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The current study examined the reliability of a measure of ear advantage and the total scores derived from the dichotic listening task. The scores for both measures were found: (1) not to differ from the normal distribution, and (2) to be reliable over items, tests, and time. However, the total scores were dependent upon stimulus materials and experience. In addition, a psychometric classification model was proposed and it was found that the majority, at least 51.6% of the subjects, did not exhibit a truly measureable ear advantage. Finally, it was argued that total scores as well as ear advantage should be considered in the analysis of dichotic listening studies.

In recognition of increased usage of cluster analytic techniques, the current study attempted to examine sampling bounds for tests and subjects on one cluster-analytic procedure. Specifically, the WAIS subtest scores from a heterogeneous group of subjects with CNS involvement were first, factor analyzed and then clustered by means of Ward's hierarchical procedure. This methodology had been previously applied to two different samples of aphasics and aphasia batteries. In both these aphasic studies, an underlying severity dimension of language dysfunction was found. In contrast, in the current study, salient feature groups were found. Moreover, these groups were distributed in a sequential or hierarchical model in terms of specific cognitive deficits. From these data, it is argued that two major parameters in determining the resulting cluster structures are the homogeneity/heterogeneity of the sample and test battery employed. Although such a statement is obvious, the theoretical ramifications are large, in that the cluster structure may be a function of test weighting or sample diversity, not the phenomenon of interest. However, the cluster structures found in the current study were consistent with historical models of cognitive dysfunction and also lend support to hierarchical models of sequential cognitive impairment. These findings are discussed in terms of their clinical and experimental ramifications with respect to grouping subjects in terms of WAIS profiles.

Statistical means of shortening the Speech Sounds Perception Test were examined. Stepwise multiple regression analyses indicated that a 30-item version correlated quite highly with the 60-item version. Group means for representative clinical groups were presented, but no strong differences emerged using either version. Inclusion of length of stay and number of previous admissions as covariates did little to enhance the predictive validity of either form. Finally, the correlation of the 30-item test with demographic variables showed that age correlated most, followed by occupational status. These results were interpreted as indicating that the 30-item version could be used while maintaining the clinical utility of this test.

The ten-block Tactual Performance Test (TPT-10) has been criticized as a clinical instrument due to the long administration time and accompanying psychological distress. The shorter children's six-block version (TPT-6) has been proposed as a potential substitute. The current study examined the internal consistency, the test/retest reliability and the construct validity of the TPT-6. The results indicate that the TPT-6 is a very reliable instrument and is similar to the TPT-10 in terms of construct validity. Most importantly, the actual administration time is approximately one third that of the TPT-10.