Anyone who has spent time around animals suspects that personality, or consistent ways of behaving and thinking, is not unique to humans. Pavlov certainly thought his dogs had personalities, and he is not alone.

Our two Australian shepherds certainly have plenty in common–smarts, loyalty, a “velcro dog” need to be near us, and well, loudness. After that, though, each is very different. Ronnie, the oldest, is a diva with a bit of a temper. Attempts to groom her require medieval armor. Rosy, the youngest, is a bouncy goofball who wouldn’t hurt anyone, well, unless they invaded her home without permission. Can you tell which is which?

Australian Shepherds

If dogs can have personalities, we shouldn’t be surprised to find that other primates do, too. A group of Austrian researchers has studied Marmosets, smaller, New World primates, and has found that they vary substantially in traits like boldness and exploration. Their ratings of individual personalities were quite stable over four years and held in both captive and wild populations. The personalities weren’t completely fixed. Animals that moved up the social hierarchy over the four-year interval increased their boldness score. It’s hard to say whether becoming bolder made them more dominant or being in a position of more power led to more boldness. Or there is always the possibility of third variables leading to both greater boldness and power.

It makes sense that personality should have evolutionary roots. My students sometimes ask why it would be adaptive to be neurotic or disagreeable, which are definitely valid questions. It seems to me that the answer lies in the environment. For example, if food is scarce, bold birds enjoy more reproductive success than timid birds, because the former are more willing to forage widely for food. In contrast, if food is plentiful, timid birds enjoy more reproductive success, as the bold birds continue to forage widely when there is no need to do so, taking unnecessary risks.

One of my favorite examples of animal personality, though, is the work of Jennifer Mather and the octopus. She talks about shy Emily Dickinson and the notorious Lucretia McEvil. One wonders what kind of octopus behavior Lucretia evidenced to earn her name!