According to Psychology Dictionary, mechanistic interactionism and reciprocal interactionism are two differing theories of interactionism that psychologists and sociologists have developed in order to determine which factors, if any, could help in the prediction of specific outcomes of varying interactions.
John F. Kihlstrom of the University of California, Berkeley, states that interactionism is the attempt to understand why, when a human interacts with a situation, the specific outcome of that interaction occurs versus any other potential outcome. Psychology Dictionary notes that the theory of mechanistic interactionism takes into account only traits and situations when attempting to determine outcome. The theory of reciprocal determinism, also called dynamic interactionism or reciprocal determinism, takes account of behavioral aspects as well as traits and situation to determine outcomes.
Coy Stoker of the University of Phoenix uses hypothetical examples to help simplify and clarify these two theories: Assume there exists a student who earns poor grades in distance learning courses, has low self-esteem and poor study habits. The theory of mechanistic interactionism might support the theory that all distance learning (the situation) students who have low self-esteem (the trait) will get poor grades (the outcome). Thus, self-esteem level and learning type are the only relevant factors when attempting to understand why the student did poorly, or to predict the most likely grade the student will earn. With reciprocal interactionism, however, the behavioral habits of the student (not studying enough) would also be considered. With any of these three aspects unaccounted for, an accurate understanding or prediction could not be made.