If you have watched an ABA session, you have probably heard a therapist give a short, clear instruction such as "touch red" or "what is it?" That instruction has a technical name: the discriminative stimulus, usually written as SD (and said "S-dee"). Understanding the SD helps parents see how ABA teaches new skills step by step, and how to help those skills show up at home, at school and in the community across North Carolina.
A discriminative stimulus is a cue that signals reinforcement is available for a specific behavior. When the SD is present and the child responds correctly, something good follows. When the SD is absent, that same behavior does not pay off. Over time, the child learns to respond when the cue is there and not when it is missing.
A simple everyday example: a ringing phone is an SD for answering. You pick up when it rings because someone is on the line. You do not pick up a silent phone and say "hello," because no one will answer.
The SD is the "A" in the ABC model of behavior. It is one specific kind of antecedent: one that has a history of signaling that a certain behavior will be reinforced.
The opposite of an SD is the S-delta, written S∆. An S-delta is a cue that signals reinforcement is not available for a behavior.
When a child reliably responds to the SD and not to the S-delta, ABA calls that behavior under stimulus control.
A discrete trial is a short teaching unit. Each trial has the same parts, and the SD is where every trial starts once the child is attending:
You can read more about the full teaching format in our guide to discrete trial training.
SDs and motivating operations are both antecedents, so they are easy to mix up. An SD tells the child that reinforcement is available. A motivating operation changes how much the child wants that reinforcement right now. A vending machine is an SD for pressing buttons, but you only care about pressing them when you are hungry. Hunger is the motivating operation.
A child who only responds to one therapist's exact words in one room has not fully learned the skill. Real life is full of different people, words and settings. That is one reason in-home and school-based ABA is so useful: the SDs your child learns to respond to are the same ones they meet every day, such as a parent's voice at dinner or a teacher's instruction in class. The team practices with many people and materials so the skill carries over.
Our parent guidance sessions show families how to give effective instructions during real routines like meals, bath time and getting ready for school.
1. A therapist holds up a picture of a ball and says "what is it?" The child says "ball."
Answer: The SD is the picture plus the question "what is it?"
2. A trial begins with which part: the inter-trial interval, the SD, the reinforcement or gaining attention?
Answer: Once the child is attending, the trial begins with the SD.
3. A child only says "bye" when a therapist waves, not when a parent leaves the room.
Answer: The wave has become the SD. The team needs to teach other SDs, such as a parent saying "bye," to generalize the skill.
4. A red light at an intersection is an SD or S-delta for driving forward?
Answer: S-delta. Driving forward will not be reinforced (and is unsafe) when the light is red.
SD stands for discriminative stimulus. It is a cue that signals a specific behavior will be reinforced.
Many SDs are spoken instructions, but an SD can also be an object, a picture, a sound or a situation, such as a ringing phone or a plate of food on the table.
The SD is the cue that should eventually trigger the behavior on its own. A prompt is extra help added so the child can respond correctly while learning, and it is faded over time.
Yes. ABA for children with autism is covered by most insurance payors in North Carolina. See the plans we accept on our insurance page.
Sunny Skies ABA provides in-home and school-based ABA therapy for children and young adults with autism, ages 2 to 21, across North Carolina. Our team teaches skills using the cues your child meets in everyday life. Book a free consultation to learn more.
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