Adulthood transitions which are defined by personal agency and deliberately charted growth opportunities in intellectual, occupational, and psychosocial domains are called

These are called developmental individualization. The developmental individualization is the own educational, social and cultural experiences in order to develop their identity, including their own sense of life and its purpose. This experience is unique and ends defining identity in emerging adulthood.

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The best sociological research method would have to be using experiments although it has some disadvantages as well