It's really only since I met my wife, six years ago, that I've become aware of my inability to identify faces. In fact, it's part of our origin story.
Arriving at her flat for our second date, I knocked on the door and was greeted by a woman I didn't recognise, which isn't to say I knew it wasn't her, but rather that it could have been anyone.
I was mildly panicked so, to buy some time while I tried to find a way toward the truth, I blurted out the following stupid comment, which I hoped would cover me in any eventuality: "You look different to what I remember!"
Seconds later, my girlfriend appeared. The woman in the doorway, who was her flatmate, turned out to be taller, heavier, with different coloured hair cut much shorter, and a strong German accent.
Zanna loves telling this story to people to illustrate my woeful facial-recognition inadequacy, which has since become legend in our relationship and, increasingly, beyond.
Recently, she and I started watching a show called The Americans, in which two Russian spies pretend to be suburban American parents while also doing a lot of nefarious undercover spy stuff. In an early episode, there was a long set piece featuring the show's main character - a man who had been in nearly every scene up to that point - wearing a fake moustache. At the end of the scene, I said to Zanna, "Who was that?"
She asked if I was serious, and when I told her I was, she said, "These disguises are going to make this show very difficult for you, aren't they?"
And so on.
I frist of the condition of prosopagnosia, or face blindness, a few years back in a 60 Minutes story, in which a serious sufferer, shown a picture of her own daughter, was unable to recognise her, even after the presenter gave her the clue that it was a member of her family.
Once I discovered the term "face blindness", I began to use it all the time. I would use it as a conversation starter: "Have you heard of face blindness?" I would ask people I had just met. Invariably they hadn't, which would give me an opportunity to regale them with boring tales of my suffering like the ones above.
Famous sufferers include Stephen Fry, Oliver Sacks and possibly Brad Pitt. A few years back, Pitt told Esquire magazine he was going to have himself tested for the condition because it was affecting his life. "So many people hate me because they think I'm disrespecting them," Pitt told the magazine. "I took one year where I just said, 'This year, I'm just going to cop to it and say to people, okay, where did we meet?' But it just got worse. People were more offended ... You get this thing, like, 'You're being egotistical. You're being conceited.' But it's a mystery to me, man."
Things can be in your head but you lose the catalogue card.
Faces are so important that part of our brain is dedicated to recognising them. Sometimes this area might be damaged by some event - a stroke, for instance - that causes people to become face-blind. It used to be thought that this was the only way face blindness could develop, but about 15 years ago researchers discovered it can also be developmental, with a strong genetic component.
But issues with your face recognition centre are not the only reason you might be no good at recognising people. You might just have a crappy memory. As University of Auckland psychology professor Will Hayward, who is an expert in the field of face recognition, puts it: "Things can be in your head but you lose the catalogue card."
"Whether a face is difficult to perceive or whether it's difficult to remember, your experience might be quite similar."
I can recognise family, friends, colleagues, most well-known or distinctive-faced actors and even a reasonable number of acquaintances. Written down like that, it's almost possible to think I don't have a problem at all.
"Are you sure you really can't recognise faces?" asked Haiyang Jin, who is a PhD student doing research into face recognition at the University of Auckland. "Or do you think maybe you're just a little worse than other people?" I wasn't sure.
"Because," he went on, "most people think they're not so good about recognising faces but they don't actually have face blindness."
It turns out that this is all quite easily settled. There is an online test that will score your face blindness and, after I spoke with Jin, I did it. It's an academically respected test called the "Cambridge face memory test", is used for serious research, and is very, very hard.
Towards the end of the test, you have to memorise six bald-headed faces and then pick them out of a series of subsequent line-ups, in which the faces are distorted by some sort of crazy digital noise. Almost every answer I gave was a guess. I was reasonably certain my score would be among the very worst ever recorded.
After 15 minutes or so and dozens of impossible questions, the results page read: "Thank you for taking part in this experiment. Your accuracy in the experiment was: 68 per cent. The average score on this test is around 80 per cent correct responses for adult participants. A score of 60 per cent or below may indicate face blindness."
I was a bit below average, but not terrible at all, and almost certainly not suffering from face blindness. My facial recognition skills were disappointingly, boringly, ordinary.
I asked Hayward why this was the case, when I could categorically point to endless embarrassing examples of my facial incompetence.
"You know how everyone thinks they're a better driver than everybody else?" he said.
"Memory and recognising people is kind of the reverse. We all think we're terrible but actually it's quite a hard job and so we're not necessarily as bad as we think."
My wife is, without doubt, one of the greatest face-recognisers I have ever met. She is the sherpa of my televisual understanding, the ear-whisperer of my social gatherings. Unfazed by fake moustaches, costume changes, wigs, haircuts and sudden weight gains, she is a 35-year-old who frequently points people out to me and says: "I went to primary school with her."
I asked her to take the Cambridge test one night. She didn't want to. She was tired and sick and, I suspect, simultaneously checking Facebook.
"This is really hard," she complained at one point. She scored 96 per cent.