What is Single Stimulus?
Single Stimulus (also called "Successive Choice") is the most basic trial-based assessment. You present one item at a time to the client. You record whether they approach/accept it or reject it.
Example: "Here is a ball." (Client takes it). "Here is a cup." (Client pushes it away).
For your RBT practice test, remember that this method is best for clients who cannot choose between two items (poor discrimination skills) or have visual impairments.
Pros and Cons
Pro: Very simple. Good for lower-functioning clients who get confused by arrays.
Con: It generates "False Positives." A client might take everything you hand them just because they like holding things. It doesn't tell you they like the ball more than the cup, only that they like both.
Procedure
1. Present Item A.
2. Allow 5-10 seconds for engagement.
3. Remove Item A.
4. Present Item B.
5. Repeat for all items (usually several times in random order).
RBT Practice Exam Scenario
Question: "The client grabs both items during a Paired Stimulus assessment and cannot be blocked. What assessment should the RBT switch to?"
Answer: Single Stimulus. By only offering one item, you remove the possibility of grabbing both.
Frequently Asked Questions About Single Stimulus
What is another name for Single Stimulus?
Successive Choice method.
Who is this assessment designed for?
Clients who have difficulty making choices, scanning a field of two items, or who have profound disabilities.
What is the major flaw of Single Stimulus?
It tends to identify many items as "preferred" without ranking them. It produces False Positives.
How do I calculate the result?
Percentage of trials the item was approached/accepted. (e.g., Ball was accepted 80% of the time).
Is it faster than Paired Stimulus?
Yes, because there is no decision-making time required by the client.
What if the client rejects everything?
Then your pool of potential reinforcers is poor, or the client is satiated. Try new items or a different time of day.