15 month old babies recognize fairness
15 month olds spent more time looking at the "unequal outcome" when an actor in a video distributed food equally and unequally.. "suggesting it surprised them by violating their basic sense of fairness." when then asked to pick a favorite of two new toys and then to share one, "of the infants who shared their favorite toy, 92 percent had also been surprised by the unfair outcome in the videos."
Lena Groeger, "Baby Justice, "Scientific American Mind, march-April 2012, 12. based on PLoS One aritcle from 10.11