Peterson Reports Identical Twins' IQs Converge With Age Regardless of Environment

What was said

"If you take twins, identical twins separated at birth, and you test them repeatedly for IQ as they age, what you'd expect is that their IQs would get more different as their experiences diverge. That isn't what happens. What happens is that as they age, their IQs get more similar until regardless of how they were raised, by the time they're 60, if you test one twin and the other, they're so similar that it's like you test the same person twice."

Jordan Peterson described research showing that identical twins separated at birth show increasingly similar IQs as they age, with near-identical scores by age 60 despite different upbringings. This counterintuitive finding contradicts expectations that divergent environments would produce different cognitive outcomes. Peterson used this to illustrate the extreme stability of IQ across the lifespan and the limited role of environment in determining intelligence.