Perception of missing fundamentals in zebra finches and Bengalese finches

Perception of missing fundamental is widespread in vertebrate animals but seldom it is discussed with the relationship with vocal signals used by the animals. We tested the perception of missing fundamentals in two species of closely related finches with widely different vocal signals. Zebra finches and Bengalese finches were trained, in a Go-Nogo operant task, to discriminate between two harmonic complexes that were constructed by adding integer multiples of a 400 Hz or a 652 Hz. Both stimuli produced the perception of missing fundamentals to human listeners. After the birds learned the task, 4 sine waves, the fundamental frequency of each of the training stimuli and the geometric average frequency of each, were presented as probe stimuli along with the original training stimuli. Both species responded more to the missing fundamental of the Go stimuli than to that of Nogo stimuli. However, both species of birds responded more to the geometric averages of the stimuli than to the missing fundamentals. Thus, in these birds, the perception of the spectral pitch is dominant over the perception of the periodicity pitch and this tendency was not dependent upon the types of vocalizations each species produced.