In your 20s it’s quantity, in your 30s it’s quality: The prognostic value of social activity across 30 years of adulthood.

Social connection, a leading factor in the promotion of health, well-being, and longevity, requires social knowledge and the capacity to cultivate intimacy. Life span development theorists have speculated that social information-seeking goals, emphasized at the beginning of early adulthood, give way to emotional closeness goals in later stages of early adulthood. Drawing on developmental theory (Baltes Baltes, 1997), this 30-year prospective study assessed social activity at age 20 and age 30 with experience sampling methods, and psychosocial outcomes (social integration, friendship quality, loneliness, depression, and psychological well-being) at age 50. Results supported the hypothesis that the quantity (but not the quality) of social interactions at age 20, and the quality (but not the quantity) of social interactions at age 30 predict midlife psychosocial outcomes. Longitudinal structural models revealed that age-20 interaction quantity had a direct, unmediated effect on age-50 social and psychological outcomes. The effects of age-20 interaction quality on midlife outcomes, on the other hand, were mediated by age-30 interaction quality. Our findings are consistent with the idea that selection and optimization serve important functions in early adulthood, and that engaging in developmentally appropriate social activity contributes to psychosocial adjustment in the decades that follow.