Discriminative stimulus
A stimulus in whose presence a behavior has been reinforced, and in whose absence it has not, so the behavior becomes more likely when the stimulus is present (SD).
A discriminative stimulus (SD, often said "ess-dee") signals that a particular response is likely to be reinforced. Because the behavior has been reinforced when the SD was present and not reinforced when it was absent, the behavior comes to occur more often in its presence. A ringing phone is an SD for answering: answering a ringing phone produces a voice on the other end, while picking up a silent phone does not.
In teaching, the SD is usually the instruction or materials that should set the occasion for the correct response: "What's your name?", a picture to label, or a peer saying "Hi". It is the first part of the three-term contingency and of each discrete trial. RBTs present the SD clearly, once, and in the form written in the plan, and make sure the learner is attending.
An SD does not force behavior; it makes it more likely because of past reinforcement. It is different from a motivating operation, which changes how valuable the reinforcer is at that moment. It is also different from a prompt, which is extra help added to the SD and later faded so the SD alone controls the response.
The opposite of an SD is an S-delta, a stimulus in whose presence the response has not been reinforced.
Example and non-example
| Example | When the RBT holds up a cup and asks "What is it?", the client says "cup" and receives praise. The question with the cup present is the SD for saying "cup". |
|---|---|
| Non-example | The RBT points to the correct picture after saying "Touch the cup." The point is a gestural prompt added to help, not the SD the client should eventually respond to. |
Don't confuse it with
| Motivating operation | An MO changes how valuable a reinforcer is; an SD signals that the reinforcer is available for a response. |
|---|---|
| Prompt | A prompt is temporary extra help; the SD is the natural cue that should control the response once prompts are faded. |
Test yourself
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Question 1During discrete-trial teaching, which description of the instruction the RBT presented is objective?
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A: Placed 3 picture cards down and said, "Touch dog". The environment includes what the RBT does. Describing the materials and the exact words lets anyone know what stimulus was presented.
- B: "Usual" does not say what was actually presented.
- C: "Fun and engaging" is a judgment, not a description.
- D: This names the program but not the materials or words used.
Task A.5 · 40-hour curriculum section C
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Question 2An RBT says "Point to dog" with three picture cards on the table. The client does not respond, so the RBT says "Point to dog. Point to dog. Dog!" What is the main problem with repeating the instruction?
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B: The client may learn to wait for repeated instructions. An instruction should be given once, then the RBT follows the plan's prompting or error-correction step if the client does not respond. Repeating it can teach the client that the first instruction does not matter.
- A: Discrete-trial instructions should be brief and clear; adding words makes the cue harder to follow, not easier.
- C: The client needs the cards in view to respond to a receptive instruction.
- D: Giving the reinforcer after no response would reinforce not responding.
Task C.3 · 40-hour curriculum section E
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Question 3A plan lists the instruction for a target as "Touch nose." Which way of presenting it follows the plan best?
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A: Say "Touch nose" once, clearly, when the client is attending. An instruction should be brief, clear and delivered as written, once, when the client is oriented to the RBT or the materials. Unplanned prompts and extra words change the procedure.
- B: Extra words make the instruction long and inconsistent with the plan.
- C: Pointing adds a gestural or model prompt that the plan did not call for.
- D: Giving the instruction when the client is not attending makes an error or no response more likely.
Task C.3 · 40-hour curriculum section E
Answer every question to see your score.
On the RBT exam
This term belongs to task C.3 Discrete-trial teaching in content area C, Behavior Acquisition, which is 19 of the 75 scored questions.