What you learned in school
Developmental psychology textbooks taught that children are born as "blank slates" (tabula rasa) with no innate characteristics, abilities, or predispositions. Students learned that all personality traits, intelligence, and behavior patterns came entirely from environmental influences and learning experiences. This theory, popularized by John Locke, was presented as scientific fact in psychology courses, with the nature versus nurture debate heavily weighted toward nurture as the sole determining factor in human development.
What we know now
Developmental psychology taught that children are born as "blank slates" (tabula rasa) and that all behavior, personality, and abilities come from environmental influences and learning. Nature versus nurture was seen as entirely nurture. Modern research shows that children are born with innate predispositions, temperaments, and genetic influences that interact with environmental factors. Twin studies and adoption studies demonstrate significant genetic components to personality, intelligence, and behavior. Development results from complex interactions between genetic predispositions and environmental influences, not just environmental shaping of blank slates.