The affect/effect theory of the mediation of teacher expectation effects is presented, and a research agenda is suggested for the investigation of this theory. In addition, some methodological issues in psychology are reviewed. The affect/effect theory states that a change in the level of expectations held by a teacher for the intellectual performance of a student is translated into a change in the affect shown by the teacher toward that student and the degree of effort shown by that teacher in teaching that student. The affect/effect theory is consistent with much experience and research. The following aspects of the theory are considered: (1) dynamic features; (2) communication channels; (3) molar versus molecular variables; (4) redundancy versus specificity; (5) channel discrepancy; (6) interactional synchrony; and (7) direct intervention. Future efforts should extend the affect/effect theory to domains other than education. The methodological features of psychology reviewed include: a discussion of effect size; a consideration of what constitutes successful replication of research; and a review of the benefits of meta-analysis, both obvious and less apparent. A 52-item list of references is included. (SLD)