1) Behavior either verbal or nonverbal, under the control of verbal antecedents. In some usages, any verbal antecedent qualifies as a rule (as when one is told to do or say something). In others, rules are only those verbal antecedents that specify contingencies (as when one is told what will happen if one does or says something); such rules may alter the functions of other stimuli. Some rules are self-produced; the most effective verbal antecedents are those one generates oneself. Whether rule-following occurs in the presence of a rule is often ambiguous (one may repeat a rule to oneself at the time of following it); for that reason, rules do not necessarily qualify as discriminative stimuli even though they function as verbal antecedents.

2) The effects of instructions, advice, maxims, and laws on the listener's behavior. In this view, rules are seen as complex discriminative stimuli and the principles that govern stimulus control regulate the behavior of the listener.

3) Behavior under the control of a rule.