Sibling Lessons in Game Theory

The last slice of cake, the last slice of pie, the ice cream served in one bowl: at first, the ability to allocate my portions from theirs was part of their divine rights of parents, and I more or less accepted this. At five, my parents began permitting me to choose which dish was mine. The slices of cake were always disappointingly similarly sized, so this didn't change a lot, but I enjoyed the power.

I distinctly remember my dad sitting me down on the floor with a slice of cake and two plates. "Today's your turn to divide the cake, and I choose." I set a very small portion on one plate, and left 70% of the cake on another for myself. He began reaching, very slowly, for the larger plate, eyes locked on it, wordlessly explaining in no uncertain terms what was about to happen. I scowled, "Let me try again."

When Isaac was three and old enough to express his interest in cake, it was my duty as the six-year-old to divide the cake and let him select. Isaac was not the same sort of opponent as my parents. At first he could be tricked by putting the smaller portion near him, and after a few rounds of that he could be tricked by my pretending to hide the smaller portion from him and acting like it was somehow better. Just as they later did when the addition of Firefly lead to kickback and collusion dynamics, the divider was severely punished for such dishonest play. Rules emerged: plates had to be equally presented, divisions were final once the first person took a plate, choosers could only select a plate for themselves, and all games were discrete instances: debts incurred in one game couldn't be repaid in another.

It was a long while before Issac was ready to play as the divider, but one day my parents informed me he was. A long bar of brownies was placed on a plate, and my brother pulled off a small square from the end and put it on the second one. I grinned and reached for the larger one as my brothers face scrunched up in a scowl.

"That's not fair."

"It's the rules."

Isaac sighed, annoyed, "You're suppose to want the little one!"