Human Voice Recognition Depends on Language Ability Tyler K. Perrachione,1* Stephanie N. Del Tufo,1 John D. E. Gabrieli1,2*
T he ability to recognize individual conspe- cifics from their communicative vocal- izations is an adaptive trait evinced widely
among social and territorial animals, including humans. Studies of human voice recognition com- pare this ability to nonverbal processes, such as human perception of faces or nonhuman animals’ perception of vocalizations (1). However, the hu- man voice is also the principal medium for the human capacity of language, as conveyed through speech. Human listeners are more accurate at iden- tifying voices when they can understand the language being spoken (2), an advantage thought to depend on listeners’ knowledge of phonology— the rules governing sound structure in their lan- guage. Leading theories of dyslexia propose that impoverished phonological processing often un- derlies impaired reading ability in this disorder (3, 4). We therefore hypothesized that, if voice recognition by human listeners relies on linguis- tic (phonological) representations, listeners with dyslexia would be impaired compared with con- trol participants when identifying voices speaking their native language (because of impaired pho- nological processing) but unimpaired in voice rec- ognition for an unfamiliar, foreign language (where both individuals with and without dys- lexia lack relevant language-specific phonologi- cal representations).
We assessed partici- pants with and without dyslexia for their ability tolearntorecognizevoices speaking either the listen- er’s native language (En- glish) or an unfamiliar, foreign language (Manda- rin Chinese). In each lan- guage, participants learned to associate five talkers’ voices with unique car- toonavatarsandweresub- sequently tested on their ability to correctly identify those voices. The partic- ipants’ task was to indi- cate who of the five talkers spoke in each trial [five- alternative forced choice; chance = 20% accuracy (5)]. Despite using the samevocabulary,allspeak- ers of a language differ in
their pronunciations of words (6), and listeners can use their phonological abilities to perceive these differences as part of a speaker’s vocal iden- tity. A repeated-measures analysis of variance revealed that, compared with controls, dyslexic participants were significantly impaired at recog- nizing the voices speaking English but unim- paired for those speaking Chinese (group × condition interaction, P < 0.0006) (Fig. 1).
English-speaking listeners with normal read- ing ability were significantly more accurate iden- tifying voices speaking English than Chinese (paired t test, P < 0.0005), performing on average 42% better in their native language (7). English- speaking listeners with dyslexia were no bet- ter able to identify English-speaking voices than Chinese-speaking ones (paired t test, P = 0.65), with an average performance gain of only 2% in their native language. Correspondingly, dyslexic listeners were significantly impaired compared with controls in their ability to recognize English- speaking voices (independent-sample t test, P < 0.0021). Dyslexic listeners were as accurate as controls when identifying the Chinese-speaking voices (independent-sample t test, P = 0.83), demonstrating that their voice-recognition deficit was not due to generalized auditory or memory impairments. Moreover, for the dyslexic partic-
ipants, greater impairments on clinical assess- ments of phonological processing were correlated with worse accuracy for identifying English- speaking voices (both Pearson’s r > 0.6, P < 0.015). Although the diagnostic criterion for dys- lexia is impairment in developing typical reading abilities, these data show that reading difficulties are accompanied by impaired voice recognition. This inability to learn speaker-specific represen- tations of phonetic consistency may reflect a weakness in language learning that contributes to impoverished long-term phonological represen- tations in dyslexia.
For humans, the ability to recognize one anoth- er by voice relies on the ability to compute the differences between the incidental phonetics of a specific vocalization and the abstract phonolog- ical representations of the words that vocalization contains. When the abstract linguistic representa- tions of words are unavailable (because the stim- ulus is unfamiliar, as in foreign-language speech) or impoverished (because native-language pho- nological representations are compromised, as in dyslexia), the human capacity for voice recog- nition is significantly impaired. This reliance on our faculty for language distinguishes human voice recognition from the recognition of conspecific vocalizations by other nonhuman animals.
References and Notes 1. P. Belin, S. Fecteau, C. Bédard, Trends Cogn. Sci. 8, 129
(2004). 2. T. K. Perrachione, P. C. M. Wong, Neuropsychologia 45,
1899 (2007). 3. L. Bradley, P. E. Bryant, Nature 301, 419 (1983). 4. J. D. E. Gabrieli, Science 325, 280 (2009). 5. Materials and methods are available as supporting
material on Science Online. 6. J. Hillenbrand, L. A. Getty, M. J. Clark, K. Wheeler,
J. Acoust. Soc. Am. 97, 3099 (1995). 7. Native Chinese-speaking controls exhibit the opposite
pattern, recognizing Chinese-speaking voices more accurately than English-speaking ones (2), revealing the critical factor to be listeners’ language familiarity, not properties inherent to the voice stimuli or languages themselves.
Acknowledgments: We thank J. A. Christodoulou, E. S. Norton, B. Levy, C. Cardenas-Iniguez, J. Lymberis, P. Saxler, P. C. M. Wong, C. I. Moore, and S. Shattuck-Hufnagel. This work was supported by the Ellison Medical Foundation and NIH grant UL1RR025758. T.K.P. is supported by an NSF Graduate Research Fellowship.
Supporting Online Material www.sciencemag.org/cgi/content/full/333/6042/595/DC1 Materials and Methods Fig. S1 Table S1 References (8–16)
21 April 2011; accepted 16 June 2011 10.1126/science.1207327
BREVIA
Fig. 1. (A) Mean voice-recognition performance of dyslexic and control lis- teners (error bars indicate SEM). All individuals scored above chance (20%), shown as baseline. (B and C) Relationships between clinical measures of language (phonological) ability in dyslexia and voice-recognition ability. CTOPP, Comprehensive Test of Phonological Processing.
1Department of Brain and Cognitive Sciences, Massachu- setts Institute of Technology (MIT), Cambridge, MA 02139, USA. 2McGovern Institute for Brain Research and Harvard- MIT Division of Health Sciences and Technology, Cam- bridge, MA 02139, USA.
*To whom correspondence should be addressed. E-mail: tkp@mit.edu (T.K.P.); gabrieli@mit.edu (J.D.E.G.)
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