A series of auditory signal‐detection experiments was run under conditions of signal‐parameter uncertainty. This uncertainty was effected by allowing one signal parameter, either signal frequency or starting time, to vary randomly across the sequence of experimental trials. These experiments, run monaurally, employed a simple yes‐no detection procedure, signal plus noise occurring on half of the trials and noise alone occurring on the other half. A series of comparison experiments using the same observers was run under identical conditions, with the addition of a simultaneous cue signal in the contralateral ear. This cue was present on both signal and no‐signal trials and was identical, in all parameters except amplitude, to the signal that might have been presented to the detecting ear. The results demonstrated (a) the previously noted result—that a simultaneous contralateral cue degrades performance at relatively high signal‐to‐noise levels—and (b) a new result—that at low signal levels such a cue facilitates performance of the detection task. The degrading effect is a function of the cue signal energy. The resulting psychometric functions suggest an interpretation in terms of a crossmasking and uncertainty‐reduction hypothesis.

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