11 - Are Two Ears Always Better than One? The Capacity Function Says No

Abstract

In an application of Systems Factorial Technology (SFT), we assessed the fundamental questions of whether across-frequency (spectral) integration for the binaural and monaural auditory systems follows a parallel architecture and has similar efficiency. Using an OR task and the double-factorial design, we measured reaction times (RTs) for the detection of one vs. two pure tones presented to either one ear (monaural) or across the ears (binaural). Data revealed no substantial advantage of the binaural presentation over the monaural presentation. That is, RTs of the single targets and the dual targets were very similar for both monaural and binaural presentations. System architecture was analyzed, and generally speaking, the architecture was parallel for both monaural and binaural conditions. Capacity measures demonstrated limited capacity for all conditions as well, indicative of a small redundancy benefit for both monaural and binaural presentation contexts. Although the parallel architecture is frequently assumed for spectral integration in the auditory system, is it also generally assumed to be highly efficient. Our data obtained at high accuracy do not support an efficient integration system. One possible explanation for the different results between accuracy and RT studies could be related to an auditory mechanism that operates efficiently under low-accuracy scenarios but not at high.