A computer can now accomplish what almost all of us as human beings have done almost since birth—recognize people’s faces. For most of us, this probably began with the ability to recognize our mother. One of the joys of parenting comes when a toddler erupts enthusiastically when you return home. This reaction, which lasts until the onset of the teenage years, relies on the innate facial-recognition capabilities of human beings. While this is fundamental to our daily lives, we almost never pause to think about what makes it possible.
