Studies Where Gaps Persist Despite Equalized Environments

1. Minnesota Transracial Adoption Study • Design: Black, biracial, and White infants adopted into White, middle-class families in Minnesota. • Findings: • As children, Black and biracial adoptees scored well above national Black averages — strong evidence of environmental uplift. • By adolescence, average scores diverged again: White adoptees ≈106, biracial ≈99, Black adoptees ≈89. • Critiques: • Equalizing family SES ≠ equalizing peer environment, discrimination, or racial identity stress. • Some adoptees were placed later or under selective conditions. • Attrition and different test batteries complicate comparisons. • Counters: • Even within the same families, mean differences persisted into adolescence, suggesting environment raises averages but doesn’t fully eliminate gaps in this design. • The pattern is consistent across multiple test batteries and waves. • Even environmental theorists acknowledge this is the hardest case for their position.

Citation: Scarr & Weinberg (1976, Intelligence); Weinberg, Scarr & Waldman (1992, Intelligence).

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2. Texas Adoption Project • Design: Hundreds of adoptees reared in middle-class homes; IQs of both biological and adoptive parents measured. • Findings: • Adoptees’ IQs resembled biological parents more than adoptive parents, showing strong heritability. • At the same time, adoption into advantaged homes raised average scores. • Critiques: • Sample was mostly White, so not directly a race-gap study. • Possible selective placement inflated genetic resemblance. • Counters: • Demonstrates the principle: environment lifts the whole distribution, but genetic differences remain visible within the same rearing context. • Longitudinal data show both genetic and environmental effects over time.

Citation: Horn, Loehlin & Willerman (1979, Behavior Genetics); Loehlin, Horn & Willerman (1989, Personality and Individual Differences).

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3. SES-Controlled Large-Scale Datasets • Design: National longitudinal samples (e.g., NLSY/AFQT, NAEP) where Black and White individuals are compared after matching or controlling for parental education, income, and related SES variables. • Findings: • Gaps shrink substantially but often do not vanish. Residuals of ~0.5 SD (7–10 IQ points) remain in some analyses. • Critiques: • SES controls are incomplete — they don’t capture school quality, wealth, neighborhood safety, health disparities, toxin exposure, or cumulative disadvantage. • Gaps have narrowed markedly over decades, inconsistent with a fixed genetic explanation. • Counters: • Residuals are real and cannot be dismissed; they represent variance unexplained by measured SES. • Long-term trend data (e.g., NAEP) show that policy, resources, and social changes can close much of the gap.

Citation: Herrnstein & Murray (1994, The Bell Curve); Neal (2006, Handbook of the Economics of Education); Reardon, Kalogrides & Shores (2019, American Journal of Sociology); NAEP Long-Term Trend Data.

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4. Smaller Adoption and Foster Care Studies • Design: Transracial adoption in Britain and Europe; biracial children reared in Japan. • Findings: • Minority adoptees gained substantially over national averages. • In some cases, their averages remained slightly below White adoptees in the same homes. • Critiques: • Small sample sizes, often nonrandom placements, and institutional rearing environments complicate conclusions. • Counters: • Consistency across multiple settings shows substantial environmental effects; where gaps persist, they tend to be smaller than national averages.

Citation: Tizard (1972, Race); Tizard & Phoenix (1974, New Society); Eyferth (1961, Archiv für die gesamte Psychologie); Nakao & Treas (1994, Social Science Research).

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The Bigger Picture • Persistent Gaps: Some adoption studies and large-scale SES-controlled datasets show that residual group differences remain even under attempts to equalize rearing conditions. • Critiques: These designs don’t fully equalize environment — schooling, peer context, health, and discrimination are all hard to control. • Counters: The fact that residuals persist shows we cannot dismiss genetic explanations entirely. At the same time, environmental levers (education, health, toxins, nutrition, early interventions) have been shown repeatedly to narrow or close most of the gap.

ChatGPT wrote this according to my specifications.

I will. On a train rn. I can cite them tonight. Hopefully you’ll respond.

Don’t call me dumb just because I disagree with your point. Keep the conversation civil and stop acting like an immature child or find another place to voice your opinion without insulting other people.

Common sense says many things about genetics. In fact it’s the basis behind my entire premise which you didn’t even address. Genetics plays a role in the physicality and even temperament of a race (testosterone is measurably different across races). What black magic makes intelligence the only factor that is independent of race? Common sense says it’s a factor.

Common sense also says environment is the greater factor. If a person lacks practice or education vs. a person who practices math puzzles everyday. Obviously that is the bigger causal factor by common sense.

Both are factors by common sense. Environment is the bigger factor also by common sense but by that same reasoning genetics is not insignificant. The best way to put it is that environment influences IQ but genetics influences potential.

Why appeal to common sense? Because there’s lack of solid causal evidence. Evidence exists, but the replication crisis and the lack of causal experimentation makes all the tests not as solid as the correlative tests.

The stupidest thing here is that we are not in disagreement on what the evidence points too. It’s just I’m able to rely on induction and logic to predict conclusions where scientific evidence is lacking while you’re entire model of the world is essentially “if the science doesn’t exist then it must not be true“

If the science doesn’t exist, it means it’s unknown. I hope this was educational for you.

I’ll point to some resources when I have time. Im currently not able to cite them atm.