Psychologist Alison Gopnik explores new discoveries in the science of human nature.
Seventeen years ago, my son adopted a scrappy, noisy, bouncy, charming young street dog and named him Gretzky, after the great hockey player.
Gretzky transformed into a serene guardian of the new baby, sitting quietly curled up next to him.
Almost as soon as he could walk, Augie loved wrestling with what was, objectively, a sharp-toothed carnivore twice his size.
When Gretzky died last October, Augie was heartbroken.