Temporal Acuity and the Identification of Temporal Order: Related, but Distinct, Auditory Abilities

Abstract

Nearly a half century ago, Ira Hirsh published the first of many articles establishing the difference between (A) auditory temporal acuity (the ability to distinguish two sounds by their temporal properties) and (B) the limits of the perception of the temporal order of sounds. The thresholds for both A and B are described in terms of stimulus onset asynchrony (SOA). For many sounds, A is in the order of microseconds if the two sounds are delivered dichotically, one to each ear, and reaches two to three milliseconds when both are presented to one ear. The limits of B are much greater, generally 20 milliseconds or more for pairs of sounds, and roughly the same limits are found for pairs of stimuli from more than one sensory modality: light-sound, sound-touch, light-touch. Although still not well understood, several experiments on these topics suggest that A is limited by more peripheral mechanisms of sensory processing, whereas B involves higher levels of the nervous system, where perceived temporal relations may be subject to control via mechanisms of selective attention, as in prior entry phenomena. Some evidence suggests a very broad range of SOA over which temporally correlated stimuli may be brought into registration, perhaps to enhance their mutual effects on the extraction of common information.