myth-busting: what's a teacher to do?

I just finished talking about the interior of the Earth to my intro class. I drew (semi-)concentric circles. I passed around pieces of peridotite from the Alps. I talked about squishiness in the asthenosphere. I made fun of The Core.

And I'm willing to bet that on Friday, when I start talking about the tectonic origins of igneous rocks, a large fraction of the class will believe that the mantle is liquid. And another large fraction of the class will think that most magmas come from the outer core.

There have been papers in the Journal of Geoscience Education about ways to recognize student misconceptions in order to correct them, and I've tried a lot of the techniques. But maybe there's a fundamental problem with myth-busting.

Last week, the Washington Post published an article about psychology research on the persistence of myths. One study followed adults who had read a flyer from the Center for Disease Control on facts about the flu vaccine - three days later, older adults remembered 40% of the myths as factual. To make matters worse, they thought the CDC was the source of their information. (Younger adults did better, but not that much better.) Other studies found that repetition, regardless of the source, makes people remember statements as true... and that people forget the not part of a statement after time.

So when I say "the mantle is not a liquid," that might make students remember that the mantle is liquid - and they might someday cite me as their source.

So... what's a teacher to do? Students will try to fit new knowledge into their preconceptions, even when the preconceptions are wrong. So it seems that de-bunking is necessary, especially for some fundamental ideas (geologic time, for instance). But is there any way to deal with misconceptions that doesn't reinforce them?

- Do students remember things better when they've figured them out for themselves? (Does the amount of time spent puzzling make a difference? Are projects that take up a large part of the semester more effective than a hands-on experiment during lecture? And what happens when the fundamental concepts are hard to directly observe, or when the evidence (such as S-waves traveling through the mantle) is difficult to understand?)

- Does it help to use lots of different senses/ways of learning about something? (Does it help to both hear and read, or to hear and read and see and do? Does it help to have touched a sample, or to have played a game, or acted out a process?)

- Is humor effective? Will students remember me snarking about the Giant Amethyst Geode of Death in The Core, for instance? Do students remember mockery? (I would imagine that it's better if I'm mocking someone else - say, Hollywood - rather than mocking a classmate.)

- They say that repetition is effective. So, out of all the way-too-many concepts we cover in Earth Systems Science, what should I repeat? (Geologic processes are slow - I say that many times in many different lectures. I mention certain minerals - quartz, for instance, and calcite - a lot. I've defined "igneous rocks" in about three different lectures already. So I do this a little. But are there other things, important misconceptions, that I should be hammering away at?)

On a related note, I've always told students to study their old quizzes and exams to help figure out what they don't understand. But maybe that's a problem, too - maybe students remember their incorrect answers even more when they use old quizzes to study.

And on another related note - I wonder if this psychological issue is part of the reason why new scientific theories take a while to take hold. (Why are Kuhn's scientific revolutions necessary? Why doesn't science proceed by baby steps?) And is there a lesson for teachers in something like the acceptance of plate tectonics? What was it, exactly, about that American Geophysical Union meeting in 1966 that convinced people? There was supposedly a session on sea-floor spreading that drew a standing-room-only crowd, a session with one talk after another supporting earlier work on magnetism of the ocean floor. Was it the quality of the data, or the volume of the data, or the repetition? Or was everyone at the meeting already prepared to be convinced?