What is prompt fading in ABA?

A prompt makes a correct response possible, but a response that only occurs after help is controlled by the help. Fading is the planned handover from the instructor's cue to the one the skill should eventually answer to - the question rather than the model of the answer, the dirty hands rather than the guidance toward the tap. Behavior analysts call that handover transfer of stimulus control, and it is the mechanism most skill acquisition ultimately rests on.

Response prompts are usually faded along the dimension of intrusiveness. Most-to-least fading starts with enough support to guarantee a correct response and steps down through it - full physical to partial physical to a shadowed hand to a gesture - while least-to-most begins with the smallest prompt and escalates only when needed. Graduated guidance works inside the trial rather than between trials, with the instructor reducing physical pressure moment to moment and withdrawing entirely as the learner's movement takes over.

Timing can be faded instead of form. Time-delay procedures keep the prompt intact but insert a pause between the instruction and the help - a fixed interval in constant time delay, a gradually lengthening one in progressive time delay. The learner keeps a guaranteed route to being correct while gaining room to respond first, and every response that happens during the delay is direct evidence the skill is coming under natural control.

Stimulus prompts fade differently because they live in the materials rather than in the instructor. Making the correct card larger, brighter, or closer, then shrinking that difference across trials, fades the stimulus itself; stimulus shaping changes the form of the materials until they match what the learner will encounter normally. These schedules run independently of response-prompt fading, and a program using both needs to be explicit about which is being faded when.

The decision to step down belongs to the data, not the calendar. Programs set a criterion - a number of consecutive independent or minimally prompted responses - and fade when it is met, then step back up on a pattern of errors rather than on a single one. Skipping levels because a session felt good is how a stable target starts producing errors, and holding a level past criterion is how a plateau gets built into the graph.

The failure mode the whole procedure exists to prevent is prompt dependence: a learner who waits, because waiting has reliably produced assistance. Prompts delivered a beat early are the usual cause, and unplanned prompts are the hardest version to catch - a glance at the correct card, standing nearer the right door, a change in the instructor's tone. They work like any other prompt, and because nobody wrote them down, nobody fades them.

This is also why prompt level is recorded trial by trial rather than only accuracy. Two learners at the same percentage correct can be in completely different places, one responding independently and one fully guided, and the graph will not tell them apart unless the level of support is in the data. Watching that level fall over sessions is what shows a skill being acquired rather than propped up.