A prompt makes the right response happen. Fading makes sure it keeps happening once the prompt is gone.
Why it matters
The goal of teaching is a response that occurs to the natural discriminative stimulus (SD), such as a question or a written word, without extra help. Prompts are supplementary antecedents, so they have to go. If you remove them too slowly, the learner may wait for help every time (prompt dependence). If you remove them too abruptly, errors pile up.
Practice items for this task ask you to name a fading procedure from a description, tell time delay apart from prompt hierarchies, and tell stimulus prompts from response prompts.
Key ideas
- Transfer of stimulus control is the point. Every fading method shifts control of the response from the prompt to the natural SD.
- Response prompts vs. stimulus prompts.
- Response prompts are things you do to cue the response: verbal instructions, models, gestures, and physical guidance.
- Stimulus prompts change or add to the teaching materials: making the correct card bigger, darker, or closer, or adding a picture above a word.
- Time delay (also called prompt delay) fades a response prompt by moving it later. The prompt stays the same; only the interval between the SD and the prompt changes, giving the learner a chance to respond first.
- Constant time delay: the first trials use a 0-second delay (SD and prompt together). After that, every trial uses the same fixed delay, such as 4 seconds.
- Progressive time delay: trials also start at 0 seconds, but the delay grows gradually across trials or sessions, for example 1 s, then 2 s, then 3 s, up to a set maximum.
- Time delay keeps errors low. Early 0-second trials let the learner respond correctly from the start, so it is often described as near-errorless.
- Stimulus fading changes the materials, not your behavior. You exaggerate a feature of the correct stimulus (size, color, intensity, position) so the learner responds correctly, then gradually remove the exaggeration until only the natural stimulus is left. A variation fades the incorrect choices in gradually instead.
- Stimulus shape transformation changes form. You start with a shape the learner already responds to (a drawing of a fish) and gradually change it, step by step, into the target stimulus (the printed word FISH).
- Move on data, not on the calendar. Advance the delay or the fading step when the learner meets a criterion, and step back if errors climb.
- Reinforce independence more richly. Many programs deliver a stronger reinforcer for unprompted correct responses than for prompted ones.
Tip
Ask "What is changing across trials?" If it is the time before help arrives, it is time delay. If it is the look of the materials, it is stimulus fading or shape transformation. If it is the type or amount of help, it is a prompt hierarchy such as most-to-least or least-to-most.
Definitions
- Transfer of stimulus control: shifting control of a response from a prompt to the natural discriminative stimulus.
- Time delay: a response-prompt fading method that systematically varies the interval between the natural SD and the prompt.
- Stimulus prompt: a change to, or addition to, the antecedent materials that makes a correct response more likely.
- Stimulus fading: gradually removing an exaggerated feature of a stimulus until the learner responds to the natural stimulus alone.
- Stimulus shape transformation: gradually changing the form of an initial stimulus into the target stimulus while keeping the response correct.
- Prompt dependence: responding that occurs only when a prompt is present, often because prompts were not faded systematically.
Examples from a session
Fading in four settings
- Constant time delay (clinic): To teach Jonah, age 5, to tact animals, the RBT shows a picture, says "What is it?", and immediately says "cow." After two sessions at 0 seconds, every trial uses a 4-second delay. When Jonah says "cow" before the prompt, he earns a short game of tickles; after a prompted answer, he gets brief praise.
- Progressive time delay (school): Ms. Okafor teaches Lina, 10, to read sight words. The delay before she models each word starts at 0 seconds and increases by 1 second each session until it reaches 5 seconds.
- Stimulus fading (home): To help Ravi, 3, choose his own cup at the table, his cup starts out bright blue and twice the size of his sister's. Across days, the size difference shrinks and the color becomes the family's usual gray.
- Stimulus shape transformation (adult day program): Teresa, 45, learns to read EXIT. Her teaching card starts as a picture of a doorway and changes in small steps until only the printed word is left.
- Non-example (not stimulus fading): Dev's correct card stays large and bright in every session. Nothing is faded, so control stays with the prompt.
Common mistakes / exam traps
- Forgetting the 0-second trials. Both constant and progressive time delay usually begin with 0-second trials. In constant time delay, the delay jumps to a single fixed value; in progressive, it grows step by step.
- Mixing up stimulus prompts and response prompts. Pointing or saying the answer is something you do (a response prompt). Enlarging or coloring the correct card changes the materials (a stimulus prompt).
- Fading the wrong feature. In stimulus fading, the exaggerated feature is what goes away. The natural SD stays.
- Leaving prompts in place too long. Plan fading steps before teaching to avoid prompt dependence.
Exam trap
Time delay vs. least-to-most: both let the learner respond before help arrives. The difference is the help itself. In least-to-most, the help grows in steps (gesture, then model, then physical). In time delay, one prompt stays the same; only its timing changes.
Exam trap
In a time delay stem, a correct answer given before the prompt is an unprompted correct response, and a correct answer given after it is a prompted correct response. Rising unprompted corrects show that stimulus control is transferring.
Quick check
Over several sessions, a BCBA has an RBT wait 0 seconds, then 1 second, then 2 seconds, and so on, before modeling the answer to 'What's your phone number?' for Malia, age 16. Which procedure is this?
Related topics
- Choosing prompting procedures: errorless, most-to-least, and least-to-most (G.7)
- Teaching simple and conditional discriminations (G.6)
- Building motivating operations and discriminative stimuli into interventions (G.5)
- Shaping across dimensions of behavior (G.11)
- Recognizing stimulus control (B.12)
- Recognizing stimulus discrimination (B.13)