Figure 1.

Stimulus protocols for testing if ferrets automatically distinguish harmonic complex tones from inharmonic complex tones. (Top) In baseline sessions, ferrets were trained to detect pure-tone targets terminating a one-to-six-stimulus sequence of inharmonic complex tone reference sounds. Cues available for distinguishing the targets from the references were (i) differences in the quality of perceptual fusion and (ii) differences in timbre. (Bottom) In probe sessions conducted after ferrets attained proficiency in baseline sessions, a small fraction of the reference sounds were replaced by harmonic complex tone probe sounds. If harmonic complex tones were perceptually fused, then they might have been confused occasionally with the pure-tone targets, thereby indicating that ferrets can automatically distinguish harmonic tones from inharmonic tones.