 Some proponents of the “Leibreiztheorie” (or somatic-stimulus theory) of dreaming attempted to go beyond anecdotal observations to conduct controlled experiments. Weygandt (1893) investigated the influence of various factors including breathing, blood circulation, temperature changes, urge to urinate, sleeping position, and visual or auditory stimulation during sleep on dream content (see Schredl 2010 for details). Singer (1924) proposed experiments on stimulus incorporation in dreams can inform claims on the ontology of dreaming: If dreams are sensations, a particular auditory stimulus should increase the frequency of dreams in nearby sleepers as well as the frequency of sound in their dreams, and it should decrease the range of quality and intensity of these dreams, making them overall more similar and predictable.