Verbal behavior as a form of operant behavior. Verbal behavior as a form of operant behavior. Verbal behavior is often a form of operant responding (R) occasioned by discriminative stimuli (SD) and resulting in delivery of consequent stimuli (SC). The arrow leading from the consequent stimulus SC back to the verbal behavior R indicates that the consequent stimulus increases the probability of (or “reinforces”) the verbal behavior. S. Stevens Negus Pharmacol Rev 2019;71:225-266 Copyright © 2019 by The Author(s)‏