ABSTRACT

It has taken some homely and simple procedures to reveal beautiful and elegant relations in the behavior of the sensory system. Recently invented procedures have shown that whenever the stimulus increases, the intensity of the sensation grows in accordance with a common basic principle. In every sense modality, sensation is a power function of stimulus. The principle seems clear and straightforward now, but it was a zigzag path with many wrong forks that led finally to the discovery that equal stimulus ratios produce equal sensation ratios. That is the basic principle that underlies the psychophysical law. The ratio invariance tells us that the psychophysical law is a power function.