Psychometric functions for informational masking

Abstract

The term informational masking has traditionally been used to refer to elevations in signal threshold resulting from masker uncertainty. In the present study, the method of constant stimuli was used to obtain complete psychometric functions (PFs) from 44 normal-hearing listeners in conditions known to produce varying amounts of informational masking. The listener's task was to detect a pure-tone signal in the presence of a broadband noise masker (low masker uncertainty) and in the presence of multitone maskers with frequencies and amplitudes that varied at random from one presentation to the next (high masker uncertainty). Relative to the broadband noise condition, significant reductions were observed in both the slope and the upper asymptote of the PF for multitone maskers producing large amounts of informational masking. Slope was affected more for some listeners and conditions while asymptote was affected more for others; consequently, neither parameter alone was highly predictive of individual thresholds or the amount of informational masking. Mean slopes and asymptotes varied nonmonotonically with the number of masker components in a manner similar to mean thresholds, particularly when the estimated effect of energetic masking on thresholds was subtracted out. As in past studies, the threshold data were well described by a model in which trial-by-trial judgments are based on a weighted sum of levels in dB at the output of independent auditory filters. The psychometric data, however, complicated the model's interpretation in two ways: First, they suggested that, depending on the listener and condition, the weights can either reflect a fixed influence of masker components on each trial or the effect of occasionally mistaking a masker component for the signal from trial to trial. Second, they indicated that in either case the variance of the underlying decision variable as estimated from PF slope is not by itself great enough to account for the observed changes in informational masking.

Informational masking of speech in children: Effects of ipsilateral and contralateral distracters

“…When the target is presented to one ear and the distracter to the other, children produce much higher detection thresholds ͑poorer performance͒ than adults. These results, as well as the results from studies in which a puretone target and distracter are presented to the same ear ͑Lutfi et al., 2003a, 2003bOh and Lutfi, 1998;Oh et al, 2001͒, offer a useful picture of the developmental course of puretone informational masking. However, it is not clear how the results from pure-tone detection experiments might generalize to a more realistic everyday selective attention task.…”

“…The recent models of informational masking, developed in the context of the pure-tone detection paradigms, suggest that listeners base their detection decisions on the weighted sum of outputs of a bank of auditory filters or channels ͑Lutfi, 1989͑Lutfi, , 1993Lutfi et al, 2003a;Oh and Lutfi, 1998;Richards, Tang, and Kidd, 2002;Tang and Richards, 2003;Wright and Saberi, 1999͒. The large differences in informational masking between children and adults and the large individual differences in thresholds are well predicted by the version of the model proposed by Oh and Lutfi ͑1998͒.…”

Spatial unmasking of birdsong in human listeners: Energetic and informational factors

“…III A. It has been noted previously that more "informational" maskers tend to give rise to shallower psychometric functions than more "energetic" maskers ͑Festen and Plomp, 1990;Kidd et al, 1998;Lutfi et al, 2003͒. One reason that has been put forward for this is that informational maskers are generally less homogeneous than energetic maskers. If the different maskers in the inhomogeneous set are differentially effective ͑and give rise to psychometric functions with different thresholds͒, then averaging across these maskers will give rise to a shallower slope even if each maskerspecific psychometric function is equally steep ͑see Durlach et al, 2005͒.…”

Auditory masking: Need for improved conceptual structure

“…͑Important IM research has been done by Watson, Neff, Lutfi, Kidd, Brungart, Richards, Wright, Freyman, and Shinn-Cunningham, as well as their associates-see references in Lutfi et al, 2003;Brungart et al, 2005;Watson, 2005;Durlach et al, 2005;Kidd et al, 2006͒. Although efforts have been made to clarify definitional issues ͑Durlach et al, 2003a; Watson, 2005͒, these issues are far from settled.…”