What is behavior?

I was going to entitle this entry “What is an Ethologist?” I decided, however, that this begs a question that is a bit more interesting, hence the title I selected.

The conventional definition of “ethology” is “the scientific study of animal behavior.” The field took shape in the early part of the 20th century, growing out of the sciences of zoology and physiology. From zoology came the goals and methods of comparative biology for understanding the diversification and modification of traits as species evolve. From physiology came the quest to understand the biological machinery underlying complex organismal traits. Scientists trained in these older traditions realized that methods developed for the study of bones, muscle twitches and glandular secretions could be applied to the more ephemeral and variable domain of behavior. In recognition of the importance of this new field, the 1973 Nobel Prize for Physiology or Medicine was awarded to three pioneering ethologists–Konrad Lorenz, Niko Tinbergen, and Karl von Frisch.

Now we come to the question-begging part. If ethology is the study of behavior, what is that thing–behavior–that is the focus of study? It turns out to be a hard question to answer. Actually, it is an easy question to answer, but a hard one on which to find agreement among the answers different people provide. That’s the point of an article published in July 2009 in one of the leading journals in the field, Animal Behaviour. The article’s title: Behavioural biologists do not agree on what constitutes behaviour.

Before reading further, I encourage you to do what I did when I read that title–I decided on my own definition. That didn’t take long. I have thought about the topic for a long time, having taught the subject for many years, and having once been an editor of Animal Behaviour. So, I already had an opinion: behavior (back to American spelling) is what animals do as opposed to how they are built (morphology) or how their internal systems work (physiology). To extend this a little, behavior constitutes actions (including lack of movement) that may have consequences for the animal’s biological fitness, and that are mediated by internal systems for sensing the environment and controlling the body.

Before reading the article, I anticipated some of the objections that might be raised to my own definition. What about behaviors seen in non-animals such as plants (e.g. such as vines that climb) or microbes (such as bacteria that swim up and down chemical gradients)? What about physiological or morphological changes that are mediated by internal control system and that clearly have a behavioral role, but that don’t fit the notion of the animal “doing” something (e.g., changes in the color of the beak and plumage of male starlings when the breeding season arrives)? I knew my definition was a little ambiguous, but it still captures a big chunk of what ethologists study.

Such ambiguity is precisely the point of the Animal Behaviour article, which used two kinds of surveys to expose the fuzzy boundaries of people’s definitions of behavior. The first survey asked people to agree or disagree with a series of statements offering definitions of behavior. The second survey asked people to classify several phenomena as “behavior” or “not behavior.” The participants were practicing scientists whose work had something to do with behavior (including members of the Society for Plant Neurobiology–who knew?).

The results showed first that there was a lot of disagreement among people about how behavior should be defined, and what kinds of phenomena qualify as behavior. Even more striking was that people often disagreed with themselves: for example, they recognized things as behavior that were at odds with the definition they favored.

Perhaps this outcome isn’t so surprising. After all, behavioral phenomena are hard to pin down even when everyone would agree upon their classification as behavior and not something else. Consider the fox squirrel that I am watching out my window right now. It is moving over the lawn, alternating periods of travel with pauses, digging occasionally, burying occasionally, looking up occasionally. These behaviors vary in their expression each time they are done, and you can be sure that they vary among individuals. They unfold in an ongoing, highly variable sequence, making it hard to segment into elemental parts that can be measured, isolated, and reduced to underlying physiological explanations.

These  challenges inherent in studying behavior don’t undermine the legitimacy of ethology as a rigorous science.  They do, however, make the achievements of the early ethologists (including Darwin, who was the first ethologist of them all) all the more astonishing.

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About ethologist

Professor in the Zoology Department at Michigan State University
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