[EDIT September 1, 2014: “The Kids Marshmallow Experiment” linked below is no longer a YouTube video. Here is an updated link to a different video of the same experiment: Marshmallow Test Reproduced]
The Each semester, my last topic of week 1 is experimental design. I talk about the difference between discovery and hypothesis-driven science, go briefly through “the scientific process,” and then introduce students to the elements of an experiment. I first show a brief Consumer Reports video on how sunscreens are tested. That video sets the stage for discussing independent variables, dependent variables, standardized variables, and controls.
Then I show a YouTube video of “The Kids Marshmallow Experiment.” The video depicts snippets of an experiment in which an investigator leaves a young child sitting alone at a table with a single marshmallow on a plate. As the investigator leaves the room, she tells each child that if he or she doesn’t eat the marshmallow before the investigator gets back, the reward will be a second marshmallow. It’s fun to watch these small children try to resist temptation during the agonizing wait for the investigator’s return.
I used this video during two semesters as a springboard for having students design their own experiments. That is, after showing the video, I have students jot down their observations, write questions the video raises, develop testable hypotheses, make predictions, and design experiments to test their hypotheses.
This activity was reasonably successful the first time I tried it, except that the questions that the students wanted to investigate were not what I had hoped for. They asked relatively simple questions about whether the childrens’ behavior varied with age or sex, but not more creative and challenging questions about psychology or human behavior. Since one of the objectives of this exercise is to have students wrestle with the difficulty of answering questions about humans, I felt my instructions missed the mark.
Yesterday I did the activity again, only this time I had students generate questions about what the subjects of the marshmallow experiment would be like at age 20. This small change made a big difference. The students thought of very interesting ideas, including “Would the kids who waited to eat the marshmallow be more likely to make long-term investments when they are 2o years old?” “Will the ones who didn’t manage to wait be more likely to have substance abuse problems?” “Will the kids who took bites of the marshmallow be less inclined to follow instructions at age 20?” “Will children with more self control at a younger age have higher test scores at age 20?” “Will the children who tried to sneak a tiny piece of marshmallow grow up to be less honest?” The students subsequently wrestled with substantive, important decisions about how best to structure their experiments, much more so than they have in past semesters.
However, this time I noticed a secondary problem. When I asked students to jot down their observations about the video, they often wrote what they had noticed about the physical setting, the number of marshmallows, the number of children, and how the kids interacted with the marshmallow (touching it, smelling it, licking it, pinching it, and so on). These observations were a bit of a distraction from the types of questions that I eventually wanted them to ask. So the next time I do this activity, I will make one more change. I will ask students to write down their observations specifically about the different types of behavior they noticed among the children. Hopefully this new change will focus student attention on deeper issues, such as how some children could resist temptation whereas others could not, and they will build on those observations to ask meaningful questions about how those patterns might influence future behavior.
This experience is a good reminder of how important it is to give yourself a few minutes or so after class to reflect on how well the students met your expectations and learning objectives. Documenting your observations right away will not only save you precious time as you prepare for the activity in the future, but it will also make sure your teaching continues to improve each semester.