Average IQ scores by age
Pro Research Analysisby 
Searched over 200M research papers
Age and Average IQ Scores: Key Patterns
IQ Score Changes by Age Group
Research shows that IQ scores generally increase with age during childhood and adolescence, reflecting cognitive development and learning. For example, a study of Sudanese children aged 9 to 13 found a relatively fast age-related increase in cognitive test scores, even compared to British norms, though the overall average IQ was lower in this population (67–68) . In Cambodia, school students aged 6 to 18 had average IQ scores near 100, with scores rising with age and school grade . These findings suggest that as children grow older, their IQ scores tend to rise, at least through adolescence 610.
Stability and Variability of IQ Scores Over Time
While IQ scores tend to increase with age in childhood, their stability over time can vary. Longitudinal studies have found that individual IQ scores can fluctuate significantly before adulthood. For instance, a study of Guatemalan high socioeconomic status individuals showed that 59.5% experienced IQ score changes greater than one standard deviation during childhood, and pre-adult IQ explained only 12% of the variance in intelligence scores at ages 64–76 . However, other large-scale studies, such as the Scottish Mental Surveys, found that IQ differences measured at age 11 showed notable stability into old age, though some cognitive changes and sex differences in aging were observed .
Factors Influencing Average IQ Scores by Age
Socioeconomic and demographic factors play a significant role in average IQ scores across age groups. Parental education, especially maternal education, is a strong predictor of children's IQ scores, as shown in a study of over half a million 15-year-olds from 74 countries . School motivation, self-determination, and academic confidence also significantly predict IQ scores in adolescence . Additionally, studies in Brazil found that increases in average IQ scores over time were more pronounced among women and those from families with moderate income, and were associated with mothers aged 20 or older at the time of birth .
The Role of Schooling and Education
Schooling has a substantial effect on IQ scores, particularly during adolescence. A study in Norway demonstrated that increasing compulsory schooling from 7 to 9 years led to a significant rise in IQ scores measured at age 19, highlighting the impact of education on cognitive development during the teenage years .
Comparability and Measurement of IQ Scores Across Ages
Different intelligence tests tend to correlate well at the group level, but individual scores can vary depending on the test used, especially for those with above- or below-average IQs . The use of ratio IQs (RIQ) as a substitute for standard IQ scores is problematic, as RIQs tend to overestimate IQ in younger children and underestimate it in older children, making them unreliable for tracking IQ across ages .
Conclusion
Average IQ scores generally increase with age during childhood and adolescence, influenced by cognitive development, education, and socioeconomic factors. However, individual IQ scores can fluctuate before adulthood, and the stability of these scores into later life varies. Parental education, school motivation, and access to schooling are key factors that shape average IQ scores by age. When interpreting IQ scores across different ages, it is important to consider the type of test used and the broader context of the individual's environment and educational opportunities 23456789+1 MORE.
Sources and full results
Most relevant research papers on this topic