Final answer:
Large-sample studies have found that the personality traits agreeableness and conscientiousness tend to increase as adults age, with agreeableness peaking between 50 to 70 years and conscientiousness increasing through young adulthood into middle age.
Step-by-step explanation:
According to large-sample studies reported in the literature on Big Five personality traits, the personality traits that have been shown to increase as adults grow older are agreeableness and conscientiousness. Research indicates that agreeableness tends to increase with age and peaks between 50 to 70 years. In contrast, conscientiousness increases through young adulthood into middle age, reflecting improved ability to manage personal relationships and careers.