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On May 24, 2023, Steven Pinker and Richard Thaler, two of the world’s leading behavioral scientists, engaged in a wide-ranging discussion on rationality, AI, overcoming collective action problems, and more. The conversation was part of the Think Better speaker series hosted by the Roman Family Center for Decision Research at the University of Chicago Booth School of Business. The title of the talk was “"Irrationality: Is the Brain Half Empty or Half Full?" and brought together Pinker, the Johnstone Family Professor of Psychology at Harvard University and Thaler, the Nobel laureate and the Charles R. Walgreen Distinguished Service Professor of Behavioral Science and Economics at Chicago Booth.


The conversation between Thaler and Pinker was inspired by their previous informal discussions while both were in residence at Berkeley. While Thaler approaches rationality—and predictable irrationality—from the perspective of a behavioral economist, Pinker approaches it as an evolutionary psychologist. In Pinker's recent book Rationality, he emphasizes the importance of understanding tools like probability, logic, correlation, causation, game theory, and rational choice theory in our everyday lives. He argues that while these tools are not naturally ingrained in human thinking, they provide a benchmark for rationality. Pinker addressed the need to explain why people believe in irrational theories like QAnon and explored the connection between rationality and social justice movements.

The discussion touched upon famous examples of judgment and decision-making fallacies, such as the story of “Linda the feminist bank teller,” which exemplifies the conjunction fallacy.  In this scenario, participants are asked to choose between two statements about Linda after reading a brief story about her life and interests: one stating she is a bank teller and the other stating she is a bank teller and a feminist. Despite the second statement being a subset of the first and therefore less likely, many people mistakenly perceive it as more probable due to the representativeness heuristic. While this scenario demonstrates how cognitive biases can influence decision-making and lead to illogical judgments, Pinker reevaluates the benefits of these biases and what rationality really means.


Pinker also discussed the connection between human cognitive abilities and our evolutionary past. Using the example of long-standing traditions and practices of hunter-gatherer tribes, Pinker suggested that humanity’s ability to observe and reason gave them the edge to survive. Humans might not be as fast as gazelles, but understanding where the animals were running allowed hunters to track and eventually exhaust and eventually catch their prey. Certain tribes still have the remarkable skill of discerning animal tracks, honed over centuries of survival. These tribes, often the last of an isolated culture, offer a fascinating glimpse into the cognitive abilities of our ancestors. Such expertise in tracking and distinguishing animal footprints may indicate an early form of Bayesian logic.


Thaler pivoted the conversation towards behavioral economics, where the concept of predictable irrationality was examined in the context of saving for retirement. Behavioral economists observe that humans do not always exhibit the level of rationality assumed by classical economic models. The struggle to save adequately for the future is cited as an example of our inherent fallibility in decision-making, a problem that has only emerged as societies have evolved over the past century. Pinker suggested that these behaviors are not so irrational in their pre-modern contexts. Someone who does not save for retirement may be perceived as irrational, but before people lived so long, it made sense to use one’s resources more quickly. As modern institutions, such as reliable banks, long lifespans, and predictable environments, are relatively recent developments, our cognitive wiring may not have adapted to these changes.


Thaler and Pinker addressed the prevalence of irrationality in contemporary culture, citing examples such as vaccine hesitancy, belief in homeopathy, and astrology. They argue that many cases of irrational behavior stem from limited knowledge and a lack of exposure to the relatively new institutions that society has created. With access to education and the dissemination of critical thinking skills, humans can overcome these biases and learn to harness the benefits of modern institutions.


The conversation touched upon the evolutionary arms race between cheaters and those adept at detecting deceit. Examples from the natural world, such as brood parasites among birds, shed light on the perpetual battle between exploiters and their potential victims. Human interactions also involve trust and exploitation, with con artists exploiting social trust for personal gain. Pinker highlighted the crucial role of trust in human interactions and how con artists exploit this trust. He explained that trust is a necessary component for society to function smoothly, but it also creates opportunities for exploitation. As individuals become better at detecting cheaters, the pressure mounts on exploiters to become more sophisticated and crafty. Pinker emphasized that even the most trustworthy individuals can fall victim to well-crafted cons, creating cracks and loopholes for exploitation.


Drawing upon his expertise in perception and cognition, Pinker drew parallels between visual illusions and cognitive illusions. He explained that just as visual illusions expose the limitations of the human visual system, cognitive illusions expose the fallibility of human cognition. However, Pinker cautioned against concluding that cognition is fundamentally flawed based on these illusions. He emphasized that, like the visual system, cognition has evolved to be highly functional and effective in processing information and making accurate judgments.


Pinker addressed his characterization as an optimist and explained his perspective on the trajectory of human progress. He pointed out that objective measures of human well-being, such as reduced mortality rates, increased life expectancy, and advancements in science, indicate a positive trend over time. He attributed skepticism toward progress to cognitive biases, particularly the availability heuristic, which leads individuals to overestimate negative events due to their salience in memory.

When questioned about concerns regarding the negative impacts of AI, Pinker highlighted the irrationality of solely focusing on the negative outcomes of any technology. He emphasized that technologies, including AI, have both positive and negative consequences. Pinker dismissed extreme doomsday scenarios, such as AI dominating or accidentally wiping out humanity, highlighting that these concerns often stem from anthropomorphizing AI and misconceptions about its goals and motivations.


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