Reactance is a motivational reaction to offers, persons, rules, or regulations that threaten or eliminate specific behavioral freedoms. Reactance occurs when a person feels that someone or something is taking away his or her choices or limiting the range of alternatives.
It's a damnable thing, a real thing, a useful thing to know of, and yet far too few people know of it.
Reactance theory assumes there are "free behaviors" individuals perceive and can take part in at any given moment. For a behavior to be free, the individual must have the relevant physical and psychological abilities to partake in it, and must know they can engage in it at the moment, or in the near future.
"Behavior" includes any imaginable act. More specifically, behaviors may be explained as "what one does (or doesn't do)", "how one does something", or "when one does something". It is not always clear, to an observer, or the individuals themselves, if they hold a particular freedom to engage in a given behavior. When a person has such a free behavior they are likely to experience reactance whenever that behavior is restricted, eliminated, or threatened with elimination.
In the phenomenology of reactance there is no assumption that a person will be aware of reactance. When a person becomes aware of reactance, they will feel a higher level of self-direction in relationship to their own behavior. In other words, they will feel that if they are able to do what they want, then they do not have to do what they do not want. In this case when the freedom is in question, that person alone is the director of their own behavior.
When considering the direct re-establishment of freedom, the greater the magnitude of reactance, the more the individual will try to re-establish the freedom that has been lost or threatened. When a freedom is threatened by a social pressure then reactance will lead a person to resist that pressure. Also, when there are restraints against a direct re-establishment of freedom, there can be attempts at re-establishment by implication whenever possible.
Freedom can and may be reestablished by a social implication. When an individual has lost a free behavior because of a social threat, then the participation in a like free behavior by another person similar to himself will allow him to re-establish his own freedom.
In summary the definition of psychological reactance is a motivational state that is aimed at re-establishment of a threatened or eliminated freedom. A short explanation of the concept is that the level of reactance has a direct relationship between the importance of a freedom which is eliminated or threatened, and a proportion of free behaviors eliminated or threatened.