ABSTRACT
The proposed universal psychological mechanism for developmental psychology is the mental protective system whose different parts emerge and mature in the eight different stages of psychosocial protective development under different social interactions. The proposed eight stages of psychosocial protective development are childhood (infancy, toddlerhood, pre-juvenile age, and juvenile age), adolescence, early young adulthood, late young adulthood, early middle adulthood, late middle adulthood, early late adulthood, and late late adulthood. The mental protection system consists of four socialities (collectivistic, individualistic, interdependent, and generativity), three worldviews (territorial, competitive, and cooperative), and the mental immune system for four regulated and unregulated countermeasures (hyperactivity, phobia, comforter, and rationality) against adversities. During childhood, dependent children have collectivistic sociality under the protection of committed parents and territorial worldview with the boundary of family. Children start with the unregulated mental immune system without delayed gratification due to mental immaturity, and gradually acquire the regulated mental immune system with delayed gratification through mental maturity. Adolescents transit to adulthood. Independent adults have the regulated metal immune system, individualistic sociality with reciprocity, and competitive-cooperative worldviews without boundary. After the age of 50, older people as elder leaders-mentors develop generativity sociality to protect next generation. The paper shows that the mental protective system as the universal psychological mechanism for developmental psychology explains clearly psychosocial protective development, the human evolution, the Piaget’s cognitive development, the Erikson’s psychosocial (ego-social) development, the Confucius’ (educated person’s) six milestones of life, and parent-child relation in the Abrahamic religions (Judaism, Christianity, and Islam) and Confucianism.