Full context:   Erik H. Erikson (1901–1993) explained the challenges throughout the life course. The first stage in the life course is infancy, where babies learn trust and mistrust. The second stage is toddlerhood where children around the age of two struggle with the challenge of autonomy versus doubt. In stage three, preschool, children struggle to understand the difference between initiative and guilt. Stage four, pre-adolescence, children learn about industriousness and inferiority. In the fifth stage called adolescence, teenagers experience the challenge of gaining identity versus confusion. The sixth stage, young adulthood, is when young people gain insight into life when dealing with the challenge of intimacy and isolation. In stage seven, or middle adulthood, people experience the challenge of trying to make a difference (versus self-absorption). In the final stage, stage eight or old age, people are still learning about the challenge of integrity and despair.< This concept has been further developed by Klaus Hurrelmann and Gudrun Quenzel using the dynamic model of "developmental tasks".