Open Thread: September 2011

Pavitra

If it's worth saying, but not worth its own post (even in Discussion), then it goes here.

If continuing the discussion becomes impractical, that means you win at open threads; a celebratory top-level post on the topic is traditional.

If it's worth saying, but not worth its own post (even in Discussion), then it goes here.

If continuing the discussion becomes impractical, that means you win at open threads; a celebratory top-level post on the topic is traditional.

I don't understand the basis for the Cosmides and Tooby claim. In their first study, Cosmides and Tooby (1996) solved the difficult part of a Bayesian problem so that the solution could be found by a "cut and paste" approach. The second study was about the same with some unnecessary percentages deleted (they were not needed for the cut and paste solution--yet the authors were surprised when performance improved). Study 3 = Study 2. Study 4 has the respondents literally fill in the blanks of a diagram based on the numbers written in the question. 92% of the students answered that one correctly. Studies 5 & 6 returned the percentages and the students made many errors.

Instead of showing innate, perfect reasoning, the study tells me that students at Yale have trouble with Bayesian reasoning when the question is framed in terms of percentages. The easy versions do not seem to demonstrate the type of complex reasoning that is needed to see the problem and frame it without somebody framing it for you. Perhaps Cosmides and Tooby are correct when they show that there is some evidence that people use a "calculus of probability" but their study showed that people cannot frame the problems without overwhelming amounts of help from somebody who knows the correct answer.

Reference

Cosmides, L. & Tooby, J. (1996). Are humans good intuitive statisticians after all? Rethinking some conclusions from the literature on judgment under uncertainty. Cognition 58, 1–73, DOI: 10.1016/0010-0277(95)00664-8

I agree. I was hoping somebody could make a coherent and plausible sounding argument for their position, which seems ridiculous to me. The paper you referenced shows that if you present an extremely simple problem of probability and ask for the answer in terms of a frequency (and not as a single event), AND you present the data in terms of frequencies, AND you also help subjects to construct concrete, visual representations of the frequencies involved by essentially spoon-feeding them the answers with leading questions, THEN most of them will get the corre... (read more)