THE TEMPORAL WEIGHTING OF THE LOUDNESS OF TIME-VARYING SOUNDS REFLECTS BOTH SENSORY AND COGNITIVE PROCESSES

  • Daniel Oberfeld

Abstract

In two experiments, listeners judged the loudness of sounds consisting of 10 contiguous 100-ms wide-band noise segments. On each trial, the sound pressure levels of the segments weredrawn independently from a normal distribution. Analyses of the trial-by-trial data were usedto estimate temporal perceptual weights ("molecular psychophysics"). In Experiment 1, threelevel profiles were presented (flat, and increasing or decreasing over the first three segments).The temporal weights showed a primacy effect and an increase of the weights with mean level,compatible with previous results [Oberfeld, Canad. J. Exp. Psych. 62, 24-32 (2008)]. Trialby-trial feedback had no significant effect on these patterns of weights, indicating that thepotential for top-down control is limited. In Experiment 2, weights for a flat level profile werecompared to weights for profiles with a 3, 6, or 9 dB increase in level during the first threesegments. The weights in the latter two conditions differed significantly from the weights forthe flat profile. It is demonstrated that these results indicate two independent mechanisms: aprimacy/recency weighting pattern compatible with processing of the segment levels asserially sorted information, and an increase of the weights with mean level that could be dueto either the specific sensory continuum underlying the decision process, or to selectiveattention to the louder elements.
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