But if we make kids share, they walk away resentful, not generous.

And not surprisingly, they're less likely to share after that.

Kids aren't developmentally ready to share before they're five or six years old.

Children under the age of five have a different sense of time than we do.

The fact that the timer's been ticking away for five minutes seems to them like a split second.

So, they don't understand what's happening when we say, "You've had it for long enough; it's the other kid's turn."

We're teaching children that if they cry loud enough, they get what they want.

That they matter more than someone else.

So it teaches kids to cling to their toys, to be greedy.

If we want children to be generous, we have to let them voluntarily choose the experience of giving something to the other person.

What if we put them in control of when they gave up the toy?

Maybe in your family, you don't want the child to use the toy all day, and so the rule is that when you have a toy, you use it until the next meal.

When one of the kids wants a toy, the other one says, "No, I need a long turn.

I need it until lunch time."

If the child is in charge of that decision, when they do give the toy up, they reap the emotional gains from that.

They feel generous, and they want to repeat it.

When parents hear these ideas, the first thing they think of is: "What about the child who has to wait for a toy?”

Because we assume the second child is having a total meltdown.

So in the beginning, they will need adult support to wait.

You hug them, you hold them.

And once they have a chance to express their feeling that life is not fair, that they don't get what they want when they want it, what we find is that after kids have a chance to cry, they're done with it.

They're not waiting, really, for the dump truck anymore.

They're on the ground working with the snowplow.

That's actually an important part of children's emotional development: learning they can withstand those big emotions and they can make it through to the other side.

And they can focus on something else.

And when they learn that, they become much more resilient.

Kids who are generous develop so many qualities that will help them for the rest of their lives.

So, imagine when those two kids grow up and they're in a workplace, or a marriage, or simply on the street when somebody cuts somebody off in traffic.

Every relationship will benefit from them developing this ability as a child.