A new study suggests that loud and unruly toddlers in their "terrible twos" know that their tantrums make everyone around them miserable.

While researchers have known how toddlers understand what other people around them are seeing, they didn't know whether toddlers understood that sound was also experienced by those around them.

A new study tested 48 children aged two and three years old by giving them the choice to play with a noisy toy, or a quiet toy. Both types of toys were popular among the children. Then the researcher left the room and returned with a baby doll that seemed to be sleeping. Half the children were told "Look, the baby's sleeping," and the other half were told "Naptime is over." Then the children were offered the same two toys - one noisy and one quiet.

Those who were told that the baby was sleeping were more likely to chose the quiet toy, suggesting that they understood how their actions affected their environment. Jerks.