We saw it all along: visual hindsight bias in children and adults.

We traced the developmental origins and trajectory of the hindsight bias. Three-, 4-, and 5-year-old children and adults identified gradually clarifying images of degraded common objects on a computer. Half the time, observers did not know in advance what the object would become. The rest of the time, observers knew the object's identity in advance and estimated when a naive same-age peer would identify the clarifying object. In two experiments, children and adults demonstrated hindsight bias by using advance knowledge to overestimate their same-age peers' ability to identify the objects. The magnitude of this bias declined across age in one experiment, but remained relatively stable over age in the other experiment. These findings link developmental psychology and adult cognitive science.