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The idealized scientist might start by questioning everything and assuming nothing. However, one usually has to make starting assumptions to get things going. For instance, David Hume proved that the notion that science works at all is founded on the un-provable assumption that the future will conform to the past (i.e., if e=mc2 yesterday, it will do so again tomorrow).
Starting assumptions can get a bit less metaphysical though. Here is a very telling line in linguist David Pesetsky's influential Zero Syntax from 1995:
It follows from the hunch just described that hypotheses about language should put as small a burden as possible on the child's linguistic experience and as great a burden as possible on the biologically given system, which we call Universal Grammar (UG). Of course, the role of experience is not zero, or else every detail of language would be fixed along genetic lines. Nonetheless, given that linguistics tries to explain, the null hypothesis should place the role of experience as close to zero as possible.
In contrast, there has been a strong trend in psychology -- and folk science, for that matter -- to assume everything is learned and prove otherwise.
Ultimately, if science proceeds as it should, we'll all converge on the same theory somewhere in the middle. In the meantime, wildly divergent starting assumptions often unfortunately lead to folks simply talking in different languages.
A good example is a recent exchange in Trends in Cognitive Sciences. Waxman and Gelman had recently wrote an article about how children's assumptions about the world (they called these assumptions "theories") guide learning even in infancy. Sloutsky wrote a letter to complain that Waxman and Gelman had failed to explain how those assumptions were learned. Gelman and Waxman responded, in essence: "Who says they're learned?"
All three are intelligent, thoughtful researchers, and so at the risk of simplifying the issue, Sloutsky's problem with the "innate theories" theory is that nobody has given a good characterization of how those theories are instantiated in the brain, much less how evolution could have endowed us with those innate theories. Sloutsky assumes learning unless proven otherwise.
However, Waxman and Gelman's problem with Sloutsky is that nobody has a good explanation -- even in theory -- of how you could learn anything without starting with some basic assumptions. At the very least, you need Hume's assumption (the future will conform to the past) to even get learning off the ground.
Both perspectives have their strengths, but both are also fatally flawed (which is not a criticism -- there aren't any perfect theories in cognitive science yet, and likely not in any science). Which flaws bother you the most depends on your starting assumptions.
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Comments
Testable Assumptions
September 18, 2009 by Anonymous, 9 weeks 1 day ago
Comment id: 44834
Hume's "proof" does not seem correct to me. I see no reason why I cannot hypothesize that something will change tomorrow: that one plus one will not equal two, that the angles of a triangle will not sum to 180 degrees, that the speed of light will be different, the number of schizophrenics in the population will increase, or that the weather will be unchanging. I can then remeasure these things and see if my hypothesis is correct. Though I cannot "prove" anything, given enough repeats, I can build up a pretty good confidence whether or not something is constant. (How often does science "prove" anything?) Looking backward over time also works, so I can safely say that math and geometry don't need to be constantly verified. Physical constants have been shown to be constant enough for most purposes, but not enough for some astrophysics, so continuing to improve our knowledge of these is worthwhile. I guess that there are probably many psychological measurements/assumptions that have not been measured as well or over as long a period of time as needed, so continuing those certainly makes sense.
The comment about differing assumptions leading to speaking different languages was interesting. I don't know how many times I have heard two people (sometimes one of them being me) "arguing" over a point without understanding each other well enough to know where exactly they were in agreement and disagreement.
not a proof
September 23, 2009 by coglanglab, 8 weeks 3 days ago
Comment id: 44941
I think we may be talking past each other:) Hume's proof isn't that the laws of Nature don't change. What he proved is that we have to assume this in order to get science off the ground, since science is about hypothesis testing (that is, predicting the future!). I think that your argument assumes the same point, right?
experimentalist vs theorist?
September 23, 2009 by Anonymous, 8 weeks 3 days ago
Comment id: 44943
I think I am beginning to understand. This is sounding like some of my arguments with theorists. Being an experimentalist, I think of measurements as being the ultimate evidence (or "proof", if you will). But I interpreted your statements about Hume's proof as if it were something we had to always take to be true instead of what I would think of as a first approximation (like the way fluid flow calculations sometimes first assume that all molecular motion is completely random to find out what the flow actually is). In any case, you are correct that repeatability is something I usually assume when I make measurements. Not being much of a mathematician, I don't know if this is absolutely necessary or just a convenience (since it is usually true or nearly so), but it is very educational.
This sounds like what I have read from your articles and elsewhere about the trouble people have in realizing that something that seems obvious to them is not necessarily so to others. What would really be nice is to be able to identify when this sort of thing was the cause of disagreement and how to get around it. I suspect this may be the cause of a large percentage of the political disagreements that seem to be getting more and more intransigent lately.