One of the striking features of the field of science education as represented in the chapters in this Handbook is that it is influenced by the prevailing learning theory of the day. Few would argue that perspectives on learning have changed drastically over the past 100 years. Even the most superficial analysis indicates at least five "general families" of learning theory held dominance in educational matters over the part century-mental discipline. natural unfoldment, apperceptions, behaviorism, and cognitive science, These differing perspectives have influenced how science education researchers view learning, teaching, and the assessment of both.