In his discussions of his experiments, Pavlov mentions primarily using a bright light, a tone played on an organ, or a metronome set to a certain pulse to instill conditioned reflexes. Given the established story about using a bell while dogs were feeding I was bemused to read the following in Lecture IV: "In contradistinction to this we must state with regard to acoustic stimuli that very loud sounds such as the violent ringing of a bell did not, in comparison with weaker stimuli, quickly establish a conditioned reflex. It can be assumed that powerful acoustic stimuli call out some other important reaction in the body (e.g., motor), which hinders the development of the salivary response."