Mechanistic reductionism- simplifies complex human behaviour to mechanics of mind (e.g, conflict between id, ego & superego) & early childhood experience (psychosexual stages). Ignores other important influences on behaviour (e.g, biochemistry & genetics). E.g, in 50s & 60s one of main explanations for autism was distant mothers (autism was withdrawal from the lack of involvement). Oversimplification of underlying processes of autism.