‘Intelligence is a very general mental capability that, among other things, involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience. It is not merely book learning, a narrow academic skill, or test-taking smarts. Rather, it reflects a broader and deeper capability for comprehending our surroundings—“catching on,” “making sense” of things, or “figuring out” what to do.’
Gottfredson (1997)
IQ is not simply a measure of intelligence, it is the most accurate (i.e. reliable and valid) of all psychological tests and assessments at predicting the performance of simple tasks, academic success, job performance, health, longevity, functional literacy, socioeconomic advancement, ‘social pathologies’ and is correlated with brain size. If we conduct various different cognitive tests that measure seemingly unrelated skills, the results will be positively correlated. The application of factor analysis shows us that there is one primary dominant factor: we call this intelligence (and it coincides with our ‘common sense’ interpretation of intelligence). See Spearman (1904), Carroll (1994), Neisser, et al. (1996), Gottfredson (1997), Jensen (1998), Mackintosh (1998), Deary (2001).
From Carroll (1993, p. 16):
aptitude is a cognitive ability that is possibly predictive of certain kinds of future learning success.
achievement is the extent that certain behaviors have been learned.
"...an ability is clearly a measurement of aptitude for some particular future learning success if, in a sample of individuals tested both in aptitude and in achievement in some specified learning or training activity at two points of times, once before training (time A) and once after training (time B):
On that basis, my own definition:
intelligence is the ability of an individual to perform a novel cognitive task.
Heritability is the proportion of total phenotype variance attributable to genetic variance.
G = variance of the genetically diverse population in a uniform environment
E = variance of genetically identical subjects in different environments
heritability = G/(G+E)
Sources of evidence:
| Age | Broad heritability | Narrow heritability |
|---|---|---|
| 4–6 | 0.42 | |
| 7–20 | 0.55 | |
| late adolescence | 0.75 | |
| adults | 0.80 | 0.71 |
Broad heritability is a measure of the heritability attributable to all kinds of genes, whilst narrow heritability is a measure of the action of additive genes only.
Academics who subscribe to the above notions listed here.
| Region | Mean IQ |
|---|---|
| Northern North America | 97.0 |
| North America | 98.0 |
| Middle America | 87.0 |
| Central America | 83.2 |
| Caribbean | 80.4 |
| Northern South America | 88.0 |
| Western South America | 86.8 |
| Central South America | 85.0 |
| Eastern South America | 87.0 |
| Southern South America | 95.2 |
| Northern Europe | 98.9 |
| Western Europe | 99.2 |
| Central Europe | 100.5 |
| Eastern Europe | 96.0 |
| Southwestern Europe | 98.2 |
| Southern Europe | 100.4 |
| Southeastern Europe | 93.0 |
| Northern Africa | 81.2 |
| Western Africa | 67.5 |
| Central Africa | 66.8 |
| Eastern Africa | 68.3 |
| Southern Africa | 72.7 |
| Southeastern Africa | 72.0 |
| Middle East | 84.9 |
| Northern Asia | 96.0 |
| Central Asia | 88.5 |
| Eastern Asia | 100.8 |
| Southwestern Asia | 90.0 |
| Southern Asia | 81.0 |
| Southeastern Asia | 89.7 |
Clusters:
Africa (excluding Northern Africa): 68.6
Southern Asia: 81.0
Europe: 98.6
Eastern Asia (excluding mainland China): 105.2
The mean IQ of countries lies within the range 59 (Equatorial Guinea and Sao Tome/Principe) to 107 (Hong Kong). The mean IQ for the population of the entire world is 88.8. The median of the mean IQ of countries is 84. For countries with a mean IQ above 90 there exists a positive correlation between wealth and IQ. The six countries described as belonging to the ‘Axis of Evil’ and ‘Beyond the Axis of Evil’ (Cuba, Iran, Iraq, Libya, North Korea and Syria), with the exception of North Korea have mean IQs in the range of 84 and 87.
Yes, Lynn (2006, p. 66–68) gives six reasons.
No. Herrnstein and Murray (1994, p. 280–286, 649–661), Jensen (1998, p. 360–369), Levin (2005, p. 62–73).
Deary, et al. (2000) found that the corrected correlation between test scores at age 11 and age 77 was 0.73.
I (Sewell 2007) performed a meta-study of 26 articles that measure adult male and female intelligence which produced an average difference in g of a male advantage of about 2 IQ points.
The Reference Frame: IQ in different fields
Herrnstein and Murray (1994, p. 307–309)
Jensen (1998, p. 318–333)
Levin (2005, p. 128–130)
Lynn (2006, p. 5–6)
http://en.wikipedia.org/wiki/Flynn_effect