I just read about a really cool research study.
http://www.sciencedaily.com/releases/2011/11/111128152416.htm
The researchers took a bunch of 8 month old infants and had them watch puppets. Some puppets were mean puppets and others were nice puppets. Other puppets came along and either treated the mean puppets kindly or punished the mean puppets by taking away toys. Can these 8 month old babies understand between right and wrong? Well...To see which puppets the babies liked the best, the babies were told to either give toys to the puppets or take toys away from the puppets. If you were a puppet who was kind to the mean puppets...the babies didn't like you! They took away your toys. If you were a mean puppet....the babies didn't like you either. Ahh...but if you were a puppet who punished the mean puppets?...Guess what...the babies loved you. They gave you toys! And if you were a nice puppet (not nice to the meanie puppet) the babies liked you too. These babies knew what it looked like to treat someone kindly. They also understood the concept of justice. How amazing. These babies wanted justice when they saw cruelty to others.
Children innately know right from wrong! Look at Romans 1:20
For since the creation of the world God's invisible qualities--his eternal power and divine nature--have been clearly seen, being understood from what has been made, so that men are without excuse.
How cool that you can see an understanding of right and wrong in babies who can't even talk yet. They already have an innate understanding of the moral code that God has placed in creation.