The document provides an overview of child development theories, emphasizing the information processing theory which likens brain function to computer processing, and Urie Bronfenbrenner's ecological systems theory that highlights the interplay between environment and biology in shaping development. It outlines various systems such as microsystem, mesosystem, exosystem, macrosystem, and chronosystem that affect a child's growth. Additionally, it summarizes key 20th-century theories in psychoanalysis, behaviorism, and biology.