Theorizing about the nature, control, and implications of adolescent development has been going on for at least 2000 years in Western culture, utilizing observational and essentially irrelevant and indiscriminate measurement research techniques. However, because these investigations were flawed by prejudgment and excessive subjectivity, the findings tended to be disorganized, irrelevant, incredible, non-explanatory and platitudinous. The most scientifically significant conceptual and research approach to adolescent development in my lifetime was made by Muzafer Sherif (Sherif | Theory and Problems of Adolescent Development Third Edition by David P Ausubel, Hardcover | Indigo Chapters