Non-genetic factors driving individual differences in reading, writing and numeracy in Australian students: Insights from discordant monozygotic twins

Abstract

Purpose To identify factors other than genetic endowment that influence achievement in reading, writing and numeracy in “high-stakes” testing in elementary and high school students in Australia. Method Monozygotic twin pairs who were consistently discordant in levels of achievement across at least three school grades in one or more of the three academic domains were selected from a large twin sample. Parents were interviewed by a panel to gather facts and insights that could explain the within-pair discordancies. Results Longitudinally stable discordancies were rare (about 5% of pairs), and mostly discordancies did not generalize across academic domains, suggesting a degree of specificity in non-genetic influences. Biological factors, like anoxia in one twin or ear infections in one, figured in about one quarter of cases. Academic self-concept differentiated within pairs, and in some cases a triggering event could be identified such as a prize awarded to one twin but not the other or a teacher of low competence assigned to one twin. Behavioural characteristics, such as perfectionism or its opposite (“near enough is good enough”) and determination to succeed or its opposite (“couldn’t care less”), were identified by parents. Enjoyment of a subject differentiated within pairs as well, with enjoyment sometimes generalized as “creative” or “scientific” orientations. Conclusions Identifying non-genetic external and internal factors affecting literacy and numeracy is important because they offer the best hope for intervention. Ways of bolstering academic self-confidence, determination and enjoyment could help students realize their “natural” potentials.