Sex differences in simultaneous masking with random-frequency maskers.
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Auditory Perception↗
Biomedical subjects
T M Dethlefs
Publications and source records attributed to T M Dethlefs.
Individual differences in simultaneous masking with random-frequency, multicomponent maskers.
Individual differences were examined for 49 listeners in a simultaneous-masking task with random-frequency, multicomponent maskers and a 1000-Hz signal. Across conditions, the maskers were broadband noise or complexes of 2-100 sinusoids whose frequencies were randomly chosen with each presentation. Maskers were equal rms waveforms, presented at 60 dB SPL. Thresholds for the multicomponent maskers spanned a range of up to 59 dB across listeners within conditions without distinct groupings. When divided into quartiles, mean thresholds for listeners in the lowest quartile increased monotonically with the number of masker components and peaked below values produced by broadband noise. Listeners in the upper quartile had nonmonotonic functions with a broad peak around 10-20 components, with values above those produced by broadband noise. Quiet thresholds and masked thresholds for the broadband-noise masker did not distinguish "high-" from "low-threshold" groups. Lowering masker uncertainty (frequencies randomized between but not within trials) or introducing temporal differences by shortening the signal both improved performance by as much as 40 dB, dependent on the masking produced with maximum uncertainty. Training effects within experiment (excluding an initial training period) were examined for all listeners and for five listeners across two consecutive experiments. Eleven of forty-nine listeners (22%) showed systematic improvement averaging 12 dB within experiment, independent of high or low original thresholds. For the five tested longer, four improved by 5 dB or more in at least one condition, but the change in performance occurred primarily during initial training for the second experiment. The large individual differences documented present a challenge to the development of models for masking produced by masker-frequency uncertainty.
Adolescent↗
Informational masking for multicomponent maskers with spectral gaps.
Simultaneous maskers comprised of a few random-frequency sinusoids can produce considerable informational (uncertainty-based) masking if the component frequencies are drawn from a wide range and changed with each stimulus presentation. The present experiments examined the effect on informational masking of removing masker energy from large frequency regions around the signal. Threshold for a 1000-Hz signal was measured in the presence of maskers comprised of 2, 4, 6, 10, 50, or 100 random-frequency sinusoids, notched-noise, or two fixed-frequency sinusoids. The multicomponent maskers had a maximum frequency range of 300-3000 Hz, typically excluding a 160-Hz band around the signal. In comparison conditions, masker frequencies were limited to the high or low side of the signal, or the gap around the signal was progressively widened. Four listeners showed substantial informational masking which was not eliminated even by extreme spectral gaps in the maskers. Four other listeners showed much smaller effects of masker uncertainty across all conditions. Notched-noise measures of auditory-filter width did not distinguish the two subject groups, but indices of processing efficiency were typically poorer for the high-threshold listeners, as were measures of both the width and processing efficiency of presumed "attentional filters" under conditions of masker-frequency uncertainty.
Acoustic Stimulation↗
Patterns of social preference across different social contexts in golden lion tamarins (Leontopithecus rosalia).
We investigated the role of mutual and circumstantial factors in maintaining exclusive social relationships in a New World primate. Four breeding pairs of golden lion tamarins (Leontopithecus rosalia rosalia) were allowed to interact with their mate or an unfamiliar, opposite-sex adult in each of 4 different social contexts: in view of the mate, out of the mate's view, with only the mate present, and with only the unfamiliar animal present. Males and females were in proximity to, approached, and sniffed their mates significantly more often than they did unfamiliar tamarins. These behaviors suggest a preference for the familiar mate. However, when mates were absent, tamarins demonstrated significantly higher levels of approach and sniffs toward unfamiliar animals. These patterns of behavior indicate that circumstantial factors, such as social context, may regulate social interactions between paired tamarins and unfamiliar, opposite-sex conspecifics.
Aggression↗