From the Editor; April/May 2006; Scientific American Mind; by Mariette DiChristina; 1 Page(s)

It was one of those seemingly mundane moments, but I was thunderstruck when I realized the implications. Tossing on a cardigan, I happened to notice my toddler intently staring at me to figure out how to push a button through a hole in her sweater. Suddenly, I realized how much we learn how to do things and how to behave around others just by watching and copying.

At the time, nearly a decade ago, I had little idea about how extensively my child was mentally rehearsing my actions as she studied me. Since then, science has learned much more. When we see someone engaged in any activity--yawning, dancing, smiling--cells called mirror neurons that are scattered throughout the brain create an instant replay in our heads. Investigators believe that these cells may be the keys to cultural development and may even be responsible for humanity's collective "great leap forward" 50,000 years ago, as David Dobbs explains in his article, "A Revealing Reflection."