Evidence for the Scarr-Rowe Effect on Genetic Expressivity in a Large U.S. Sample

Area of Science:

• Behavioral Genetics
• Human Behavioral Genetics
• Psychiatric Genetics

Background:

• The Scarr-Rowe effect describes a gene × environment (G×E) interaction where IQ heritability is reduced in individuals with lower socioeconomic status (SES).
• Understanding G×E interactions is crucial for explaining individual differences in cognitive abilities and their developmental trajectories.

Purpose of the Study:

• To investigate the Scarr-Rowe effect using the continuous parameter estimation model (CPEM) in a large, genotyped adult sample from the Wisconsin Longitudinal Study.
• To operationalize the differential expressivity of polygenic scores for educational attainment and IQ (EA3) on the phenotype of IQ across the full range of SES.

Main Methods:

• Employed the continuous parameter estimation model (CPEM) on a large genotyped adult sample (Wisconsin Longitudinal Study).
• Utilized a parental SES factor-weighted composite to measure childhood SES.
• Analyzed gene × environment (G×E) interactions between polygenic scores (EA3) and parental SES on IQ.

Main Results:

• Found significant evidence for the Scarr-Rowe effect: the genetic expressivity of EA3 on IQ increased with parental SES (β = 0.08, p = 4.71×10-10).
• The effect was consistent across male and female subsamples and robust to statistical adjustments for SES measurement.
• CPEM provided greater statistical power to detect the small-magnitude G×E effect compared to conventional two-way interaction models.

Conclusions:

• The study confirms the Scarr-Rowe effect, demonstrating that genetic influences on IQ are modulated by socioeconomic status.
• CPEM is a powerful tool for detecting subtle G×E interactions, offering advantages over traditional methods in human behavioral genetics research.
• Findings highlight the complex interplay between genetic predispositions and environmental factors in shaping cognitive abilities throughout the lifespan.