RBT Module 3: Lesson 1 – Readings

RBT: Hi, I’ve been hearing about discriminative stimuli and stimulus classes in ABA. Can you explain the difference?

BCBA: Of course. In ABA, a stimulus is any event or situation that can be perceived by our senses, like something we see, hear, touch, smell, or taste. It plays a role in behavior change. Two related ideas are discriminative stimuli and stimulus classes. A discriminative stimulus describes a stimulus’s learned function, while a stimulus class groups stimuli that share a characteristic. These are not two separate categories of stimuli.

RBT: So, what’s a discriminative stimulus?

BCBA: A discriminative stimulus (SD) is a specific type of stimulus. It’s like a cue that tells the individual that if they perform a particular behavior in its presence, they’ll get reinforcement. For example, when a teacher says, “Raise your hand if you know the answer,” the teacher’s voice is the SD that signals reinforcement (like praise) for raising one’s hand.

RBT: Got it. What about a stimulus class?

BCBA: A stimulus class is a broader concept. It’s a group of stimuli that share similar characteristics and can evoke the same or similar responses. These stimuli might not look or sound the same, but they have common features that make them functionally equivalent in their effects on behavior.

RBT: Can you give an example to clarify the difference?

BCBA: Sure. If we teach a child to touch a red square when we say “Touch red,” then:

• The stimulus is the red square.
• The discriminative stimulus (SD) is the instruction “Touch red.”
• The stimulus class includes all red objects (red circle, red triangle, etc.), because they all share the property of being red.

RBT: That makes sense. Understanding this helps with teaching and generalizing skills, right?

BCBA: Exactly. Recognizing SDs and stimulus classes helps us promote generalization and design effective interventions. Let me know if you’d like more examples!