Can a Sensory System be Specified by Its Internal Noise?

The detection model is used to describe the detection of scarcely discernible noiseless signals by human observers. Detection is hampered by an internal noise generated by the sensory system itself. In the present study, it appears that increments of loudness of a tone and increments of intensity of a light can be detected independently and simultaneously. Here, the internal noise is specific for the system responsible for this detection. On the other hand, detection of an increment in duration of visual and auditory signals is completely correlated. This correlation and the similarity of the detectability of the two kinds of signals indicate that a “duration center” exists, serving to estimate the duration of both visual and auditory signals. The methods developed are useful for identification of separate or common parts of sensory systems.