Life Span Growth and Development-Oprah Winfrey As we grow up, different factors influence our behavior and, ultimately, how our lives turn out. This influence starts at a young age when an infant begins to grip the finger of his caretaker. A familiar face gives the infant a sense of security and comfort. Teenagers start to make more involved decisions like who to invite to a birthday party. When teenagers get older, they begin to get passionate about more intimate issues like politics, arts, or the environment. This trend continues until adulthood, where an individual is required to make family and career decisions. An external factor influences every decision we make in our lives, be it political, social, or economic factors.