After all, if you don’t set boundaries — there won’t be any. Or even worse, there will be boundaries, but they’ll be set by default — or by another person — instead of by design.

Reading a book is among the most high-leverage activities on earth.

At one point, we had become concerned with how much screen time had crept into our family. Between television, computers, tablets, and smart phones it had become just too easy for the children to waste time on nonessential entertainment. But our attempts to get them to change these habits, as you can imagine, were met with friction. The children would complain whenever we turned the TV off or tried to limit their “screen time.” And we as the parents had to consciously police the situation, which took us away from doing things that were essential. So we introduced a token system.9 The children were given ten tokens at the beginning of the week. These could each be traded in for either thirty minutes of screen time or fifty cents at the end of the week, adding up to $5 or five hours of screen time a week. If a child read a book for thirty minutes, he or she would earn an additional token, which could also be traded in for screen time or for money. The results were incredible: overnight, screen time went down 90 percent, reading went up by the same amount, and the overall effort we had to put into policing the system went way, way down. In other words, nonessential activity dramatically decreased and essential activity dramatically increased.