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Language universality and language diversity along vowel belts and roads Zeynep Gokcen Kaya, Yair Lakretz, Joe Collins, Alessandro Treves,Understanding each other through verbal communication requires, first of all, understanding each other’s phonemes. This often overlooked constraint is non-trivial already among native speakers of the same language, given the variability with which we all articulate our phonemes, and it becomes challenging when interacting with non-native speakers, who have developed neural representations of different sets of phonemes. How can the brain make sense of such diversity? Traditionally, phoneme representation in the brain has been studied with the simple notion of a tree-like structure of hierarchically clustered discrete items [1]. This is particularly inappropriate in the case of vowels, which to a first approximation can be characterized as points on a two-dimensional manifold spanned by the first and second formant frequencies; yet different languages (and even individual speakers) differ significantly in where they ‘put their vowels’ on such a manifold. Our goal is to understand the neural representation of phonemes, and how it can be learned in early development and modified in the course of life-long learning, without making any prior assumption on its organization, but allowing for the continuous and the multifactorial aspects that defy hierarchies and discreteness. We use both behavioral (phoneme confusion frequencies) and neural measures (the spatio-temporal distribution of phoneme-evoked neural activation). Using EEG, we replicate and extend a classical study on sub-phonemic features underlying perceptual differences between phonemes [3]. Comparing the responses of native listeners to that of Italian, Turkish, Hebrew, and (Argentinian) Spanish listeners to a range of American English vowels and consonants, we confirm the superiority of native listeners at identifying the phonemes of their mother tongue [2], but also find specific patterns of errors for speakers of different languages. Beyond the analysis of percent correct scores, and transmitted information, we frame the problem in terms of attractors, in analogy to those which have been well studied in spatial memory. Do different phoneme attractors exist in different languages? We find that at the consonant feature level, for these five languages, the largest basins of attraction appear at different places of articulation. With vowels, instead, we use ‘belts’, that is short stretches along which formant frequencies are varied quasi-continuously, to determine the local metric that best describe, for each language, the vowel manifold as a non-flat space constructed in our brain, perhaps with mechanisms similar to those investigated for spatial cognition in rodents. This research may lead to refine methods of foreign language instruction, in particular facilitating the acquisition of non-native phonemes. References [1]. Bouchard KE, Mesgarani N, Johnson K, Chang EF: Functional organization of human sensorimotor cortex for speech articulation. Nat. Neurosci 2013, 495:327-332. [2]. Cutler A, Weber A, Smits R, Cooper N: Patterns of English phoneme confusions by native and non-native listeners. J. Acoust. Soc. Am. 2004, 116(6):3668-3678. [3]. Miller GA, Nicely PE: An Analysis of Perceptual Confusions Among Some English Consonants. J. Acoust. Soc. Am. 1955, 27(2):339–352. (责任编辑：admin) |