chapter  6
The Minnesota Study of Twins Reared Apart II
IQ and Personality Studies
Pages 23

This chapter examines the publications reporting MISTRA data in the two main areas of TRA study investigation: IQ and personality. It focuses on the Achilles heel of the twin method, which is the assumption that MZTs and DZTs experience similar or equal childhood and adult environments. Human behavioral genetics has been an insufficiently self-critical discipline. Behavioral geneticists and psychometrists view IQ tests as a measure of general intelligence. According to Bouchard and colleagues, 'The study of IQ is paradigmatic of human behavior genetic research'. In the publication Bouchard and colleagues presented a figure showing 'correlations of IQ, for adults, for five critical kinship relationships under two conditions of rearing, together and apart', with DZA pairs constituting one of these 'critical kinship relationships'. The CPI is also a widely used psychological test, and is said to assess 'folk concepts' and normal personality characteristics.