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Changes in subjects' performance on dichotic pairs of CV's were observed over an eight-week period. Results are of practical significance in that certain performance characteristics were found to remain invariant with practice or reach an asymptotic value after 300-400 trials. The results are also of theoretical interest, however, in that unchanging patterns of response may reflect the operations of processes which are more ''built-in'' to the perceptual system, whereas changes in performance with practice may reflect the operation of more ''plastic'' processes responsible for phonetic feature decoding. Also emphasized is the importance of considering both the amount of practice and individual differences when interpreting some aspects of dichotic results. Subject Classification: [43]70.30, [43]70.70. [ABSTRACT FROM AUTHOR]

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]

Preliminary findings in our laboratory have suggested that the 'lag effect' [M. Studdert-Kennedy, D. Shankweiler, and S. Schulman, J. Acoust. Soc. Am. 48, 599-602 (1970); C.I. Berlin, S. Lowe-Bell, J.K. Cullen Jr., and C.L. Thompson, J. Acoust. Soc. Am. 53, 699-708 (1973)] may change at intensities below 75 dB SPL. An experiment is currently underway studying the 'lag effect' at intensities of 50-80 dB SPL and preliminary data suggest there may be a lead effect at low intensities which reverses as both competing syllables are presented at higher intensities. [Supported by National Institutes of Health, USPHS Grant No. NH 11647-01.] [ABSTRACT FROM AUTHOR]

Previous single-unit studies, round-window cochlear potentials, and behavioral audiometry had shown the most sensitive frequencies of moose hearing to lie between 10 and 20 kHz. Analysis of distress calls of normal adult wild and laboratory mice shows a peak of vocal output under stress at 10-12 kHz, with energy present past 100 kHz; most laboratory mice with genes for deafness show reduced ranges of distress-cry output, but with peaks similar in frequency to the normal. However, one strain of congenitally deaf mice (Df/Df) emits calls virtually identical to the normal-hearing mouse, and these calls are sufficient to elicit scurrying behavior from normal-hearing mice. Results are interpreted re: genetic patterns of communication for survival. [Supported by grants from the National Institute of Neurological Diseases and Blindness.] [ABSTRACT FROM AUTHOR]

Dichotic and monotic performance data were obtained from a patient with a lesion involving thalamic and parathalamic structures. Information gained from the patient's neurological examination, arteriograms and ventriculograms suggest the lesion is confined to the area of the medial geniculate and/or the brachium of the inferior colliculus on the right side. Data will be presented showing normal monaural and monotic performance in 'target-challenge' speech identification tasks [Berlin et al., IEEE Trans. Audio Electroacoust, AU-21, 189 (1973)], but differential effects in dichotic target-challenge identification tasks, depending on whether the target was presented to the right ear or left ear. [Supported by National institues of Health, USPHS Grant No. NH 11647-02.] [ABSTRACT FROM AUTHOR]

Synthetic CVs competed against 'bleats' (second and third formant transitions, both kindly supplied to us by D. Pisoni and colleagues) alternately in the right and left ears of 10 subjects. Both right and left ears were suppressed by the presence of the bleat in the other ear, but the left ear suffered more interference than the right ear. The nonsemantic and unintelligible nature of the bleats, coupled with their ability to generate an REA when competing against CVs, heightens the importance of acoustic factors in the dichotic right-ear advantage for CVs. However, the results do not suggest that there are no other contributing factors to the REA, and should not be so construed. [Supported by National Institutes of Health, USPHS Grant No. NH 11647-01.] [ABSTRACT FROM AUTHOR]

Eight normal subjects were tested in a dichotic consonant-vowel identification task where synthetic tokens of the stops + [æ] ranging in duration from 40 to 296 msec were used as challenges against 296-msec tokens from the same synthetic set. Subjects were required to identify both items in a dichotic pair. As challenge durations were reduced, their dichotic performance dropped paralleling monaural intelligibility, voiceless items being more severely affected than voiced items. Performance for the nonshortened items increased as the duration of the challenges dropped, in a manner not entirely reflecting the challenge intelligibility loss. Additionally, a 'backward-masking' effect of temporally remote vowel segments on competing consonant identification was clearly shown. [Supported by National Institutes of Health, USPHS Grant No. NH 11647-01.] [ABSTRACT FROM AUTHOR]

In previous work with normal subjects, performance trading for the masked and unmasked ear was shown in a dichotic consonant-vowel identification task with unilateral masking [C.L. Thompson, D. Samson, J.K. Cullen Jr., and L.F. Hughes, J. Acoust. Soc. Am. 55, 435(A) (1974)]. This study tested four subjects with temporal lobe lesions involving the superior gyrus in a similar task. When masking was applied to the ear contralateral to the lesion, both contralateral and ipsilateral ear performance were affected only slightly. When masking was applied to the ear ipsilateral to the lesion, performance of the ipsilateral ear decreased. Contralateral ear performance did not increase, however, until the ipsilateral signal-to-noise ratio was reduced to 12 dB. These data suggest lesions of the superior temporal gyrus serve to effectively decrease the signal-to-noise ratio for speech information presented through the lesion-contralateral ear. [Supported by National Institutes of Health, USPHS Grant No. NH 11647-01.] [ABSTRACT FROM AUTHOR]

Measurement of electrophysiological thresholds for specific frequencies in animals has been limited due to spectral problems when using brief broadband pulse stimuli necessary to elicit synchronous neural discharge. Frequency specific stimuli usually fail to yield responses any closer than 10-20 dB to actual behavioral thresholds. When a compound action potential obtained from a pulse or tone-burst stimulus is subtracted from a potential obtained with the original stiumuls plus a low-intensity continuous pure-tone masker, estimates of thresholds are near behavioral thresholds than measurements obtained using short duration stimuli alone. The effects of presentation rate (27.7 to 77.7/s), number of sweeps (625 to 10 000), and level of the continuous tone stimulus (-10 to 50 dB SPL) in a series of guinea pigs have been examined. Optimal recording conditions yielded thresholds to sine waves that are within 5 dB of behavioral data presented by Heffner et al. [J. Acoust. Soc. Am. 49, 1888-1895 (1971)], and somewhat less sensitive than data presented by Prosen et al. [J. Acoust. Soc. Am. 63, 559-566 (1978)]. [Work supported by DRF.] [ABSTRACT FROM AUTHOR]

Previous data [S. S. Lowe, J. K. Cullen, Jr., C. I. Berlin, C. L. Thompson, and M. E. Willett, J. Speech Hearing, Res. 13, 812-822 (1970); C. I. Berlin, M. E. Willett, C. L. Thompson, J. K. Cullen, Jr., and S.S. Lowe, J. Acoust. Soc. Amer. 47, 75-76 (1970)] show that when the onsets of the six English stops are aligned in dichotic CV pairs, voiceless CVs are more intelligible than voiced. This experiment reports the effect of maintaining onset alignments but changing voicing onset times (VOT) of the syllables. Thus, two types of voiceless CVs (+60 and +90 msec VOT) and two types of voiced CVs (-30 and 0 VOT) competed with each other in a dichotic paradigm. Changing VOT for the voiceless items had little effect on overall intelligibility. Using a 0-msec VOT voiced item, however, generated greater probability that the voiceless dichotic items would be perceived correctly. The relationship of this observation to the 'lag effect' and suppression of one item by another will be discussed. [ABSTRACT FROM AUTHOR]

These data represent further analyses of experiments previously reported [C. I. Berlin, C. L. Loovis, S. S. Lowe, J. K. Cullen, Jr., and C. L. Thompson, J. Acoust. Soc. Amer. 48, 70-71 (1970)]. Analysis of the errors made by normal subjects reveal that at simultaneity unvoiced consonants are better perceived than voiced consonants, especially when the unvoiced compete with the voiced consonants. When two voiced consonants compete, the V-V competition yields intelligibility about as good as the U-U competition; however, when U and V compete, then the intelligibility of the unvoiced syllable goes up while the intelligibility of the voiced syllable drops. As time asynchronies are introduced, the intelligibility of the unvoiced consonants remains constant while the intelligibility of the voiced consonant in the competing pair increases until, by 90-msec temporal offset, intelligibility of both voiceless and voiced CVs are the same. A preliminary hypothesis on switching during analysis time will be presented. [ABSTRACT FROM AUTHOR]

At previous meetings of this Society (November 1969, April 1970), we reported that when stimuli are lagged in the dichotic mode, normal listeners perceive the lagging stimulus better than the leading stimulus between 30 and 90 msec. We have studied patients with circumscribed temporal lobe lesions under these conditions and have observed: (1) No lag effect; the contralateral ear to the lesion does more poorly at simultaneity as well as at time staggers out to 500 msec. (2) When the words compete monotically, a laterality effect can also be seen in which the contralateral ear to the lesion does more poorly in reporting monotic competing messages. (3) Data suggest that the patients behave 'monotically' with respect to two-ear stimulation when one temporal lobe has been compromised. (4) As recovery takes place, differences between the ipsi-lateral and contralateral ear get larger, implying further asymmetry developing between the hemispheres. [This research was supported by NS-07095.] [ABSTRACT FROM AUTHOR]

Our attempts to attract mothers of CBA/J mice with real or synthetic ultrasonic infant distress cries have been unsuccessful. We synthesized cries in the 50- to 70-kHz range, and also used recordings of high-pass filtered true cries, but neither mature male nor female mice, nor even recently parous female mice, were systematically attracted to this signal. We subsequently discovered that our CBA/J mice, despite their widespread use as laboratory animals with 'normal' hearing, have late degeneration of hair cells at the basal turn. Evoked cortical potentials at high intensities showed little responsiness above 50 000 cycles in nine-month-old animals. Surface preparations of the organ of Corti show normal hair cells at four weeks, but serious deterioration is seen in the hair cells of the basal turn by nine months. This may be a recent (perhaps mutational) occurrence in the CBA/J strain because vertical sections of the organ of Corti (Guild's method), have shown no such degeneration in reports of others. [Work supported by the National Institute for Neurological Diseases and Blindness.] [ABSTRACT FROM AUTHOR]

Rhyming monosyllabic pairs that differ only by the initial plosive consonant were recorded on separate channels to be 'simultaneous in onset' within 5 msec. Onsets of the words were also staggered by 10, 20, 30, 40, 50, and 100 msec (±2.5 msec). Unvoiced consonants are perceived more readily in the simultaneous listening task. When control for frequency of occurrence of voiced versus voiceless consonants is made, central laterality effects are overshadowed by overriding intelligibility of voiceless consonants. The significance of these findings with respect to temporal coding of speech will be discussed. [Work supported by the National Institute for Neurological Diseases and Blindness.] [ABSTRACT FROM AUTHOR]

Two experiments on the CBA-J mouse demonstrate that the unconditioned galvanic skin-response (GSR) magnitude elicited by tones ranging from 2 kHz to 40 kHz were largest between 5 kHz and 20 kHz. This orderly relationship held at intensities of 60, 70, 80, 90, and 100 dB SPL. The growth of response magnitude with intensity followed a power law (100.17-0.22, depending on frequency), and is probably related to the nature of the mouse's vocal output under stress, which has its peak intensity at 10 kHz. [Supported by grants from the National Institute of Neurological Diseases and Blindness.] [ABSTRACT FROM AUTHOR]