Bias in Petrie's alternate-form procedure for kinesthetic aftereffect.

Kinesthetic aftereffect, commonly administered with alternate forms given on two separate occasions, has been used to assess individual differences in personality and perceptual style. Recent criticisms have questioned whether this task gives a worthwhile measure of individual differences. This paper represents a further response to such criticisms by extending to Petrie's alternate-form procedure our argument that lack of test-retest reliability is associated with practice effects which differentially bias second-session scores. Findings indicate that second session bias does occur with this procedure, and, as expected, there was an inverse relationship between magnitude of retest reliability and differential bias. Although use of the alternative-form procedure is contraindicated, a single-session procedure remains a promising personality measure since it is not affected by differential bias.