From time to time, we all have trouble remembering a person's name. I've learned a few tricks over the years, like studying the class roster before back-to-school night and the names in the "CC" box on the email invitation, but mostly, I introduce myself repeatedly and hope for the best. I've never been able to carry off Joan Rivers' trick for saving face when you've forgotten a name: After getting the person to identify herself, Rivers says something like, "Of course—you just look so much younger with that haircut." The social blunder of the forgotten name is quickly lost in the pleasure derived from the compliment.

Until I was deep in the research for Carved in Sand, I didn’t realize that my problem wasn’t limited to name-blanking. Unfortunately, I'd forget people in their entirety. It was as if I'd never seen them before. I assumed it had something to do with being hopelessly self-involved, but as it turned out, I was dealing with a neurological tic. The name for this was prosopagnosia, or face blindness.

According to a recent article in New Scientist, prosopagnosia was first identified in 1947 by German scientist Joachim Bodamer, a neurologist who described the condition in a 24-year-old patient who, as a result of a brain trauma, couldn’t recognize friends or family. That must have been stressful around the holiday table. More recently, researchers have acknowledged a second kind of prosopagnosia, a developmental disorder, that is present from a very early age. It's reassuring, in a strange way, to learn that my face blindness is shared by as much as 2 percent of the population.

This gap in my abilities may be genetic. My father used to whisper desperately to me as we walked down Madison Avenue: "Who is that woman coming toward us?" Studies of children who have this disorder report that a prosopagnosic child is a shoo-in to have a prosopagnosic parent. What a gift. I got my father's long legs, his big ears and feet, his ability as a public speaker and his total unreliability in a social arena.

After reading that article, a New Scientist reader wrote in about her particular version of blindness, or perhaps deafness: she cannot distinguish voices on the telephone. She can't reliably tell her grown daughter from her boss, which must have made for some interesting conversations. I can identify: Calling her at home at some odd hour, I have mistaken my associate's forty-five-year-old husband for her fourteen-year-old son—and worse, her eleven-year-old son—for his temporarily absent mother. It's another good reason to identify yourself when you answer the phone—or when you meet someone at a cocktail party. You never know if you will be remembered. Just try not to take it personally.

For more about prosopagnosia, see Carved in Sand chapter 4, “Blocking, Blanking and Begging for Mercy.”