Binaural release from informational masking in a speech identification task.

Binaural release from informational masking (IM) was examined in a speech identification task. Target and masker sentences were processed into mutually exclusive frequency bands, thus limiting energetic masking (EM), and presented over headphones. In a baseline condition, both were presented monotically to the same ear (TmMm). Despite minimal frequency overlap between target and masker, the presence of the masker resulted in reduced performance, or IM. Presenting the target monotically and the masker diotically (TmMo) resulted in a release from IM. Release was also obtained by imposing interaural differences in level (ILDs) and in time (ITDs) on the maskers (T(m)M(ILD), T(m)M(ITD)). Any masker with a perceived lateral position that differed from that of a truly monaural stimulus resulted in a similar amount of release from IM relative to TmMm. For binaural targets and maskers (T(o)M(ILD), T(o)M(ITD)), release was seen whenever ITDs or ILDs differed between target and masker. These results suggest that binaural cues can be very effective in reducing IM. Because mechanisms based on differences in perceived location make predictions that are similar to those of nonlocation-based binaural mechanisms, a variant of the equalization-cancellation model is also considered.