Simfish/InquilineKea's Thoughts


Thoughts on IQ (I should expand this)
November 18, 2010, 3:14 pm
Filed under: Uncategorized

Note: I *do* believe that IQ scores measure something. The fact is that you can’t deny their high heritability of 0.8 with parental IQ, so SOMETHING must have been inherited. The real question is how well IQ scores actually explain performance in the real world, and whether they explain performance better for some groups than other groups (in particular, I would expect that IQ scores are less predictive of performance in areas of high environmental variability *and* among non-neurotypicals [especially those with autism, ADHD, or
schizophrenia])

Okay, some facts about IQ that need to bear mentioning:

– Just because you have an IQ of 130 doesn’t mean that your IQ is actually 130. The fact is, if everyone retook the test 2-3 times (and many people DO take the test multiple times and the institution will usually take the best score they got), then a person with IQ scores of 120, 123, and 130 could say that his IQ is 130, and a person with IQ scores of 129,129, and 129 can only say that his IQ is 129. If 2.6% of the population got an IQ of over 130 on a particular IQ test, then MORE THAN 2.6% of the population can claim to have an IQ of over 130 simply because some people will score higher than 130 on some tests but not others. I’m not sure how high people’s test scores usually vary though (my impression is that it isn’t very high, except possibly among certain severe ADHD sufferers). If you took their *average* score, it would probably be a better metric, but it would then discount the people whose IQs have improved after studying (and yes, there are some people who can improve their IQ scores after studying – in fact – I have not seen anything saying that none of the subskills are not improvable – other than perhaps reaction time). And just because you’ve improved after 4 months of studying doesn’t mean that your IQ is lower than other people with the same IQ score as you (since they may have started out doing things that tend to improve IQ scores. Vocabulary, in particular, is prominent on the verbal component of IQ tests, and is extremely improvable, even though many people don’t improve their vocabulary even after months of studying)

Furthermore, some people are naturally more prone to stupid mistakes than others, and some people may not even have the motivation to do their best on IQ tests.

I’m not saying that these degrade the validity of IQ tests. Personally, I think these factors don’t affect IQ distributions by much in THIS environment, but if IQ tests were used instead of SAT tests for college admissions, then it may create a systematic bias in favor of certain groups that study harder. In PARTICULAR, what puzzles me the MOST is why many people DON’T score higher on the Verbal SAT after retakes EVEN THOUGH the Verbal SAT was 50% vocabulary before its last revision (and vocabulary is DEFINITELY improvable). Also, this creates a systematic bias in favor of people who easily memorize definitions.

– According to CTY, people must be at least in the 99.5th percentile to get into its programs (since students have to qualify through a proxy for IQ first, and then score in a certain percentile on the SAT). That corresponds to an IQ of ~140. Having met many people who have gone to CTY programs, I’ll definitely say that they’re much smarter than average, but not necessarily at the level of 140 (or the 99.5th percentile). Furthermore, people’s IQs will saturate at a certain age, so some people’s IQ might saturate at age 13 whereas other IQs might saturate at age 16. The MOST extreme example of this: 6 month olds chimpanzees are actually SMARTER than 6 month old humans (simply because chimps mature faster). I’m quite sure that 6 month old crows are even SMARTER (because they mature even faster). The amount of material 6 month old crows learn and process would EASILY put 6 month old humans to shame.

– Fluid IQ increases to the age of around 16, after which it starts to gradually decline. ALSO, since females mature earlier than males, there is some evidence that their IQs also peak earlier than males. Furthermore, the correlation between parental IQ and child IQ increases monotonically with age to around 0.8 in adulthood. This means that childhood IQ scores (and many have last taken it in childhood) cannot be taken as authoritative.

– Since environmental factors contribute MORE to IQ in childhood than adulthood, we may actually estimate that CTY students (most of whom probably have been exposed to far more enriching behavior than average) will probably regress towards the mean once they become adults.

– Furthermore, IQ at a certain age is compared to ALL people of a certain age. The problem is that people’s IQs all decline at different rates (the brain definitely starts shrinking in one’s 20s), and this decline is often highly dependent on environmental factors such as nutrition (basically, diabetes and high blood glucose means higher decline) and cardiovascular health (more efficient hearts will pump more blood to the brain and slow the decline in IQ). Plus, decline is also dependent on genetic factors. So, an athletic person with consistently low blood glucose levels could EASILY have an age-16 IQ of 120 and an age-50 IQ of 150, simply because his IQ didn’t decline as fast as most people his age.

– Also, IQ scores fail to predict academic performance among Aspies. More of my thoughts here: http://lesswrong.com/r/discussion/lw/346/iq_scores_fail_to_predict_academic_performance_in/

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