The hypothesis considered is that external evaluation of learning that a student may do for its intrinsic value may lessen the student's existing interest. Instructional movies were presented to students; in some cases students were told that they would (or in some cases, might) be tested on the contents, and in others they were not told this. The first group subsequently reported less interest in the movie topics and in allocating future class time or effort to these topics. The hypothesis was borne out, and it is also suggested that personality factors or conditions such as test anxiety, high academic ability, and the evaluation conditions may be influential. A brief list of references, tables of study results, and the pre- and posttests are appended. (MSE)