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Intelligence and Family Size in Libya

Alsedig Abdalgadr Al-Shahomee and Richard Lynn


The Standard Progressive Matrices (SPM) was administered to a sample of 720 school students aged 13 to 18 years (mean age 15.5 years) in Libya. The results show (1) males obtained higher scores than females in all age groups although none of these is statistically significant; (2) the sample obtained a British-scaled IQ of 82.3; (3) there was a negative correlation between SPM scores and number of siblings of -.421. This may indicate less favorable conditions for intellectual development in larger families, or differential reproduction favoring less intelligent parents. Assuming differential reproduction by intelligence is the mechanism, the decline of genotypic intelligence can be estimated as approximately 2.75 IQ points a generation.

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