I was sick today, so after I got dressed this morning, I went back to bed, lay under the fuzzy blanket, and read Death on the Nile.

I’d read it before – I think I’ve read every Agatha Christie mystery. I like reading them again because I always notice new details, and they’ve become textbooks for me. Christie is so good at creating plots and leading readers through them. So I read her for lessons in plotting and in how to direct the reader’s attention.

Today I noticed something that I’ve noticed before, which is how quickly she sketches characters. She does it by appealing to stereotypes we have. Her characters are all stereotypes in a way. In Death on the Nile, Linnet Ridgeway is the beautiful blond heiress. Christie sketches her quickly by having her wear a simple white dress that only certain other female characters realize is phenomenally expensive. When we are told that, most of us instinctively know exactly what Christie means. We’ve seen such dresses and know what sorts of women wear them. And if we haven’t – well, in a sense Christie indoctrinates us into a world in which there are such women, and we begin to understand the code. We begin to understand that certain things mean certain other things. As Hercules Poirot points out, the fact that Mr. Fanthorp wears an Old Etonian tie means that he simply wouldn’t interrupt a conversation taking place between people he doesn’t know – and the fact that he does is therefore meaningful.

Characters in Christie fit into these stereotypes. And I was thinking, while I was reading, of the extent to which we use such stereotypes in real life. I don’t mean simply to think about other people in stereotypical ways. I mean to project ourselves, our sense of who we are. It’s as though appearance is a series of codes. We know the codes (although different people might know different codes), and we use them to create our public selves.

For example, when I was a lawyer working in Manhattan, it was obvious that the female lawyers and the (almost all female) secretaries dressed differently. The secretaries tended to wear dresses. The female lawyers tended to wear suits. The secretaries wore more and different jewelry, typically more expensive. The female lawyers wore fewer pieces of jewelry, smaller pieces, often pearls. (Did you know that there is a whole subset of the female population that is given pearls? Typically for a teenage birthday. I was given pearls for my sixteenth birthday. But Ophelia was given hers at her christening.) There were differences in hairstyle. Even the hands: secretaries often had painted nails. Lawyers never did. (My mother lectured me when I was a teenager and wanted to paint my nails. Professional women, she told me, do not paint their nails. In an Agatha Christie world, she would have been telling me that ladies never do.)

I’ve always been fascinated by these codes, probably because I was an immigrant, and therefore a social outsider. Social outsiders tend to notice the codes of the society they’re in. With these codes, you can establish who you are, because people recognize and read them. (They tend not to acknowledge them, except in movies in which the secretary becomes a powerful businesswoman. Then you will see her transform, her hair and makeup change, her clothes change. With absolutely no discussion of how appearance is read, particularly as a marker of social and educational class. We don’t like to talk about social class, as Americans.) And you can play with the codes. There are people who are more difficult to read because they’re deliberately playing with the codes. They tend to be creative types, the CEO of the computer company who wears jeans. But probably a specific brand of jeans, because even people playing with the codes usually want to signal that they know the codes, they’re just being rebellious and cool. Unless they are genuine eccentrics. Artist are genuine eccentrics. They will present themselves in ways that don’t make sense in terms of any of the codes. They have a tendency not to care, or to create their own codes.

All of which has to do with how you can present your characters.

For Christie, the stereotypes are actual identities. That’s part of the detective fiction genre. For Arthur Conan Doyle too, as well as for Dorothy Sayers, people tend to behave as they should according to type. If you know their type, you know how they will behave.

But for us, the stereotypes are about self-presentation. We can use them to talk about how a character thinks of herself. A character with a nose ring, for example, is presenting herself differently than a character wearing a string of pearls. They are both appealing to and using stereotypes to help create the identities they present to other people. It’s not about who they are, but about who they think they are and want to be.

How am I dressed today? In what has become a virtual uniform this past year: jeans, a long-sleeved cotton t-shirt (navy blue), white Keds. Small silver earrings, a Timex watch. With my hair caught back in a silver clip. It’s preppy, academic, Lexington. It says that I’m likely to read long books and watch independent films. If it’s an indicator of social class, I would call the class “overeducated and underpaid.” Of course, it’s also comfortable. But that’s part of the stereotype as well .

I wonder what sort of murder I would commit in an Agatha Christie mystery?  I might murder another writer.  Probably using some sort of poison, a classic like arsenic or digitalis from foxglove leaves.  Or I might murder someone over a bad review.  But I would certainly behave according to type.