Temporal Order Discrimination Within the Dolphin Critical Interval

Human psychophysical experiments (Patterson and Green 1970, Ronken 1970, and others) have shown that human listeners can detect the difference between unequal amplitude click-pairs that arises from the order of the two clicks. The clicks of each pair are separated by a few milliseconds. Standard Fourier analysis indicates that this “time reversal” has no effect on the power spectrum. The apparent conclusion to be drawn is that human audition is phase sensitive, since only the phase spectrum can be different. As with many mathematical models, the conclusion is only as good as the assumptions upon which the model is based. The assumption which is in conflict here is that the waveform is known for all time, both past and future, since Fourier analysis employs integration with unbounded upper and lower time limits. The inability of (biological) systems to predict exactly ALL future details of a stimulus (or for that matter, to store ALL past details) inevitably leads to alternate mathematical formulations with less restrictive assumptions.