Daniel Kahneman cofounded the field of behavioral economics with his friend and colleague Amos Tversky in the late 20th century. Kahneman's 2011 book, Thinking, Fast and Slow, describes the underpinnings of the discipline for a lay audience. In July 2024, I wrote this five-star review of Thinking, Fast and Slow on my Goodreads.
Even the best book pop-sci has to offer isn’t infallible to the ongoing replicability crisis in the social sciences. In chapter 3, for instance, Daniel Kahneman writes about how hungry parole judges approve fewer parole cases before meals vs. after meals:
A disturbing demonstration of depletion effects in judgment was recently reported in the Proceedings of the National Academy of Sciences. The unwitting participants in the study were eight parole judges in Israel. They spend entire days reviewing applications for parole. The cases are presented in random order, and the judges spend little time on each one, an average of 6 minutes. (The default decision is denial of parole; only 35% of requests are approved. The exact time of each decision is recorded, and the times of the judges’ three food breaks—morning break, lunch, and afternoon break—during the day are recorded as well.) The authors of the study plotted the proportion of approved requests against the time since the last food break. The proportion spikes after each meal, when about 65% of requests are granted. During the two hours or so until the judges’ next feeding, the approval rate drops steadily, to about zero just before the meal. As you might expect, this is an unwelcome result and the authors carefully checked many alternative explanations. The best possible account of the data provides bad news: tired and hungry judges tend to fall back on the easier default position of denying requests for parole. Both fatigue and hunger probably play a role.
So the chances of getting your parole approved drops from 65% to “about zero” depending on if your case is heard by a hangry judge? If you think this effect seems too big to be true, you’d be correct. Further research from Weinshall-Margel and Shapard (2011) found that the ordering of parole cases is not random. The Israeli parole board tries to complete all cases from one prison before it takes a break and start with a new prison after it comes back. Within a single session, prisoners with lawyers generally go first and unrepresented prisoners go last. Ultimately, a much stronger indicator of whether or not someone is granted parole is whether or not they have an attorney. While prisoners with council are approved 67% of the time, prisoners without council are only approved 39% of the time.
This is just one of many examples. Much of chapter 4 is based around priming effects (e.g. if you see the words TOWEL, SHAMPOO, and BATH, you’re more likely to think SO_P was supposed to be SOAP instead of SOUP). Priming effects have been particularly difficult to reproduce, and Kahneman himself commented on their lack of empirical rigor in an open letter in 2012 and a response to a blog post in 2017.
Thinking, Fast and Slow’s shortcomings don’t come from malice or deception on Kahneman’s part. In fact, Kahneman can be seen as an exemplar for ethical and effective science communication. Nothing in Thinking is sensationalized or oversimplified for a general audience. Kahneman cites every study and has a thorough understanding of the literature he references. Psychology and behavioral economics, like the social sciences more broadly, are simply reckoning with how to conduct scientific research that is robust and reproducible.
A few months ago, I wrote this journal entry in my notes app as I was sitting in a behavioral economics lecture:
A few months ago, I wrote this journal entry in my notes app as I was sitting in a behavioral economics lecture:
Studying economics is cool because profs will be like “so this is a major paper in behavioral economics, n=40” and you wonder why there's a replicability crisis in the social sciences
In addition to small sample sizes, it always shocks me how much social science research is conducted exclusively using college undergraduates. Kahneman even comments on how people tend to distrust these kinds of studies in Thinking’s introduction before citing many studies (including his own!) conducted only using undergrads, often from elite universities. What’s going to happen if/when many of these findings don’t hold up to the general public?
It’s easy to become cynical in the face of this information. Thinking seems to be mentioned in the same breath as books like The Power of Habit and How to Win Friends and Influence People. Is modern psychology really just glorified self-help with an objective, authoritative tone? Perhaps the issue here is the inherent tension between science and science communication. Science is an active process, ever-evolving as the standards we hold our research to evolve as well. Science communication, on the other hand, is a stagnant image that captures people trying to make sense of the world with the tools they had available to them at the time. Instead of feeling cynical, it makes me optimistic that our understanding of psychology has progressed so quickly that we can be critical of a book that was published less than 15 years ago.
It’ll be interesting to see how much of Thinking holds up as our understanding of psychology (and, more broadly, how to conduct robust science) continues to evolve. If nothing else, Thinking will always be able to be seen for what it is: the father of behavioral economics writing with an unmatched passion for understanding the human mind.
It’s easy to become cynical in the face of this information. Thinking seems to be mentioned in the same breath as books like The Power of Habit and How to Win Friends and Influence People. Is modern psychology really just glorified self-help with an objective, authoritative tone? Perhaps the issue here is the inherent tension between science and science communication. Science is an active process, ever-evolving as the standards we hold our research to evolve as well. Science communication, on the other hand, is a stagnant image that captures people trying to make sense of the world with the tools they had available to them at the time. Instead of feeling cynical, it makes me optimistic that our understanding of psychology has progressed so quickly that we can be critical of a book that was published less than 15 years ago.
It’ll be interesting to see how much of Thinking holds up as our understanding of psychology (and, more broadly, how to conduct robust science) continues to evolve. If nothing else, Thinking will always be able to be seen for what it is: the father of behavioral economics writing with an unmatched passion for understanding the human mind.