A UK and German study published in Current Biology reveals that 3-year-olds understand injustice, and will act to fix it, according to NPR. When puppeteers acted out situations in which one puppet stole a cookie from another puppet, children would return the cookie to its rightful owner 60 percent of the time. (That's in comparison to 80 percent of the time in which children would take back their own cookies that were stolen.)
The study also compared the reactions of 3-year-olds to the reactions of 5-year-olds, and found that the older children were more likely to dole out punishment to culprits. The younger age group focused on comforting victims and righting wrongs.
