What is shaping in ABA?
Shaping is a teaching procedure that reinforces successive approximations of a target behavior, so a skill the learner cannot yet perform is built gradually from responses they already can.
Some skills cannot be prompted into existence because nothing close to them exists yet. Shaping solves this by starting with whatever the learner currently does that is closest to the goal - a rough approximation - and reinforcing it until it is reliable. Then the criterion moves: only a slightly better approximation earns reinforcement, and the earlier version no longer does.
A classic example is vocal language. A learner working toward saying 'water' might first be reinforced for any vocalization, then for a 'w' sound, then 'wa', and so on until the full word is reached. The same logic applies to tolerating a toothbrush for longer intervals, staying seated for more of a work session, or writing letters with progressively better formation.
The judgment in shaping is when to move the criterion. Raise it too fast and responding collapses because reinforcement effectively disappears; hold it too long and the learner gets stuck on an approximation that is now easy. Clinicians read that timing from the data - a stable, high rate at the current step is the signal to advance.
Shaping is often confused with chaining, but they solve different problems. Chaining links separate steps of a sequence together, each step already in the learner's repertoire or taught directly. Shaping refines a single response along one dimension - loudness, duration, accuracy, closeness to a model - until it matches the target.
Because each criterion change is a clinical decision, clear definitions matter. A written shaping plan states the terminal behavior, the current approximation that earns reinforcement, and what the next step will be, so every therapist on the case reinforces the same thing and session data reflects one consistent standard rather than each person's private judgment.