Behavior Genetics

, Volume 14, Issue 6, pp 579-585

First online:

Effects of inbreeding on Raven Matrices

  • Nirupama AgrawalAffiliated withDepartment of Psychology, University of Rajasthan
  • , S. N. SinhaAffiliated withDepartment of Psychology, University of Rajasthan
  • , Arthur R. JensenAffiliated withSchool of Education, University of California

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Indian Muslim school boys, ages 13 to 15 years, whose parents are first cousins, were compared with classmates whose parents are genitically unrelated on the Raven Standard Progressive Matrices, a nonverbal test of intelligence. The inbred group (N=86) scored significantly lower and had significantly greater variance than the noninbred group (N=100), both on raw scores and on scores statistically adjusted to control for age and socioeconomic status. Genetic theory predicts both of these effects for a polygenic trait with positive directional dominance.

Key Words

inbreeding depression intelligence Raven matrices heritability polygenic theory