This paper discusses research exploring the performance factors involved in studies which test for formal operations. It is suggested that several previous studies dealing with formal operations confound performance and competence in determining the extent of subjects' formal operations schemata. Factors which might account for performance differences are: (1) tasks chosen by the investigators to measure formal operations thought, (2) the degree to which the investigators use a direct method of task presentation and questioning, (3) the number of dimensions along which tasks vary, (4) the content area of the task, (5) sex differences, and (6) intelligence differences. Results of a series of experiments with elementary, junior high, and high school students which tested the extent to which these factors affect formal operations performance are presented. (BRT)