Three-term contingency

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The three-term contingency (also known as the ABC contingency) in operant conditioning describes the relationship between a behavior, its consequence, and the environmental context. The three-term contingency was first defined by B. F. Skinner in the early 1950s.[1] It is often used within ABA to alter the frequency of socially significant human behavior.



The antecedent stimulus occurs first in the contingency and signals that reinforcement or punishment is available on the contingency of a specific behavior. A discriminative stimuli, or SD, directly affects the likelihood of a specific response occurring.[2]


The behavior, also referred to as the response, is any observable and measurable action a living organism can do. In the three-term contingency, behavior is operant, meaning it changes the environment in some way.


Diagram of consequences in operant conditioning

The consequence to a behavior can be reinforcing or punishing. Reinforcing consequences increase the likelihood of a behavior occurring in the future; it is further divided into positive and negative reinforcement. Punishing consequences decrease the likelihood of a behavior occurring in the future; like reinforcement, it is divided into positive and negative punishment.

The effectiveness and value of a consequence is determined by the motivating operations the organism has. For example, deprivation of food can make food more effective as a consequence, and the satiation of hunger can make food less effective as a consequence.[3]


  1. ^ Skinner, B. F. (Burrhus Frederic) (1953). Science and human behavior. New York,: Macmillan. ISBN 0029290406. OCLC 191686.
  2. ^ David., Pierce, W. (2004). Behavior analysis and learning. Cheney, Carl D. (3rd ed.). Mahwah, N.J.: L. Erlbaum Associates. ISBN 9780805844894. OCLC 51566296.
  3. ^ O., Cooper, John (2007). Applied behavior analysis. Heron, Timothy E., Heward, William L., 1949- (2nd ed.). Upper Saddle River, N.J.: Pearson/Merrill-Prentice Hall. ISBN 0131421131. OCLC 74942760.