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The great American poet Henry Longfellow once wrote, "as the evening twilight fades away, the sky is filled with stars, invisible by day."

Is Longfellow's sentiment a fitting metaphor for aging? New research published in the Journal of Research in suggests Longfellow may have been as a lay psychologist as he was a poet. Personality, in some respects, may become more beautiful as we age.

Psychologists from the United States and Canada examined four dimensions of personality from a sample of 166 mid- to later-life women (ages 43-72). Data were collected in four waves and spanned a 28-year time period (1986-2014).

The researchers were interested in how the personality constructs of generativity, stagnation, ego integrity and despair changed over time. Generativity is defined as active participation in promoting a healthy future for current and future generations. It is defined by one's agreement with self-descriptive statements such as, "Is able to see the heart of important problems," "Behaves in a sympathetic or considerate manner," and, "Tends to proffer advice." Stagnation, on the other hand, refers to the lack of growth of a healthy personality and is defined by statements such as, "Is uncomfortable with uncertainty and complexities," and, "Gives up and withdraws in the face of frustration and adversity." Ego integrity refers to a person's hard-won and in the face of adversity. It is defined by statements such as, "Is calm, relaxed in manner" and, "Is subjectively unaware of self-concern; feels satisfied with self." Finally, despair refers to the absence of ego integrity and is reflected in statements like, "Feels a lack of personal meaning in life," and, "Has hostility toward others."

Charting these four personality dimensions over time, the researchers found that generativity and ego integrity rose steadily from age 43 into one's 60s and 70s. Stagnation, on the other hand, peaked in one's late 50s and then began a downward trajectory that lasted into one's 70s. Out of the four personality dimensions measured, despair peaked earliest (in one's early 50s), but decreased dramatically in one's 60s and 70s.

In other words, the positive facets of personality increase with time while the negative facets recede. The result of this reconfiguration is a healthier personality in later-life than in . The authors write, "The trajectories of each pair of constructs diverged, although at somewhat different points in the life cycle. Despair appeared to decline earlier than stagnation, perhaps either enabling or resulting from a rise in ego integrity, while generativity and ego integrity were both continuing concerns throughout the period. Later, stagnation too declined, perhaps because the continuing later rise of ego integrity engenders a sense of personal development."

The researchers argue that this pattern of results points to a successful resolution of developmental concerns at different stages of life. "Personality," they write, "continues to develop throughout adulthood, with new personality strengths continuing to emerge in these last stages of development."

So, what's the takeaway? It might be as simple as believing it's never too late to see improvement on the horizon. Or, as Longfellow put it, the stars will come out as the evening sky fades away.