Frequency range size and the frequency range constraint in auditory perception by European starlings (Sturnus vulgaris)

We report data bearing on the ability of European starlings to generalize a serial auditory pitch pattern discrimination from one frequency range to another. In earlier research (e.g., Hulse & Cyrix, 1985), European starlings failed to generalize such a discrimination from one 1-octave range of frequencies to another 1-octave range above or below the initial training range. The starlings thus demonstrated a hitherto unknown phenomenon, thefrequency range constraint. In the present research, we first explored the frequency limits over which the range constraint might hold. The constraint was obtained after initial training in both a narrow (1÷2-octave) and a wide (3-octave) training range. The latter range encompasses a substantial portion of the entire frequency range audible to starlings. Therefore, the constraint is independent of the size of the training range. No known principles of stimulus discrimination or generalization account for the constraint. We also obtained further evidence on starlings’ sensitivity to relative pitch in auditory pattern perception. We used probe stimuli to explore pattern discrimination in narrow local regions of the wide frequency range. The probe data showed that, in spite of the frequency range constraint, the starlings were able to process pitch patterns on a relational basis. The results join earlier data indicating that both absolute and relative pitch processing may be involved in the natural auditory communication of songbirds.