Most-to-Least vs Least-to-Most Prompting Hierarchies

Understanding Prompts

A prompt is an extra stimulus added to the instruction to increase the likelihood of a correct response. Prompts are temporary supports and must be faded so that the response comes under the control of the natural discriminative stimulus. Because the BCBA exam covers prompting in many contexts, from skill acquisition to behavior reduction, it is worth understanding the options and tradeoffs in depth.

Types of Prompts

Response Prompts

Response prompts are provided by an instructor and relate to the learner's response.

• Full physical prompt: Hand-over-hand guidance through the entire response.
• Partial physical prompt: A lighter touch, such as a tap on the elbow, to initiate the response.
• Model prompt: The instructor demonstrates the response.
• Gestural prompt: Pointing, nodding, or looking toward the correct response.
• Verbal prompt: Providing the answer or a partial answer, such as the first sound of a word.
• Positional prompt: Placing the correct item closer to the learner.

Stimulus Prompts

Stimulus prompts are changes to the stimulus itself.

• Within-stimulus prompts: Alter the relevant feature, such as making the correct card larger or brighter.
• Extra-stimulus prompts: Add something that is not part of the stimulus, such as a circle drawn around the correct choice.

Stimulus prompts are faded through stimulus fading, or through stimulus shaping, where the form of the stimulus changes gradually until it matches the target.

Most-to-Least Prompting

In most-to-least (MTL) prompting, the instructor begins with the most intrusive prompt required to ensure a correct response and gradually moves to less intrusive prompts across trials or sessions.

Procedure

1. Select a prompt hierarchy, for example: full physical, partial physical, model, gesture, independent.
2. Begin teaching at the level that guarantees a correct response.
3. Reinforce each correct response.
4. After a set criterion, such as 2 or 3 consecutive correct responses at a prompt level, move to the next less intrusive prompt.
5. If errors occur, return to the previous prompt level.

Strengths

• Minimizes errors, which supports errorless learning.
• Useful for dangerous skills or skills where errors are costly.
• Helpful for learners who show frustration after incorrect responses.
• Appropriate for skills involving motor movements.

Limitations

• Can lead to prompt dependence if fading is slow.
• May be unnecessarily intrusive for learners who could respond with less support.
• Requires careful planning of when to fade.

Graduated Guidance

Graduated guidance is a form of MTL prompting in which the instructor adjusts the physical guidance within a trial, moment by moment, based on the learner's response. The instructor gives only as much physical help as needed and fades toward a shadow, in which the hands follow the learner without touching.

This approach is common for teaching motor tasks such as washing hands, writing, or tying shoes. It requires skilled implementers who can respond to the learner's movements in real time.

Least-to-Most Prompting

In least-to-most (LTM) prompting, also called the system of least prompts, the instructor begins with the instruction alone, then provides progressively more intrusive prompts if the learner does not respond correctly.

Procedure

1. Present the instruction and allow a set response interval.
2. If the learner does not respond or responds incorrectly, provide the least intrusive prompt, such as a gesture.
3. If still incorrect, provide the next level, such as a model.
4. Continue until the learner responds correctly, using a physical prompt as a last resort.
5. Reinforce, with higher reinforcement for responses at lower prompt levels.

Strengths

• Provides the learner with opportunities to respond independently on every trial.
• Reduces the likelihood of prompt dependence.
• Efficient for learners with some existing skills.
• Provides useful data on which level of prompt is needed.

Limitations

• Allows more errors, which may be frustrating for some learners.
• May take longer in a given trial because it may require multiple prompt levels.
• Less appropriate when errors would be dangerous or highly aversive.

Choosing Between MTL and LTM

• New skill with no existing responses: MTL helps the learner experience success quickly.
• Learner has partial skills: LTM lets the learner show what they can do independently.
• History of frustration or escape behavior around errors: MTL or time delay reduces errors.
• Risk of prompt dependence: LTM or time delay encourages independent responding.
• Motor skill: Graduated guidance is often best.

Preventing Prompt Dependence

• Plan how and when to fade the prompt before you begin teaching.
• Differentially reinforce independent responses over prompted responses.
• Use data-based decision rules for moving between prompt levels.
• Avoid unintentional prompts such as eye gaze or consistent position of the correct item.
• Pair the prompt with the natural SD so that control transfers.

Data Collection

Record the prompt level required on each trial using codes such as I for independent, G for gestural, M for model, and P for physical. Graph the percentage of independent responses and the average prompt level over time. Decision rules might be: move to a less intrusive prompt after two consecutive sessions at 80 percent or better, and move to a more intrusive prompt if accuracy falls below 50 percent for two sessions.

How This Appears on the BCBA Exam

You may be given a description of an instructor beginning with hand-over-hand and gradually reducing support, and be asked to name the procedure, which is most-to-least prompting. You may also see questions that ask which procedure will result in the fewest errors (MTL or time delay) or which is most likely to produce independence quickly (LTM). Know the difference between response prompts and stimulus prompts, and between prompt fading and stimulus fading.

Key Takeaways

• MTL starts with maximum help and fades; LTM begins independently and adds help as needed.
• MTL supports errorless learning; LTM promotes independence.
• Graduated guidance adjusts physical support moment to moment.
• Always plan prompt fading and reinforce independence more than prompted responding.