The probable and the possible at 12 months: intuitive reasoning about the uncertain future.

How do infants predict the next future event, when such a prediction requires estimating the event's probability? The literature suggests that adult humans often fail this task because their probability estimates are affected by heuristics and biases or because they can reason about the frequency of classes of events but not about the probability of single events. Recent evidence suggests instead that already at 12 months infants have an intuitive notion of probability that applies to single, never experienced events and that they may use it to predict what will happen next. We present a theory according to which infants' intuitive grasp of the probability of future events derives from their representation of logically consistent future possibilities. We compare it and other theories against the currently available data. Although the evidence does not speak uniquely in favor of one theory, the results presented and the theories currently being developed to account for them suggest that infants have surprisingly sophisticated reasoning abilities. These conclusions are incompatible with most current theories of adult logical and probabilistic reasoning.