MORE DETAILED RESULTS

There were 5 questions related to strength of membership in the LW community which I standardized and combined into a single composite measure of LW exposure (LW use, sequence reading, time in community, karma, meetup attendance); this was the main predictor variable I used (time per day on LW also seems related, but I found out while analyzing last year's survey that it doesn't hang together with the others or associate the same way with other variables). I analyzed the results using a continuous measure of LW exposure, but to simplify reporting, I'll give the results below by comparing those in the top third on this measure of LW exposure with those in the bottom third.

There were 5 intelligence-related measures which I combined into a single composite measure of Intelligence (SAT out of 2400, SAT out of 1600, ACT, previously-tested IQ, extra credit IQ test); I used this to control for intelligence and to compare the effects of LW exposure with the effects of Intelligence (for the latter, I did a similar split into thirds). Sample sizes: 1101 people answered at least one of the CFAR questions; 1099 of those answered at least one LW exposure question and 835 of those answered at least one of the Intelligence questions. Further details about method available on request.

Here are the results, question by question.

Question 1: Jack is looking at Anne, but Anne is looking at George. Jack is married but George is not. Is a married person looking at an unmarried person?

• Yes
• No
• Cannot be determined

This is a "disjunctive reasoning" question, which means that getting the correct answer requires using "or". That is, it requires considering multiple scenarios. In this case, either Anne is married or Anne is unmarried. If Anne is married then married Anne is looking at unmarried George; if Anne is unmarried then married Jack is looking at unmarried Anne. So the correct answer is "yes". A study by Toplak & Stanovich (2002) of students at a large Canadian university (probably U. Toronto) found that only 13% correctly answered "yes" while 86% answered "cannot be determined" (2% answered "no").

On this LW survey, 46% of participants correctly answered "yes"; 54% chose "cannot be determined" (and 0.4% said"no"). Further, correct answers were much more common among those high in LW exposure: 58% of those in the top third of LW exposure answered "yes", vs. only 31% of those in the bottom third. The effect remains nearly as big after controlling for Intelligence (the gap between the top third and the bottom third shrinks from 27% to 24% when Intelligence is included as a covariate). The effect of LW exposure is very close in magnitude to the effect of Intelligence; 60% of those in the top third in Intelligence answered correctly vs. 37% of those in the bottom third.

original study: 13%
weakly-tied LWers: 31%
strongly-tied LWers: 58%

Question 2: Would you prefer to receive $55 today or $75 in 60 days?

This is a temporal discounting question. Preferring $55 today implies an extremely (and, for most people, implausibly) high discount rate, is often indicative of a pattern of discounting that involves preference reversals, and is correlated with other biases. The question was used in a study by Kirby (2009) of undergraduates at Williams College (with a delay of 61 days instead of 60; I took it from a secondary source that said "60" without checking the original), and based on the graph of parameter values in that paper it looks like just under half of participants chose the larger later option of $75 in 61 days.

LW survey participants almost uniformly showed a low discount rate: 92% chose $75 in 61 days. This is near ceiling, which didn't leave much room for differences among LWers, and in fact there were not statistically significant differences. For LW exposure, top third vs. bottom third was 93% vs. 90%, and for Intelligence it was 96% vs. 91%.

original study: ~47%
weakly-tied LWers: 90%
strongly-tied LWers: 93%

Question 3: A certain town is served by two hospitals. In the larger hospital, about 45 babies are born each day. In the smaller one, about 15 babies are born each day. Although the overall proportion of girls is about 50%, the actual proportion at either hospital may be greater or less on any day. At the end of a year, which hospital will have the greater number of days on which more than 60% of the babies born were girls?

• The larger hospital
• The smaller hospital
• Neither - the number of these days will be about the same

This is a statistical reasoning question, which requires applying the law of large numbers. In Tversky & Kahneman's (1974) original paper, only 22% of participants correctly chose the smaller hospital; 57% said "about the same" and 22% chose the larger hospital.

On the LW survey, 84% of people correctly chose the smaller hospital; 15% said "about the same" and only 1% chose the larger hospital. Further, this was strongly correlated with strength of LW exposure: 93% of those in the top third answered correctly vs. 75% of those in the bottom third. As with #1, controlling for Intelligence barely changed this gap (shrinking it from 18% to 16%), and the measure of Intelligence produced a similarly sized gap: 90% for the top third vs. 79% for the bottom third.

original study: 22%
weakly-tied LWers: 75%
strongly-tied LWers: 93%

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