The Mills Study began in the late 1950s as a part of the program of research on creativity conducted at the Institute of Personality Assessment and Research (IPAR; now known as the Institute of Personality and Social Research, or IPSR). Questionnaires and inventories were administered to representative samples of the senior classes of 1958 and 1960 at Mills College, a private college for predominantly white, middle-class women in Oakland, California. In addition, a subsample was assessed on-site by the IPAR staff. The study was presented as an investigation of "creativity, leadership, and plans for the future in modern young women." Five years after graduation a follow-up was conducted, with the focus still on creativity (Helson, 1967).

At the heart of the Mills Study is an emphasis on a comprehensive understanding of each person as a whole, in multiple contexts. Reflecting this, a wide range of assessment tools have been used in the study. Measures have captured inner factors of the sort proposed by psychologists such as Erikson, Jung, Loevinger, and Vaillant; as well as demographic data. The measurement process has included inventories, scales, questionnaire ratings, diaries, and open-ended material. Standard inventories and scales that have been used include the CPI-D, ACL, and ERQ.

This depth and range of material created an excellent foundation for a shift into a longitudinal study of adult development, which has continued to this day.

During the women's movement, women's roles changed a great deal. Subsequent follow-ups in 1980-81, 1989-90, and 1997-98 added measures related to social roles, cultural influences like women's movement, and other social contexts. See a brief summary of sociocultural context as it relates to our participants' lives in George, Helson, and John,(2011).

The Mills women are now in their early 70s, and we are currently collecting follow-up information from about 100 of the participants who are still alive. We are gathering data about the main events in the women's lives, narrative accounts of late middle age, measures of their feelings about life in their early 70s, their well-being (overall and in various domains), Adjective Check List data, CPI personality data, and demographic information.

(Parts of this history were adapted from Helson, R. H., & Kwan, V. S. Y. (2000). Personality development in adulthood: The broad picture and processes in one longitudinal sample. In S. E. Hampson (Ed.), Advances in Personality Psychology (Vol. 1, pp. 77-106). East Sussex, England: Psychology Press.)