Educational psychology dates back to the time of Aristotle and Plato. Plato and Aristotle researched individual differences in the field of education, training of the body and the cultivation of psycho-motor skills, the formation of good character, the possibilities and limits of moral education. Some other educational topics they spoke about were the effects of music, poetry, and the other arts on the development of individual, role of teacher, and the relations between teacher and student. Plato saw knowledge acquisition as an innate ability, which evolves through experience and understanding of the world. This conception of human cognition has evolved into a continuing argument of nature vs. nurture in understanding conditioning and learning today. Aristotle observed the phenomenon of "association." His four laws of association included succession, contiguity, similarity, and contrast. His studies examined recall and facilitated learning processes.