Don't Know Much Of Biology

Just think about what it takes to learn biology. Not textbook biology, the kind you learn in high school with microscopes and dissecting kits. Rather, the kind you learn on your own, as a young child encountering the vast and diverse world of living things. How does the human mind link together things as varied as hippos and lichen and mosquitoes and rhododendrons? And how do we sort this diversity into meaningful categories? In short, how do we think about life?

Psychologists are very interested in how the mature mind sorts the living world, and where we put ourselves in relation to other life forms. That’s the stuff of philosophy and religion and morality. But it’s not as obvious as one would think. Take motion, for example. Many living things move, but so do rivers and clouds and rocket ships. And some living things, like coral, don’t appear to move at all. So it’s not just the fact of motion that defines life, but the why and how. Young children find this confusing and make a lot of mistakes about what’s animated and what’s not. Only over time do we outgrow our primitive, childish ideas and replace them with a sophisticated view of the natural world.

Or do we? Do we really discard all our naive thinking as we experience the world and learn about its complexity? University of Pennsylvania psychologists Robert Goldberg and Sharon Thompson-Schill have been exploring these questions in the laboratory, with intriguing results. Here’s one of their experiments:

The psychologists showed a group of college students a long list of words, one at a time and very rapidly. Some were the names of plants, others animals, and still others non-living things. The non-living things were further divided into non-moving objects like brooms; non-moving natural things, like boulders; moving artifacts like trucks; and finally, natural moving things, like rivers. The idea was to see how quickly and accurately the volunteers used movement and “naturalness” to classify these various things as living or non-living.

The scientists were particularly interested in how we think about plants, where we put them in the grand scheme of things. Plants are an interesting anomaly because—at least to young children—they don’t “do” anything; instead, we do things to them, like climb them and water them and prune them. If they move at all, their movement is very subtle. Not surprisingly, kids often misclassify plants as non-living.

But how about college students? Well, it appears that they too make mistakes, even with all that formal education: The volunteers in the study were much more hesitant in classifying plants, suggesting that they had to slow down to deliberately overrule their naïve taxonomy; and they also made more outright errors. They were also slower to size up moving things in general, and non-living natural things—suggesting that movement and naturalness were the features that stymied them.

To be fair, these weren’t biology majors. And we all know that kids can slip into college without much in the way of rigorous scientific training. But here’s the really interesting part. The psychologists ran basically the same experiment with biology professors, people who make their living teaching university students about the natural world. Indeed, the volunteers in this second study had been teaching college-level biology for a quarter century, on average, and at highly prestigious schools.

And guess what. As reported in the April issue of the journal Psychological Science, the profs did better than the undergraduates, but not as brilliantly as one might from the scientific elite. Even these experts were significantly worse at classifying plants than they were at categorizing animals. That is, even a lifetime of advanced scientific training didn’t trump the naïve impulse to view plants as artifacts.

Children may be natural-born taxonomists, but they’re not all that good at it. That’s because they have a deep-wired urge to see the world as designed and simple, and to be at the center of it all. Apparently that impulse never goes away entirely.

For more insights into the quirks of human nature, visit “We’re Only Human” at www.psychologicalscience.org/onlyhuman. Selections from the blog also appear regularly in the magazine Scientific American Mind and at www.sciam.com.