iq percentile chart by age

Introduction

The relationship between IQ and age has been a subject of extensive research, with various studies examining how IQ scores change over time and the factors influencing these changes. This synthesis aims to provide a cohesive understanding of the findings from multiple research papers on the topic of IQ percentile charts by age.

Key Insights

Heritability of IQ Increases with Age:
- The heritability of IQ increases with age, reaching an asymptote of about 0.80 at 18-20 years and continuing at that level into adulthood. Shared environmental influences decrease across age, approximating about 0.10 at 18-20 years and continuing at that level into adulthood.
Stability and Predictive Value of Early IQ Scores:
- IQ scores in early childhood can predict later IQ scores, but there are variations. For example, nonverbal IQ scores in individuals with autism spectrum disorder showed that most adults who scored in the intellectual disability range also had low scores as children, although actual scores declined from age 2 to 19.
- The Ages and Stages Questionnaire at 36 months can predict IQ at 5-6 years, with a threshold score of 270 being optimal to identify children at risk of an IQ below 85.
- Childhood IQ scores can predict adult educational and occupational status, with predictive correlations approaching those of contemporaneous adult IQs by the second grade.
Sex Differences in IQ:
- Longitudinal studies show that girls have a slight IQ advantage at ages 7 and 11, but by age 16, boys have a slight IQ advantage.
Age-Adjusted IQ Norms:
- Age-adjusted IQ scores can be estimated using continuous norming techniques, which provide stable estimates by smoothing age norms analytically rather than developing them on separate age groups.
- Specific age norms for older adults (ages 56 to 97) have been developed, allowing for accurate IQ estimation in this age group.
IQ Constancy Over Time:
- IQ scores tend to remain relatively stable over time, with no significant changes observed in most between-year comparisons in children aged 5 to 13 years.
Impact of Education on IQ Scores:
- When educational attainment levels are controlled, the decline in mean Verbal IQ with age disappears, although declines in Performance IQ and Full Scale IQ remain.

Conclusion

The research indicates that IQ scores are influenced by a variety of factors, including age, heritability, early childhood development, and education. While IQ scores tend to be stable over time, they can be influenced by environmental factors and educational attainment. Age-adjusted norms and continuous norming techniques provide more accurate estimates of IQ across different age groups. Understanding these dynamics is crucial for accurately assessing and interpreting IQ scores across the lifespan.

Iq percentile chart by age

Summary

Introduction

Key Insights

Conclusion

Sources and full results

The Wilson Effect: The Increase in Heritability of IQ With Age

The heritability of IQ increases with age, reaching an asymptote of 0.80 at 18-20 years of age and continuing at that level well into adulthood, while shared environmental influence decreases across age.

Measurement of Nonverbal IQ in Autism Spectrum Disorder: Scores in Young Adulthood Compared to Early Childhood

Nonverbal IQ scores in individuals with autism spectrum disorder (ASD) generally remain within the average range from age 3 to 19, but actual scores decline from age 2 to 19.

Ages and Stages Questionnaire at 3 Years for Predicting IQ at 5–6 Years

The 36-month Ages & Stages Questionnaire (ASQ) score at 36 months can effectively predict IQ at age 5-6 years, with low maternal education level being a major risk factor for lower IQ in preschool children.

Estimating WAIS IQ from the Shipley Institute of Living Scale using continuously adjusted age norms.

This study developed a reliable and stable procedure for estimating age-adjusted WAIS IQ scores from the Shipley Institute of Living Scale, providing a brief but accurate IQ estimate in clinical and research settings.

A longitudinal study of sex differences in intelligence at ages 7, 11 and 16 years

At age 16, boys have an IQ advantage of 1.8 IQ points over girls, supporting Lynn's hypothesis that males develop higher average intelligence than females.

IQ Constancy and Age

IQ consistency and age show a perfect relationship, with correlations increasing with age, but no sex differences in IQ changes were observed.

Mayo's older americans normative studies: WAIS-R norms for ages 56 to 97

MAYO IQs are very similar to traditional WAIS-R IQs for ages 56-97, enhancing the use of the WAIS-R beyond age 74 and aiding future research designed for older adults.

Childhood IQ's as Predictors of Adult Educational and Occupational Status

Childhood IQ's can predict adult education and occupational status, but not long-term predictions for individual normal children.

Age and intelligence of a group of juvenile delinquents

Boys aged 14 and over have a slightly higher mean IQ than those below 14 years, but no significant differences were found between sexes.

Age and WAIS-R intelligence in a national sample of adults in the 20- to 74-year age range: A cross-sectional analysis with educational level controlled

Intelligence declines in Performance IQ and Full Scale IQ from age 20 to 74, but not in Verbal IQ, even after controlling for education.

Try another search