Behaviorism is a theory of learning that believes all behaviors are acquired through conditioning by the environment, not innate or based on internal mental states. According to behaviorism, learning is achieved through rewarding correct responses and reinforcing behaviors. In education, this led to an emphasis on direct instruction to achieve rigidly defined objectives, rote memorization, repetition of skills, and adherence to procedures over understanding or situated learning. Critics argue this behaviorist approach promoted a teacher-centered model of instruction that dominated 20th century classrooms.