Introversion and a single nucleotide polymorphism in PER3 gene: demure female students prevail among carriers of the rare allele

Genetic basis and evolutionary mechanisms responsible for maintaining variation in broad personality traits remain the mysteries. Recently, Extraversion that is the most known broad personality trait has been linked to a variable number tandem repeat polymorphism in PER3 gene. Data collected from 88 female students of the Novosibirsk State Pedagogical University were analyzed to examine associations of a PER3 single nucleotide polymorphism (rs228697) with self-ratings on 172 personality-relevant nouns. These nouns were previously selected for the structuring Russian personality trait descriptors and scoring six broad personality traits regarded as constellations of narrow personality traits. Differences in self-ratings of 20 minor allele carriers and 68 homozygotes for the major allele were revealed for 15 nouns. Twelve of them were associated with just two constellations, Extraversion-Assertiveness and Self-Assurance-Masculinity (8 and 4, respectively). Yes-response was given by the majority (>10) of minor allele carriers to 7 of 15 nouns (“reticence”, “secretiveness”, “modesty”, “reservedness”, “shyness” from Extraversion-Assertiveness, “bashfulness” and “indecisiveness” from Self-Assurance-Masculinity). The results confirmed the link between Extraversion and polymorphism in PER3 gene. For maintaining such underlying genetic variation natural selection might favor two distinct behavioral specializations determined by alternative traits at the poles of a narrow personality dimension, e.g. Boldness vs. Modesty.