The primary finding of the Minnesota Study of Twins Reared Apart was that genetic factors play a very strong role in shaping psychological traits such as intelligence, personality, interests, and attitudes, and that being raised together in the same home adds surprisingly little extra similarity.

Core result in simple terms

Researchers found that identical twins who were separated in infancy and raised in different families grew up to be about as similar in key traits as identical twins raised together.

This pattern suggested that heritability is high for many traits , and that shared family environment (same home, parents, etc.) has only a modest effect on adult differences for those traits.

What traits were strongly genetic?

Across more than 100 pairs of separated twins studied over about two decades, researchers reported strong genetic influence on multiple domains.

  • Intelligence (IQ scores of identical twins reared apart were highly correlated, often around 0.7–0.75).
  • Personality traits such as extraversion, emotional stability, and other standard personality dimensions.
  • Interests, social attitudes, and some life-style habits (including things like leisure activities and even aspects of posture).
  • Additional findings also pointed to genetic influence on variables like religiosity, well‑being, and, in some reports, sexual orientation.

Nature vs. nurture message

From a nature–nurture perspective, the study became famous because it shifted expectations toward a larger role for nature (genes) in many psychological outcomes.

At the same time, the researchers noted that environment still matters, but much of its impact seems to come from unique, individual experiences rather than simply sharing the same household.

TL;DR: The Minnesota twins reared apart study concluded that identical twins grow strikingly similar in intelligence, personality, and many life preferences even when raised in different families, implying a strong genetic contribution and a relatively small added effect of being reared together.

Information gathered from public forums or data available on the internet and portrayed here.