Two studies in Hawaii failed to reveal evidence of heterosis in mental abilities when the offspring of incrosses and outcrosses from various ethnic groups were compared. The first study utilized tests of educational achievement and aptitude applied to all children in grades 4 through 12 in public schools in Hawaii in the period 1967-1970. The second study used the Hawaii Family Study of Cognition cohort of 1818 Honolulu area families given fifteen paper and pencil tests of cognitive ability during 1972-1976. In both studies significant differences in test scores were evident among the ethnic groups, while the HFSC revealed confounding generational differences.
Ashton, Geoffrey C. and Mi, Ming-Pi
"Mental Abilities of Children of Incross and Outcross Matings in Hawaii,"
2, Article 29.
Available at: https://digitalcommons.wayne.edu/humbiol/vol55/iss2/29