Dooling, R.J. and Searcy, M.H. (1979). The relation among critical ratios, critical bands, and intensity difference limens in the parakeet (Melopsittacus undulatus). Bulletin of the Psychonomic Society, 13, 300-302.

Intensity difference limens obtained for the parakeet using amplitude modulated pure tones indicate a Weber fraction (D I/I) of about .23 to .43 over a range of five test frequencies. These values are lower than previous measures of intensity resolving power in this species and are in perfect agreement with previously published critical ratio and critical band data for the parakeet.