People tend to look for simple linear patterns to explain the world around us. As infants, we perform acts that lead to direct and observable consequences: we cry and so we get picked up; we push the ball and it rolls away from us. These patterns are reinforced in early science education, when teachers and students compile lists of things that float and things that sink, for example. As we grow from childhood to adulthood, we continue to seek out efficient and easily observable patterns.
But the connection between action and outcome is not always a linear one, according to Tina Grotzer at the Harvard Graduate School of Education. Take pollution: “If you dump oil or garbage down the drain in Cambridge, you have no way of knowing that it is actually affecting the water in Boston harbor. You don’t make the connection, because you can’t see the outcome," says Grotzer. Consequences don't always follow a directly observable pathway — and our tendency to look for these simple patterns can impede science learning.
In a $1.4 million grant from the National Science Foundation entitled “Learning to RECAST Students’ Causal Assumptions in Science through Interactive, Multimedia Professional Development Tools,” Grotzer — a principal investigator for Project Zero — is taking a closer look at the ways in which students understand causality. She has developed a science curriculum, the Understandings of Consequence Project, challenging students’ prior notions of cause and effect.
In the first phase of the study, Grotzer and her team visited science classrooms, grades 3 through 11, to observe and interview students. What they found was that students tended to make a series of assumptions when searching for scientific explanations. These explanations largely assumed that causality is constructed from obvious and perceptible agents, and that a cause is close in time and space to its effects. Furthermore, the students did not take into account the indirect consequences of actions.
For example, when studying the food web, students tend to assume that green plants matter only to the animals that eat them, and not to the animals that prey on the green plant-eating animals. Actually, the contrary is true: if green plants were to disappear, the population of green plant-eating animals would diminish, leading to scarcity of food for the animals that eat them, and so on throughout the food web.
In response, Grotzer developed a curriculum, part of which is already in use in the Cambridge Public Schools, to help students question and restructure their notion of causality. Activities are designed to help students question their assumptions and to reveal the underlying causal structure.In a segment on density, for example, the teacher takes two jars of liquid, one filled with water and the other with isopropyl alcohol. A large piece of candle is dropped into the isopropyl alcohol and a smaller piece in the water. The large piece sinks and the smaller piece floats.
When the teacher asks for an explanation, students tend to say that the larger candle sinks because it’s heavier. When the teacher switches the pieces of candle, the larger piece floats in the denser water, and the smaller piece sinks to the bottom in the less dense isopropyl alcohol — as the larger one did. “When I shift the candles, the kids’ eyes always get so big,” says Grotzer. “It totally shifts their mindset.”
Global warming is an example of a nonlinear chain of events that both adults and school children struggle to understand, according to Grotzer. “When we were kids,” she explains, “people used to throw their garbage out of the car window. You could see it accumulating along the roadside. When there was a campaign to stop people throwing their garbage out of the window, you could see the difference. With global warming, the greenhouse gases are not obvious: you don’t see them, you don’t know they are there, and so you don’t necessarily know that you are contributing.”
Understanding global warming is further complicated by the fact that it’s both spatially and temporally removed. “It’s very hard to pay attention to something when the effect has a time delay,” says Grotzer. “It diffuses responsibility. The effects are also spatially removed so it’s hard to connect our own actions to public health issues happening on the other side of the world, such as the rise of certain kinds of mosquitoes. We are used to agent-oriented causality. We act and make something happen. If you can’t connect your action to an outcome, then it’s easy to lose the sense of urgency about it.”
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Tina Grotzer's research is helping students to develop a deeper understanding of causality in a complex world by addressing their science knowledge and common cognitive default patterns. It impacts their ability to become global and environmentally aware citizens.