Brief report: autistic traits in twins vs. non-twins--a preliminary study.

Parents filled out the Social Responsiveness Scale for twin boys and girls and for boys and girls who were not twins.

The team then compared the scores to see if twin status changed how many mild autistic traits were reported.

Twin boys earned slightly higher SRS scores than non-twin boys, hinting at more sub-threshold autistic traits.

Twin girls scored the same as non-twin girls, so the effect was limited to males.

Isaksson et al. (2019) used a co-twin control method and showed that, once family factors are held constant, the link between autistic traits and poor mind-reading disappears. This suggests the slightly elevated SRS scores in Alexander’s twin boys may reflect shared family genetics or environment rather than a true trait spike.

Kupzyk et al. (2011) tracked almost four hundred twin pairs and found clumsiness and autistic traits share roughly two-thirds of their genetic influences, giving a concrete mechanism for why twins—who share DNA—might score a bit higher.

Zubizarreta et al. (2025) also ran a within-twin analysis and saw camouflaging stress effects vanish after family controls, echoing the same “check the family context” warning.

When you see a boy twin hover near the SRS cutoff, remember the score might be nudged up by shared family liability rather than a clinical concern. Re-test, gather developmental history, and compare with co-twin performance before labeling or referring. Use the same caution when twins join social-skills groups; their “autistic” score could be a family echo, not a treatment need.