Pretesting as determinant of attitude change in evaluation research.

Studied the biasing effects of a pretest on subsequent posttest results in 2 experiments. The problem of Exp I, with 119 undergraduates, was the evaluation of a programed textbook used by psychology freshmen. It used a separate-sample pretest-posttest design and showed that a pretest containing mostly negative statements on programed instruction confounded posttest results. Exp II, using a different treatment, studied the pretest effects of positive or negative statements on 162 undergraduates. The positive version counteracted the development of negative feelings toward the treatment. The negative version did not show a similar sensitizing effect. This was considered a consequence of the controversial character of the treatment and the obligatory participation of Ss. The negative statements perhaps confirmed existing attitudes. Three suggestions to control for pretest sensitization effects are given: Use research designs with control conditions, separate the pretest phase from the posttest phase, and emphasize designs without pretests