State Colony, Woodbine, N . J . Lower Penns Neck Public School, N . J .PROBLEM Considerable I& discrepancies in groups of retardates have been obtained between the Leiter International Performance Scale (LIPS), the Stanford Binet (SB) and the Wechsler Verbal (WAIS-V) and Performance (WAIS-P) scales (11 3, 5). In some experiments, Performance I& was superior, in others Verbal I&. Variation in intelligence level was thought to contribute significantly to these discrepancies. This study investigated differences between the above tests over a wide I& range. The following sources of variation are considered: test difficulty in terms of overall differentiation between tests; nature of test in terms of a Performance/Verbal test dimension; intelligence level in'terms of five grades maximally varying as to I&; and, finally, kind of intelligence level in terms of three level criteria varying along a Performance /Verbal dimension.
METHODSubjects. Seventy-five retardates, who completed all tests, were drawn from the resident helper male population of Woodbine State Colony. The main selection criterion served to produce greatest possible I& variation.Tests. The tests selected are the LIPS, a pure performance scale; the SB (Form L), a mixed performance/verbal scale; the WAIS V and P subscales which are dealt with separately because of the differential effects between verbal and performance tests. The sample means, with standard deviations in brackets, are as follows: 61.69 (14.30), and WAIS Full Scale = 58.47 (10.56). They increase in the order LIPS -SB -WAIS, as expected from the literature. The correlations between the four test scores are as follows: LIPS us. SB = 0.77, us. WAIS-P = 0.78, and WAIS-V us. WAIS-P = 0.71. With one exception (LIPS us. WAIS-V), these coefficients are fairly uniform.For cross-validation of the Wechsler Performance /Verbal discrepancy effects, described in a separate paper(2), a score of WAIS-P minus V (P-V) was derived. The present mean is 1.67 (SD = 10.52).Chronological age. Age varied considerably about the mean of 36.91 years, SD being 11.88. Correlations between this factor and the test scores are as follows: LIPS = -0.12, SB = 0.00, WAIS-V = 0.13 and WAIS-P = 0.26. Only the latter coefficient is significant at the 5% level, indicating that age plays no significant role in the present analysis.Procedure. The tests were administered in a balanced order to control for sequence effects. The Binet and Wechsler tests were scored in the conventional manner. The scoring procedure for the LIPS was as suggested in a personal letter by Dr. R. G . Leiter: MA multiplied by 100 and divided by a constant of 156 with 5 I& points added (for Ss of more than 13 years). This procedure differs somewhat from that described in the manualc4).The criteria for the Performance/Verbal dimension were the LIPS, the rank order combined WAIS-V: LIPS and the WAIS-V score. The first and last score differ most with regard to both the Performance /Verbal dichotomy and intercorrelation. Variation in intelligence level was effect...
