Auditory contralateral induction: An early stage in binaural processing

Binaural interaction was studied using headphones presenting signals (tones or filtered speech) to one ear and noises of various spectral compositions to the other. Every half-second, the sides receiving the signal and noise were reversed. The noise was always perceived to alternate from side to side, but the signal appeared to be stationary and diffusely localized about the midsaggital plane when the noise contained the spectral components of the signal at appropriate intensity levels. This delateralization of a monaural signal results from a process called “contralateral induction” (CI). Additional observations indicate that CI corresponds to an early stage in binaural interaction which generally escapes notice because of further perceptual processing.