Understanding Behavior Chains
A behavior chain is a specific sequence of discrete responses, each associated with a particular stimulus condition, that when linked together produce a complex behavior. Each step in the chain serves a dual function: the completion of one step serves as a conditioned reinforcer for the previous response and as a discriminative stimulus (SD) for the next response. Understanding how behavior chains work is fundamental to teaching complex skills in applied behavior analysis.
Consider the behavior chain of hand washing. The chain might include: turning on the water, wetting hands, picking up soap, lathering hands, rinsing hands, turning off the water, and drying hands with a towel. Each step cues the next, and the final step in the chain produces the terminal reinforcer (clean, dry hands and any associated social reinforcement).
Task Analysis: The First Step
Before implementing any chaining procedure, you must first develop a task analysis. A task analysis breaks down a complex skill into its component steps, listed in the correct sequence. The quality of your task analysis directly impacts the success of your chaining procedure.
To create an effective task analysis, you can use several methods:
- Observe a competent individual - Watch someone who can perform the task and record each step they complete
- Perform the task yourself - Complete the task while noting every action required
- Consult an expert - Ask someone skilled in the task to list each step
After creating the initial task analysis, validate it by having someone unfamiliar with the task follow the steps. If they can complete the task successfully using only the written steps, the task analysis is sufficiently detailed. If they struggle, you may need to break certain steps into smaller components.
Forward Chaining
In forward chaining, instruction begins with the first step in the chain. The learner is taught to independently perform the first step, and the instructor completes all remaining steps. Once the learner masters the first step (meets the mastery criterion), the second step is added, so the learner now independently performs steps one and two. This process continues until the learner completes the entire chain independently.
When to Use Forward Chaining
Forward chaining is a good choice when the first steps in the chain are the easiest to learn or when the natural order of the task is important for the learner to experience from the beginning. It is also useful when the learner has some ability to perform the initial steps but needs instruction on later steps.
Example: Teaching Tooth Brushing with Forward Chaining
Step 1: The learner picks up the toothbrush (taught first). The instructor completes all remaining steps (applying toothpaste, brushing teeth, rinsing, etc.). Once the learner independently picks up the toothbrush across multiple trials, Step 2 is added: picking up the toothbrush and applying toothpaste. The instructor completes the remaining steps. Training continues in this manner until the learner completes the entire tooth brushing routine independently.
Backward Chaining
In backward chaining, instruction begins with the last step in the chain. The instructor completes all steps except the final one, and the learner is taught to independently perform only the last step. Once mastered, the instructor completes all steps except the last two, and the learner independently performs those final two steps. This process continues in reverse until the learner completes the entire chain from the beginning.
Advantages of Backward Chaining
Backward chaining has a unique advantage: the learner experiences the terminal reinforcer after every training trial. Because the learner always completes the last step, they always contact the natural reinforcer that follows chain completion. This can increase motivation and make the procedure especially effective for learners who need frequent contact with reinforcement to maintain engagement.
When to Use Backward Chaining
Backward chaining is particularly effective when the last steps in the chain are the easiest, when the learner benefits from contacting the terminal reinforcer during every training trial, or when the learner has difficulty sustaining attention through longer sequences. It is one of the most commonly used chaining procedures for teaching self-care and daily living skills.
Example: Teaching Putting On a Shirt with Backward Chaining
The instructor guides the learner through all steps except the last one (pulling the shirt down over the torso). The learner independently completes the final pull-down step. Once mastered, the instructor guides through all steps except the last two (pulling both arms through the sleeves and pulling down). The learner independently completes those two steps. Training continues in this pattern.
Total Task Chaining
In total task chaining (also called total task presentation or whole task chaining), the learner attempts every step in the chain during every training session. The instructor provides prompts as needed for any step the learner cannot complete independently and allows the learner to perform independently any steps they have already mastered.
When to Use Total Task Chaining
Total task chaining is best suited for learners who can already perform some steps in the chain independently or who can learn multiple steps simultaneously. It is efficient because the learner practices the entire chain during each session rather than waiting for individual steps to reach mastery before adding new ones. This procedure is often used for tasks that the learner has partial competence with or for relatively simple chains.
Example: Teaching Dish Washing with Total Task Chaining
During each session, the learner attempts all steps: turning on water, adding soap to the sponge, scrubbing the dish, rinsing the dish, and placing it in the drying rack. The instructor provides physical or verbal prompts for any steps the learner cannot perform independently. Over time, prompts are faded as the learner gains competence on each step. Data are collected on the percentage of steps completed independently across sessions.
Comparing the Three Procedures
All three chaining procedures can be effective, and the choice between them depends on the learner's characteristics, the nature of the task, and practical considerations. Forward chaining allows the learner to experience the natural beginning of the chain first. Backward chaining ensures contact with the terminal reinforcer during every trial. Total task chaining is the most efficient when the learner has partial skills or can handle learning multiple steps at once.
Research has not consistently demonstrated the superiority of one chaining procedure over the others across all contexts. Clinical decision-making should be guided by the individual learner's needs, the complexity of the chain, and the learner's current skill level.
BCBA Exam Considerations
For the BCBA exam, you should be able to define each chaining procedure, identify which procedure is being used in a clinical scenario, explain the advantages and disadvantages of each, and recommend the most appropriate procedure based on learner characteristics and task features. Practice identifying the key differences: forward chaining starts at the beginning, backward chaining starts at the end, and total task chaining addresses every step during every session.