Petar Milojev and Chris Sibley report that the stability of personality increases through youth, peaks in mid-life and then gradually reduces again into old age, presumably in response to the variations in social and biological pressures we experience at the different stages of life.
The researchers asked their participants to complete short personality questionnaires twice, two-years apart. The questionnaires measured the Big Five traits (extraversion, agreeableness, conscientiousness, neuroticism, and openness to experience) and also an honesty-humility factor. The researchers then looked to see how the "rank-order stability" of people's traits (how their scores ranked compared to other people's) varied across that two-year gap, and how this stability varied as a function of age.
The participants' personalities showed "impressive" stability, as you'd expect since personality is meant to be a description of people's pervasive traits. Extraversion was the most stable trait, and agreeableness the least. However, the key finding was that personality stability varied through the lifespan, increasing from the 20s to the 40s and 50s, and then declining towards old age, up to age 80. This broad pattern was found for all traits, except for agreeableness, which showed gradually reduced stability through life. For conscientiousness, openness to experience, and honesty-humility, trait instability had returned at the oldest age to the levels seen at the youngest age.
For the five traits that showed an inverted U-shape pattern of changing stability through life, Milojev and Sibley found that the specific point of peak stability varied - extraversion and neuroticism showed highest stability in the late 30s, while the other traits (openness, honesty-humility, and conscientiousness) showed peak stability in the late 40s, early 50s. The researchers said these "domain specific" variations in personality stability point to different environmental and social demands influencing different personality traits to varying degrees at slightly different times of life.
"This report further highlights the need to test ... the effects of events that might cause the lower stability [of personality] in younger and older adulthood," the researchers said. "In addition our finding of systematically different peaks in stability between different personality dimensions suggest the need to further investigate age-specific changes in environmental and social pressures that are associated with such domain-specific effects."
Milojev, P., & Sibley, C. (2014). The stability of adult personality varies across age: Evidence from a two-year longitudinal sample of adult New Zealanders Journal of Research in Personality, 51, 29-37 DOI: 10.1016/j.jrp.2014.04.005
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Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.