"...events, operations, and stimulus conditions with value-altering motivating effects that are unlearned" (Michael, as cited in Cooperet al, 2007, p. 377).

Surrogate CMOs replace and have the same effect as the motivating operation that it was previously paired with.

Reflexive CMOs create a circumstance in which its own removal serves as the reinforcement.

Transitive CMOs make other stimuli more effective reinforcers.

"A stimulus in the presence of which responses of some type have been reinforced and in the absence of which the same type of responses have occurred and not been reinforced; this history of differential reinforcement is the reason an SD increases the momentary frequency of the behavior" (Cooper et al, 2007, p. 694).

"An environmental variable that (a) alters (increases or decreases) the reinforcing or punishing effectiveness of some stimulus, object, or event; and (b) alters (increases or decreases) the current frequency of all behavior that has been reinforced or punished by that stimulus, object, or event" (Cooper et al., 2007, p. 699).