A Reevaluation of the 1990 “Minnesota Study of Twins Reared Apart” IQ Study

In 1990, Thomas J. Bouchard, Jr. and colleagues published the widely cited 1990 “Minnesota Study of Twins Reared Apart” (MISTRA) Science IQ study. To arrive at conclusion that “IQ is strongly affected by genetic factors,” Bouchard omitted their control group reared-apart dizygotic twin (“DZA”) IQ-score correlations. Near-full-sample correlations after study’s 2000 endpoint show monozygotic (“MZA”) DZA did not differ a statistically significant level, suggesting study failed first step in determining scores are influenced heredity. After bypassing model-fitting technique they used most non-IQ MISTRA studies, researchers assumed MZA correlation alone “directly estimates heritability.” This method was based on unsupported assumptions researchers, largely overlooked confounding influence cohort effects. then decided to count environmental influences recognize as influences. I conclude discover cognitive ability across studied population, should be evaluated context psychology’s replication problem.