Is personality in early and middle adulthood set like plaster or persistently changing? According to McCrae &Costa (1994), "Traits are said to reach maturity by age 30", and not change after reaching 30. By refuting the plaster hypothesis we can determine that personality in early and middle adulthood is persistently changing.
The two versions of the plaster hypothesis states that there should be no change in the Big Five personality traits after age 30 and if there is a change, it should occur more slowly than it did before age 30. The first Big Five traits, Conscientiousness, rejected the first version of the hard plaster but supported that the change after age 30 was slower than that before age 30. Although it supports the plaster hypothesis, it proves that personality ". . . clearly did not stop changing" (Sirvastava, John, Gosling, & Potter, 2003). In Agreeableness, variance from ages 31-60 changed considerably, and the change after age 31 was greater than that of 21 -30. Neuroticism had different results for men and women. Men did not have a notable change before or after 30, support for the plaster hypothesis. Women declined consistently repudiating the plaster hypothesis. Openness is a "clear rejection of the . . . plaster hypothesis"(Sirvastava, John, Gosling, & Potter, 2003). Not only is there an extreme shift after age 30, but the change after 30 was stronger than that of before 30. Extraversion also had different outcomes for men and women. Women had a significant decline after 30, men inclined but it was hardly noticeable. The change of 21-30 was not stronger than that of 21-60, failing to reinforce the plaster hypothesis. .
These findings display that changes were different for each of the Big Five personality traits, and occasionally different for males and females. In fact there was evidence that bluntly challenges the hypothesis. The truth that there is an absence of substantiated evidence for the plaster hypothesis insists that personality in early and middle adulthood is persistently changing.