Modern visualization techniques in science education present a challenge of sorting out the contributions of perception to understanding science. These contributions range over degrees to which perception is influenced by belief (including systematic sets of beliefs which comprise scientific theories) and social setting. This paper proposes a (first-approximation) categorization of these perceptions. A perception is categorized according to the degree of influence on it from belief and social setting. The contributions of perception to understanding scientific phenomena are drawn from the history of the discovery of the secrets of pendulum motion.