Fish personalities?!

My mobile buzzed: I had a text message from my husband. I’m bored. Call me. He was driving to New England and stuck in traffic.

I called. He asked how my day had been. How was that boring meeting? It was great, I said. I got to talk to a fellow grad student about a project of his during the coffee break. We were talking about a new way of studying fox personalities, using a method he had applied in his study of fish personalities.

Husband: Wait. What personalities?

Me: Fish.

Husband: Did you say fish?

Me (wondering if the connection is bad): Fish.

Husband: The things with scales that swim?

Me: Fish! Yes!

Husband: ...have personalities?

Oh. Right. Sometimes I forget that my world is not other peoples’ world.

Me: Yes! Some are shy and some are bold.

Husband: Oh right. Continue.

I mean, what’s personality, really?  We make it sound like a big deal when we say that fish have them. My boss doesn’t even like me to say that our foxes have them when I am writing grant applications.

When you break it down to these small traits, like shyness and boldness, it makes more sense, though, right? Some fish are shy: when you put food in their tank, they hide a little bit longer before they will come out to eat. Some are bold: not only do they explore more and hide less, they are more likely to attack other fish who try to take their fishy belongings. If you haven’t observed these differences, I assume it's because you haven’t kept fish.


Different personalities are better (“more adaptive,” if we’re speaking Science instead of English) in different environments. An environment with lots of predators? Better to be shy, more cautious, and check out the surroundings before going for some food that's floating out there in the open. An environment with fewer predators, but lots of other fish of the same species as you? You had better go get that food fast before someone else does, rather than waiting to see if the coast is clear.

So it makes sense for a species to have a reservoir of personality types. This way, when an environment changes (there’s a new predator, or increased population density), that variation is there to be drawn upon. Lots more birds around to eat the fish all of a sudden? The fish with shyer personalities will do better, the ones with bolder personalities will do worse, and the population will gradually come to have more shy fish in it, so that the population as a whole can survive the change in environment.

For sure, human personality is a lot more complex than fish personality. But that is exactly why my friend’s lab studies fish: better to try to understand a simple system first before tackling the more complex one. A lesson I don’t seem to have learned, jumping right in with my questions about dog personality. Oh well.

[If you’re a dog trainer or just interested in dog genetics, you can learn about the genetics of dog behavior with me this summer in an online course with the APDT!]