What is ABC data in ABA?
ABC data is a descriptive record of behavior in context - what happened immediately before it (antecedent), what the behavior looked like, and what followed it (consequence) - collected to build hypotheses about why the behavior occurs.
Behavior never happens in a vacuum, and ABC recording is the discipline of capturing its surroundings. Each entry answers three questions: what was going on right before the behavior, what exactly did the learner do, and what happened next - who responded, what was gained, what was removed.
Across enough entries, patterns surface. If aggression reliably follows the presentation of demands and reliably ends with the task being withdrawn, escape is the working hypothesis. If it clusters when attention shifts to a sibling and draws an adult back, attention is. The individual entry proves nothing; the pattern across entries is the evidence.
ABC data comes in two broad flavors. Narrative ABC is open-ended - observers describe events in their own words, which is rich but slow and inconsistent across people. Structured ABC uses predefined checklists of common antecedents and consequences, which is faster, more consistent, and far easier to summarize, at the cost of nuance outside the checklist.
Its limits matter as much as its uses. ABC data is correlational - it shows what tends to co-occur with the behavior, not what causes it. It feeds the hypothesis stage of a functional behavior assessment; confirming function, when needed, is the job of more controlled analysis. Treating an ABC pattern as proof is one of the classic assessment mistakes.
The practical failure mode is burden: an ABC form that takes minutes per incident won't be filled out during a difficult session. Formats that let the observer record in a few taps - and prompt for the fields that matter - are what make descriptive assessment usable at caseload scale rather than only in the clinic's best week.