International Journal of Comparative Psychology

Rats were trained under go-no go conditions to discriminate among complex acoustic stimuli (short musical sequences). In order to investigate the role of different stimulus attributes in discriminative performance, two short musical excerpts differing in their melodic pattern, but maintaining the number, pitch, and duration of notes constant were provided in two different timbres, to obtain four different complex auditory stimuli. According to the experimental condition, the discriminative stimuli were, therefore, different in structure, in timbre or in both aspects. The animals were able to discriminate efficiently among the musical sequences only when cues furnished by timbre were available, whereas melodic differences made no difference. In the experimental setting used, the rat's discrimination of complex auditory stimuli appears, therefore, to be based neither on the melody nor on a compound of melody and timbre,but simply on the properties of the timbre of the stimuli.