When a ringing bell is presented to a cat, it may evoke a turning of the head toward the sound source. If that same stimulus is repeated over and over again, the probability and magnitude of this orienting response decrease. This phenomenon is called habituation. If a mouse now runs in front of the cat and then the bell is rung again, the cat may reorient to the bell. This phenomenon is called dishabituation. By recording electrical activity in the first central synapse in the auditory system or using another stimulus that elicits an orienting response of the same size, it can be shown that habituation cannot be explained by either sensory adaptation or muscle fatigue (Thompson and Spencer, 1966). Thus, even though the original response no longer occurs, the stimulus still evokes the same electrical activity in early auditory structures...