WISC-WISC-R Differences-Fact or Artifact?

While numerous comparative studies between the WISC and the WISC-R have consistently found lower scores on the latter, these results are called into question since two previous investigations have found that, in fact, there was a significant interaction between the order and version of the two scales when using a cross-over counterbalanced design. In the present study, utilizing previously published data, such an interaction was found in that no significant differences were obtained when the WISC was administered prior to the WISC-R. Highly significant differences were found when the order was reversed. The conclusion is drawn that the pre-viously reported differences are at least in part due to an artifact of design causing inflated scores to be obtained on the WISC when the WISC-R is ad-ministered first. In light of this finding previous investigations need to be reexamined. A literature review of current comparative studies is presented as well as implications for further research. Numerous comparative studies have begun to emerge on the WISC-R (Wechsler, 1974) with most comparisons being between it and the 1949 WISC (Wechsler, 1949). In some 20 studies all but one has consistently shown lower IQs on the WISC-R, although as Swerdlik (1977) points out, the majority of these studies have some methodology problems ranging from subject selection to design and analysis errors. Over half of the studies have been conducted with educably mentally retarded (EMR) subjects with the majority of these being comparisons completed during mandatory revaluations for continued special classroo