Video (not quite 10 minutes):
He uses garlic cloves instead of stones, but it's a similar analogy to a piece I linked to previously when I wrote about face blindness before.
My ex-husband really liked movies and TV shows, so a big part of our relationship was watching movies and TV shows together. And over time it became apparent we had very different strengths and weaknesses for recognizing the same actors in different roles.
The wife of Peter Falk played in some of the episodes of Columbo. After learning that, we would try to identify her. She didn't play a recurring character. She always played someone different and they tried to cover up the fact that the same actress was used repeatedly, so they tried to dress her very different.
I was better at identifying her than he was because this was typically about changes in hairstyle and clothes and makeup. If you recognize faces, that's a huge advantage.
But Christopher Lloyd, who plays Doc Brown in Back to the Future, also played a Klingon in one of the Star Trek movies. My husband knew instantly that it was the same actor and I was like "Noooo. You're messing with me. That's not Doc Brown."
My ex recognized voices vastly better than I did. He knew it was the same actor as soon as Lloyd spoke.
Marine biologists typically catalog whales by distinctive fin markings. That's probably kind of like how face blind people experience identifying people. They intentionally track something kind of like that because they just don't have this magic face identification software most people have.
Crows all look black to the human eye and most people would probably say crows pretty much all look alike, but under UV light they are brightly colored and probably look very distinctive to other crows who can probably see those patterns. That's probably roughly how face blind people experience dealing with other people. We all look like "black crows" to them and we're like "No, no, no. That's not how people look at all. Look at the pretty colors! Everyone looks so different."
My ex had a distinctive gait. I could identify him from the back in uniform in a crowd of uniformed soldiers. My understanding is this type of thing is much more common with people who are face blind: They recognize people by something like their gait or they are talented at identifying people by their bare feet or some other detail that would never make the radar of most people.
The guy in the clip above says he didn't know he was face blind. He thought he was just bad at remembering names.
I think a lot of people don't know. My ex had trouble recognizing me at the airport when I flew to Germany a month after him and that was weird, but when he came home from work and I was at home, the woman at home was his wife. So we weren't typically in circumstances that made it clear he was not normal in some way.
My oldest didn't know how to express or even identify what some of his issues were. When he was five, I would ask him how school was and he would say "Fiine." and I felt like I was missing something important but I didn't know how to ask a five year old "What's this answer mean? Because it doesn't sound like you are really fine. What's going on with school?"
So when he was something like thirteen or fourteen, he used my email address to talk to the woman who told me what face blindness was because her child was something like six years old and the child was really bright, yet couldn't really tell adults what was going on.
So my son was old enough to kind of speak for her and talk about what it's like to be six and everyone seems to know who everyone is and you don't and they think you should.
The law uses fingerprints to identify people because of a case of mistaken identity. In 1903, Will West and William West were incarcerated at the same prison and had strikingly similar features. For a short time, prison staff thought the new prisoner was guilty of murder which he denied. And then they realized the murderer was already incarcerated there.
Dunbar's Number suggests that humans are biologically designed for a "tribe" of about 150 people. In the modern world, it's rare for people to be limited to that number of acquaintances.
Our software is not really designed for dealing with cities of thousands or tens of thousands or hundreds of thousands of people. Someone who isn't particularly good with faces but only knows 150 people total probably has no trouble keeping them straight.
This is sort of a First World Problem. And the reality is most people aren't as good at this as they imagine they are.