PERSONALITY STABILITY AND CHANGE IN EARLY ADULTHOOD - A BEHAVIORAL GENETIC-ANALYSIS

Seventy-nine monozygotic and 48 same-sex dizygotic twin pairs completed the Multidimensional Personality Questionnaire twice, averaging 20 years of age at first and 30 years at second testing. There were significant mean decreases in measures of Negative Emotionality (NE), increases in measures of Constraint (CO), but no significant mean changes for measures of Positive Emotionality (PE). Variance decreased for measures of NE but remained stable for measures of PE and CO. Biometrical analyses revealed that (a) NE variance reduction was due to diminishing genetic influences, (b) personality stability was due largely to genetic factors, and (c) although some evidence for genetic influence on personality change was observed, change was determined largely by environmental factors. It is concluded that the stable core of personality is strongly associated with genetic factors but that personality change largely reflects environmental factors.