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A common mistake that people make is confusing Discriminating Stimulus (SD) with the Stimulus Delta  (SΔ). However, it is a very easy distinction. Here is how to tell the difference. 

Discriminating Stimulus (SD)

A SD signals that a reinforcer is available for a response. So example,

Example 1.) Jenny, an ABA therapist, is working with Ben, a four year old boy. Jenny brings an iPad that is fully charged to the session.  Ben is learning to request. Ben asks for the iPad and Jenny let’s Ben play with the ipad. The iPad is an SD for Ben asking for the iPad because it signals that the iPad is available as a reinforcer. 

Example 2.) Jackie is working with Dylan, a three year old boy with Autism. Jackie tells Dylan to touch his head. Dylan touches his head and Dylan gets reinforcement when he touches his head. In this case “touch your head” was an SD for Dylan touching his head because it signaled a condition in which reinforcement was available.  

Example 3.)  Georgia is a preschool teacher. During free time, sometimes painting is available. When painting is available, Georgia has a picture of paint with a smiley face. When the children see the picture of the paint with a smiley face, they ask to paint. The picture of paint with a smiley face is an SD because it signals that painting is available and asking for painting will result in reinforcement (painting) for the kids. 

Stimulus Delta  (SΔ)

A SΔ signals a reinforcer is  NOT available for a response. For example,  

Example 1.) Jenny, an ABA therapist, is working with Ben, a four year old boy. Jenny brings an iPad that has a dead battery to the session.  Ben is learning to request. Ben asks for the iPad and Jenny shows Ben the iPad’s battery is dead. Ben stops asking for the iPad. The iPad is an  SΔ for Ben asking for the iPad because it signals that the iPad is not available as a reinforcer. 

Example 2.) Jackie is working with Dylan, a three year old boy with Autism. Jackie tells Dylan to touch his head. Dylan touches his nose. No reinforcement is provided. Touch your head is an SΔ under the condition of Dylan touching his nose.  

Example 3.)  Georgia is a preschool teacher. During free time, sometimes painting is available. When painting is NOT available, Georgia has a picture of paint crossed off with an unhappy face. When the children see the picture of the paint with an unhappy face, they do not ask to paint. The picture of  paint with an unhappy face is an SΔ because it signals that painting is NOT available and asking for painting will  NOT result in reinforcement (painting) for the kids. 

This article is useful for registered behavior technicians (RBT) or students who are studying to become board certified behavior analysts (BCBAs). Understanding (Applied Behavior Analysis) ABA terms is critical for both being an effective ABA therapist and passing your BCBA exam

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In an effort to help you study for your BCBA exam more effectively, this post is written in a “study note” form rather than as a long form blog post. 

They are my personal study notes I am sharing with you as a gift. I am spending my time studying so they are not edited. I am grateful for your understanding in overlooking the grammar! Happy Studying

References

Cooper, J. O., Heron, T. E., & Heward, W. L. (2007). Applied Behavior Analysis (3rd Edition). Hoboken, NJ: Pearson Education.

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