Followup to: Do you have High Functioning Aspergers Syndrome?
EDIT: To combat nonresponse bias, I'd appreciate it if anyone who considered the poll and decided not to fill it in would go and do so now, but that people who haven't already seen the poll refrain from doing so. We might get some idea of which way the bias points by looking at the difference in results.
This is your opportunity to help your community's social epistemology!
Since over 80 LW'ers were kind enough to fill out my survey on Aspergers, I thought I'd post the results.
4 people said they had already been diagnosed with Aspergers Syndrome, out of 82 responses. That's 5%, where the population incidence rate is thought to be 0.36%. However the incidence rate is known to be larger than the diagnosis rate, as many AS cases (I don't know how many) go undiagnosed. An additional 4 people ticked the five diagnostic criteria I listed; if we count each of them as 1/2 a case, LW would have roughly 25 times the baseline AS rate.
The Less Wrong mean average AQ test score was 27, and only 5 people got at or below 16, which is the population average score on this test. 21 people or 26% scored 32 or more on the AQ test, though this is only an indicator and does not mean that 26% of LW have Aspergers.
To put the AQ test results in perspective, this paragraph from Wikipedia outlines what various groups got on average:
The questionnaire was trialled on Cambridge University students, and a group of sixteen winners of the British Mathematical Olympiad, to determine whether there was a link between a talent for mathematical and scientific disciplines and traits associated with the autism spectrum. Mathematics, physical sciences and engineering students were found to score significantly higher, e.g. 21.8 on average for mathematicians and 21.4 for computer scientists. The average score for the British Mathematical Olympiad winners was 24. Of the students who scored 32 or more on the test, eleven agreed to be interviewed and seven of these were reported to meet the DSM-IV criteria for Asperger syndrome, although no formal diagnosis was made as they were not suffering any distress. The test was also taken by a group of subjects who had been diagnosed with autism or Asperger syndrome by a professional, the average score being 35 and 38 for males and females respectively.
If we take 7/11 times the 26% of LW who scored 32+, we get 16%, which is somewhat higher than the 7-10% you might estimate from the number of people who said they have diagnoses. Note, though, that the 7 trial students who were found to meet the diagnostic criteria were not diagnosed, as their condition was not causing them "distress", indicating that for high-functioning AS adults, the incidence rate might be a lot higher than the diagnosis rate.
What does this mean?
Well, for one thing it means that Less Wrong is "on the spectrum", even if we're mostly not falling off the right tail. Only about 1 in 10 people on Less Wrong are "normal" in terms of the empathizing/systematizing scale, perhaps 1 in 10 are far enough out to be full blown Aspergers, and the rest of us sit somewhere in between, with most people being more to the right of the distribution than the average Cambridge mathematics student.
Interestingly, 48% of respondents ticked this criterion:
Severe impairment in reciprocal social interaction (at least two of the following) (a) inability to interact with peers, (b) lack of desire to interact with peers, (c) lack of appreciation of social cues, (d) socially and emotionally inappropriate behavior
Which indicates that we're mostly not very good at the human social game.
EDIT: Note also that nonresponse bias means that these conclusions only apply strictly to that subset of LW who actually responded, i.e. those specific 82 people. Since "Less Wrong" is a vague collection of "concentric levels" of involvement, from occasional reader to hardcore poster, and those who are more heavily involved are more likely to have responded (e.g. because they read more of the posts, and have more time), the results probably apply more to those who are more involved.
Response bias could be counteracted by doing more work (e.g. asking only specific commenters, randomly selected, to respond), or by simply having a prior for response bias and AQ rates, and using the survey results to update it.
The bigger response bias problem comes from the fact that the survey was presented as a survey about Asperger's, which means that people who are on the autism spectrum probably tended to be more interested in it and more likely to respond to the survey. For instance, a survey about sexual orientation at Cognitive Daily found that rates of homosexuality increased from about 5% of respondents when the sexuality question was tacked on to an unrelated survey to about 15% when the poll was advertised as being about sexual orientation.
Perhaps LW should develop a convention for having surveys where the purpose of the survey isn't explained until after people have taken it.
OK, so if take the homosexuality survey as a data point, we can say that selection bias in a survey can increase the reported rate of a behavior by 3 (5% homosexual in normal population, 15% when the survey is about sexual orientation).
If we assume the same increased rate applies in this case, we can divide 5% by three and get 1.666%, still far above the normal 0.36% of the general population.