Analysis · Education
Why Identical Twins Cannot Fully Settle the Value of University
By AWEI · AI-compiled · Published · Analysis prepared · 1 source · doi.org
Two identical twins take different educational paths. Can their later paychecks reveal what university is worth? The comparison looks unusually persuasive: shared genes and upbringing remove many competing explanations. But a 2011 study found that the twins already differed before university began.
Kevin C. Stanek, William G. Iacono and Matt McGue examined this assumption using the Minnesota Twin Family Study. Their observational analysis included 869 identical and 463 fraternal twin pairs. In 133 identical pairs, one twin reported attending a four-year university by age 20 while the other did not. This tested a research method; it did not randomly assign education.
The crucial evidence came from assessments at age 17. Within those identical pairs, the future university attendee had, on average, higher verbal IQ, higher school grades and a higher score on a personality composite designed to predict university attendance. These differences were generally small but statistically significant. Academic motivation did not differ significantly within those pairs.
Across individuals, verbal IQ, grades and the personality composite also had modest associations with income at age 29. That creates a potential alternative explanation for later earnings differences: some relevant characteristics preceded university. The study did not establish how much these characteristics caused any pay gap, or calculate a definitive causal return to education.
The income comparison was particularly limited. Only 48 identical pairs with different university attendance histories had income data and both twins working full time. Their earnings difference was not statistically significant, which does not establish that university has no financial benefit. The sample was largely white and from Minnesota, and the education measure captured attendance by a particular age, not degree completion.
For evaluating education claims, the useful question is what the comparison actually controls. Identical twins substantially reduced measured differences between attendees and non-attendees, but did not erase them. A credible earnings claim still needs attention to characteristics measured before education and to the uncertainty remaining afterward.
Sources used for this article (1)
Direct links to the publisher reports used to prepare this article.
- Source 1
- Returns to Education: What Do Twin Studies Control? Kevin C. Stanek, William G. Iacono, Matt McGue
