Robert A. Lutfi
Dept. of Commun. Disord. and Waisman Center, Univ. of Wisconsin, Madison, WI 53706
Recently, Kidd and Watson [J. Acoust. Soc. Am. (to be published)] identified what appears to be a rule of auditory perception that governs the detectability of changes in components of unfamiliar tone sequences. According to the proportion-of-total-duration (PTD) rule, each individual component of a random sequence of tones is resolved with an accuracy that is a function of its proportion of the total duration of the sequence. In the present paper, the PTD rule is shown to be an incident of a more general phenomenon governing the perception of tone sequences previously reported by Lutfi [J. Acoust. Soc. Am. 91, 3391--3401 (1992)]. The general rule may be stated as follows: each component of a random sequence is resolved with an accuracy that is a function of its proportion of the total variance (PTV) in the sequence. The generality of the PTV rule is supported by three observations: the PTV rule predicts a PTD effect but the reverse is not true; the PTV rule predicts the effects of number and duration of targets in the data of Kidd and Watson where, in both cases, the PTD rule fails; and the PTV rule describes behavior consistent with a broad class of ideal detectors in auditory pattern discrimination tasks. It seems that the PTV rule reflects a general property of auditory analysis wherein the perception of an auditory pattern is dominated by it's most variable features. [Work supported by NIDCD.]