IQ and
Success.

1 The Predictive Power of IQ

IQ is among the most robust and well-validated predictors of life outcomes in all of psychology. Decades of longitudinal research involving millions of individuals have established that cognitive ability, as measured by standardized IQ tests, correlates significantly with a wide range of important outcomes.

According to research published in Psychological Bulletin and meta-analyses by Schmidt & Hunter (1998), general mental ability (g) is the single best predictor of job training success and job performance across all occupations. The validity coefficients for IQ range from .30 for low-complexity jobs to .70+ for high-complexity professions.

2 Education and Academic Achievement

The relationship between IQ and educational attainment is one of the strongest findings in psychological research:

• Correlations of .50-.70 between IQ and grade point average across academic levels, from elementary school through graduate education
• Years of education completed correlate approximately .55 with IQ scores—higher IQ individuals tend to pursue more education
• Test performance on standardized exams (SAT, GRE, etc.) correlates .80+ with IQ measures
• Academic honors and dropout rates show strong associations with cognitive ability

A landmark study by Deary et al. (2007) found that IQ measured at age 11 predicted educational attainment by age 25 with remarkable accuracy. This longitudinal evidence demonstrates that cognitive ability measured early in life has lasting predictive validity.

Importantly, the IQ-education relationship is bidirectional: higher IQ facilitates learning, and education in turn produces modest increases in IQ scores (approximately 1-5 points per year of schooling).

3 Career and Occupational Outcomes

Cognitive ability strongly predicts job performance across virtually all occupations, but particularly for complex roles:

• High-complexity jobs (professional, managerial, technical): IQ-performance correlations of .50-.70
• Medium-complexity jobs (skilled trades, clerical): Correlations of .35-.55
• Low-complexity jobs (unskilled labor): Correlations of .20-.35
• Training success: Correlations exceeding .50 across all job types

Research from the American Economic Review and occupational psychology demonstrates that IQ predicts not just initial job performance but also career advancement, leadership emergence, and adaptability to new job demands.

Certain professions show particularly high average IQ levels: physicians (~125), attorneys (~120), engineers (~115), teachers (~110). These differences reflect both selection effects (higher-IQ individuals choosing and gaining entry to demanding professions) and job demands (complex roles requiring higher cognitive ability for success).

4 Income and Socioeconomic Status

Cognitive ability correlates moderately but consistently with income and socioeconomic status:

• Income correlation: Approximately .30-.40 with IQ, increasing somewhat in knowledge-economy contexts
• Wealth accumulation: Research by Zagorsky (2007) found each IQ point worth approximately $200-600 in annual income
• Poverty avoidance: Higher IQ significantly reduces probability of falling into poverty
• Net worth: Associations weaker than income due to spending/saving behaviors independent of IQ

The income-IQ relationship persists after controlling for education, suggesting cognitive ability has value beyond its effects on educational attainment. However, the relationship isn't destiny—many high-IQ individuals have modest incomes, and some lower-IQ individuals achieve financial success through entrepreneurship, social skills, or fortunate circumstances.

Research published in the Intelligence journal shows that IQ measured in childhood predicts adult income decades later, even after control for family socioeconomic background.

5 Health and Longevity

Perhaps surprisingly, IQ correlates with physical health outcomes and lifespan:

• Mortality risk: Each 15-point IQ deficit associated with approximately 20% higher mortality risk
• Chronic disease: Lower IQ linked to higher rates of cardiovascular disease, diabetes, and other conditions
• Health behaviors: Higher IQ associated with better diet, exercise habits, medication compliance
• Accident rates: Lower cognitive ability predicts higher accident and injury rates

The landmark Scottish Mental Surveys followed individuals tested at age 11 for decades. Whalley & Deary (2001) found that childhood IQ predicted survival into late adulthood—a one standard deviation increase in IQ was associated with 21% lower mortality risk.

The mechanisms likely include: better understanding of health information, more future-oriented decision-making, higher incomes enabling better healthcare, and possibly shared genetic factors influencing both brain function and overall physiological integrity.

6 The Limits of IQ as a Predictor

While IQ is a powerful predictor, it's essential to understand its limitations:

• Diminishing returns: Above a certain threshold (~120-130), additional IQ points contribute less to success. Other factors become more important.
• Non-cognitive factors: Conscientiousness, emotional stability, and social skills independently predict success, sometimes as strongly as IQ.
• Opportunity and luck: Access to education, mentorship, economic conditions, and chance events all matter.
• Domain specificity: Creative achievement, entrepreneurial success, and relationship quality have weaker IQ correlations.
• Motivation and interest: A motivated average-IQ person often outperforms an unmotivated high-IQ person.

As Nobel laureate James Heckman has emphasized, "soft skills" and character traits are also crucial for success. IQ matters, but it's not deterministic.

7 Practical Implications

Understanding your cognitive profile through ACIS can inform practical decisions:

• Educational planning: Match academic challenges to ability levels; identify where extra support may be needed
• Career selection: Consider cognitive demands of different professions; play to your strengths
• Learning strategies: Higher fluid reasoning suggests capacity for self-directed learning; stronger crystallized intelligence suggests leveraging existing knowledge
• Realistic expectations: Understand your likely ceiling in cognitively demanding fields while recognizing that effort and strategy can optimize your outcomes
• Compensatory strategies: Where cognitive abilities are weaker, develop systems and habits that compensate

Your ACIS profile is information for decision-making, not a fixed destiny. Use it wisely to understand yourself and plan strategically.

8 Key Research References

For those interested in the primary research:

• Schmidt, F.L. & Hunter, J.E. (1998). The validity and utility of selection methods in personnel psychology. Psychological Bulletin, 124(2), 262-274.
• Deary, I.J. et al. (2007). Intelligence and educational achievement. Intelligence, 35(1), 13-21.
• Gottfredson, L.S. (1997). Why g matters: The complexity of everyday life. Intelligence, 24(1), 79-132.
• Whalley, L.J. & Deary, I.J. (2001). Longitudinal cohort study of childhood IQ and survival up to age 76. BMJ, 322(7280), 819.
• Zagorsky, J.L. (2007). Do you have to be smart to be rich? The impact of IQ on wealth, income and financial distress. Intelligence, 35(5), 489-501.
• Strenze, T. (2007). Intelligence and socioeconomic success: A meta-analytic review of longitudinal research. Intelligence, 35(5), 401-426.
• Batty, G.D. et al. (2007). IQ and mortality: A population-based cohort study. International Journal of Epidemiology, 36(3), 538-553.
• Kuncel, N.R., Hezlett, S.A. & Ones, D.S. (2004). Academic performance, career potential, creativity, and job performance: Can one construct predict them all? Journal of Personality and Social Psychology, 86(1), 148-161.
• Judge, T.A., Colbert, A.E. & Ilies, R. (2004). Intelligence and leadership: A quantitative review and test of theoretical propositions. Journal of Applied Psychology, 89(3), 542-552.
• Duckworth, A.L. et al. (2007). Grit: Perseverance and passion for long-term goals. Journal of Personality and Social Psychology, 92(6), 1087-1101.
• Nisbett, R.E. et al. (2012). Intelligence: New findings and theoretical developments. American Psychologist, 67(2), 130-159.