Three-term contingency
The basic unit of operant behavior: an antecedent stimulus, the behavior that follows it, and the consequence that the behavior produces (often written A-B-C or SD-R-SR).
The three-term contingency describes how antecedents, behavior and consequences fit together. An antecedent (often a discriminative stimulus) is present, a behavior occurs, and a consequence follows that affects whether the behavior happens again in the presence of that antecedent. A simple example: the teacher says "Line up" (antecedent), the student walks to the door (behavior), and the teacher says "Thanks for lining up!" (consequence).
The three-term contingency is the foundation for much of what an RBT does. Discrete trials are built on it (SD, response, consequence). ABC data used in descriptive assessment record the same three parts. Discrimination training works by reinforcing a response in the presence of one antecedent and not another.
Understanding the three-term contingency helps an RBT see why consistency matters. If the consequence for a behavior changes from one session to the next, or the antecedent is presented differently each time, the learner gets mixed information about what works when.
Some descriptions add a fourth term, the motivating operation, in front of the antecedent, because an MO affects whether the consequence is valuable at that moment.
Example and non-example
| Example | A peer says "Want to play?" (antecedent), the client says "Yes" and joins the game (behavior), and the peer hands them a ball (consequence). Joining in becomes more likely the next time a peer invites them. |
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| Non-example | Recording only that a client screamed 14 times during a session describes the behavior's frequency but not its antecedents and consequences, so it is not an analysis of the three-term contingency. |
Don't confuse it with
| ABC data | ABC data are a recording method that documents the three parts as they happen; the three-term contingency is the behavioral relation itself. |
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Test yourself
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Question 1An RBT says "Touch cup" while a cup, a spoon and a plate are on the table. The client touches the cup, and the RBT immediately says "You touched the cup!" and hands over a token, as the plan directs. In this trial, the praise and token are the:
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B: Consequence. Whatever the RBT delivers after the response is the consequence part of the trial. Here, praise and a token followed a correct response, so they are the consequence meant to reinforce it.
- A: The discriminative stimulus is the instruction "Touch cup" (with the materials), which comes before the response.
- C: A prompt is extra help given before or during the response; the praise and token came after a correct response.
- D: The intertrial interval is the short pause after the consequence and before the next instruction.
Task C.3 · 40-hour curriculum section E
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Question 2Discrete-trial teaching is built on the three-term contingency. What are its three terms?
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B: Antecedent, behavior, consequence. The three-term contingency is antecedent, behavior and consequence. In a discrete trial these are the instruction (SD), the learner's response, and the reinforcer or error correction that follows.
- A: These are phases of an intervention, not the parts of a contingency.
- C: These are teaching steps for building independence, not the three-term contingency.
- D: The intertrial interval is a pause between trials; the third term of the contingency is the consequence.
Task C.3 · 40-hour curriculum section A · 40-hour curriculum section E
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On the RBT exam
This term belongs to task C.3 Discrete-trial teaching in content area C, Behavior Acquisition, which is 19 of the 75 scored questions.