In a first study, researchers from the Max Planck Institute for Human Development and the University of the Balearic Islands analyzed the development of research on statistical reasoning from a historical perspective. In the 1960s, adults were still considered to be good intuitive statisticians. From the 1970s, however, this notion was overturned. Since then, studies on so-called “heuristics and biases” have concluded that human reasoning is prone to systematic errors. According to this approach, the heuristics—mental shortcuts or rules of thumb—that people use for statistical reasoning produce systematically biased judgments that are inconsistent with the rules of probability theory and statistics.