top of page

Nobel Prize, RCTs, and Cookies in Class

Banerjee, Duflo, and Kremer are three economists that just won the Nobel Prize in Economics for their work in development economics. Specifically, they won the award for their practical application of theory to discover what actually works and what does not work to help improve the lives of those in developing countries.

To do that, they developed and conducted Randomized Control Trials (or RCTs) in Africa, India, and other places. They examined effects of interventions in schools on test performance, microfinance programs on wellbeing, prices for healthcare on usage, and more. While these three economist had many other co-authors on their various papers, they are attributed with leading a change in development economics to where it is today with the widespread use of RCTs.

So, what is a Randomized Control Trial, or as we call it an RCT?

First, think of a science lab experiment. If a scientist wants to see the effect of a drug, for example, she would inject that drug into one cell but not another. Then she would then study the differences in the two cells over time. The only difference in the two cells should be the effect of the drug.

The idea is similar for an RCT in social sciences. You take one group of people and do something to them and the other group you keep as your control. To be clear, by “do something” to them, I don’t mean medically. I mean you give them textbooks, access to loans, incentives for teachers to show up to school, or something like that. Properly doing an RCT is difficult. You need to ensure that your control versus treatment groups look very similar. If not, then it could be differences in populations that drive any result. You also have to make sure that there is not something else that varies simultaneously with the treatment that could be driving the result. That’s why the “randomization” is so important.

To give you a concrete example, a few researchers in the Germany (not the ones that won the Nobel Prize) did an RCT at a medical school to study the impact of giving some students cookies in class on student evaluations. (No, I’m not making this up - link to the paper.)

There were two instructors for the class with twenty different sections. Each instructor had five sections where cookies were given out in class and five sections where cookies were not given out in class. They then measured the impact of cookies on students’ evaluation of the teachers and the class material.

Having each instructor with classes in the control AND the treatment was vital for the experiment. Let’s see what the problem would be if they did not do this: take two different professors, let’s call them Susan and Carter. Susan gives out cookies and Carter does not. If we found out that students gave better evaluations in Susan’s class, we would not know whether it was because she gave out cookies or because she was a better teacher than Carter. By having both Susan and Carter give out cookies in some classes and not other classes, we can control for differences in their teaching ability or preference by students. The researchers also confirmed that the students in the treatment and control groups looked very similar, suggesting differences in student body were not likely driving any findings.

So, what were the results? Drum roll…

Students gave better class evaluations if they were in sections where cookies were given out! Maybe not surprisingly, the instructors were evaluated higher; but, most interestingly, the course material was also given higher ratings in classes with cookies.

Huh? The material was better when cookies were given out? Sounds like people attributed their positive experience in the class from the cookies to liking the material better. Pretty interesting.

Moral of the story… I’m going to continue to give my students treats after their exams, and I recommend you do too. Below is an example of a cookie that I once made for my colleague’s students. It didn’t seem fair that his students were taking the exam I wrote without getting the post-test treat that my students got.

Salted Shortbread Chocolate Chip Cookies

Google “salted shortbread chocolate chip cookies” and you’ll get this recipe by Alison Roman from the New York Times, Food Network, Bon Appetite, Smitten Kitchen. She published this recipe in her cookbook, Dining In: Highly Cookable Recipes, and it is a beautiful twist on a traditional chocolate chip cookie. Rather than a typical chocolate chip cookie, they are a shortbread cookie with chocolate chunks. And to top it off, the outside is coated in raw sugar to give it an extra good crunch.


9 oz, 255 grams, or 1 cup plus 2 Tbsp. SALTED butter. Keep it cold and cut it into chunks.

½ cup (100 grams) sugar

¼ cup (50 to 55 grams) brown sugar

1 tsp. vanilla extract

2 ¼ cup (255 to 326 grams - I've done both) all-purpose flour

6 oz. or 170 grams chocolate chunks or chocolate chips


1 egg

Demerara or raw sugar (the kind you see at starbucks)

Sea salt

In a stand mixer, beat the butter and sugars until all of the butter is incorporated and the mixture is slightly fluffy. Add flour and mix on low or with a spatula. Stir in chocolate chunks or chips.

Split dough in half and roll into logs and wrap them up. I either wrap in plastic wrap, parchment paper, or foil. Place in fridge for 2 hours, or up to a few days. Recipes also say you can freeze them now - I've never tried that.

Preheat the oven to 350. Crack egg into bowl and lightly beat with a fork. Spread egg over the logs of dough using your hands or a cooking brush. Sprinkle raw sugar over the log so that there is raw sugar covering the whole thing.

Slice cookies and place onto cookie sheet. Before putting them in the oven, sprinkle some sea salt on top (don't forget!). Bake for about 12 minutes until lightly golden. Leave them on the cookie sheet for a few minutes before transferring them to a cooling rack. Once chocolate has cooled slightly, you can eat them, or enjoy over the next couple of days!

Recommended to share with students.

bottom of page