Music & Language Studies

EDMONDSON, Jerold A., Jin-Lieh Chan, G. Burton Seibert, and Elliott D. Ross. “The Effect of Right-Brain Damage on Acoustical Measures of Affective Prosody in Taiwanese Patients.” Journal of Phonetics 15 (1987): 219-33.

Examined eight right-handed native-speakers of Taiwanese, a tone language. All patients showed signs of emotional flattening in their speech, though none showed deficits in the production of tone or other segmental aspects of speech. As the authors wrote:

The major emphasis of this paper is to investigate loss of affective prosody from focal right-brain damage in patients who speak a tone language. (220)

Comparison was made to findings for similar patients who were native-speakers of English.
The acoustic signals produced by patients’ speech utterances was analyzed along 12 parameters. In general, as expected, it was found that somewhat different parameters are normally involved in altering the affective content of an utterance. Unexpectedly, however, the researchers found that there was a flattening of frequency modulation, even at the local level. Although the degree of flexibility available in normal tonal speech is significantly narrower than for non-tonal speech, it yet remains an important marker of emotional affect.

The authors believe the explanation for this finding may lie in the fact that tones in context are allowed some prosodic variation from their citation forms without disrupting lexical information. Although the presence of tones in a language clearly places constraints on the manipulation of F0… enough freedom or play in the required precision of tone contrasts appears to remain for speakers to exploit this freedom for affective purposes. (230)

In conclusion:

it was once again found that communicative abilities of humans are lateralized according to behavior itself (affective vs. linguistic) and not according to the physical/acoustical carrier that expresses this behavior. …[A]lthough difference acoustic profiles underlie affective prosody for Taiwanese vs. English patients, the behavioral consequences are the same, i.e. affective flattening of voice. Thus, human languages show the features of a composite that is the product both of specific neurological organization of brain tissue and of the brain’s ability to react to the acoustical properties of a particular language, i.e. tone vs. non-tone, during the experience of language acquisition.

Thus, we have further evidence that expectancies play a major role in the perception and production of speech sounds, such that when language exploits aspects of pitch manipulation as part of the segmental level, as is the case in tone languages, such features are processed in the brain in fundamentally different ways from the same parameters when not within a segmentally contrastive context, even for speakers of tone languages. It is yet to be understood just how the perceptual apparatus is able to obtain this effect from the acoustic signal, though the motor theory of speech perception suggested elsewhere appears to provide one likely explanation.