Dichotic and monotic interactions between speech and nonspeech sounds at different stimulus onset asynchronies

Subjects’ identification of stop-vowel “targets” was obtained under monotic and dichotic, forward and backward, masking conditions. Masks, or “challenges,” were another stop-vowel or one of three nonspeech sounds similar to parts of a stop-vowel. Backward masking was greater than forward in dichotic conditions. Forward masking predominated monotically. Relative degree of masking for different challenges suggested that dichotic effects were predicated on interference with processing of a complex temporal array of auditory “features” of the targets, prior to phonetic decoding but subsequent to basic auditory analysis. Monotic effects seemed best interpreted as dependent on relative spectrum levels of nearly simultaneous portions of the two signals.