Shaping is the process of reinforcing successive approximations to a desired behavior. Complex actions are built gradually by rewarding steps that come closer and closer to the final performance.

A trainer who wants a dog to press a lever may first reinforce any movement toward the lever, then only movement that brings the paw near it, then actual contact, and finally a full press. Each criterion is raised only after the previous one is performed reliably. Shaping is essential when the target behavior is unlikely to occur spontaneously and therefore cannot be reinforced directly.

The technique is used in animal training, in teaching new skills to children, and in clinical behavior modification. It requires careful observation, precise timing of reinforcement, and systematic raising of the standard. When done well, shaping produces behaviors that would have been difficult or impossible to obtain by waiting for the finished response.

Large behavioral changes are often achieved by reinforcing a series of small ones.