Grammatical Reasoning: A Stable Performance Yardstick

A grammatical reasoning test was evaluated in a repeated-measures paradigm, using subjects as their own controls. Twenty-three subjects took the test on 15 consecutive workdays in a standard environment. Test scores were evaluated for temporal stability of the daily means, variances, and intertrial correlations. These criteria are related to assumptions of repeated-measures analysis of variance, interpretation of environmental studies, measurement of ability, and subjects' motivation to perform the test repeatedly. On the basis of these considerations, the grammatical reasoning test is an excellent performance test for repeated measurement. After only four trials of practice, the means increase linearly, the variances are constant, and the intertrial correlations are large and unchanging. Stable intertrial correlations indicate that the grammatical reasoning test measures the same thing on each of many repeated trials.