Sibling‑reports cut hair‑color bias

Ask respondents about their siblings’ hair colour rather than their own to reduce self‑report and attention biases when measuring visible phenotypes; environmental effects like sun‑exposure and ambiguous categories (blonde vs light brown) can otherwise create artifactual sex differences. A targeted sibling survey can reveal whether popular claims (e.g., women are far likelier to be blonde or redheaded) survive tighter within‑family controls. — Simple within‑family survey designs can overturn sensational, media‑amplified claims about sex differences and so should be used before such claims shape cultural and policy conversations.