Increment detection of bandlimited noises in the chinchilla

A positive reinforcement, adaptive tracking procedure was used to study the intensity discrimination abilities of six chinchillas to noise signals. Increment detection thresholds were obtained using a two-down, one-up tracking rule. The effect of overall noise masker level and the effect of noise bandwidth on increment detection thresholds were studied. The continuous noise masker and the signal increment had equal bandwidths. Increment detection thresholds are independent of overall level for wideband noise; the asymtotic DL for wideband noise is 1.334 dB. In addition, increment detection thresholds decrease as the bandwidth of the noise increases. The observed slope of the bandwidth function for the chinchilla is independent of overall level and is around - 2.8 dB/decade. The slope of the bandwidth function obtained for the chinchilla is similar to values reported for human subjects under similar conditions, but is less than the slope predicted by the ideal energy detector model.