ABSTRACT
For a considerably long period, psychology was mainly interested in the question of how personality changes as a result of maturation and life experience. A remarkable series of longitudinal studies has shown that this question is misleading because personality happens to be very stable. Researchers have now agreed that the basic structure of personality is relatively stable through the individual’s life: “Once an extravert, always an extravert” as Eysenck said in 1997 (p.201). William James was quite right in suggesting that personality is fully developed by age 30 and will remain stable, being set like plaster from this time on (James, 1890). Across instruments, sexes, age, and test-retest intervals, there is a consistent evidence of substantial stability of all basic personality traits, with median correlation ranging from .50 to .80 for intervals as long as 30 years. When these correlations are corrected for unreliability of measuring instruments, they can be close to .90 or above (Costa & McCrae, 1988).
