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"N = 23; Full Scale IQ" Enough for me to pretty much stop reading right there. Isn't 23 far too small? If there is signal there, you probably need more sampl

• nabla9 10y ago
  The size of N tells very little alone. N=23 can be enough. For example, N = 1 is enough if the rat can solve crossword puzzles. Effect size is so large that probability that you could guess which rat is in the control group and which is not is close to 1.0.
• gwern 10y ago
  The people who claim that high-IQ types are doomed and will be 'The Outsiders' and will be discriminated against to the point that 90%+ of them will not get appropriate higher education (I won't link to the pseudo-statistics that supposedly 'proves' this) are claiming very large effect sizes (and blaming that for why they need shelter in high-IQ societies). In this case, such large effects can be rejected pretty soundly; with the sample sizes given, 23 vs 1058, you have 80% power to detect `pwr.t2n.test(n1=1058, n2=23, power=0.80, alternative="greater")` ~> d=0.52 (which is, for example, about half the size of the black-white IQ gap, and considered a 'medium' effect size). In addition, the longitudinal cohort studies of the gifted like Terman, Hunter, TIP, or SMPY, do not find any signs of severe emotional/behavioral/social difficulties, the genetic correlations (https://en.wikipedia.org/wiki/Genetic_correlation#Intelligence https://en.wikipedia.org/wiki/Genetic_correlation#Intelligen...) are all in the wrong direction, adults are more able than kids to self-select into stimulating environments (possibly why heritability of intelligence increases with age), and so on. A new review paper which is relevant: "From Terman to Today: A Century of Findings on Intellectual Precocity" http://emilkirkegaard.dk/en/wp-content/uploads/From-Terman-to-Today-A-Century-of-Findings-on-Intellectual-Precocity.pdf http://emilkirkegaard.dk/en/wp-content/uploads/From-Terman-t... , Lubinski 2016. From a statistical perspective, this result doesn't tell us much about gifted adults not because the sample size is far too small, but because IQ scores at age 5-6 inherently don't predict adult IQ sufficiently well. This subsample of 23 kids with mean IQ of 134.6, selected because they are past the 130 threshold, are going to regress to the mean as they grow up. With the usual r=0.5 of 5yo/adult scores, their adult mean IQ will be more like 117 - which is above average but not 'gifted' by anyone's criterion. To try to study gifted adults by starting with them as kids, you would need to start another standard deviation up, around 150 IQ, which would be extremely difficult. (The correlation rapidly increases up to middle school, which is why TIP/SMPY don't suffer from this issue as much: much higher threshold and also much more reliable tests.)
  • skrap 10y ago
    Wow, thanks for the very detailed and interesting reply! You say: > "With the usual r=0.5 of 5yo/adult scores, their adult mean IQ will be more like 117" As a total layperson, this is surprising! I would have thought that smart kids would have tended to stay smart, rather than have whatever effect be subject to a regression to the mean. Is this relationship well-established?
    • gwern 10y ago
      Well, smart kids do tend to stay smart: 117 is still above average. It's just that they don't necessarily stay as unusually smart, for the same reason that unusually dumb kids don't stay exactly as dumb (regression to the mean cuts both ways). When you filter for kids with 130IQs at age 5, you're picking out kids who are smart, but also ones who were in a great mood that day, who biologically developed earlier than their peers, who got lucky in avoiding infections or injuries or the many other idiosyncratic things that damage intelligence, and so on. (And the opposite for those who score very unusually low.) That luck is not guaranteed to repeat itself, so... they regress to the mean. As they get older, more of the brain is developed and has reached its limits, and there's less noise from things like whether one happened to develop working memory a bit faster than one's peers as people hit their genetic and physiological limits, and the predictive power of an IQ test score increases considerably. By middle school, you're talking more like r=0.9.
  • jnicholasp 10y ago
    I assume you're referencing Grady Towers' essays about high IQ people feeling like 'Outsiders'. His argument, I think, was that high IQ does not inherently doom people to be outsiders/fail to get appropriate education/be unhappy and mal-adjusted/etc., but that high IQ is a potentially alienating trait and that it is the alienation - in those cases where the high IQ person doesn't have enough peers, support, and meaningful challenge - that does the damage. What do you think of that argument, and do you know of any relevant research on that aspect of the question? It anecdotally resonates with my experience, and seems to be a prominent subsection of the responses in most threads of this type, but I would like to know what formal attempts have been made to measure it, if any exist. Also, again IIRC, I thought Towers reassessed one of Terman's longitudinal studies and found that there was a correlation between the highest IQ individuals and social/emotional mal-adaption. Do you disagree with Towers' assessment?
• jwatte 10y ago
  Yes, like in most social and behavioural science, unfortunately.