Parents: If you want your kids to be better at sharing, get them to be better at cooperating.

That’s the gist of a new German study we read about in the journal Nature. It found that young children are more likely to share rewards fairly, if they had to work together to get them.

In the study, psychologists gathered more than 200 two- and three-year olds to play a marble game. Some of the kids were grouped into pairs, where they had to help each other pull on ropes to get marbles. The rest of the kids were free to collect marbles on their own, and play by themselves.

The result? Researchers found that the kids who helped each other wound up sharing their marbles fairly 75 percent of the time.  But the kids who didn’t have to work together rarely shared.

Why would this happen? Psychologists believe sharing is a behavior that’s rooted in the days when we had to hunt to survive. The thinking is those who hunted in groups were more likely to survive, because they learned to share what they caught and killed.  On the flipside, those who hunted alone were more likely to be eaten!  That’s why experts say the key to getting your kids to share toys, is to have them work together to earn those toys in the first place.