Small songbirds have a difficult analysis problem: their head is small compared to the wavelengths of sounds used for communication providing only small interaural time and level differences. Klump and Larsen (1992) measured the physical binaural cues in the European starling (Sturnus vulgaris) that allow the comparison of acoustical cues and perception. We determined the starling's minimum audible angle (MAA) in an operant Go/NoGo procedure for different spectral and temporal stimulus conditions. The MAA for broadband noise with closed-loop localization reached 17°, while the starling's MAA for open-loop localization of broadband noise reached 29°. No substantial difference between open-loop and closed-loop localization was found in 2 kHz pure tones. The closed-loop MAA improved from 26° to 19° with an increase in pure tone frequency from 1 to 4 kHz. This finding is in line with the physical cues available. While the starlings can only make use of interaural time difference cues at lower frequencies (e.g., 1 and 2 kHz), additional interaural level difference cues become available at higher frequencies (e.g., 4 kHz or higher, Klump and Larsen 1992). An improvement of the starling's MAA with an increasing number of standard stimulus presentations prior to the test stimulus has important implications for determining relative (MAA) localization thresholds.
“Representational Momentum” (RM) is a mislocalization of the endpoint of a moving target in the direction of motion. In vision, RM has been shown to increase with target velocity. In audition, however, the effect of target velocity is unclear. Using a perceptual paradigm with moving broadband noise targets in Virtual Auditory Space resulted in a linear increase in RM from 0.9° to 2.3° for an increase in target velocity from 25°/s to 100°/s. Accounting for the effect of eye position also reduced variance. These results suggest that RM may be the result of similar underlying mechanisms in both modalities.
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