The phone that knows your face

Usually, my iPhone recognizes me instantly. But on rare occasions, I am holding my own phone, looking straight at it, and it tells me: “Face Not Recognized.”

If you have ever had that moment, you know how unsettling it can feel. What changed? Did I pick up someone else’s phone? Sometimes it is something simple: the tilt of the phone, poor lighting, or a smudge on the lens. But other times it is not so simple. You may be tired, slightly swollen, not well. I find myself wondering: were my glasses off? Was I dehydrated, or just different enough that the system hesitates? Did I simply not look lik...