What Is Shaping in Applied Behavior Analysis?
Shaping is a fundamental behavior-change procedure in applied behavior analysis (ABA) that involves differentially reinforcing successive approximations toward a target behavior. Unlike prompting or modeling, shaping is uniquely suited for building behaviors that do not yet exist in a learner's repertoire. If a learner has never produced a response even remotely close to the target, shaping provides a systematic path from what the learner can do now to what you want them to do eventually.
For the BCBA exam, you need a thorough understanding of shaping procedures, the criteria for moving through approximation steps, and the clinical judgment involved in deciding when to raise or lower your criteria. This post walks through everything you need to know.
The Core Components of Shaping
Shaping relies on two interrelated processes: differential reinforcement and successive approximations. Differential reinforcement means reinforcing responses that meet your current criterion while placing all other responses on extinction. Successive approximations are the intermediate behaviors that progressively resemble the terminal (final) target behavior.
Consider teaching a child to say the word "water." Initially, you might reinforce any vocalization at all. Once vocalizations become consistent, you shift your criterion to only reinforce sounds that begin with a "w" sound. Next, you require "wa," then "wah-ter," and finally the full word "water." Each step is an approximation, and each criterion shift moves the learner closer to the goal.
When Should You Use Shaping?
Shaping is the procedure of choice when the target behavior is not currently in the learner's repertoire and cannot be evoked through simpler methods like instructions, prompts, or modeling. It is also useful when:
- The learner needs to improve the quality, duration, latency, or force of an existing behavior
- You want to increase the complexity or accuracy of a response over time
- The target behavior is a novel motor skill, verbal response, or social behavior that the learner has never performed
- Other teaching procedures (discrete trial training, prompt fading) have not been effective
On the BCBA exam, you may be given a scenario describing a learner who cannot produce the target behavior at all. The correct answer will often involve shaping, especially if the question specifies that prompts and models have been tried without success.
Steps for Implementing a Shaping Procedure
Effective shaping requires careful planning before you begin. Here are the key steps in order:
Step 1: Define the Target Behavior
Write a clear, observable, and measurable definition of the terminal behavior. For example, "The learner will independently tie their shoes within 60 seconds" or "The learner will produce a complete sentence of at least five words when requesting a preferred item."
Step 2: Identify the Starting Behavior
Observe what the learner can currently do that is related to, or in the direction of, the target behavior. This starting behavior is your first approximation. It should occur at a rate high enough that you can reinforce it regularly. If the starting behavior never occurs, you may need to choose a different starting point.
Step 3: Plan the Approximation Steps
Outline the intermediate steps between the starting behavior and the terminal behavior. These steps should be small enough that the learner can succeed but large enough to make meaningful progress. Planning your steps in advance helps avoid getting stuck at an intermediate level.
Step 4: Differentially Reinforce Each Approximation
Reinforce only responses that meet the current criterion. Responses that no longer meet the criterion should be placed on extinction. Use a reinforcer that is potent enough to maintain responding at a high rate throughout the process.
Step 5: Shift the Criterion Progressively
When the learner consistently meets the current criterion, raise the bar to the next approximation. If the learner stops responding or shows signs of frustration, you may need to temporarily lower the criterion (a process sometimes called "backing up") before moving forward again.
Common Mistakes in Shaping
The BCBA exam frequently tests your ability to identify errors in shaping procedures. Watch for these common pitfalls:
- Moving too quickly: Advancing the criterion before the current approximation is well established leads to extinction bursts and lost progress
- Moving too slowly: Reinforcing the same approximation for too long can result in a behavioral "plateau" where the intermediate behavior becomes so strong that it resists change
- Inconsistent reinforcement criteria: If you sometimes reinforce responses below the current criterion, the learner receives mixed signals about what behavior is expected
- Failing to use extinction: If you continue reinforcing previous approximations while also reinforcing the current one, the learner has no reason to change
Shaping Across Different Dimensions of Behavior
Shaping can target any measurable dimension of behavior. You might shape the topography (form) of a response, the duration (how long it lasts), the latency (how quickly it begins), the force or magnitude (how intensely it is performed), or the accuracy (how closely it matches the model). Understanding this flexibility will help you on exam questions that present shaping scenarios targeting less obvious behavioral dimensions.
Exam Tips for Shaping Questions
When answering BCBA exam questions about shaping, remember that the defining features are differential reinforcement and successive approximations used together. If a scenario only describes differential reinforcement without changing the criterion over time, it is not shaping. If a scenario describes prompting and fading, it is not shaping either, even though both procedures can produce new behaviors. Pay close attention to whether the question describes a behavior that does not yet exist in the learner's repertoire, as this is the hallmark indicator that shaping is the correct procedure.