THE PERCEPTUAL CUES FOR PROCESSING TEMPORAL ORDER OF TONES DIFFERING EITHER BY FREQUENCY (SPECTRAL TOJ) OR BY PERCEIVED LOCATION (SPATIAL TOJ)
Quantitative estimates of the ability to correctly perceive auditory temporal order (TOJ) have traditionally been measured either by the inter-stimulus interval (ISI) necessary when two tones of different frequency are presented to one ear (spectral TOJ) or by the ISI necessary when a tone to one ear is followed by the same tone to the other ear (spatial TOJ). We argue that the perceptual basis for spectral TOJ differs fundamentally from that of spatial TOJ. The latter is based on temporal discrimination; the former on frequency discrimination. First, stimulus onset asynchrony (SOA) is the major relevant variable for correct spatial TOJ (R2=.97), but not for spectral TOJ (R2=.54). Second, the effect of training on Spectral TOJ (range: 45 to 9msec) is much superior to Spatial TOJ (range: 65msec to 67msec). Third, subjects are capable of correctly discriminating spectral TOJ even when ISI=5msec, much shorter than the ISI necessary for temporal discrimination.