluster analysis was performed on the WAIS-R subtest scores of a closed-head-injured (CHI) sample (n = 233) in an attempt to replicate and extend the findings of Crosson, Greene, Roth, Farr, and Adams (1990). The same analysis was also run with a healthy sample (n = 326) recruited to match the general adult population in terms of demographic variables; a subsample matched to the CHI sample was also formed (n = 117). Eleven clusters were extracted from the CHI sample, five of which contained 10 or more members. There was a low degree of correspondence between these latter clusters and the six subtest patterns clusters reported by Crosson et al. The importance of Verbal/Performance discrepancies in the formation of clusters in CHI was examined by comparing Verbal/Performance composites against arbitrary composites in CHI and healthy samples. In the CHI sample both sets of composites yielded significant effects but a larger effect size was obtained for the Verbal/Performance composites. However, the same pattern of results was observed in the healthy samples. Finally, a combined cluster analysis (N = 559) revealed that, although there was a significant difference in the number of CHI and healthy participants in each cluster, there was a high degree of overlap in cluster membership.