The emergence of probabilistic reasoning in very young infants

How do people make rich inferences from such sparse data? Recent research has explored this inferential ability by investigating probabilistic reasoning in infancy. For example, 8- and 11-month-old infants can make inferences from samples to populations and vice versa (Denison & Xu, 2010a; Xu & Denison, 2009; Xu & Garcia, 2008a). The current experiment investigates the developmental origins of this probabilistic inference mechanism with 4.5- and 6-month-old infants. Infants were shown 2 large boxes, 1 containing a ratio of 4 pink to 1 yellow balls, the other containing the opposite ratio. The experimenter sampled from, for example, the mostly pink box and removed a sample of either 4 pink and 1 yellow balls or 4 yellow and 1 pink balls on alternating trials. Six-month-olds but not 4.5-month-olds looked longer at the 4 yellow and 1 pink sample (the improbable outcome) than at the 4 pink and 1 yellow sample (the probable outcome).