one conclusion that can be drawn from the studies regarding rat learning and brain structure (greenough, et al., 1990; wallace, et al., 1992) is that early psychological experience affects the development of the nervous system and will absolutely determine whether or not the individual will develop a psychological disorder later in life. early psychological experience does not result in physical changes to the nervous system but can still influence whether or not one develops a psychological disorder. early psychological experience affects the development of the nervous system and influences vulnerability to psychological disorders later in life. early psychological experience has little to do with brain structure or later development of psychopathology.