The answer is: The children were more likely to show increases in aggressive behavior when aggressive behavior was rewarded.
Human beings are wired to constantly seek something that provide positive value of us. When we do a certain type of activity and obtain a reward from it, our brain will see that activity as a 'source of positive value' thus create our unconcious desire to repeat that activity again. This is why The children were more likely to show increases in aggressive behavior when aggressive behavior was rewarded.
