DefinePK

Abstract

A twin study using 30 identical (Monozygotic MZ) and 30 fraternal twins (Dizygotic DZ) was conducted to assess the role of genotype, environment, and their interaction. All the twins were males and reared together. Raven's Standard Progressive Matrices (SPM) was taken as a measure of general intelligence 'g'. Genotype x environment effect was nonsignificant. Non-iterative least square weighted analysis was applied for goodness of fit for genetic (additive genetic variance DR and dominance HR) and two environmental (within family environment EI and between family environment E2) components. A model comprising additive genetic variance (DR) and within family environmental variance (El) was a good fit to the data, explaining 89.80% of narrowsense heritability. However, much of the variance could be explained only by the additive genetic variance component (DR). Addition of dominance (HR) or between family environment (E2) component failed to explain rest of the variance. It is concluded that general intelligence is largely determined by the genetic factor, particularly the additive genetic variance.