heuristic. They proved analytically conditions under which semi-ignorance (lack of recognition) can lead to better inferences than with more knowledge. These results were experimentally confirmed in many experiments, e.g., by showing that semi-ignorant people who rely on recognition are as good as or better than the Association of Tennis Professionals (ATP) Rankings and experts at predicting the outcomes of the Wimbledon tennis tournaments. Similarly, decisions by experienced experts (e.g., police, professional burglars, airport security) were found to follow the take-the-best heuristic rather than weight and add all information, while inexperienced students tend to do the latter. A third class of heuristics, Fast-And-Frugal trees, are designed for categorization and are used for instance in emergency units to predict heart attacks, and model bail decisions made by magistrates in London courts. In such cases, the risks are not knowable and professionals hence face uncertainty. To better understand the logic of Fast-And-Frugal trees and other heuristics, Gigerenzer and his colleagues use the strategy of mapping its concepts onto those of well-understood optimization theories, such as signal-detection theory. The short book Classification in the Wild (2020, MIT Press), uses examples such as how American citizens decide to vote for their president or how paramedics prioritise treatment at a medical emergency, to show how to build heuristics such as Fast-And-Frugal trees and tallying models, as well as how to test and compare their accuracy and transparency with state-of-the art algorithms from other fields, including machine learning. A critic of the work of Daniel Kahneman and Amos Tversky, Gigerenzer argues that heuristics should not lead us to conceive of human thinking as riddled with irrational cognitive biases, but rather to conceive rationality as an adaptive tool that is not identical to the rules of formal logic or the probability calculus. He and his collaborators have theoretically and experimentally shown that many cognitive fallacies are better understood as adaptive responses to a world of uncertainty—such as the conjunction fallacy, the base rate fallacy, and overconfidence. The adaptive toolbox The basic idea of the adaptive toolbox is that different domains of thought require different specialized cognitive mechanisms instead of one universal strategy. The analysis of the adaptive toolbox and its evolution is descriptive research with the goal of specifying the core cognitive capacities (such as recognition memory) and the heuristics that exploit these (such as the recognition heuristic). Risk communication Alongside his research on heuristics, Gigerenzer investigates risk