Transfer of Stimulus Control – Fading Prompts

Objectives

  • Review common prompts that are used to promote learning
  • Define stimulus control and transfer of stimulus control
  • Describe stimulus control transfer procedures to fade prompts (in order to allow learners to become more successful at new learning tasks)
  • Review case examples of stimulus control transfer procedure with learners

Applied Behavior Analysis (ABA)

There is much research on the success of ABA methodologies to teach a variety of skills to learners of all types, not just those with ASD or other developmental disabilities. A critical component to the success of ABA teaching is the systematic use of prompts.

Prompts

A prompt is a supplemental stimulus that controls the target response but is not a part of the natural SD that will eventually control the behavior (Touchette & Howard, 1984). Essentially, it is an additional cue or hint that is paired with the instruction that is used to help the learner give an appropriate response. Prompts help the learner understand how to respond, and allow for immediate success and reinforcement. Prompts are critical for successful teaching during the initial stages of acquisition especially when working with learners who have ASD or other developmental disabilities. In the initial stages of learning, prompts allow for fewer errors and increase the efficiency of the learning process in addition to making learning more successful for the learner.

Types of Prompts

Stimulus Prompts – Prompts that are added to the stimulus, or SD, or Antecedent that are going to help the learner better respond. In other words, it is a cue that is used in conjunction with the SD or instructional materials, meaning that it is paired with that instruction or task. There are three main types of stimulus prompts:

  • Movement Cues: Gestures, pointing, tapping, glancing, etc.
  • Position Cue: manipulating the proximity of the target, distractor items or stimuli are placed further away from the learner
  • Redundancy: physically altering or exaggerating part of the stimuli to emphasize it to the learner

Response Prompts – Prompts that are added to the learner’s response to help them react more effectively to the new instruction

  • Verbal Directions: telling the learner what to say or do in order to respond appropriately (can be vocal or written or visual)
  • Modeling: physically demonstrates the desired response to the learner which allows them to imitate
  • Physical Guidance: manually guiding the learner through part or all of the desired response

Stimulus Control

So when we add prompts to a new instruction, to a new SD, or to a new target we are helping the learner appropriately respond to that target, however the prompt is what controls the response. So the control over the learner’s response is held by the prompt and not the SD, which is not natural in the learner’s environment and therefore control must be shifted from the prompt to the stimulus.

When we pair the prompt with the stimulus instruction we are attempting to transfer control of the behavior over to the instruction.

Over time, this prompting is faded, so that the stimulus is able to gain complete control.

Example:

Learner receives instruction “come here” with complete physical guidance to walk to the instructor. Learner receives praise and a hug.

Learner receives instruction “come here” with partial physical guidance to walk to the instructor. Learner receives praise and a hug.

Learner receives instruction “come here”. Learner walks to instructor. Receives praise and a hug.

So, when the prompt that was first required for the learner to respond to the SD is no longer needed, and the SD itself elicits the behavior we say that there has been a transfer of stimulus control. The transfer of stimulus control is the goal of all new learning tasks.

Transfer of Stimulus Control

There are various ways to transfer stimulus control from the prompt to the SD

Methods for transferring stimulus control

  • Prompt fading – Used for fading response prompts. It is the gradual removal of a prompt over several teaching trials until the SD alone evokes the response and the learner is able to respond accurately and independently to the target SD. Prompt fading is used for fading response prompts. There are two procedures for fading prompts:
    • Most-to-least prompting: Prompt intrusiveness gradually decreases as correct responses occur, typically used when teaching a new skill (errorless learning). This is done several ways one of which is the therapist using a stronger prompt, which is then reduced over time until the prompting is faded. Similarly, it can be done by reducing the intensity of one prompt or switching to less intrusive prompts. Can also be used when a combination of prompts are required to teach a skill, and whether faded in tandem or one at a time the process is the same.
    • Least-to-most prompting: Amount of assistance is gradually increased until the learner gives an appropriate response. Typically used when prompting a previously learned skill, however it can be used when teaching a new response as well. Here, when the learner makes an error the therapist uses the weakest possible prompt, and continues to increase the strength of the prompt until the learner is successful. Least-to-most is used to promote the greatest level of independence that the learner is capable of and helps to avoid prompt dependency.
      • PROMPT FADING HIERARCHY: In order to determine what type of prompt to use first (which is determined by the BCBA), or the order in which prompts should be used, it is helpful to determine a prompt hierarchy. This applies to both forms of prompt fading. And the hierarchy will look different for every task and every learner based upon their abilities and their individual program. For example:

  • Prompt delay: Increases the amount of time between the SD and the prompt. The therapist presents the SD and waits a specific amount of time, and then presents of the prompt if the response is not made. There are two types of prompt delays:
    • Constant time delay: A constant time delay begins with the presentation of the SD and no delay to the prompt. In the next trial, the SD is presented followed by a fixed delay of 3 seconds and then the prompt. The hope here is that in the 3 second delay the learner will respond with the correct answer.
    • Progressive time delay: In progressive time delay the process is similar to the above, except that you begin at 0 and for each trial you extend the delay by 1 second until the student is answering independently and accurately to the SD.
  • Stimulus fading: Prompts that have been paired with the stimulus are gradually reduced and then removed. In other words, prompts are faded–made smaller, lighter, less salient. For example in pairing a picture of a train with the word train, over successive trials the picture would remain the same but the font in the word would fade until the word was no longer visible.

The type of procedure used to fade assistance will depend on the type of prompt used as well as the needs of the learner and the specific skill being taught

  • Response Prompts: prompt fading, prompt delay
  • Stimulus Prompts: stimulus fading

The BCBA will instruct therapists to use a specific procedure to fade prompts

In order to help a learner to become as independent as possible, it is important for therapists to consistently apply and fade prompts according to the supervisor’s instruction. Remember, the goal of ABA is to help learners become as successful and independent as possible. Transfer of stimulus control by fading prompts and other supports is a critical part of this process.

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