title: A source of variance in IQ unique to the lower-scoring monozygotic (MZ) cotwin.
mesh_terms: D004777:Environment; D005260:Female; D006801:Humans; D007361:Intelligence Tests; D008297:Male; D014427:Twins / Q000523:psychology*; D014429:Twins, Dizygotic / Q000523:psychology; D014430:Twins, Monozygotic / Q000523:psychology*