A Guide to ABA Therapy

Functions of Behavior

Three – Term Contingency

Three – Term Contingency is a foundational aspect of ABA Therapy. Many times referred to as the “ABCs of behavior”, it generally highlights how behavior is influenced by our environments, as well as how the consequences of these behaviors can shape its propensity for future occurrences.


The three step process, or the “ABCs”, we are referring to are:

  1. Antecedent: events or actions that come BEFORE a behavior or response
  2. Behavior: resulting action from the antecedent
  3. Consequence: event or action that comes AFTER a behavior or response

Within our teaching environments, the RBT will be looking for a specific response or behavior from the child after delivering a specific opportunity. When the desired response or behavior occurs, a desirable reinforcer is presented for the child. This increases the likelihood that the response or behavior will occur again. The child will recognize that certain behaviors or responses will give them access to what they want.


Understanding the three-term contingency will also allow the supervising clinician to know why a challenging behavior is happening or determine its function. The BCBA will look at the consequence, or what is maintaining, the challenging behavior.  How or why your child is getting what they “want” by engaging in the challenging or undesired behavior.

ABA says there are four main functions of problem behavior.  Your child will engage in the challenging behavior to either gain attention, escape or avoid a non-preferred task or situation, to gain access to tangibles or something they desire, or automatic reinforcement.  Automatic reinforcement can be thought of as something that appeals or offends the senses.

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