The issue of personality development is concerned with the antecedents of personality structure. The field of personality development is part of the area of developmental psychology. Occasionally, prenatal events are important in personality development. More often, complex social events and complex learning shape personality development. The culture in which we are reared, and the pervasive influence of that culture, are very important in personality formation.
Some theories emphasize the crucial effect of early childhood experiences.
Other theories do not believe that early childhood experiences have an indelible effect upon personality structure. The development of complex patterns of human behavior, however, is difficult to study because humans cannot be subjected to the same types of experimental manipulations that other organisms can be subjected to. Such experimental studies are scientifically unethical. Much of what we know about human development is, therefore, based upon correlational and naturalistic studies. The early years of life have thus been studied intensively.