Once I read about that theory somewhere:
Alphas are like children, Betas like adolescents, Gammas like adults, Deltas like seniors.
That is certainly correct and quite interesting because the different types even represent different aspects of childhood, adolescence and so on. Does someone have a link where I can read about it?
Alphas - the children
Betas - the adolescents
Gammas - the adults
Deltas - the seniors