 Do human beings systematically violate the norms of probability and statistics? Petersen and Beach (1967) thought not. On their view human beings are intuitive statisticians  (section 5.1),  so probability theory and statistics are a good, first approximation of human judgment and decision making. Yet, just as their optimistic review appeared to cement a consensus view about human rationality, Amos Tversky and Daniel Kahneman began their work to undo it. People are particularly bad at probability and statistics, the heuristics and biases program  (section 7.1)  found, so probability theory, statistics, and even logic do not offer a good approximation of human decision making. One controversy over these negative findings concerns the causes of those effects—whether the observed responses point to minor flaws in otherwise adaptive human behavior or something much less charitable about our habits and constitution.