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In two experiments on normals we presented CV nonsense syllables both dichotically and monotically, with onsets of the syllables separated by 0, 15, 30, 60, and 90 msec (first experiment) and 0, 90, 180, 250, and 500 msec (second experiment). We found that when one of the CV's trailed the other by 30-60 msec, the trailing CV became more intelligible than when it was given simultaneously; the leading syllable's intelligibility dropped from its 'simultaneous' level when leading by 15 and 30 msec. The leading message was more intelligible between 15 and 250 msec when the two channels were mixed monotically. In the dichotic simultaneous conditon, voiceless consonants were more intelligible than voiced, especially in voiced-voiceless pairs. When the voiced CV trailed the voiceless CV, the former became almost as intelligible as its voiceless counterpart. A left hemisphere 'speech processor' was postulated, with suppression of information from ipsilateral sources during contralateral stimulation. The postulated 'speech processor' may be involved in acoustic-signal-vocal-tract control functions. [ABSTRACT FROM AUTHOR]

When dichotic nonsense syllables are presented to temporal lobectomy patients at equal intensities, the ear contralateral to the site of the lesion performs more poorly than the ipsilateral ear; if the ipsilateral ear is stimulated below threshold, the contralateral ear performs near 100%. However, if the intensity of speech in the ipsilateral ear is increased above SRT, the contralateral scores drop markedly as intelligibility increases in the ipsilateral ear. This 'trade off' does not occur when noise is the competing stimulus. This phenomenon is interpreted as a sign of 'speech identification' and is suggested as a potential technique for differentiating speech from nonspeech elements. [ABSTRACT FROM AUTHOR]

The article cites a research study focusing on dichotic listening. A number of authors have written about the development of the dichotic right ear advantage in children. Researchers interpret these dichotic listening data for children between the ages of five and ten as showing no significant change with age in the degree of right ear advantage. This study has shown that not only is the size of the right ear advantage contingent upon the precision on onset-alignment, but that the voiceless constant volumes (CVs) are much more intelligible dichotically than voices CVs. To the phonetically and linguistically oriented researcher, the careful use of dichotic stimuli whose acoustic differences can be specified, assesses the phonetic versus acoustic contribution of the stimuli to the right ear advantage. Most writers are in agreement that language skills in certain areas, and certainly reading and writing skills, improve between the ages of 5 and 13. It must be concluded, therefore, that the right ear advantage, as measured by dichotic listening to nonsense CVs, is not an index of total overall language performance.