Is a hypothetico-deductive approach preferred because it at least sets a claim to be tested? Is this really a delusion because researchers are always trying to find ways to "save" their preferred hypotheses?

-- Barry Pole (bazzap@hotmail.com), August 29, 2002

Answers

The hypothetico-deductive is only one of a number of approaches used in psychology. Certainly one of its advantages is that the terms are set ahead of time, not only the claim to be tested, but the kind of evidence that will be accepted as confirming (and as disconfirming) the hypothesis. That researchers sometimes attempet to "save" their hypoetheses, post hoc, in the face of apparently disconfirming evidence is not really that much of a concern because they operate in a community of other scientists. There are as many (probably more) attempting to disconfirm a given hypothesis as there are attempting to confirm it. What is more, a post hoc interpretation is usually seen for what it is among fellow scientists. Few are accepted at face value, or even considered seriously unless they add empirical content to the claim, which of course will lead to an even more difficult test the next time round.

-- Christopher Green (christo@yorku.ca), September 03, 2002.

Thanks for the response. I accept that psychologist use other methods apart from the hypthetico-deductice approach, however it does seem to be the perferred method. Most undergraduate courses in research design ( at least the ones I have attended) seem to concentrate on this approch. It is a requirement for an honours thesis (in Australia) and no other approach is allowed. I think what I should have asked is " Why is it the perferred method?"

-- Barry Poole (bazzap@hotmail.com), September 04, 2002.

I think it depends on how broadly one defines hypothetico-deductive. Because theories are so vague in even experimental psychology, the best we can normally do is use statistical models to show that it is *not* the case that *nothing* is going on (i.e., reject the null hypothesis). This might be seen as a kind of backward statistical reconstruction of hypothetico-deductivism, but it certainly isn't the "real thing." In real hypothetico-deductivism the theory and some statement of initial conditions are used to deductively generate specific predictions (by "specific" I mean things like "The value of the variable will increase by exactly 10%). The hypothesis is confirmed by the prediction coming true (more or less exactly). In psychology, by contrast, the typical "predicition" is more like "something will happen, rather than nothing") and if anything happens (i.e., the value of the variable changes "significantly" in any way) it is said that the hypothesis was confirmed. Of course, with predictions that vague, there are uncounted zillions of things that may have led to the change. Imagine, by contrast, a psychological theory so well specified that it led deductively to the prediction that a certain treatment would cause IQ to change upward by exactly 3 points (rather than merely predicting flacidly that IQ would change). Now *that* would be real hypothetico-deductivism. Pretty rare stuff in psychology these days.

-- Christopher Green (cgreen@chass.utoronto.ca), September 04, 2002.