In lesson one, we talked about how when teaching using ABA, we often create a prosthetic social and physical environment to encourage learners to engage in a target behaviour. This means that we add prompts ? extra physical and social stimuli ? to the learner?s environment. However, the ultimate goal is for the learner to perform the skills in meaningful environments where they contact the natural reinforcer for a behaviour that is useful to them. This is why, in most cases, we immediately start to fade out those prompts to move a learner towards independence. Prompt fading ? or sometimes, just fading – is the term used to refer to this process.
Prompt fading is a stimulus control transfer procedure. This means that the goal is to transfer stimulus control from the ?extra? stimulus to the target stimulus.
For example, if you were teaching a young child to stop at a red light, you might initially provide a verbal or physical prompt to get them to stop. Over time, you would fade out this prompt, so that the learner stopped because of the red light rather than because of the prompt.
Prompts are, in effect, extra help and when stimulus control has transferred to the target SD, that help is no longer required.
How do we fade prompts?
The amount of time taken to fade a prompt depends on the learner, the target behaviour and the context. Sometimes, fading a prompt is quite simple. For example, if somebody new joins a workplace, they may only need a single verbal prompt to know where to sign in and after that, they do so without prompting. But for most problems that a behaviour analyst is asked to solve, prompt fading is a longer process that involves the more gradual and systematic fading of prompts.
The nature of the prompt (response prompt or stimulus) prompt often determines how a prompt is faded.
Response Prompt Fading
A response prompt involves the behaviour of another person (usually an instructor). As you?ll remember from our last lesson response prompts include things like verbal prompts, physical prompts, gestural prompts and model prompts.
Let?s look at how someone might fade out physical prompts using the example of a parent teaching a young child to wash their hands.
Initially, the parent might provide a high level of physical guidance ? providing hand-over hand prompts to their child. As the child starts to get better at the task, the parent might provide move to providing gentle guidance from above the wrist. If the child continues to succeed with this lesser prompt, they might move to providing guidance using an occasional physical prompt from the elbow.
Similarly, a parent trying to teach their child to use the word ?please? at the end of a request, might initially provide a verbal prompt. Later, they might provide a partial verbal prompt just providing the first sound of the word.
Stimulus Prompt Fading
A stimulus prompt involves adding, removing or altering a stimulus to promote the target behaviour.
You?ll remember from our last lesson, we talked about the example of a soccer coach teaching a trainee goalkeeper to stop a ball. Initially, the coach kicks the ball lightly. This means he has altered the intensity of the target stimulus (a shot on goal). Fading this type of prompt would involve gradually increasing the intensity until the goalkeeper is stopping shots of normal intensity.
If a teacher was trying to teacher was trying to teach a child to discriminate between dogs and other types of animals using positioning prompts, he might initially start by positioning an array of three animal pictures, with the picture of the dog 3 inches closer to the learner. If that child then learned to point to the dog with a 3 inch positional prompt, the teacher might reduce the prompt to 1 inch. If the child succeeded a that level, the teacher might then remove the positional prompt entirely and present the dog picture (the target SD) equally distant from the other animal pictures.
Similarly, a teacher trying to teach trying to teach a learner to recognise the word ?Dog? might initially use flashcards with a picture of a dog on it. That extra stimulus might be faded out by making the picture of the dog smaller and smaller, or more and more transparent in response to the learner?s progress.
Time Delay
Another method for fading prompts that can be used with both stimulus and response prompts is Time Delay. When using a time-delay, you present the target SD, wait a certain number of seconds, and then if the correct response does not occur, you provide the prompt.
Using our earlier description of a parent teaching a child to use the word please at the end of the request, a parent might start off by immediately providing a verbal prompt to ?Say Please?. Later, they might wait three seconds in order to give the child the opportunity to say ?please? before giving a verbal prompt. As the child got better at remembering to say please, they might increase the delay to 5 seconds. The delay would increase until the child was reliably saying please without the need for prompting. That is, the target response had transferred to the appropriate SD.
Prompt Hierarchies
We can classify prompts along the lines of intrusiveness. The level of intrusiveness refers to how much assistance is provided to the learner. Some prompts such as hand-over-hand physical prompts are very intrusive, while others, such as adding a visual prompt are not very intrusive.
We can arrange types of prompts into hierarchies based on their intrusiveness. For instance, if teaching a learner to say, ?Stop? when presented with a picture of a stop sign, the prompt hierarchy might look something the following: Full verbal prompt (?Stop?), Partial Verbal (?St?), Time delay 5 seconds and independence. In this scenario, the full verbal prompt, is the most intrusive, while independence is the least intrusive.
One way in which we could use this prompt hierarchy is by using Least to Most (LTM) prompting. When using LTM prompting, a learner is provided with an opportunity to respond independently to an instruction or other SD. If they respond incorrectly (or do not respond at all), the RBT will engage in a more intrusive prompt for the next learning opportunity.
In our example where a teacher is helping a learner to say ?Stop? when presented with a picture of a stop sign, this would mean that one the first opportunity, the learner would be given an opportunity to respond independently. If they got it incorrect, the learner would be given a time delay on the second learning opportunity. If that was not successful in helping to produce the correct response, a partial verbal prompt would be given on the third learning opportunity. On the fourth opportunity, they?d receive a full verbal prompt.
Another way of using a prompt hierarchy is by using Most to Least (MTL) prompting which is sometimes called Errorless Learning. With MTL prompting the most intrusive prompt is used first and is then faded to successively less intrusive prompts for subsequent learning opportunities if the learner is successful.
In our example where a teacher is helping a learner to say ?Stop? when presented with a picture of a stop sign, this would mean that one the first opportunity, the learner would be given a full verbal prompt, then a partial verbal prompt on the next opportunity if the learner was successful and then a time delay on the following trial. Only on the fourth trial would the learner get an opportunity to respond independently. It is because there is a minimal chance of a learner making an error that this method is known as Errorless learning.
Combining Different types of Prompts
When teaching a skill using a single type of prompt (e.g. verbal or physical), it is usually relatively easy to distinguish between a more or less intrusive prompt. However, sometimes we may need to use multiple types of prompts to transfer a behaviour to an appropriate SD.
For example, if teaching somebody to wash their hands before preparing a meal, a prompt hierarchy might be: Full verbal prompt (?Wash your hands?), Partial verbal prompt (Wash your ?.), a model prompt (demonstrate washing hands), or a physical prompt (hand-over-hand guidance).
There is no universal prompt hierarchy. It depends on the skill and the context. However, in general, those that person sees (model prompts, stimulus prompts, positional prompts and gestural prompts) are considered less intrusive than those a person hears (full or partial verbal prompts) and those one hears are considered less intrusive than those one feels through touch (full or partial physical guidance).
Choosing a Prompt Fading Method
As an RBT, your supervisor will generally provide you with guidance or direction on the type of prompt fading method to use.
A decision may be made to use MTL prompting if the learner cannot perform a skill at all or if a learner finds making mistakes very aversive. It can also result in some tasks being completed quicker which can be an advantage if a learner finds the outcome of a task very reinforcing and gets frustrated by delays.
A drawback of this approach is that sometimes, it can be harder to fade out prompts as learners develop prompt dependency. As the name suggests, prompt dependency happens when a learner becomes dependent on the presentation of a prompt to engage in a behaviour.
A decision might be made to use LTM prompting if a learner can already perform a skill some of the time and if they do not find errors aversive. For many learners, prompts are faded more quickly when using LTM prompts and the risk of prompt dependency emerging decreases.
Prompt Fading and Measurement
As you may remember from Module 1, in ABA we utilise measurement and data-based decision making. While it goes beyond the scope of the present lesson, it is important to know that when we use the data we collect to decide when to fade prompts and when to decide if a behaviour is reliably occurring in the presence of the naturally occurring antecedent.