The death of Daniel Kahneman at the age of 90 has left a major void in the field of behavioral sciences and in the broader intellectual community.
His scientific contributions, many of them in collaboration with cognitive psychologist Amos Tversky, transformed the disciplines of psychology and economics. They also had outsized consequences for philosophy, political science, and many other disciplines.
I first met Danny in 1984, when I was still a student. I moved to Vancouver, Canada to study in his laboratory at the University of British Columbia, which he shared with psychologist Ann Triesman. Although Danny was not yet as famous as he would become, his genius was widely recognized.
Three then or future Nobel Prize winners visited the class. A young Richard Thaler spent a year with us and Thomas Schelling and Francis Crick came along. Nevertheless, Danny had time for everyone. Sometimes, even today, I give the advice Danny gave me to my students and colleagues.
In 2002 Danny received the Nobel Memorial Prize in Economic Sciences. He subsequently became perhaps the most influential and distinguished public writer in the behavioral sciences (equaled by his close friend and collaborator Richard Thaler). Danny's 2011 book Thinking, Fast and Slow is a classic in popular science literature.
In it he popularized and developed the idea of two systems of thought. One of the two systems is fast, efficient, confident, and error-prone (system one), while the other is slow, resource-consuming, full of doubt, and perhaps slightly less error-prone (system two).
These systems work together. System one tells us that dessert will likely be delicious and worth considering, while system two steps in to check the calorie count before we dive in.
In academia it would be difficult to pinpoint Danny's most important contributions, but prospect theory, outlined in his 1979 paper with Tversky, is by far the most cited. The article challenged the prevailing economic view that people are fundamentally 'rational', even though they are prone to error.
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Many scientists realized that this could not be entirely correct. But Danny and Tversky showed that integrating important psychological principles into economics could explain many puzzling observations about human nature.
Nudge psychology
The prospect theory paper also provided more than a dozen experimental demonstrations for their claims. Teachers (like myself) still use these demonstrations in the classroom, so reliable are the results they report.
A simple example: given a choice between a sure bet of $100 and a 50/50 chance of winning $200, most people will take the $100. But if people have the choice between definitely losing $100 and a 50/50 chance of losing $200, people will take the 50/50 chance. People are risk averse when it comes to profits, but risk-seeking when it comes to losses.
Prospect theory continues to generate new research and is fundamental to the science of nudging. Nudge theory is the idea that our behavior can be successfully influenced by 'soft' interventions. One of its central principles is loss aversion, which means that people are more sensitive to losses than to gains of equal size.
If you want people to bring their own mug to a coffee shop, charging for a paper cup (loss) is more effective than giving them a discount if they bring their own cup (gain). The idea that behavior can be influenced by such biases is now part of the bread and butter of behavioral science.
Other findings from prospect theory included the tendency for people to be "anchored" when making quantitative judgments. For example, if you make an offer on a house, the seller's valuation will likely shift toward your offer. Danny also described the planning fallacy, the tendency for projects to cost more, deliver less, and take longer than expected.
Another fascinating area of Danny's work explored how a person's feelings and judgments about events depend on their imagined alternatives to those events. One way imagination works is by 'undoing' events. The easier they are to undo, the greater the effect they have on us. This rule was central to Norm Theory, his 1986 paper with Dale Miller.
An example of how undo works: if a car crashes into the wall three feet from where we are standing, we think we just missed death, and we are relieved. But if tomorrow a car drives exactly where we are today, we probably think less about it. Our imagination automatically creates a scenario where we are standing one meter to the left now, but not a scenario where we are standing in the same spot tomorrow.
The science of well-being
Danny was also a pioneer in the field of well-being analysis. Our reflections on an experience are more likely to be influenced by our interpretation of it than the positive or negative feelings we have during an experience.
For example, the peak-end rule is that the extent to which we like a past experience depends on the best or worst part of that experience, and how it ended. Danny showed that men undergoing colonoscopies would report a better experience if the painful intrusion was a longer period of moderate pain, rather than a period that ended earlier but with more pain.
One way Danny distinguished himself from other researchers is that his work was driven not only by the desire to contribute to a field of research, but also to create new fields. And then, if possible, answer any questions they ask. That is why his research, even published many decades ago, still serves as a basis for new ideas and debates.
I last met Danny less than a year ago. I visited his house in New York for dinner. At one point during the evening, Danny said people stopped by to say goodbye.
His eyes smiled and he held up his hand as he said it - a smile and a gesture I've seen him use many times, a mix of "I'm not offended," "You shouldn't be offended by my bluntness," and " Don't let me be offended'. I'll explain." I didn't want to face what he said, but I understood. He was clear about the prospect of death. He was not afraid of death, he was not afraid of anything.
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