A student reads a flyer on the campus bulletin board that says a researcher is searching for students to volunteer for a long-term study. Participation includes completing testing that measures traits such as temperament, attitudes, and adaptability, as well as being available for follow-up for the next 10 years. The researcher who is developing this study is most likely

interested in personality development

Explanation:

Personality development: In psychology, the term personality development is defined as an individual's development of the different organized patterns of his or her attitudes and behaviors that generally makes him or her distinctive from that of another person. An individual's personality development arises via the specific ongoing interaction of environment, temperament, and character.

Different psychologists mentioned various stages of personality development in an individual's life.

In the question above, the researcher who is developing the given study is most likely interested in personality development.