2.2 The Antecedent–Behavior–Consequence (ABC) Model

Antecedent (A) is whatever happens immediately before the behavior -- the trigger or setting event. This can be something specific (a demand was placed, a toy was taken away, a transition was announced) or more general (the child is tired, hungry, or in a loud environment). Behavior (B) is the observable, measurable action itself -- described specifically enough that another observer would recognize it (e.g. "child screamed for approximately 10 seconds and dropped to the floor," not "child had a tantrum"). Consequence (C) is whatever happens immediately after the behavior -- how the environment, caregiver, or peers responded.

The IRIS Center at Vanderbilt University, a widely used training resource in special education and behavioral training, describes the ABC model this way: antecedents and consequences can occur naturally in the environment, and they can also be deliberately used to change behavior -- because what happens before and after a behavior directly affects how likely that behavior is to happen again (IRIS Center, "The ABC Model"). For example: if a teacher gives an instruction (antecedent), a child completes the task (behavior), and the teacher praises them (consequence), the praise may make task completion more likely next time. If a child refuses to share (behavior) and the peer simply walks away to play elsewhere (a natural consequence), that outcome may discourage the refusal in the future -- or, just as easily, may reinforce it if being left alone was what the child wanted.

To use the ABC model in real time, it helps to have a simple three-column recording sheet. Every time the target behavior occurs, write down what happened right before, describe the behavior itself in neutral terms, and write down what happened right after -- including who responded, how, and how quickly. Collecting this across multiple occasions, not just one, is essential, because a single instance can be a coincidence, while a pattern across five or ten instances reveals something real.

Practical takeaway: Carry an ABC data sheet (paper or digital) into every observation session. Even a rough, quickly-jotted ABC note is more clinically useful than a polished paragraph written from memory an hour later.