Perception & Psychophysics 1997,59 (2), 165-179 Lexical tone in Cantonese spoken-word processing ANNE CUTLER Max Planck Institutefor Psycholinguistics, Nijmegen, The Netherlands and HSUAN-CHIH CHEN Chinese University ofHong Kong, Hong Kong In three experiments, the processing of lexical tone in Cantonese was examined, Cantonese listen­ ers more often accepted a nonword as a word when the only difference between the nonword and the word was in tone, especially when the FO onset difference between correct and erroneous tone was small, Same-different judgments by these listeners were also slower and less accurate when the only difference between two syllables was in tone, and this was true whether the FO onset difference be­ tween the two tones was large or small, Listeners with no knowledge of Cantonese produced essen­ tially the same same-different judgment pattern as that produced by the native listeners, suggesting that the results displaythe effects of simple perceptual processing rather than of linguistic knowledge. Itis argued that the processing of lexical tone distinctions may be slowed, relative to the processing of segmental distinctions, and that, in speeded-response tasks, tone is thus more likelyto be misprocessed than is segmental structure. Sounds produced by the human voice vary along mul­ In stress languages, stressed syllables may be distin­ tiple dimensions. Languages use these dimensions in dif­ guished from unstressed syllables in duration, amplitude, ferent ways to distinguish utterances, Inparticular, there Fa movement, and segmental structure. In many stress are wide differences from one language to another in the languages, stress position within the word is fixed, and, "suprasegmental," or prosodic, features: variations in fun­ hence, stress is not lexically distinctive. Where stress is damental frequency, amplitude, and duration, which are lexically distinctive, such as in English, Dutch, and Rus­ not a function ofintrinsic characteristics ofphonetic seg­ sian, it is only infrequently the case that the prosodic fea­ ments. Lexical stress and lexical tone are the two princi­ tures alone accomplish the lexical distinction. Thus, in pal methods by which languages use prosodic features to English, the distinction between SUBject and subJECT distinguish one word from another. (uppercase representing a stressed syllable) or between In tone languages, a lexically distinctive function is CONtents and conTENTS involves vowel differences in served by the fundamental frequency (Fa) level or con­ the initial syllable, as well as prosodic intersyllable differ­ tour realized on a syllable, Thus, the Cantonese consonant­ ences. Pairs such as FORbear andjorBEAR or FOREgo­ vowel (CY) sequence [si] with the high falling Tone 1 ing andjorGOing, in which the vowels do not differ across means "poem," with the middle rising Tone 2 means stress versions, are rare, "history," with a low-level Tone 6 means "time," and so Both tone and stress are realized principally on the por­ on. (There are six tones in Cantonese, ofwhich three have tion ofa syllable that most readily allows variation in Fa, additional abbreviated versions realized only on short amplitude, and duration-namely, on the quasi-steady­ syllables with a voiceless stop coda.) state portion, the vocalic nucleus ofthe syllable. Percep­ tion ofthe prosodic features is closely involved with per­ ception ofthe vowel on which they are realized. The perceptual question with which the present study This research was supported by Earmarked Grants from the Research is concerned is the processing oftonal and segmental in­ Grants Council ofHong Kong, by a Visiting Scholarship to the first au­ formation in the recognition of spoken Cantonese. This thor from the Chinese University of Hong Kong, and by a Visiting Fel­ is related to the important theoretical question ofthe role lowship to the second author from the Max Planck Institute for Psycho­ ofprosodic features in word recognition, The recognition linguistics. The authors are grateful to Connie Ho, Kit-Kan Tang, Lai-Hung Au Yeung, Siu-Lam Tang, Him Cheung, Ching Yee Chow, of spoken words is, above all, a very efficient process, and Arie van der Lugt for their extensive assistance during various Longer words can often be effectively recognized before phases ofthese experiments. The authors also thank an anonymous re­ their ends (Marslen-Wilson & Welsh, 1978), and coar­ viewer, Denis Burnham, and Laura Walsh Dickey for useful comments ticulatory information in one segment can be used to pre­ on an earlier version of the paper, and Inge Doehring and Rian Zen­ dervan for graphical assistance. Correspondence should be addressed dict a following segment (e.g., listeners can tell that they to A. Cutler, Max Planck Institute for Psycho linguistics, PO Box 310, are hearing can and not cat in the vowel, before the final 6500 AH Nijmegen, The Netherlands (e-mail: [email protected]). segment has begun; Ellis, Derbyshire, & Joseph, 1971). 165 Copyright 1997 Psychonomic Society, Inc. 166 CUTLER AND CHEN In English, the experimental evidence suggests that­ tered (Slowiaczek, 1990). Furthermore, English language possibly for the very reason that maximum efficiency is users appear to prefer to categorize vowels along a vowel aimed for-prosodic stress information is not exploited quality dimension (full vs. reduced) over a prosodic di­ prelexically. That is, the process oflexical access (achiev­ mension (stressed vs. unstressed; Fear, Cutler, & Butter­ ing contact with an entry or entries in the mental lexicon) field, 1995). operates without the use ofpurely prosodic information. In a tone language such as Cantonese, however, tonal For instance, word recognition cannot be facilitated by distinctions between words are pervasive. The situation prior information about stress pattern (Cutler & Clifton, of the English listener, who can afford simply to ignore 1984). And listeners who hear either FORbear or for­ prosodic information in computing the prelexical access BEAR in a sentence show speeded recognition of words code, in no way resembles that ofthe Cantonese listener, related to either ofthem (i.e., either ancestor or tolerate; for whom prosodic information is constantly decisive in Cutler, 1986), suggesting that both the lexical entry for word identification. There is, in fact, very little experi­ FORbear and the lexical entry for forBEAR have been mental evidence as yet available on how lexical tone in­ activated by the input, injust the same way as the lexical formation is processed in spoken-word recognition. There entries for a homophone such as sale/sail are both acti­ is, of course, clear evidence from standard word recog­ vated when either one is heard (Swinney, 1979). nition paradigms that listeners use tonal information to Cutler (1986) argued that recognition efficiency in En­ determine word identity. Fox and Unkefer (1985) con­ glish could be served by omitting prosodic information ducted a categorization experiment in which a contin­ from the prelexical access code because, in the case of uum was constructed varying from one tone ofMandarin stress information, the prosodic information is relative: to another. The crossover point at which listeners switched Stressed syllables do not have an absolute level ofdura­ from reporting one tone to reporting the other shifted as tion, amplitude, or pitch movement but rather have just a function of whether the CV syllable upon which the more ofeach than unstressed syllables do. Thus, hearing tone was realized formed a real word when combined only an initial syllable for- is not necessarily sufficient to in­ with one tone or only with the other tone (in comparison form the listener whether or not that syllable bears pri­ with control conditions in which both tones, or neither mary stress; unambiguous recognition is only possible tone, formed a real word in combination with the CV). once the second syllable has arrived. Thus, if listeners This effect of word/nonword status also appears with were to base their access of lexical entries on prosodic ambiguous consonants (e.g., a continuum from [d) to [t]) information in words such as FORbear/forBEAR, they in CVC syllables, both in word-initial position (Ganong, would have to delay initiation of the lexical access pro­ 1980) and word-final position (McQueen, 1991). In­ cedure until information about the word's second sylla­ deed, it also appears when the manipulation determining ble had arrived, and this delay would be inconsistent word versus nonword status is stress pattern (TIgress vs. with maximum efficiency. diGRESS; Connine, Clifton, & Cutler, 1987). Given the In fact, because minimal pairs such as FORbear/ evidence cited above that lexical stress information is not forBEAR are very rare, and because most pairs ofwords used prelexically, Fox and Unkefer's result cannot be that vary in stress also vary in segmental structure, the considered evidence of precisely how tone information omission ofprosodic information from the lexical access is processed. code in English would carry remarkably little cost. Nevertheless, there are some intriguing suggestions Specifically, the language would have a few more homo­ that the processing of tonal information may cause the phones; FORbear/forBEAR and its dozen or so fellow listener more difficulties than may the processing ofseg­ minimal stress pairs would join the huge set of existing mental information. All of these, as it happens, come from homophones such as sale/sail. For the recognition ofmost studies with Chinese languages. For instance, in a study by words, segmental information would suffice to compute Tsang and Hoosain (1979), Cantonese subjects heard sen­ a unique code for accessing the appropriate lexical entry. tences presented at a fast rate and were required to choose Indeed, studies ofthe effects ofmis-stressing on word rec­ between two transcriptions of what they had heard; the ognition in English suggest that listeners are more sensi­ transcriptions differed only in one character, represent­ tive to changes in vowels than to changes in stress pattern ing a single difference of one syllable's tone, vowel, or per se. Thus in "elliptic speech" (speech in which certain tone+ vowel.