Perceptual adaptation to time-compressed speech was analyzed in two experiments. Previous research has suggested that this adaptation phenomenon is language specific and takes place at the phonological level. Moreover, it has been proposed that adaptation should only be observed for languages that are rhythmically similar. This assumption was explored by studying adaptation to different time-compressed languages in Spanish speakers. In Experiment 1, the performances of Spanishspeaking subjects who adapted to Spanish, Italian, French, English, and Japanese were compared. In Experiment 2, subjects from the same population were tested with Greek sentences compressed to two different rates. The results showed adaptation for Spanish, Italian, and Greek and no adaptation for English and Japanese, with French being an intermediate case. To account for the data, we propose that variables other than just the rhythmic properties of the languages, such as the vowel system and/or the lexical stress pattern, must be considered. The Greek data also support the view that phonological, rather than lexical, information is a determining factor in adaptation to compressed speech.The acoustic/phonetic characteristics ofspeech vary as a function ofspeaker, rate ofspeech, prosody, and so forth. Yet, when we process our native language, we are hardly ever aware of such variability; indeed, these variations are apparently dealt with automatically and effortlessly by the perceptual system. However, when processing artificially degraded speech or when listening to speakers with foreign accents, it is more difficult to make suitable adjustments. Schwab, Nusbaum, and Pisoni (1985) suggest that several sentences are required to adjust to synthetically generated speech. Anecdotally, listening to speech spoken with a foreign accent can also take some time before it becomes fully intelligible. What are the mechanisms responsible for such slow adjustments? Why are some adjustments easier than others? For instance, for a This research was supported by grants from the Human Frontier Science Program and the Spanish Ministerio de Educacion y Ciencia (Contract PB97-0997) and the Catalan Government (Grup de Recerca Consolidat 5120-UB-05). We thank T. Otake (Dokkyo University), K. Forster, and M. Garrett (both at the University of Arizona) for their help in preparing and recording the Japanese and English materials. A.C. is currently at the Psychology Department, Harvard University. Correspondence concerning this article should be addressed to N. Sebastian-Galles, Universitat de Barcelona, P. de la Vall d'Hebron 171,08035 Barcelona, Spain (e-mail: sebastia@psico.psi.ub.es).native speaker of English, English spoken with a Dutch accent seems far easier to understand than English spoken with a Japanese accent. Why?Several studies have shown that language representations in adults are, to some extent, language specific. Listeners behave as if they process speech sounds through the filter of phonemic categories of their maternal language and have difficult...