No abstract

Performance in a simultaneous two-frequency detection task was studied under monaural and dichotic conditions of signal presentation. In the basic task a 630-Hz tone, a 1400-Hz tone, neither tone, or both tones occurred with equal likelihood on an experimental trial. The observer had to specify which of these events had occured. Performance was examined: (a) when the signal could occur only in the right earphone channel, and (b) when the 630-and 1400-Hz signals were confined, respectively, to the left and right earphone channels. Singlefrequency comparison conditions were also run. A performance decrement was observed in both of the twofrequency conditions compared to the single-frequency condition. However, there was no consistent difference between the monaural and dichotic two-frequency conditions. An analysis of the conditional detection probabilities revealed the presence of a cross-frequency interference effect on trials when a signal was present at the other frequency. This effect was sufficient to account for the differences between single-frequency and two-frequency detection performance.Subject Classification: 4.3, 4.7, 4.8.

Five models of 0 behavior in a two-channel exclusive-or (XOR) detection task were evaluated. The models included two types of single-channel and three types of two-channel O. Only the most efficient two-channel model adequately described human performance in a set of monaural and dichotic XOR conditions. Detectability measures derived from the XOR task matched those obtained from separate single-channel control conditions. We concluded that. in this two-channel task. the O's performance was not limited by any inability to monitor signals arriving simultaneously in two different earphone or two different frequency channels. The implications of this result for two-channel information processing and for multicomponent and sequential signal detection are discussed.101

Two-channel auditory signal detection was investigated with narrow-band noise signals masked by independent, binaurally uncorrelated noise. The two-channel tasks included conditions where the signals in each channel were correlated, uncorrelated, or opposite in phase. No significant differences were observed between the single-channel conditions and the two-channel correlated signal condition, but performance in the uncorrelated and 180° phase conditions was significantly poorer. A comprehensive analysis of cross-channel interaction indicated a cross-channel inhibitory or masking effect, which may be counteracted by the presence of lateralization cues. Constraints on signal detectability due to a limited processing capacity appeared to be negligible.

Performance on a task requiring detection of three sinusoidal signals occurring simultaneously and independently was compared to single-channel performance. The signal frequencies were 500, 810, and 1,320 Hz, and all signals were presented monaurally in noise. The data for each channel were analyzed conditional on the stimulus-response events occurring in the remaining channels and conditional on the order of report. The decrement in performance in any channel in the three-channel task was found to increase as the number of signals and/or "yes" responses present in the remaining channels increased. Increasing decrements and criterion shifts were noted conditional on the order of report. The data are consistent with a model attributing the decrements in multichannel listening tasks to the later or "cognitive" stages of processing rather than to the earlier "perceptual" processing stages.