Which discipline or reward is best for your child?

"A teacher who rewards or punishes a whole class for the good deed or misdeed of just one student is more likely to be seen as fair by 4-to-5-year-olds but as less fair by older children," said research investigator Craig Smith of the U-M Center for Human Growth and Development. "Likewise, the data suggest that most older children and adults will feel that the common practice of punishing everyone for the misdeed of one or a few is unfair."

The data found that preschool-age children were more apt to punish groups of people for the transgressions of one person in the group. It doesn't mean the little ones are necessarily harsher as people, but that they have a different idea of what's fair, Smith said.

They may actually be motivated by compassion. Based on feedback from the children in the study, they seemed reluctant to single out one person in a group for discipline.

Researchers asked children ages 4 through 10 the fairest way to hand out rewards and punishments. The 4-to-5-year-olds overwhelmingly chose to give everyone the same things regardless of merit.

In the elementary school years, this shifts to the more mature view that people should get what they deserve, and it's unfair to reward or punish an entire group for the good or bad actions of one person. This is the view that most adults take, Smith said.