In the May 18th issue of Science, there's a nice review by Paul Bloom and Deena Skolnick Weisberg  of the literature from developmental psychology that bears on the question of why adults in the U.S. are stubbornly resistant to certain scientific ideas.
Regular readers will guess that part of my interest in this research is connected to my habit of trying to engage my kids in conversations about science. Understanding what will make those conversations productive, in both the short-term and the long-term, would be really useful. Also, I should disclose that I'm pals with Deena (and with her spouse). When a friend coauthors an interesting paper (published in Science), why wouldn't I blog about it?
I'll run through the main points from developmental psychology research that the review identifies as important here, and then I'll weigh in with some thoughts of my own.
Why do American adults have a hard time embracing scientific ideas (like evolution, or the claim that minds are nothing but brains) while simultaneously embracing other ideas that scientists deem pseudo-science or worse (astrology, ESP, those "medical" "treatments" Orac blogs about on Fridays)? At least part of it comes from how people make sense of the world as babies, before they're exposed to science:
Babies know that objects are solid, persist over time (even when out of sight), fall to the ground if unsupported, and do not move unless acted upon. They also understand that people move autonomously in response to social and physical events, act and react in accord with their goals, and respond with appropriate emotions to different situations.
These intuitions give children a head start when it comes to understanding and learning about objects and people. However, they also sometimes clash with scientific discoveries about the nature of the world, making certain scientific facts difficult to learn. (p. 996)
Common sense (about how physical objects behave and how humans behave) is really handy from the point of view of making sense of your experience of the world. If someone makes a claim that doesn't fit with that common sense, it's easy to imagine that rejecting the claim is the response that leaves you in the best position to keep making sense of your world -- especially if the claim isn't connected particularly closely with your experiences. (It's easy to believe that the table is solid, but much harder to believe that the matter of the table is mostly empty space.) The article notes that in some instances where grown-ups make predictions more in accord with an Aristotelian commonsense physics than with what will actually happen, real-world experience of the physical set-ups in question can help the grown-ups refine their intuitions.
The development of young human brains -- and our early sense of what is "unnatural" or "unintuitive" -- is assumed to be pretty much a fact about the human as a critter rather than having a lot of cultural variability. (At least, the article treats this as an uncontroversial assumption, so I'm guessing much of the research in developmental biology so far at least fits with this assumption.) However, by the time you're dealing with adult humans, culture seems to play a big role in common sense:
Some culture-specific information is not associated with any particular source; it is "common knowledge." As such, learning of this information generally bypasses critical analysis. A prototypical example is that of word meanings. Everyone uses the word "dog" to refer to dogs, so children easily learn that this is what they are called. Other examples include belief in germs and electricity. Their existence is generally assumed in day-to-day conversation and is not marked as uncertain; nobody says that they "believe in electricity." (p. 997)
In other words, kids suss out what the community believes in, and they take that as a guide to how things are. (Indeed, the article points to research indicating that this kind of check of consensus, not moral introspection, is how people come to their moral intuitions as well.)
If everyone in our culture carries on as if X is perfectly uncontroversial, we tend not to question X. On the other hand, in cases where X is presented as tentative -- even in cases where we notice that someone is going to the trouble to assert X rather than taking it as give -- we may be less ready to accept X.
What makes X plausible? If we're in a position to test the claim ourselves, that could do the job, but that's not always possible:
Few of us are qualified to assess claims about the merits of string theory, the role of mercury in the etiology of autism, or the existence of repressed memories. So rather than evaluating the asserted claim itself, we instead evaluate the claim's source. If the source is deemed trustworthy, people will believe the claim, often without really understanding it. (p. 997)
A lot rides, then, on what counts as a trustworthy source. For little kids, the research suggests that assessments of trustworthiness take into account whether the source is knowledgeable (a grown-up rather than a peer, a specialist who ought to know something about the subject at hand), whether the claim is made confidently rather than tentatively, and to some extent whether the claim is perceived to go with or against the self-interest of the source (little kids can be cynical!). In case of different sources making conflicting assertions, kids will trust the declarations of the sources they deem must trustworthy.
So, who do you judge most reliable if your science teacher, your parent, your pastor, and your favorite cartoon character or movie star make conflicting claims? And how entrenched will these early decisions become? What happens when you discover that your parents (or your fourth grade science teacher) don't know everything?
Here, I get reflective about my interactions with my kids around science. I'm pretty sure they view me as something like a reliable source -- someone who has more authoritative knowledge than they do (and likely more than their science teachers do about certain subjects). On the one hand, this is fine, given that they are still at ages where they are receptive to the knowledge I'm offering them and I do know some interesting things about the physical and natural world.
On the other hand, part of the appeal of science is that it's not supposed to rest on appeal to authority!
This means that we want to get the kids into the habit of observing what's going on in the world, messing with set-ups to see what happens, and evaluating the logic of various claims and the support offered for them. But there are real limits to what we can do here. We're not likely to build a quantum gravity probe in the garage, or to put radio telescope arrays in the back yard. It's doubtful that we'll be much help in coming up with a clever experimental test of string theory for the school science fair.
Some appeals to expertise in science seem unavoidable.
Still, I think the most important message that kids should absorb about science is that its credibility comes from meeting a particular kind of burden of proof, and that asking to see the proof is just part of the transaction. Sometimes we can do the experiment ourselves, other times we may have to get by with being walked though the chain of inference from someone else's data.
Possibly emphasizing the burden of proof marks scientific ideas as tentative (and thus resistable). However, pretending none of our scientific ideas are shakable seems like a bad idea to me. After all, do we want our kids to be stuck in time scientifically, unable to embrace the new scientific findings yet to come? (Do we want our kids to trust us even less than normal teenagerhood will have them trusting us?)
I suppose what it comes down to, as I see it, is helping kids to see physical reality as an authoritative source of beliefs, too. As well, being able to ask good questions about the human sources of information -- being able to evaluate them critically regardless of how smoothly what they're saying fits with how we're already inclined to see the world -- strikes me as a potentially useful life skill.
I can't guarantee, though, that it will make my kids easier to live with as my authority as a source of information is scrutinized.
 Paul Bloom and Deena Skolnick Weisberg (18 May 2007) "Childhood Origins of Adult Resistance to Science," Science, vol. 316, 996-997.
I can think of one good reason why the sprogs would enjoy doing science with mom. They're doing science with mom. They're at the age when mom is neat and cool and fun to be with. And stuff mom likes to do is stuff that's fun to do.
Well, that and the fact that science at the age is usually about icky things like bugs, and bugs hold an inexhaustible fascination for small children. :)