4.3 Shaping, Chaining, Task Analysis & Imitation Training
Key Takeaways
- Shaping involves differentially reinforcing successive approximations to a terminal behavior while placing previous approximations on extinction.
- Shaping can alter physical topographies or dimensions within a topography, including rate, duration, latency, and magnitude.
- Task Analysis (TA) breaks complex behavioral chains into discrete steps, validated via observing experts, performing the task, or empirical testing.
- Chaining procedures include Forward Chaining, Backward Chaining, Backward Chaining with Leap Aheads, and Total-Task Presentation.
- Shaping is selected to establish brand-new behaviors, whereas chaining is selected to link existing behavioral steps into a sequential repertoire.
4.3 Shaping, Chaining, and Task Analysis
Teaching complex target behaviors requires specialized behavioral technologies that break down skills and build novel repertoires. Qualified Behavior Analysts (QBAs) master shaping, task analysis, and chaining procedures to systematically expand learner capabilities from simple approximations to fluent, multi-step behavioral chains.
Shaping: Systematic Differential Reinforcement of Approximations
Shaping is defined as the differential reinforcement of successive approximations to a terminal behavior. Differential reinforcement in shaping means reinforcing responses that meet a specific criterion (closer approximations) while withholding reinforcement (extinction) for responses that do not meet the criterion or represent previously mastered approximations.
Dimensions of Shaping
Shaping can be applied across topographies or within specific dimensions of a single topography:
- Shaping Across Topographies: The physical form or shape of the behavior changes over time. For example, shaping vocal speech starting from a grunt ("ba"), to a syllable ("ball"), to a full phrase ("I want ball").
- Shaping Within Topographies: The physical form remains constant, but performance dimensions change:
- Rate / Frequency: Increasing the number of math facts completed per minute.
- Duration: Extending the length of time a learner remains seated during circle time.
- Latency: Decreasing the time elapsed between an instructional cue and the initiation of task performance.
- Magnitude / Force: Adjusting vocal volume from a whisper to an appropriate speaking volume.
Task Analysis: Creation and Validation
A Task Analysis (TA) is the process of breaking a complex skill or series of behaviors into small, discrete, teachable steps ordered in a logical sequential chain. Developing an accurate task analysis is an essential prerequisite for any chaining procedure.
Methods for Constructing and Validating Task Analyses
QBAs validate task analyses using three primary empirical methods:
- Observing Competent Performers: Watching an expert or peer execute the target task and recording each discrete step in sequence.
- Consulting Experts: Interviewing individuals who possess specialized domain expertise regarding the necessary component steps.
- Performing the Task Oneself: The practitioner executes the behavioral sequence personally, noting every sub-step and motor adjustment required.
Before implementation, the QBA must individualize the task analysis based on the learner's age, prerequisite skill repertoire, motor capabilities, and cognitive functioning level.
Chaining Procedures
A behavior chain is a specific sequence of discrete responses, where each response produces a stimulus change that simultaneously serves as a conditioned reinforcer for the preceding response and a discriminative stimulus ($S^D$) for the subsequent response. The final response in the chain produces the terminal reinforcer.
Four Primary Chaining Methods
| Chaining Method | Instructional Procedure | Clinical Advantage |
|---|---|---|
| Forward Chaining | Teaching begins with step 1. Reinforcement is delivered after step 1 is performed independently; the trainer completes remaining steps. Once step 1 is mastered, step 2 is added. | Preserves natural behavioral order; ideal for learners who build momentum from initial success. |
| Backward Chaining | Teaching begins with the final step (Step N). Trainer completes steps 1 through N-1; learner performs final step and immediately receives the natural terminal reinforcer. | Learner experiences immediate connection to the terminal reinforcer on every trial. |
| Backward Chaining with Leap Aheads | Same as backward chaining, but steps already in the learner's repertoire are skipped ("leaped over") during training. | Accelerates instruction for learners with prerequisite component skills. |
| Total-Task Presentation | Learner is exposed to every step of the task analysis during every trial, receiving prompting as needed on steps not yet mastered. | Fastest acquisition for learners who possess many component skills or have higher cognitive functioning. |
Comparison and Selection Criteria: Shaping vs. Chaining
Determining whether to utilize shaping or chaining is a critical clinical decision for QBAs:
- Shaping is selected when the terminal behavior is a NEW topography or dimension that does not currently exist in the learner's repertoire. The process is continuous, involving gradually changing criteria.
- Chaining is selected when the component steps already exist in the learner's repertoire, but must be combined into a specific SEQUENCE.
Decision Framework for Chaining Selection
- Total-Task Presentation: Select if the learner has a high imitation repertoire, can perform many component steps, or if the chain is relatively short.
- Backward Chaining: Select if the learner easily loses motivation or benefits from contacting the terminal reinforcer immediately after executing a single step.
- Forward Chaining: Select if the sequence is strictly chronological or if the learner struggles with complex multi-step instructions.
Imitation Training
Imitation training teaches a learner to copy a model's actions so that new skills can be acquired through demonstration rather than only through shaping each topography from scratch. Clinically:
- Establish attending to the model (eye contact/orientation to the relevant action).
- Present a clear model ("Do this") with an imitative SD.
- Prompt the matching response (physical, gestural, or positional) and reinforce correct imitation.
- Fade prompts until the learner imitates novel actions under the generalized imitative repertoire.
- Probe generalized imitation—copying actions never directly taught—which becomes a behavioral cusp for rapid skill acquisition.
Differentiate imitation (matching a model's behavior) from echoic verbal behavior (matching vocal-verbal stimuli) and from mere coincidence of topography. Imitation training often precedes or accelerates chaining, play skills, and social routines; without it, DTT and NET models lose efficiency.
A behavior analyst is teaching a client to wash hands using a 7-step task analysis. The analyst prompts the client through steps 1 through 6, then requires the client to complete step 7 independently to receive a preferred sticker and verbal praise. Which chaining procedure is being used?
When deciding between shaping and chaining for a client learning a complex skill, which factor indicates that shaping is the appropriate choice?