We Understand Probability as Toddlers

Don't understand probability? Try asking a 2-year-old. A study suggests they have an instinctive understanding of the ideas involved, and that a little observation goes a long way. Researchers at the University of Washington showed 32 toddlers a machine featuring a pair of blocks and a platform, Quartz reports. An adult repeatedly demonstrated the system: Putting one block on the platform would make a marble emerge from a chute two-thirds of the time. Placing the other block on the platform could also make a marble roll out—but only one-third of the time. When the kids had a chance to operate the machine themselves, 23 out of 32, or 72%, opted for the more effective block.

Researchers tried the experiment a second time to ensure the kids weren't just counting the marbles: During the second run-through, each block led to the release of four marbles, but the probability of a marble emerging remained different. Specifically, one block released marbles four out of six times, while the other did it four out of 12 times. Still, 22 out of a new group of 32 kids knew to pick the more effective block. "Our findings help explain how young children learn so quickly, even in an uncertain and imperfect world," a researcher tells university news. "Remarkably, they learn about causality even if the people they are watching make mistakes and are right some but not all of the time." Could drawings offer another window into kids' brains? (More probability stories.)