Editing Intelligence quotient (section)

==Social correlations==

===School performance===
The [[American Psychological Association]]'s report ''Intelligence: Knowns and Unknowns'' states that wherever it has been studied, children with high scores on tests of intelligence tend to learn more of what is taught in school than their lower-scoring peers. The correlation between IQ scores and grades is about .50. This means that the explained variance is 25%. Achieving good grades depends on many factors other than IQ, such as "persistence, interest in school, and willingness to study" (p.&nbsp;81).{{sfn|Neisser et al.|1995}}

It has been found that the correlation of IQ scores with school performance depends on the IQ measurement used. For undergraduate students, the Verbal IQ as measured by WAIS-R has been found to correlate significantly (0.53) with the grade point average (GPA) of the last 60 hours (credits). In contrast, Performance IQ correlation with the same GPA was only 0.22 in the same study.<ref>{{cite book |last=Kamphaus |first=Randy W. |title=Clinical assessment of child and adolescent intelligence |publisher=Springer |year=2005 | isbn=978-0-387-26299-4}}</ref>

Some measures of educational aptitude correlate highly with IQ tests{{snd}}for instance, {{harvp|Frey|Detterman|2004}} reported a correlation of 0.82 between ''g'' ([[general intelligence factor]]) and [[SAT]] scores;{{sfn|Frey|Detterman|2004}} another research found a correlation of 0.81 between ''g'' and [[General Certificate of Secondary Education|GCSE]] scores, with the explained variance ranging "from 58.6% in Mathematics and 48% in English to 18.1% in Art and Design".{{sfn|Deary|Strand|Smith|Fernandes|2007}}

===Job performance===
According to Schmidt and Hunter, "for hiring employees without previous experience in the job the most valid predictor of future performance is the general mental ability."<ref name="Schmidt98">{{cite journal |last1=Schmidt |first1=Frank L. |last2=Hunter |first2=John E. |title=The validity and utility of selection methods in personnel psychology: Practical and theoretical implications of 85 years of research findings |journal=Psychological Bulletin |volume=124 |issue=2 |pages=262–74 |year=1998 |citeseerx=10.1.1.172.1733 |doi=10.1037/0033-2909.124.2.262 |s2cid=16429503 |url=http://www.moityca.com.br/pdfs/SchmidteHunter1998.pdf |access-date=25 October 2017 |archive-url=https://web.archive.org/web/20140602034440/http://www.moityca.com.br/pdfs/SchmidteHunter1998.pdf |archive-date=2 June 2014 |url-status=dead}}</ref> The validity of IQ as a predictor of [[job performance]] is above zero for all work studied to date, but varies with the type of job and across different studies, ranging from 0.2 to 0.6.<ref name="Hunter84">{{cite journal |last1=Hunter |first1=John E. |last2=Hunter |first2=Ronda F. |title=Validity and utility of alternative predictors of job performance |journal=Psychological Bulletin |volume=96 |issue=1 |pages=72–98 |year=1984 |doi=10.1037/0033-2909.96.1.72 |s2cid=26858912}}</ref> The correlations were higher when the unreliability of measurement methods was controlled for.{{sfn|Neisser et al.|1995}} While IQ is more strongly correlated with reasoning and less so with motor function,<ref>{{cite journal |last1=Warner |first1=Molly |last2=Ernst |first2=John |last3=Townes |first3=Brenda |last4=Peel |first4=John |last5=Preston |first5=Michael |title=Relationships Between IQ and Neuropsychological Measures in Neuropsychiatric Populations: Within-Laboratory and Cross-Cultural Replications Using WAIS and WAIS-R |journal=Journal of Clinical and Experimental Neuropsychology |volume=9 |issue=5 |pages=545–62 |year=1987 |pmid=3667899 |doi=10.1080/01688638708410768}}</ref> IQ-test scores predict performance ratings in all occupations.<ref name="Schmidt98"/>

That said, for highly qualified activities (research, management) low IQ scores are more likely to be a barrier to adequate performance, whereas for minimally skilled activities, athletic strength (manual strength, speed, stamina, and coordination) is more likely to influence performance.<ref name="Schmidt98"/> The prevailing view among academics is that it is largely through the quicker acquisition of job-relevant knowledge that higher IQ mediates job performance. This view has been challenged by Byington & Felps (2010), who argued that "the current applications of IQ-reflective tests allow individuals with high IQ scores to receive greater access to developmental resources, enabling them to acquire additional capabilities over time, and ultimately perform their jobs better."<ref>{{Cite journal |last1=Byington |first1=Eliza |last2=Felps |first2=Will |title=Why do IQ scores predict job performance? |journal=Research in Organizational Behavior |volume=30 |pages=175–202 |doi=10.1016/j.riob.2010.08.003 |year=2010}}</ref>

Newer studies find that the effects of IQ on job performance have been greatly overestimated. The current estimates of the correlation between job performance and IQ are about 0.23 correcting for unreliability and range restriction.<ref>{{cite journal |url=https://ink.library.smu.edu.sg/lkcsb_research/7188/ |title=Revisiting the design of selection systems in light of new findings regarding the validity of widely used predictors |last1=Sackett |first1=Paul R. |last2=Zhang |first2=Charlene |last3=Berry |first3=Christopher M. |last4=Lievens |first4=Filip |year=2023 |journal=Industrial and Organizational Psychology: Perspectives on Science and Practice |volume=16 |issue=3 |access-date=24 April 2023}}</ref><ref>{{cite journal|doi=10.1037/apl0000994 |title=Revisiting meta-analytic estimates of validity in personnel selection: Addressing systematic overcorrection for restriction of range |year=2022 |last1=Sackett |first1=Paul R. |last2=Zhang |first2=Charlene |last3=Berry |first3=Christopher M. |last4=Lievens |first4=Filip |journal=Journal of Applied Psychology |volume=107 |issue=11 |pages=2040–2068 |pmid=34968080 |s2cid=245594032 |url=https://ink.library.smu.edu.sg/lkcsb_research/6894 }}</ref>

In establishing a causal direction to the link between IQ and work performance, longitudinal studies by Watkins and others suggest that IQ exerts a causal influence on future academic achievement, whereas academic achievement does not substantially influence future IQ scores.<ref>{{cite journal |last1=Watkins |first1=M |last2=Lei |first2=P |last3=Canivez |first3=G |title=Psychometric intelligence and achievement: A cross-lagged panel analysis |journal=Intelligence |volume=35 |issue=1 |pages=59–68 |year=2007 |doi=10.1016/j.intell.2006.04.005|citeseerx=10.1.1.397.3155}}</ref> Treena Eileen Rohde and Lee Anne Thompson write that general cognitive ability, but not specific ability scores, predict academic achievement, with the exception that processing speed and spatial ability predict performance on the SAT math beyond the effect of general cognitive ability.<ref>{{cite journal |last1=Rohde |first1=T |last2=Thompson |first2=L |title=Predicting academic achievement with cognitive ability |journal=Intelligence |volume=35 |issue=1 |pages=83–92 |year=2007 |doi=10.1016/j.intell.2006.05.004}}</ref>

However, large-scale longitudinal studies indicate an increase in IQ translates into an increase in performance at all levels of IQ: i.e. ability and job performance are [[Monotonic function|monotonically]] linked at all IQ levels.<ref>{{cite journal |last1=Coward |first1=W. Mark |last2=Sackett |first2=Paul R. |title=Linearity of ability-performance relationships: A reconfirmation |journal=Journal of Applied Psychology |volume=75 |issue=3 |pages=297–300 |year=1990 |doi=10.1037/0021-9010.75.3.297}}</ref><ref>{{cite journal |last1=Robertson |first1=Kimberley Ferriman |last2=Smeets |first2=Stijn |last3=Lubinski |first3=David |last4=Benbow |first4=Camilla P. |title=Beyond the Threshold Hypothesis |journal=Current Directions in Psychological Science |date=14 December 2010 |volume=19 |issue=6 |pages=346–351 |doi=10.1177/0963721410391442 |s2cid=46218795 |url=https://my.vanderbilt.edu/smpy/files/2013/02/Ferriman_20101.pdf}}</ref>

===Income===
<!-- This whole section needs to be checked against the sources for missing information and undue weight -->
<!--
{| class="wikitable"
|-
|+ '''Relation between IQ and earnings in the U.S.'''
! IQ || <75 || 75–90 || 90–110 || 110–125 || >125
|-
| Age 18 || 2,000 || 5,000 || 8,000 || 8,000 || 21,000
|-
| Age 26 || 3,000 || 10,000 || 16,000 || 20,000 || 42,000
|-
| Age 32 || 5,000 || 12,400 || 20,000 || 27,000 || 48,000
|-
| colspan="6" | Values are the average earnings (1993 US Dollars) of each IQ sub-population.<ref> {{cite journal | last1 = Murray | first1 = C | year = 1997 | title = IQ and economic success | journal = Public Interest | volume = 128 | pages = 21–35}}</ref>
|}
-->

It has been suggested that "in economic terms it appears that the IQ score measures something with decreasing marginal value" and it "is important to have enough of it, but having lots and lots does not buy you that much".{{sfn |Detterman|Daniel|1989}}<ref>
{{cite web
 |url=http://www.americanscientist.org/template/AssetDetail/assetid/24538/page/4
 |title=The Role of Intelligence in Modern Society (July–Aug, 1995)
 |pages=4 (Nonlinearities in Intelligence)
 |date=July 1995
 |first=Earl B. |last=Hunt
 |publisher=American Scientist
|archive-url=https://web.archive.org/web/20060521185816/http://www.americanscientist.org/template/AssetDetail/assetid/24538/page/4 |archive-date=21 May 2006}}</ref>

The link from IQ to wealth is much less strong than that from IQ to job performance. Some studies indicate that IQ is unrelated to net worth.<ref>{{Cite news |work=The Times |location=London |title=Brains don't make you rich IQ study finds |first=Mark |last=Henderson |date=25 April 2007 |url=http://www.timesonline.co.uk/tol/news/uk/science/article1701377.ece |archive-url=https://web.archive.org/web/20080906215126/http://www.timesonline.co.uk/tol/news/uk/science/article1701377.ece |url-status=dead |archive-date=6 September 2008 |access-date=5 May 2010}}</ref><ref>{{cite web |title=You Don't Have To Be Smart To Be Rich, Study Finds |website=ScienceDaily |url=https://www.sciencedaily.com/releases/2007/04/070424204519.htm |access-date=26 August 2014}}</ref> The American Psychological Association's 1995 report ''[[Intelligence: Knowns and Unknowns]]'' stated that IQ scores accounted for about a quarter of the social status variance and one-sixth of the income variance. Statistical controls for parental SES eliminate about a quarter of this predictive power. Psychometric intelligence appears as only one of a great many factors that influence social outcomes.{{sfn|Neisser et al.|1995}} [[Charles Murray (political scientist)|Charles Murray]] (1998) showed a more substantial effect of IQ on income independent of family background.{{sfn|Murray|1998|p={{Page needed|date=January 2011}}}} In a meta-analysis, Strenze (2006) reviewed much of the literature and estimated the correlation between IQ and income to be about 0.23.<ref name="Strenze2007">{{cite journal |last1=Strenze |first1=Tarmo |date=September 2007 |title=Intelligence and socioeconomic success: A meta-analytic review of longitudinal research |journal=Intelligence |volume=35 |issue=5 |pages=401–426 |doi=10.1016/j.intell.2006.09.004 |quote=The correlation with income is considerably lower, perhaps even disappointingly low, being about the average of the previous meta-analytic estimates (.15 by Bowles et al., 2001; and .27 by Ng et al., 2005). But...other predictors, studied in this paper, are not doing any better in predicting income, which demonstrates that financial success is difficult to predict by any variable. This assertion is further corroborated by the meta-analysis of Ng et al. (2005) where the best predictor of salary was educational level with a correlation of only .29. It should also be noted that the correlation of .23 is about the size of the average meta-analytic result in psychology(Hemphill, 2003) and cannot, therefore, be treated as insignificant.}}</ref>

Some studies assert that IQ only accounts for (explains) a sixth of the variation in income because many studies are based on young adults, many of whom have not yet reached their peak earning capacity, or even their education. On pg 568 of ''[[The g Factor: The Science of Mental Ability|The g Factor]]'', [[Arthur Jensen]] says that although the correlation between IQ and income averages a moderate 0.4 (one-sixth or 16% of the variance), the relationship increases with age, and peaks at middle age when people have reached their maximum career potential. In the book, ''A Question of Intelligence'', [[Daniel Seligman]] cites an IQ income correlation of 0.5 (25% of the variance).

A 2002 study further examined the impact of non-IQ factors on income and concluded that an individual's location, inherited wealth, race, and schooling are more important as factors in determining income than IQ.<ref>{{cite journal |last1=Bowles |first1=Samuel |last2=Gintis |first2=Herbert |year=2002 |title=The Inheritance of Inequality |journal=Journal of Economic Perspectives |volume=16 |issue=3 |pages=3–30 |doi=10.1257/089533002760278686 |doi-access=free}}</ref>

===Crime===
The American Psychological Association's 1995 report ''Intelligence: Knowns and Unknowns'' stated that the [[correlates of crime#Psychological traits|correlation between IQ and crime]] was −0.2. This association is generally regarded as small and prone to disappearance or a substantial reduction after controlling for the proper covariates, being much smaller than typical sociological correlates.<ref>{{cite journal |last1=Cullen |first1=Francis T. |last2=Gendreau |first2=Paul |last3=Jarjoura |first3=G. Roger |last4=Wright |first4=John Paul |title=Crime and the Bell Curve: Lessons from Intelligent Criminology |journal=Crime & Delinquency |date=October 1997 |volume=43 |issue=4 |pages=387–411 |doi=10.1177/0011128797043004001 |s2cid=145418972}}</ref> It was −0.19 between IQ scores and the number of juvenile offenses in a large Danish sample; with social class controlled for, the correlation dropped to −0.17. A correlation of 0.20 means that the [[explained variance]] accounts for 4% of the total variance. The causal links between psychometric ability and social outcomes may be indirect. Children with poor scholastic performance may feel alienated. Consequently, they may be more likely to engage in delinquent behavior, compared to other children who do well.{{sfn|Neisser et al.|1995}}

In his book ''[[The g Factor: The Science of Mental Ability|The g Factor]]'' (1998), [[Arthur Jensen]] cited data which showed that, regardless of race, people with IQs between 70 and 90 have higher crime rates than people with IQs below or above this range, with the peak range being between 80 and 90.

The 2009 ''Handbook of Crime Correlates'' stated that reviews have found that around eight IQ points, or 0.5 SD, separate criminals from the general population, especially for persistent serious offenders. It has been suggested that this simply reflects that "only dumb ones get caught" but there is similarly a negative relation between IQ and self-reported offending. That children with [[conduct disorder]] have lower IQ than their peers "strongly argues" for the theory.<ref>''Handbook of Crime Correlates''; Lee Ellis, Kevin M. Beaver, John Wright; 2009; Academic Press</ref>

A study of the relationship between US county-level IQ and US county-level crime rates found that higher average IQs were very weakly associated with lower levels of property crime, burglary, larceny rate, motor vehicle theft, violent crime, robbery, and aggravated assault. These results were "not confounded by a measure of concentrated disadvantage that captures the effects of race, poverty, and other social disadvantages of the county."<ref>{{cite journal |last1=Beaver |first1=Kevin M. |last2=Schwartz |first2=Joseph A. |last3=Nedelec |first3=Joseph L. |last4=Connolly |first4=Eric J. |last5=Boutwell |first5=Brian B. |last6=Barnes |first6=J.C. |title=Intelligence is associated with criminal justice processing: Arrest through incarceration |journal=Intelligence |date=September 2013 |volume=41 |issue=5 |pages=277–288 |doi=10.1016/j.intell.2013.05.001}}</ref> However, this study is limited in that it extrapolated Add Health estimates to the respondent's counties, and as the dataset was not designed to be representative on the state or county level, it may not be generalizable.<ref>{{cite journal |last1=Beaver |first1=Kevin M. |last2=Wright |first2=John Paul |title=The association between county-level IQ and county-level crime rates |journal=Intelligence |date=January 2011 |volume=39 |issue=1 |pages=22–26 |doi=10.1016/j.intell.2010.12.002}}</ref>

It has also been shown that the effect of IQ is heavily dependent on socioeconomic status and that it cannot be easily controlled away, with many methodological considerations being at play.<ref>{{cite journal |last1=Mears |first1=Daniel P. |last2=Cochran |first2=Joshua C. |title=What is the effect of IQ on offending? |journal=Criminal Justice and Behavior |date=November 2013 |volume=40 |issue=11 |pages=1280–1300 |doi=10.1177/0093854813485736 |s2cid=147219554}}</ref> Indeed, there is evidence that the small relationship is mediated by well-being, substance abuse, and other confounding factors that prohibit simple causal interpretation.<ref>{{cite journal |last1=Freeman |first1=James |title=The relationship between lower intelligence, crime and custodial outcomes: a brief literary review of a vulnerable group |journal=Vulnerable Groups & Inclusion |date=January 2012 |volume=3 |issue=1 |pages=14834 |doi=10.3402/vgi.v3i0.14834 |s2cid=145305072|doi-access=free }}</ref> A recent meta-analysis has shown that the relationship is only observed in higher risk populations such as those in poverty without direct effect, but without any causal interpretation.<ref>{{cite journal |last1=Ttofi |first1=Maria M. |last2=Farrington |first2=David P. |last3=Piquero |first3=Alex R. |last4=Lösel |first4=Friedrich |last5=DeLisi |first5=Matthew |last6=Murray |first6=Joseph |title=Intelligence as a protective factor against offending: A meta-analytic review of prospective longitudinal studies |journal=Journal of Criminal Justice |date=1 June 2016 |volume=45 |pages=4–18 |doi=10.1016/j.jcrimjus.2016.02.003}}</ref> A nationally representative longitudinal study has shown that this relationship is entirely mediated by school performance.<ref>{{cite journal |last1=McGloin |first1=Jean Marie |last2=Pratt |first2=Travis C. |last3=Maahs |first3=Jeff |title=Rethinking the IQ-delinquency relationship: A longitudinal analysis of multiple theoretical models |journal=Justice Quarterly |date=1 September 2004 |volume=21 |issue=3 |pages=603–635 |doi=10.1080/07418820400095921 |s2cid=143305924}}</ref>

===Health and mortality===
Multiple studies conducted in Scotland have found that higher IQs in early life are associated with lower mortality and morbidity rates later in life.<ref>{{Cite journal |last1=Gottfredson |first1=Linda S. |last2=Deary |first2=Ian J. |date=22 June 2016 |title=Intelligence Predicts Health and Longevity, but Why? |journal=Current Directions in Psychological Science |language=en |volume=13 |issue=1 |pages=1–4 |doi=10.1111/j.0963-7214.2004.01301001.x |s2cid=15176389}}</ref><ref>{{Cite journal |last1=Batty |first1=G. David |last2=Deary |first2=Ian J. |last3=Gottfredson |first3=Linda S. |title=Premorbid (early life) IQ and Later Mortality Risk: Systematic Review |journal=Annals of Epidemiology |volume=17 |issue=4 |pages=278–288 |doi=10.1016/j.annepidem.2006.07.010 |pmid=17174570 |year=2007|citeseerx=10.1.1.693.9671}}</ref>

===Other accomplishments===
<!-- This whole section, repetitive of a section above, needs to be checked against reliable sources for missing information and due weight -->
{| class=wikitable
|+ Average adult combined IQs associated with real-life accomplishments by various tests:{{sfn|Kaufman|2009|p=126}}{{sfn|Kaufman|Lichtenberger|2006}}
! Accomplishment !! IQ !! Test/study !! Year
|-
| MDs, JDs, and PhDs || 125 || [[WAIS-R]] || 1987
|-
| rowspan=3 | College graduates || rowspan=2 | 112 || [[Alan S. Kaufman|KAIT]] || 2000
|-
| [[Alan S. Kaufman|K-BIT]] || 1992
|-
| 115 || WAIS-R ||
|-
| rowspan=3 | 1–3 years of college || rowspan=2 | 104 || KAIT ||
|-
| K-BIT ||
|-
| 105–110 || WAIS-R ||
|-
| Clerical and sales workers || 100–105 || ||
|-
| rowspan=3 | High school graduates, skilled workers (e.g., electricians, cabinetmakers) || rowspan=2 | 100 || KAIT ||
|-
| WAIS-R ||
|-
| 97 || K-BIT ||
|-
| rowspan=3 | 1–3 years of high school (completed 9–11 years of school) || 94 || KAIT ||
|-
| 90 || K-BIT ||
|-
| 95 || WAIS-R ||
|-
| Semi-skilled workers (e.g. truck drivers, factory workers) || 90–95 || ||
|-
| Elementary school graduates (completed eighth grade) || 90 || ||
|-
| Elementary school dropouts (completed 0–7 years of school) || 80–85 || ||
|-
| Have 50/50 chance of reaching high school || 75 || ||
|}

{| class=wikitable
|+ Average IQ of various occupational groups:{{sfn|Kaufman|2009|p=132}}
! Accomplishment !! IQ !! Test/study !! Year
|-
| Professional and technical || 112 || ||
|-
| Managers and administrators || 104 || ||
|-
| Clerical workers, sales workers, skilled workers, craftsmen, and foremen || 101 || ||
|-
| Semi-skilled workers (operatives, service workers, including private household) || 92 || ||
|-
| Unskilled workers || 87 || ||
|}

{| class=wikitable
|+ Type of work that can be accomplished:{{sfn|Kaufman|2009|p=126}}
! Accomplishment !! IQ !! Test/study !! Year
|-
| Adults can harvest vegetables, repair furniture || 60 || ||
|-
| Adults can do domestic work || 50|| ||
|}

There is considerable variation within and overlap among these categories. People with high IQs are found at all levels of education and occupational categories. The biggest difference occurs for low IQs with only an occasional college graduate or professional scoring below 90.<ref name=Kaufman2009/>