Operant Conditioning Demo: Backpacks and Skittles

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You have likely heard of the classroom demonstration where the students condition the instructor or a student volunteer to do some behavior by clapping (positive reinforcement) whenever the person gets closer to the behavior. Jon Skalski, Joel Lynch, and Amy Martin (2017) from Rockford University take this demo up a notch by modifying it to help students understand not only shaping, but also positive/negative reinforcement/punishment.  

Skalski (personal communication, January 19, 2017) explains:

I have a student volunteer step outside the classroom. The class selects a behavior that they would like to shape in his/her absence (like standing the corner and/or scratching the head).  The volunteer returns to the room. I place a backpack loaded with textbooks on his/her shoulders. Then, I remove a couple books when the student starts doing something that approximates what the class has selected for the volunteer to do (as a form of negative reinforcement).  I add books (as a form of positive punishment) when the student is not doing what I am trying to shape. I add skittles to a cup (positive reinforcement) and also take skittles away from the cup (negative punishment) to shape approximations of the desired outcome. Thus, the demonstration involves rewarding (both positively and negatively) and punishing (both positively and negatively) at the same time, at least in shaping a single behavior, and it is quite vivid and memorable. I then help students to process and think about the demonstration in order to make distinctions about positive and negative forms of reinforcement and punishment.


During the demonstration, Skalski changes which technique he is using from moment to moment. In doing so, students can see the impact each change has on the volunteer’s behavior.

After successfully training the volunteer to do the selected behavior. Skalski recaps what the students just saw.

Shout out to Jon Skalski for this clever demonstration!


Skalski, J., Lynch, J, & Martin, A. (2017, January). Teaching negative reinforcement; it’s not punishment. Poster session presented at the National Institute on the Teaching of Psychology, St. Petersburg Beach, FL.

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About the Author
Sue Frantz has taught psychology since 1992. She has served on several APA boards and committees, and was proud to serve the members of the Society for the Teaching of Psychology as their 2018 president. In 2013, she was the inaugural recipient of the APA award for Excellence in the Scholarship of Teaching and Learning at a Two-Year College or Campus. She received in 2016 the highest award for the teaching of psychology--the Charles L. Brewer Distinguished Teaching of Psychology Award. She presents nationally and internationally on the topics of educational technology and the pedagogy of psychology. She is co-author with Doug Bernstein and Steve Chew of Teaching Psychology: A Step-by-Step Guide, 3rd ed. and is co-author with Charles Stangor on Introduction to Psychology, 4.0.