Pretesting as determinant of attitude change in evaluation research

Two experiments were done to study the biasing effects of a pretest on subsequent posttest results. The problem of the first experiment was the evaluation of a programmed textbook used by psychology freshmen. It used a separate-sample pretest-posttest design and showed that a pretest containing mostly negative statements on programmed instruction confounded posttest results. The second experiment, using a different treatment, studied the pretest effects of positive or negative statements. The positive version counteracted the development of negative feelings towards the treatment. The negative version did not show a similar sensitizing effect. This was considered a consequence of the rather controversial character of the treatment and the obligatory participation of subjects. The negative statements perhaps confirmed existing attitudes. Three suggestions to control for pretest sensitization effects were given: (1) use research designs with control conditions; (2) separate the pretest phase from the posttest phase; and (3) give more emphasis to designs without pretests