The latest study had three prongs: biographical data of explorers and revolutionaries; a survey of 11,000 German households; and an elaborate assessment, called the Basel-Berlin Risk Study, which measured risky behavior of 1,500 people through interviews and experiments.

The Basel-Berlin Risk Study, a day’s worth of about 40 psychological tests, “is one of the most exhaustive attempts to measure risk preference,” Lejarraga said. Researchers asked participants about driving too fast, unprotected sex and other dicey behaviors. The participants also performed simple experiments. Hertwig gave the example of a game in which subjects had two options: receiving $10 (the safe choice) or gambling on a 10 percent chance to win $100.

“None of these behavioral measures showed any credible relationship between being a later-born and taking more risks,” the study authors wrote. The household survey didn’t find a relationship between self-reports of riskiness and birth order. Neither did examining the birth orders of almost 200 people who made the “risky life decision” to become revolutionaries or explorers, such as mountaineer Edmund Hillary, guerrilla fighter Che Guevara and socialist activist Rosa Luxemburg.