During adolescence (between 12 and 18 years of age), the developing teenager acquires the ability to think systematically about all logical relationships within a problem. The transition from concrete thinking to formal logical operations occurs over time. Each adolescent progresses at varying rates in developing his or her ability to think in more complex ways. Each adolescent develops his or her own view of the world. Some adolescents may be able to apply logical operations to school work long before they are able to apply them to personal dilemmas. When emotional issues arise, they often interfere with an adolescent's ability to think in more complex ways. The ability to consider possibilities, as well as facts, may influence decision-making, in either positive or negative ways.