Child IQ development with age
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Patterns of Child IQ Development with Age
Research shows that a child's IQ can change significantly as they grow. In a large longitudinal study, children changed an average of 28.5 IQ points between ages 2.5 and 17, with about one in seven children experiencing shifts of more than 40 points. These changes are not random; most children follow simple patterns of increase or decrease, with major changes often happening around ages 6 and 10. Family environment, including how much parents try to accelerate development and their discipline style, can influence these patterns, even after accounting for parental education and IQ. However, siblings do not necessarily show similar patterns of IQ change, and twins or triplets tend to have lower and less variable IQs than single-born children .
Early Developmental Milestones and Later IQ
Developmental milestones in the first two years of life, especially language skills, are strong predictors of IQ at ages 5 to 6. By 24 months, these milestones can explain about 20% of the differences in later IQ. Children who are gifted or have disabilities can often be identified by differences in early language and other cognitive skills as early as 8 to 12 months .
Brain Activity and Long-Term IQ Outcomes
Resting brain activity in early childhood is linked to IQ in late adolescence. Higher levels of certain brain wave patterns (theta EEG power), which indicate atypical development, predict lower IQ at age 18. Early interventions, such as moving children from institutional care to foster care, can improve both brain activity and later IQ, highlighting the importance of early supportive environments 36.
The Role of Schooling and Age in IQ Development
Schooling has a greater impact on the increase in intelligence test scores than age alone. The effect of formal education is especially strong for verbal abilities. This suggests that the environment provided by schooling is a key driver of IQ development during childhood .
Physical Growth and Cognitive Development
Postnatal growth, measured by height at ages 9 and 13, is a significant predictor of IQ at age 11, even after accounting for socioeconomic status. Birth weight, however, does not show a strong link to later IQ. This suggests that ongoing growth and nutrition during childhood are important for cognitive development .
Genetic and Environmental Influences
Both genetic factors and early childhood stimulation independently affect IQ at age 6. Early cognitive stimulation from parents and the home environment, as well as genetic potential, each contribute to a child's intellectual development, but they do not appear to interact with each other .
Stability and Long-Term Impact of Childhood IQ
IQ measured in childhood is relatively stable and can predict educational and occupational outcomes in adulthood, as well as health and survival into old age. However, while childhood IQ is a good predictor, it is not perfect for forecasting individual outcomes over long periods 710.
Environmental Exposures
Some studies have looked at whether prenatal exposure to environmental chemicals, such as perfluoroalkyl substances (PFASs), affects child IQ. Overall, there is no consistent evidence that these exposures have a strong effect on IQ at age 5, though more research is needed for older ages and other cognitive outcomes .
Conclusion
Child IQ development is shaped by a complex mix of early milestones, brain development, schooling, physical growth, genetics, and environment. While IQ can change significantly during childhood, especially around key ages, supportive environments and early interventions can have lasting positive effects. Both genetic and environmental factors play important but independent roles in shaping a child's intellectual growth.
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