Animal, vegetable or mineral? For most, it's still a guessing game

Kids Playing Chicken On Freeways Get Smashed. King Phil Cleans Octopi For Gene Simmons. Kings Play Chess On Fine Glass Surfaces.

In middle school, we memorized these acronyms - and half a dozen more obscene variations - to help us remember the taxonomy of living things: kingdom, phylum, class, order, family, genus, species.

But before we learned that humans are mammals and roses are plants, how did our minds organize the living world? And could these childhood perceptions have a significant impact on our adult perceptions of nature?

Researchers at the University of Pennsylvania sought to answer these questions, and found that our understanding of life is more muddled than we previously thought.

Psychologists Robert Goldberg and Sharon Thompson-Schill presented college students and biology professors (including volunteers from Hopkins) with a rapid-fire list of objects ranging from trucks to rivers to tulips.

The researchers found that all of the volunteers, including the professors, made numerous mistakes when asked to distinguish between living and non-living phenomena.

We would think that years of biological training, or even common sense, would give us an upper hand in the relatively simple task of determining that, say, a rose is alive and a river is not.

All that education, however, doesn't seem to significantly improve performance.

Psychologists suggest that this discrepancy may be because we never fully outgrow the perception of the natural world that we had as children.

As kids, how did we distinguish between alive and dead objects? We may have thought that non-living things don't breathe, that living things move or that if it is outside, it must be alive. The obvious problem with these criteria is that they're far too simple.

"Kids make a lot of mistakes about what is animated and what is not," wrote Wray Herbert in a recent Scientific American article.

The reason is that the distinction between non-living moving, living moving, living non-moving and non-living natural objects is fairly subtle. Without a biological background, a truck may seem more alive than a tulip (after all, the truck can move).

The rapid-fire list of words that Goldberg and Thompson-Schill showed volunteers were taken from categories that may have tripped us up as children: plants (sunflower), animals (dog), man-made objects (broom), natural features and phenomenon (rock) and non-living moving objects (car).

The researchers interpreted wrong and/or delayed answers as evidence that volunteers were still influenced by their childhood perception of the living world.

Volunteers had surprising difficulty in identifying plants as living objects compared to animals. Researchers propose that volunteers tended to hesitate because seeing plants as living is counter-intuitive to the "requirements" we may have set up as children.

Even as educated adults, we have to work to override our impulse to put plants in the same category as books or office chairs.

In addition, volunteers had delayed responses when differentiating between non-living moving objects (car) and non-moving natural things (rock). This suggests that of the requirements children create, movement and naturalness (i.e. is it outside?) are retained through adulthood.

These results might not be that surprising if all the volunteers polled were high school or college kids with not-so-stellar backgrounds in science, but the researchers repeated the same experiment on college professors from both Yale and Hopkins.

The professors did better, but not perfectly. They still had more difficulty categorizing plants than animals.

As reported in the April issue of Psychological Science, the professors were also tripped up when asked to categorize non-living objects found in nature, such as rivers, rocks or soil.

Researchers plan to continue studying our childhood perceptions about taxonomy by attempting to pinpoint this thinking to certain regions of the brains.

Repeat King Philip Came Over For Good Spaghetti as many times as you like - you may never overcome the simple taxonomic view of the world that you had when you were four.