Fossil markers of language development: phonological ‘deafnesses’ in adult speech processing

The sound pattern of the language(s) we have heard as infants affects the way in which we perceive linguistic sounds as adults. Typically, some foreign sounds are very difficult to perceive accurately, even after extensive training. For instance, French subjects find it very difficult to distinguish foreign words that only vary in the position of the main stress. In this paper, we propose to explore this effect across different languages and use it to understand the processes that govern early language acquisition. We propose to test the hypothesis that early language acquisition begins by using only regularities that infants can observe in the surface stream of speech (the Bottom-Up hypothesis), and compare it with the hypothesis that they use all possible sources of information, including lexical information (the Interactive Hypothesis). We set up a research paradigm using the stress system, since it allows to test the various options at hand within a single test procedure. We distinguish four types of stress systems corresponding to four possible sources of information that infants could use in order to determine whether stress is important or not in their language. We show that the two hypotheses make contrastive predictions as to the pattern of stress perception of adults in these four types of languages. We conclude that cross-linguistic research of adults speech perception, when coupled with detailed linguistic analysis, can be brought to bear on important issues of language acquisition.