Infants Distinguish Between Two Events Based on Their Relative Likelihood

Likelihood estimations are crucial for dealing with the uncertainty of life. Here, infants' sensitivity to the difference in likelihood between two events was investigated. Infants aged 6, 12, and 18 months (N = 75) were shown animated movies of a machine simultaneously drawing likely and unlikely samples from a box filled with different colored balls. In different trials, the difference in likelihood between the two samples was manipulated. The infants' looking patterns varied as a function of the magnitude of the difference in likelihood and were modulated by the number of items in the samples. Looking patterns showed qualitative similarities across age groups. This study demonstrates that infants' looking responses are sensitive to the magnitude of the difference in likelihood between two events.