Psychophysical tuning curves in the parskeet: A comparison between simultaneous and forward masking procedures

Abstract

In experiments with human listeners the shape of psychophysical tuning curves (PTC) has been shown to vary with the masking procedure. The present experiment was designed to see if PTC shape was also dependent on masking procedure in the parakeet. Four animals were trained to respond in the presence of tone stimuli and PTCs were measured for probe frequencies of 1.6, 2.5, or 3.5 kHz using either a simultaneous or forward masking paradigm. The sharpness of the tuning curves varied drastically with procedure and the forward masking curves had Q10dB values that were nearly double those obtained from the simultaneous masking procedure. Although there were differences in the sharpness of tuning, the PTCs from both methods remained generally symmetrical on the high- and low-frequency side of the probe signal. The results are considered with regard to two-tone suppression and pitch discrimination cues. [Work supported by Heinrich-Hertz Foundation, West Germany.]