Four experiments examined segmentation of spoken Japanese words by native and non native listeners. Previous studies suggested that language rhythm determines the segmen tation unit most natural to native listeners: French has syllabic rhythm, and French listeners use the syllable in segmentation, while English has stress rhythm, and segmentation by English listeners is based on stress. The rhythm of Japanese is based on a subsyllabic unit, the mora. In the present experiments Japanese listeners' response patterns were consistent with moraic segmentation; acoustic artifacts could not have determined the results since nonnative (English and French) listeners showed different response patterns with the same materials. Predictions of a syllabic hypothesis were disconfirmed in the Japanese listeners' results; in contrast, French listeners showed a pattern of responses consistent with the syllabic hypothesis. The results provide further evidence that listeners' segmentation of spoken words relies on procedures determined by the characteristic phonology of their native language.

The mapping of phonetic information to lexical representations in second-language (L2) listening was examined using an eyetracking paradigm. Japanese listeners followed instructions in English to click on pictures in a display. When instructed to click on a picture of a rocket, they experienced interference when a picture of a locker was present, that is, they tended to look at the locker instead. However, when instructed to click on the locker, they were unlikely to look at the rocket. This asymmetry is consistent with a similar asymmetry previously observed in Dutch listeners' mapping of English vowel contrasts to lexical representations. The results suggest that L2 listeners may maintain a distinction between two phonetic categories of the L2 in their lexical representations, even though their phonetic processing is incapable of delivering the perceptual discrimination required for correct mapping to the lexical distinction. At the phonetic processing level, one of the L2 categories is dominant; the present results suggest that dominance is determined by acoustic-phonetic proximity to the nearest L1 category. At the lexical processing level, representations containing this dominant category are more likely than representations containing the nondominant category to be correctly contacted by the phonetic input. r

Japanese listeners detect speech sound targets which correspond precisely to a mora (a phonological unit which is the unit of rhythm in Japanese) more easily than targets which do not. English listeners detect medial vowel targets more slowly than consonants. Six phoneme detection experiments investigated these effects in both subject populations, presented with native-and foreign-language input. Japanese listeners produced faster and more accurate responses to moraic than to nonmoraic targets both in Japanese and, where possible, in English; English listeners responded differently. The detection disadvantage for medial vowels appeared with English listeners both in English and in Japanese; again, Japanese listeners responded differently. Some processing operations which listeners apply to speech input are language-specific; these language-specific procedures, appropriate for listening to input in the native language, may be applied to foreign-language input irrespective of whether they remain appropriate.

Three experiments addressed the question of whether pitch-accent information may be exploited in the process of recognizing spoken words in Tokyo Japanese. In a two-choice classification task, listeners judged from which of two words, differing in accentual structure, isolated syllables had been extracted ͑e.g., ka from baka HL or gaka LH͒; most judgments were correct, and listeners' decisions were correlated with the fundamental frequency characteristics of the syllables. In a gating experiment, listeners heard initial fragments of words and guessed what the words were; their guesses overwhelmingly had the same initial accent structure as the gated word even when only the beginning CV of the stimulus ͑e.g., na-from nagasa HLL or nagashi LHH͒ was presented. In addition, listeners were more confident in guesses with the same initial accent structure as the stimulus than in guesses with different accent. In a lexical decision experiment, responses to spoken words ͑e.g., ame HL͒ were speeded by previous presentation of the same word ͑e.g., ame HL͒ but not by previous presentation of a word differing only in accent ͑e.g., ame LH͒. Together these findings provide strong evidence that accentual information constrains the activation and selection of candidates for spoken-word recognition.