How to estimate IQ for public figures?

Question

Background: I read a question on Quora that asked how intelligent is Barack Obama. A wide range of arguments were presented. The tone of the answers was not neutral because of the political context of the question. Furthermore, over the while I've read estimates of intelligence of various famous people from history (e.g., scientists, presidents, etc.). Issues were also raised about how intelligence is defined (e.g., cognitive, social, emotional or physical; achievement versus latent ability, etc.) Despite these issues, I find the topic interesting.

Questions:

• If you cannot administer a standardised intelligence test to someone, to what extent can you obtain a good estimate of their IQ from the kinds of information available about public figures?
• What is considered scientific best-practice in this regard?
• How accurate is best practice? Do any studies provide validity estimates (e.g., correlating estimates with actual IQ test scores)?

In relation to public figures, a wide range of information is often available: e.g., demographics, educational attainments, career achievement, writing samples, personal achievements, samples of public speaking, and so on. Sometimes, information such as school and university grades will be available. Of course, a lot of this information will be non-standardised. I wonder what would be a good way to collect and synthesise this information to generate a prediction.

Answer 1

Entry into the literature

As a starting point, Simonton (2009) provides an excellent introduction to the field of historiometric assessment of intelligence. To quote the abstract:

Running parallel to mainstream research on the psychometric assessment of intelligence is another tradition of research on the historiometric assessment of intelligence and closely affiliated variables. Historiometric assessment is based on four data sources: (a) personality sketches (e.g., Intellectual Brilliance), (b) developmental histories (e.g., IQ), (c) content analyses (e.g., integrative complexity), and (d) expert surveys (e.g., Openness to Experience). The first two represent major lines of intelligence research that involved key figures in the development of corresponding psychometric methods (e.g., Galton, Terman, and Thorndike), whereas the last two constitute independent research paradigms that later intersected with the first two. The literature on U.S. presidents then provides an integrated illustration of the four historiometric approaches and how they converge on the same broad conclusions. Significantly, historiometric investigations on the relation between broadly defined intelligence and adulthood achievement obtain about the same effect size as that found in psychometric research (i.e., $r$ or $\beta$ .25 $\pm$ .10). Because historiometric and psychometric studies have rather distinctive methodological advantages and disadvantages, this consistent outcome provides corrobora- tive support for both sets of empirical findings.

The review summarises various studies aiming to assess intelligence of royalty, U.S. politicians, and eminent figures.

Critical thoughts

For current and recent public figures substantial additional information would be available. In particular, many powerful predictors of IQ would often be available including university grades, scores on standardised assessments, SAT scores and so on. Furthermore, the existing literature on IQ correlates is huge and provides substantial information that could inform predictive models of IQ prediction. In contrast where such models are applied to the past, the predictive power of such models may be wrong.

I'd also be extremely wary of estimates of intelligence that yield estimates like 200 (i.e., around 7+ standard deviations above the mean). E.g.,

After comparing the chronological age in which .. achievements appeared with the mental age that they represented, Terman decided that Galton’s IQ must have been close to 200. (Simonton, 2009, p. 319)

The expertise literature has highlighted the importance of not confusing eminence with IQ. Eminence is substantially influenced by years of practice, training, focus, opportunity, and luck. IQ is useful, but the correlation between IQ and eminence is insufficient to yield the kind of certainty in prediction to result in IQ predictions above something like 3 or perhaps 4 standard deviations above the mean (i.e., 145 to 160).

References

• Simonton, D.K. (2009) The “other IQ”: Historiometric assessments of intelligence and related constructs. Review of General Psychology, 13, 315.

Answer 2

This is just my personal thought process.

The way to measure the IQ of public figures/persons in leadership positions differ than that of the IQ being measured for normal individuals. Traditionally, IQ is being represented as the Intelligence of a person in analytic/cognitive skills. Later Gardner developed the famous multiple facets of intelligence by which intelligence could be approached from multiple paradigms. This seems to be good from an individual perspective.

In case of public figures, the impact of change(probably good change) brought by them upon the group represented by them, whether it be organization or a country, should be the priority factor in estimating the IQ. Thus measuring the IQ of those figures must always be a complex model that measure the effect of change that they brought to their group as a result of them being the mentor of the group. This may sound odd, but this is what often termed as political will or lack of it in common parlance. So the IQ of a leader can be assessed by the positive changes they have made to their environment.

So going by Stenberg's Triarchic Theory of Intelligence,

• Scientists' IQ may be measured by Analytic Intelligence
• Artists' IQ may be measured by Creative Intelligence
• Public/Leaders IQ may be measure by Practical Intelligence

Personally, I feel the dimension of change (Obama always speak about change, hope he doesn't think of a change in President this time :) ), must be the biggest factor in evaluation since the decision of a leader is bound to have a impact on a large number of people. It may even change over time if the impact is felt over a long period of time. Thus the important variables would be the amount of change, the rate of change, the percentage of positive effect derived from the change, the percentage of population affected (for good) by the change and the environment (the environment itself would be made of a lot of other variables).

Answer 3

Like the first answer offered, this is just my opinion. Also accept my apologies if I'm teaching you to suck eggs.

My general approach would be to use Bayesian reasoning. For example:

$$p(A|B) = \frac{p(B|A) p(A)}{p(B)}$$

$A$ could be "IQ between 120 between 130"

$B$ could be "Entered Harvard"

You would need to make many such comparisons and combine them. You could get a probability distribution too. Of course, you need to know, for example, the IQ distribution of people who do enter Harvard. There are many opportunities for subjectivity in such an analysis, such as which variables you consider, and what you do about students who don't reveal their IQs.

A useful way to present the results would be in the form of a computer program or spreadsheet which would allow the reader to apply his own subjective judgements and see the results accordingly. My guess would be about 145, with a strong emphasis on language skills.