Eighteen-month-old infants show false belief understanding in an active helping paradigm.

Recently, several studies have claimed that soon after their first birthday infants understand others' false beliefs. However, some have questioned these findings based on criticisms of the looking-time paradigms used. Here we report a new paradigm to test false belief understanding in infants using a more active behavioral response: helping. Specifically, the task was for infants to help an adult achieve his goal - but to determine that goal infants had to take into account what the adult believed (i.e., whether or not he falsely believed there was a toy inside a box). Results showed that by 18 months of age infants successfully took into account the adult's belief in the process of attempting to determine his goal. Results for 16-month-olds were in the same direction but less clear. These results represent by far the youngest age of false belief understanding in a task with an active behavioral measure.