Contralateral cueing effects in backward masking.

The role of stimulus uncertainty in backward masking was investigated using a Monaural Detection with Contralateral Cueing (MDCC) paradigm. Cues temporally synchronous with and phase locked to the signal (20-ms segment of 500-Hz sinusoid) reduced backward masking, with the amount of reduction being independent of the phase relationship between the cue and the signal. Band-limited noise cues synchronous with the signal also reduced the amount of backward masking, with cue bandwidth having only a small differential effect on the amount of reduction. The important parameter of the cue in reducing backward masking was the temporal synchrony between the cue and the signal; a silent gap in a broadband noise served as an effective cue. These results confirm that, unlike simultaneous masking, backward masking involves a high degree of temporal uncertainty.

Critical-band effects in two-channel auditory signal detection.

Two-channel auditory signal detection was investigated with 50-msec sinusoidal signals masked by binaurally uncorrelated noise. In the two-channel tasks, the signals in each earphone channel were presented with an independent probability during the single observation interval and the observers were required to detect the inputs in a single earphone (selective-attention condition) or in both earphones (divided-attention condition). When the signals in each earphone were within the same critical band (the assumed singled processing unit in frequency domain), there was a decrement in detection performance in both the selective- and divided-attention (i.e. dichotic) conditions compared with the monaural condition. However, when signals were separated in frequency by several critical bands, a decrement in dichotic performance, as compared with monaural performance, occurred only in the divided-attention condition. These findings are discussed in terms of their implications regarding models of multichannel signal processing and the definition of input channels in terms of earphones.

Effects of certainty and uncertainty of stimulus-response correspondence on auditory reaction times.

Complex reaction time (RT) was measured for a task in which a discriminative auditory cue designated whether the right or left hand was to be used in responding. Facilitation of monaural RT compared to binaural RT occurred on trials in which both (1) the ear stimulated corresponded to the hand specified for response and (2) each of 20 male college students had received a prior signal signifying that stimulus-response correspondence would occur on the trial. RT was slower for monaural than binaural input when the monaural stimulus was applied to the ear contralateral to the hand designated by the tonal cue regardless of a prior signal signifying that stimulus-response noncorrespondence would occur on the trial. These slower RTs were attributed to an inability of subjects to inhibit their initial tendency to react toward the source of stimulation.

Processing interaction between two dimensions of nonphonetic auditory signals.

In 1974 Wood proposed a hybrid serial-parallel model to account for the within-stimulus interactions between the acoustic cue of "pitch" and the phonetic cure of "place." Three of the five experiments in this paper replicate the Wood findings with analogous, clearly nonphonetic stimuli and thus refute Wood's implicit assumption of the involvement of any uniquely phonetic processes as factors in his results. The experiments in this paper demonstrate that the patterns of interaction found by Wood are independent of the experience of the subjects, the order of cue presentation, and whether the cues are presented simultaneously or sequentially. We conclude that the given patterns of interaction are general characteristics of the auditory system. These characteristics probably are not related to backward or forward "recognition" masking but may be a function of several other general factors.