The Art and Science of Investigation: The Webs We Weave

Investigation allows students to notice and to modify mental models of the world. For example, the dominant mental model, or metaphor, for food web relationships is a spider web.

If you ask someone to imagine a spider web, they will probably envision an orb web--silk threads radiating from a center point, linked by concentric circles. The very notion suggests how everything is connected. This metaphor of connection is demonstrated in a common classroom activity in which students join in a circle, with each child playing the role of an organism in a community such as a squirrel, an oak tree, an acorn weevil, a moss, a blue jay, a mosquito. Every student in the "web" is connected laterally and across the circle with yarn. One student, the one "eliminated" from the ecosystem, steps backward, tugging on the yarn, pulling other students along until the entire web collapses.

The metaphor is powerful. But it should not be without discussion and reflection because it does not accurately portray real ecosystems. How would our concept of food webs be different if, instead of an orb web, we envisioned the erratic tangle web made by a black widow, or the funnel web of an Agelenid spider? Think of the immense, communal structures made by Neotropical social spiders, whose intergenerational webs can house thousands of spiders and span kilometers. Would these colonial webs make a better metaphor for actual food webs?

The orb web metaphor may persist despite its failings because it is simple and elegant. The danger is that people may imagine orb webs because of their symmetry, and then mistakenly project that symmetry onto natural systems. Does the orb web metaphor lead people to see ecological links as the silk threads, each relatively equal in size and quality?

The truth is that all organisms are not connected, at least not in the sense that if one species goes extinct the rest will necessarily suffer. Communities may have some key species whose role is so vital their absence significantly alters the entire system, but there are other species whose ecological role is relatively limited. There are profound ethical reasons for treating all species equally. Pragmatic reasons for doing so also exist (equality may be the safest assumption given our incomplete knowledge of nature). However, species do differ in their impact on natural communities.

The rumor that all organisms are equal in this sense may be more closely tied to human political and ethical standards than ecological reality. In the essay "Animism, Magic and the Omnipotence of Thoughts," Sigmund Freud speculates on some psychological reasons why humans misinterpret nature. He points out, for example, that historically and across cultures humans have tended to believe that by imitating storms, rain could be produced. According to Freud, elevating idealized models and associations above actual ones can help satisfy our psychological need for explanation and control. It may be that the human capacity for forming associations, a trait that lies at the center of our creativity, also makes us prone to mistake idealized associations for real ones.

It is striking how often children explain natural phenomena more or less in terms of magic by elevating idealized associations over real ones. It is easier for a child to see how wind might come from the breath of a giant than from temperature differences between adjacent air masses. One of the most interesting findings from people who have studied how children explain science concepts is that the misconceptions are rarely random. Often, most of the children in a study will misunderstand a concept in exactly the same way, based on a common set of mistaken assumptions. These studies point to the need for students and teachers to understand how mental models are constructed. Here are a few ways to start students thinking about how they think.

Visualizing Connections. Drawing often reveals hidden assumptions. Ask your students to draw a picture that accurately represents the food web in your schoolyard, for example, and invite them to examine the drawings. Did they focus on mammals and birds, even though insects are more common and diverse? Why? Did they arrange the animals in a hierarchy? Which animals are on top and which are on the bottom? As they learn more about animals, will they draw different associations?

The Big Upset. Science progresses when better mental models come along and upset cherished perceptions. Instead of assigning a paper on, say, the solar system, challenge students to write about a change in our idea of the solar system, and point them to material on Nicolaus Copernicus, Johannes Kepler, or another revolutionary. How did Wendy Freedman change our understanding of how large the universe is? What was the solar system to us before and after their work?

Communication. By becoming aware of how other people construct mental models, students learn to see their own thought patterns in a new light. Challenge students to discuss not only the ideas of their peers, but how their peers arrived at those ideas.

Investigation. Direct observation and experiment is perhaps the most powerful way to change mental models. The process of forming predictions puts assumptions on the table. By considering methods, students consider what constitutes valid evidence. It is surprising how much can be learned by allowing our mental models to stand the test of the real world.