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Differential Cerebral Lateralization of Chinese-English Bilingual Functions?
Cogniiive Processing in Bilinguals - R.J. llarris (Ediror) 0 1992 Elsevier Science Publishers B.V. All righis reserved.
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Differential Cerebral Lateralization of Chinese-English Bilingual Functions? Rumjahn Hoosain University of Hong Kong Abstract Chinese-English bilinguals in Hong Kong provide a good test of the hypothesis of greater right hemisphere involvement in bilingual language functioning, particularly from the point of view of the nature of languages involved. However, studies using hemifield and bilateral visual presentation, monaural presentation, dichotic listening, as well as time-sharing tasks provided little support for the hypothesis. A review of the Chinese-English aphasia literature was similarly non-supportive. Some experimental findings of greater ambilaterality for second language functions might only reflect task difficulty. While it is generally accepted that the left cerebral hemisphere is dominant for language functions, the possibility that bilinguals have a lateralization pattern different from monolinguals has received a lot of attention since the work of Albert and Obler (1978). That bilingual functions are less left lateralized, and more specifically that second language functions involve the right hemisphere more, have been suggested (Albert & Obler, 1978; Vaid, 1983). More recently, it is felt that such views are not justified by evidence in the literature and there is the suggestion that we should "move on to more productive research" (Paradis, 1990, p. 576). In this paper I review experimental and clinical data on Chinese-English bilinguals. If bilingual lateralization patterns are different the chances of obtaining such evidence should be good with these subjects. Discussions of bilingual lateralization often recognize a number of variables that are taken to be conducive to differential lateralization. These include language specific factors, involving ways in which languages of the bilingual differ from each other, and language acquisitional factors, involving the manner of second language acquisition as well as the age and stage of second language acquisition. It has been suggested that the greater the first and second languages are different,and the more the contexts of acquisition of the two languages are different, the more likely it is that lateralization of the second language will differ from the left dominance pattern for the native language (Vaid, 1983). Chinese-English Bilinguals One major difference between Chinese and English is in terms of the relation between script, sound, and meaning in the written language (see Hoosain, 1991a). This
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is usually indicated by labelling the two languages as ideographic and alphabetic respectively. The script-sound relations in Chinese is on a one- to-one basis, with no grapheme-to-phoneme conversion rules (with pronunciations "spelt-out" in the latter case). As a result of differences between Chinese and English orthographies, the manner of information processing can differ. For example, eye-movement patterns in adult Chinese readers and the nature of reading problems in Chinese children are quite different from those of English speakers (Stern, 1978; Woo & Hoosain, 1984). Chinese is a tonal language. Nine tones are used in the Cantonese dialect spoken by the bilingual Hong Kong subjects referred to later. This use of tonal variation to indicate meaning results in the sing-song appearance of Chinese speech to non-speakers. In language structure, Chinese grammar is said to be "meagre" (Kalgren, 1949). Chinese grammar as such is not taught in schools, for example, in Hong Kong. In contrast, English grammar is given a lot of formal treatment in these schools. Thus, the manner of learning and processing Chinese compared with English can involve diverse processes. The course of bilingual acquisition follows a typical pattern for the vast majority of the University of Hong Kong undergraduates used in studies by the author, reported later (they all participated as subjects in the experiments in connection with taking an Introduction to Psychology course). They are all native Chinese (Cantonese) speakers, and Cantonese is spoken at home as well as amongst peers. English is learned at school, in a formal manner. It is taught as a school subject in grade school through high school and is officially the medium of instruction in high school for most of the subjects, although a variable amount of Chinese or mixed speech could be actually used in the classroom. English is the medium of instruction at the university. But it is safe to say that most subjects seldom have any extended conversation in English, lasting longer than a couple of sentences. They would read their daily Chinese newspapers but would only occasionally read English newspapers. Thus, the bilingual language acquisition conditions for Chinese and English are very dissimilar, and, according to some views, could be expected to show a less comparable pattern of hemispheric involvement for the two languages (Vaid, 1983).
In terms of the stage hypothesis (Galloway & Krashen, 1980), there should be greater left hemisphere involvement in second language processing in the final stages of second language acquisition. However, there is some sense in which the Hong Kong Chinese-English bilinguals should not be considered as reaching the final stages of bilingualism. It is true that these undergraduates have reached some kind of plateau of accomplishment in their second language acquisition, somewhat comparable to that of many beginning foreign students found in American universities. There has been concern that a lot of findings in the bilingual lateralization literature are either nonsignificant or contradicting each other (Paradis, 1990). To a large extent, methodological problems (e.g., Fennell, Bowers, & Satz, 1977; Sussman, 1989) and the lack of comparability between studies have led to a feeling of absence of progress. Different studies can employ diverse types of bilingual subjects, acquiring their languages under different circumstances and in different manners, and the
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languages involved could be different. One alternative would be for different procedures to be used by the same investigators on the same type of subjects, to provide some in-depth picture of the situation. This article reviews a number of studies carried out by the author on Chinese-English bilinguals in Hang Kong, using bilateral and hemifield presentation, monaural and dichotic listening, as well as time-sharing tasks to look at various aspects of bilingual functioning and the possibility of a different lateralization pattern for the two languages involved. Other experimental studies as well as aphasia studies are also reviewed. Visual Studies Three separate studies have been conducted comparing the lateralization of Chinese and English functions in visual tasks (Hoosain, 1986, in press; Hoosain & Shiu, 1989), all using Chinese-English bilinguals at the University of Hang Kong described above. In the first study (Hoosain, 1986), high frequency two-character Chinese words and three-lettered English words were presented in a visual hemifield procedure, with items shown in the right or left visual field so that the sensory information is initially conveyed to the contralateral hemisphere. The two Chinese characters in each item, as well as the three English letters were aligned vertically. Each item was shown for 150 ms, and subjects were asked to produce the translation equivalent of each presented item (in Chinese or in English) in the other language as soon as possible. Response times for each translation and error rate were obtained. It took the subjects about a second to translate the high frequency words in the experiment. Response times were faster for items shown in the right visual field, for both Chinese and English words, although the differences did not quite reach statistical significance. However, error rates for translating both Chinese and English words were significantly smaller when the items were shown in the right visual field. It would seem that lateralization patterns for the translation tasks in the two languages are similar, both favoring visual information initially conveyed to the left hemisphere.
Hoosain and Shiu (1989) conducted a more purely visual study. Pairs of items were presented on the two sides of the fixation point simultaneously for 120 ms. Each item could be a high frequency two-character Chinese word, a high frequency four- letter and two-syllable English word, or a four-digit random number. The pair of items could be Chinese-Chinese, Chinese- English, or Chinese-number in these bilateral presentations. Error rates showed that, whether paired with another Chinese word, an English word, or a number, Chinese words were seen significantly better when shown in the right visual field. Similarly, English words (which were always paired with Chinese words) were seen significantly better when they appeared in the right visual field rather than the left. Thus, both languages indicated a left hemisphere superiority in visual processing. Hoosain (in press) tested right-handed and left-handed subjects, as well as handedness-switched subjects who were born left-handed but forced to switch their preferred hand to the right during childhood. They were shown common two-character
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Chinese words and three-letter English words, with constituent characters or letters aligned vertically. Exposure time was adjusted for each individual subject. For righthanded subjects, there was a significantly greater number who identified more of the words shown in the right visual field than those shown in the left visual field, similarly so for Chinese and English words. Although both left-handed subjects and handedness switched subjects identified more Chinese and English words presented in the right visual field compared with the left, the numbers were not significant. Thus, there was no cerebral lateralization difference between identifymg Chinese and English words. Both kinds of items showed a left hemisphere advantage, although it was significant only for the right-handed subjects. Left-handers are known to show a weaker left lateralization and it appears that handedness switched subjects function similarly to ordinary left handers. To summarise, in various experimental tasks involving visual perception of Chinese and English words, the Hong Kong Chinese- English bilingual undergraduates did not display any differential lateralization for Chinese compared to English. Incidentally, while there have been periodic reports that visual perception of Chinese words is more right lateralized than that of English, due to its ideographic characteristic, it is now quite clear that this is not a valid factor and universal perceptual factors such as exposure time and the quality of the sensory signal are responsible for such findings (Hasuike, Tzeng, & Hung, 1986; Ho & Hoosain, 1989; Hoosain, 1991a). There are a few other studies reported in the literature involving Chinese-English bilinguals in perception of Chinese and English words. Kershner and Jeng (1972) tested right-handed Taiwanese Chinese graduate students in the U S . They were shown Chinese and English words as well as geometric forms in hemifield or bilateral presentation. In the case of both Chinese and English words, subjects were able to write down what they had seen better when the items were shown in the right visual field. This pattern was obtained for the hemifield as well as the bilateral presentation procedures. For the geometric forms, performance was better when items were presented in the left visual field using the hemifield presentation procedure, although no significant difference was found with the bilateral presentation procedure. Hardyck, Tzeng, and Wang (1977) tested bilinguals who were fluent in reading Chinese and English. Single-character words and their English translation equivalents were used. No signifcant response time and accuracy results were found with these subjects when pairs of Chinese-Chinese, Chinese-English, or English-English items were presented either in the same hemifield or bilaterally, and subjects had to indicate whether items had the same physical shape or not, or whether they had the same meaning or not. Hardyck, Tzeng, and Wang (1978) used similar materials, but about 5 minutes after the tachistoscopic presentation subjects were asked to recall the items presented. There was a significant difference in recall performance in favor of Chinese words shown in the right visual field compared to the left, and there was a similar but nonsignificant difference for English. This was the first experimental study that provided indication of differential lateralization -- a weaker left lateralization for English.
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But this finding of Hardyck et al. should be evaluated in connection with their report that response times in the initial tachistoscopic presentation were faster for first language compared with second language words. Most of the bilingual subjects had Chinese as their first language, although a few had English as first language. Thus, the majority of the subjects actually spent more time with the English words than with Chinese words during initial presentation. The longer dwell times for English items also meant that there was a greater opportunity for interhemisphere commmunication in processing English items.
To conclude, experimental visual studies of Chinese and English with bilingual subjects do not point to differential lateralization for the two languages. The only exception (Hardyck et al., 1978), showing weaker lateralization for English, involves longer processing times. This issue will be discussed later. Auditory Studies Reports on auditory studies of Chinese-English bilinguals are rare in the literature. Hoosain (1984) performed a digit span test on Chinese-English bilingual undergraduates. The standard procedure for such tests was used, except that each set of random numbers, starting with a short sequence and ending with a sequence too long for the subject, was presented only to the right or left ear over a set of earphones. Also, both forward digit span and backward digit span were determined, for Chinese and for English. The digit spans obtained by this monaural procedure showed a significant right ear (left hemisphere) superiority for forward digit span in Chinese. No other condition showed any significant laterality difference, although there was still a nonsignificant right ear superiority for forward digit span in English.
On the face of it, this would be a second indication (apart from that of Hardyck et al., 1978) of weaker lateralization of English functions in Chinese-English bilinguals. The weaker lateralization for the backward digit condition (for both Chinese and English) can be considered in terms of the view that operations to produce backward digt sequences involve the right hemisphere more (Rude1 & Denckla, 1974). But the weaker lateralization for the forward digit span in English is reminiscent of the finding of Hardyck et al., only now in the auditory mode rather than the visual. The actual forward digit span for English was smaller than for Chinese, that is, subjects found memorizing English numbers more difficult. In the case of tachistoscopic presentation in the Hardyck et al. study, response times were longer for second language items (which was English for most of the subjects). Again, this means that weaker lateralization was found with the more difficult language. In a dichotic listening study (Hoosain, 1991b), Chinese- English bilingual undergraduates at the University of Hong Kong heard two groups of four common two-character Chinese words (or four common two-syllable English words), each group through one ear, using a set of earphones. The percentages of correct recall of Chinese items were 62.4% for those presented to the right ear and 43.3% for the left ear. Thus, there was a right ear or left hemisphere superiority effect. For English, the
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corresponding results were 49.0% and 34.3% respectively. Although the English performance was not as good as that for Chinese, there was a similar right ear, left hemisphere superiority effect. The two auditory studies provide mixed results for the differential lateralization hypothesis. The monaural study showed some indication of weaker lateralization for English, but then subjects found the English digit span test more difficult than Chinese. The dichotic listening study showed similar left lateralization for both Chinese and English, even though English words were more difficult to recall. Time-sharing Studies There are only a couple of studies using the time-sharing paradigm (Hoosain, 1990; Hoosain & Shiu, 1989). In both studies, undergraduates at the University of Hong Kong were asked to count backwards by 3's (e.g., to say "97, 94, 91, etc." when given "97") in either Chinese or English. They were also asked to perform a standard finger tapping test, with the right or left index finger. After baseline measures for these tasks were obtained, subjects were asked to simultaneously engage in finger tapping with the right or left hand and backward counting in Chinese or English. Finger tapping is controlled by the contralateral hemisphere. When compared with baseline tapping or counting scores, changes in the respective performances during the time-sharing trials would indicate the extent to which the right or left hemisphere is engaged in the backward counting task in either language.
In the time-sharing trials, there was an increase in backward counts performed but a decrease in the number of taps made, when compared with the respective baseline measures. The possibility that one of the concurrent tasks could be carried out better than baseline performance has been acknowledged (Kinsbourne & Cook, 1971), although there could also be some practice effect. In these two experiments, it appeared that subjects attended to the counting tasks more than to tapping during the time-sharing trials. This pattern was found in both studies. Hoosain and Shiu (1989) found that concurrent counting affected right-hand tapping (controlled by the left hemisphere) more than left-hand tapping, and similarly so for both languages. This indicated that both Chinese and English backward counting was lateralized in the left hemisphere. The effect of concurrent counting on tapping performance did not show any significant lateralization pattern. On the other hand, Hoosain (1990) found some indication of right hemisphere involvement in second language functioning. This time, the effect of concurrent counting on tapping performance did not show any significant lateralization pattern. But when subjects were counting in Chinese, improvement in counting was greater during tapping with the left hand rather than the right. When counting in English, improvement was greater during tapping with the right hand. This would suggest that the left hemisphere is more concerned with counting in Chinese and the right hemisphere more concerned with counting in English. This particular finding provided
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perhaps the strongest single indication of right hemisphere involvement in English functioning. Thus, the two time-sharing studies produced contradictory findings. In a review of the time-sharing paradigm, Sussman (1989) warned that concurrent tapping disruption rates can be affected by discrepant baseline tapping speed of the dominant and nondominant hands. But in the case of Hoosain (1990) we had a significant interaction effect of language and hand used on the enhancement of backward counting. In any case, the contradictory results from the above two studies, one showing left lateralization for both languages and one showing left hemisphere lateralization for Chinese but right lateralization for English, reminds us of the contradictory picture for bilingual laterality pointed out by Paradis (1990). There is also a question of the reliability of the time- sharing procedure. We had enhanced tapping in one study and enhanced counting in another, although identical procedures were used on similar subjects. Enhanced performance during timesharing, particular involving the hand contralateral to the language hemisphere, is seldom found (Kinsbourne & Cook, 1971). It might be noted that the Hong Kong subjects tend to have very high baseline scores in the first place, averaging over 110 taps with the right hand and 14 backward counts, in 20 seconds. The subjects in Hoosain (1990) had even better baseline Chinese backward counting, averaging 16.0 counts. Aphasia Studies There are about a dozen individually reported cases of aphasia in Chinese-English bilinguals in the literature. Although there are indications of intrahemisphere differences in locations for Chinese and English processes, there is no overall picture of differential lateralization for the two languages. The earliest reported case was that of Lyman, Kwan, and Chao (1938). A patient from Shanghai who was fluent in both Chinese and English had a large left occipito-parietal fibroblastoma. His Chinese as well as English speech and oral comprehension were good. He had some difficulties with reading English, but his reading of Chinese was very much worse. His written English was also better than Chinese. For a few decades, this study had a prominent position in the literature on Chinese aphasia and provided support for the idea of differential lateralization of the two languages of the bilingual. It is also consistent with greater ambilaterality for the second language of the bilingual. April and his colleagues (April & Tse, 1977; April & Han, 1980) reported on two cases of crossed aphasia in Chinese-English bilinguals living in New York. The two right-handed Chinese males had right hemisphere lesions resulting in aphasia. The first patient had his Chinese functions affected more than English, and it was suggested that the right hemisphere might be more involved with using an ideographic language. However, the second patient did not show any significant difference between Chinese and English performance. April and Han (1980) also reported that a review of unspecified numbers of Chinese patients in New York and in Taiwan did not indicate
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an incidence of crossed aphasia above the 4% from the European literature. While many of the Taiwan patients may not be Chinese-English bilinguals, the New York patients should most likely be bilingual. The actual number of cases that were examined was not reported by April and Han, but it was apparently enough to convince the authors to give up the idea of differential lateralization amongst the Chinese (although the authors focused on altered lateralization due to use of the nonalphabetic Chinese language rather than bilingual differential lateralization as such). T’sou (1978) reported on a female Chinese-English bilingual in Hong Kong with a left posterior temporo-parietal hemorrhage resulting in conduction aphasia. Both Chinese and English were affected, although there were some variations dueto language characteristics. Thus, she had problems particularly with the low falling tone in Cantonese, and mirror image reversal in English (saying instead of god).
In the above four cases, the patients were all Chinese dominant, although that of Lyman et al. was fluent in English. Rapport, Tan, and Whitaker (1983) studied a total of seven right- handed polyglots in Malaysia. All were fluent in English and at least one Chinese dialect, and in some cases English was the dominant language. Some also spoke Malay. Different combinations of the Wada test (with one or the other cerebral hemisphere being temporarily incapacitated), cortical stimulation (while subjects were engaged in object naming or silent reading), and clinical tests were carried out on the patients. Five of t h e seven patients had left and two had right hemisphere lesions. Rapport et a]. found no pattern of greater right hemisphere involvement in language functions, either for Chinese or for the other languages. There were two cases of weaker lateralization, with indication of right hemisphere involvement. But, in one case, the patient was a young female with a laterality quotient of +75. In the other case, the patient could have mixed cerebral dominance as a result of congenital vascular anomaly in the left hemisphere. All the patients were left hemisphere dominant for the languages or dialects tested. Cortical stimulation did provide evidence that different languages or dialects could occupy different loci within the same left hemisphere. The Chinese-English aphasia literature does not generally support a conclusion of greater right hemisphere involvement for the second language, or indeed greater right hemisphere involvement for either language. The two cases of crossed aphasia reported by April and his colleagues could well fall within the category of reports that are selective in favor of the unusual, and they were more than counterbalanced by the absence of a higher incidence of crossed-aphasia amongst Chinese patients reviewed in New York and in Taiwan. Unfortunately, the actual number of cases considered by April and Han (1980) is not known, although in the New York sample, it was from two hospitals over two years in the city, and one of the hospitals treats a large Chinese population. This would apparently amount to an unselected group study (Solin, 1989).
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Conclusion The available experimental and aphasia studies, on the whole, do not present a picture of any pattern of differential lateralization of Chinese-English bilingual functions. Even so, there are a small number of reports going against the trend that need to be considered. There are two experimental studies showing a weaker lateralization for English (Hardyck et al., 1978, Experiment 2; Hoosain, 1984). In both cases, performance for English items was poorer, with subjects requiring more response time and recalling fewer items respectively. There is indication that tasks based on visual information taking more than one second to complete tend not to obtain significant lateralization effects (Hoosain, 1991a). In these cases, interhemisphere communication probably plays a greater role and the quest for lateralization effect is doomed. A similar situation could be found where a more difficult task requires greater effort. Given that second language functioning tends to be poorer (slower, with smaller short-term memory capacity, etc.) for most bilinguals, there is a built-in bias for findings what could be taken as weaker lateralization of second language functions. These findings do not necessarily mean that the locus of processing has moved away from the left hemisphere, or that right-hemisphere based processes or strategies are dominantly being used for the second language. In the case of the time-sharing studies showing contradictory results (Hoosain, 1990; Hoosain & Shiu, 1989) further work needs to be done to clarify the reliability of the of the procedure, particularly in view of questions concerning the paradigm (Sussman, 1989). Out of the eleven cases of aphasia reported, only three were consistent with the hypothesis of differential lateralization as a result of Chinese-English bilingual experience. The two cases of crossed aphasia reported by April and his colleagues are offset by their own reference to larger samples of left lateralization for language. The case of Lyman et al. (1938) would have to remain in its place in the classical literature, without us knowing whether it was selected because of its unusual features (we do not even know the handedness of the patient). References Albert, M. L., & Obler, L. K. (1978). The bilingual brain: NeuropJychological and tieurolingubiic aspects of bilingualism. New York: Academic Press. April, R. S., & Han, M. (1980). Crossed aphasia in a right-handed bilingual Chinese man: A second case. Archives of Neurologv, 37, 342-346. April, R. S., & Tse, P. C. (1977). Crossed aphasia in a Chinese bilingual dextral. Archives of Neurology, 34, 766-770. Fennell, E. B., Bowers, D., & Sat& P. (1977). Within-modal and cross-modal reliabilities of two laterality tests. Brain and Language, 4,63-69.
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Galloway, L., & b a s h e n , s. D. (1980). Cerebral organization inbilingualism and second language. in R. C. Scarcella & S. D. Krashen (Eds.), Research in second language acquisition (pp. 74-80). Rowley, MA: Newbury House. Hardyck, C., Tzeng, 0. J. L., & Wang, W. S.-Y. (1977). Cerebral lateralization effects in visual half-field experiments. Nature, 269, 705-707. Hardyck, C., Tzeng, 0. J. L., & Wang, W. S.-Y. ( 1978). Cerebral lateralization of function and bilingual decision processes: Is thinking lateralized? Brain and Language, 5, 56-71. Hasuike, R., Tzeng, 0. J. L., & Hung, D. L. (1986). Script effects and cerebral lateralization: The case of Chinese characters. In J. Vaid (Ed.), Language processing in bilinguals: Psycholinguistic and neuropsychological perspectives (pp. 275-288). Hillsdale, NJ: Erlbaum. Ho, S. K., & Hoosain, R. (1989). Right hemisphere advantage in lexical decision with two-character Chinese words. Brain and Language, 37, 606-615. Hoosain, R. (1984). Lateralization of bilingual digit span functions. Perceprual and Motor SkilLY, 21 -22.
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Hoosain, R. (1986). Psychological and orthographic variables for translation asymmetry. In H. S. R. Kao & R. Hoosain (Eds.), Litiguiytics, psychology, and the Chinese language (pp.203-216). Hong Kong: University of Hong Kong Centre of Asian Studies. Hoosain, R. (1990, August). Cerebral lateralization of bilingual vocal-auditory functioning. Paper presented at the meeting of the American Psychological Association, Boston. Hoosain, R. (1991a). Psycholinguistic implications for linguistic relativity: A case study of Chinese. Hillsdale, NJ: Erlhaum. Hoosain, R. (1991b). Dichotic listening of Chinese and English words by bilinguals. Unpublished manuscript, University of Hong Kong, Hong Kong. Hoosain, R. (in press). Cerebral lateralization of bilingual unctions after handedness switch in childhood. Jounial of Genetic P.sychology. Hoosain, R., & Shiu, L. P. (1989). Cerebral lateralization of Chinese-English bilingual functions. Neuropbychologiu, 27, 705-712. Kalgren, B. (1949). The Chinese language. New York: Ronald.
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Kershner, J. R., & Jeng, G. R. (1972). Dual functional hemispheric asymmetry in visual perception: Effects of ocular dominance and post-exposure processes. Neuropsychologia, l0,437-445. Kinsbourne, M., & Cook, J. (1971). Generalized and lateralized effect of concurrent verbalization on a unimanual skill. QuarferlyJournal of Experitnenfal Psychology, 23, 341-343. Lyman, R. S., Kwan, S. T., & Chao, W. H. (1938). Left occipital-parietal brain tumour with observations on alexia and agraphia in Chinese and English. The Chinese Medical Journal, 3, 491-515. Paradis, M. (1990). Language lateralization in bilinguals: Enough already! Brain and Language, 3,576-586. Rapport, R. L., Tan, C. T., & Whitaker, H. A. (1983). Language function and dysfunction among Chinese- and English-speaking polyglots: Cortical stimulation, Wada testing, and clinical studies. Brain and Language, l8,342-366. Rudel, R. G., & Denckla, M. B. (1974). Relation of forward and backward digit repetition to neurological impairment in children with learning disabilities. Neuropsychologia, 2,109-118. Solin, D. (1989). The systematic misrepresentation of bilingual-crossed aphasia data and its consequences. Brain and Language, 36, 92-116. Stern, J. A. (1978). Eye movements, reading, and cognition. In J.W. Senders, D. F. Fisher, & R. A. Monty (Eds.), Eye movements and the higher psychological functions (pp. 145-155). Hillsdale, NJ: Erlbaum. Sussman, H. M. (1989). A reassessment of the time-sharing paradigm with ANCOVA. Brain and Language, 37, 514-520.
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Differential Cerebral Lateralization of Chinese-English Bilingual Functions? Rumjahn Hoosain University of Hong Kong Abstract Chinese-English bilinguals in Hong Kong provide a good test of the hypothesis of greater right hemisphere involvement in bilingual language functioning, particularly from the point of view of the nature of languages involved. However, studies using hemifield and bilateral visual presentation, monaural presentation, dichotic listening, as well as time-sharing tasks provided little support for the hypothesis. A review of the Chinese-English aphasia literature was similarly non-supportive. Some experimental findings of greater ambilaterality for second language functions might only reflect task difficulty. While it is generally accepted that the left cerebral hemisphere is dominant for language functions, the possibility that bilinguals have a lateralization pattern different from monolinguals has received a lot of attention since the work of Albert and Obler (1978). That bilingual functions are less left lateralized, and more specifically that second language functions involve the right hemisphere more, have been suggested (Albert & Obler, 1978; Vaid, 1983). More recently, it is felt that such views are not justified by evidence in the literature and there is the suggestion that we should "move on to more productive research" (Paradis, 1990, p. 576). In this paper I review experimental and clinical data on Chinese-English bilinguals. If bilingual lateralization patterns are different the chances of obtaining such evidence should be good with these subjects. Discussions of bilingual lateralization often recognize a number of variables that are taken to be conducive to differential lateralization. These include language specific factors, involving ways in which languages of the bilingual differ from each other, and language acquisitional factors, involving the manner of second language acquisition as well as the age and stage of second language acquisition. It has been suggested that the greater the first and second languages are different,and the more the contexts of acquisition of the two languages are different, the more likely it is that lateralization of the second language will differ from the left dominance pattern for the native language (Vaid, 1983). Chinese-English Bilinguals One major difference between Chinese and English is in terms of the relation between script, sound, and meaning in the written language (see Hoosain, 1991a). This
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is usually indicated by labelling the two languages as ideographic and alphabetic respectively. The script-sound relations in Chinese is on a one- to-one basis, with no grapheme-to-phoneme conversion rules (with pronunciations "spelt-out" in the latter case). As a result of differences between Chinese and English orthographies, the manner of information processing can differ. For example, eye-movement patterns in adult Chinese readers and the nature of reading problems in Chinese children are quite different from those of English speakers (Stern, 1978; Woo & Hoosain, 1984). Chinese is a tonal language. Nine tones are used in the Cantonese dialect spoken by the bilingual Hong Kong subjects referred to later. This use of tonal variation to indicate meaning results in the sing-song appearance of Chinese speech to non-speakers. In language structure, Chinese grammar is said to be "meagre" (Kalgren, 1949). Chinese grammar as such is not taught in schools, for example, in Hong Kong. In contrast, English grammar is given a lot of formal treatment in these schools. Thus, the manner of learning and processing Chinese compared with English can involve diverse processes. The course of bilingual acquisition follows a typical pattern for the vast majority of the University of Hong Kong undergraduates used in studies by the author, reported later (they all participated as subjects in the experiments in connection with taking an Introduction to Psychology course). They are all native Chinese (Cantonese) speakers, and Cantonese is spoken at home as well as amongst peers. English is learned at school, in a formal manner. It is taught as a school subject in grade school through high school and is officially the medium of instruction in high school for most of the subjects, although a variable amount of Chinese or mixed speech could be actually used in the classroom. English is the medium of instruction at the university. But it is safe to say that most subjects seldom have any extended conversation in English, lasting longer than a couple of sentences. They would read their daily Chinese newspapers but would only occasionally read English newspapers. Thus, the bilingual language acquisition conditions for Chinese and English are very dissimilar, and, according to some views, could be expected to show a less comparable pattern of hemispheric involvement for the two languages (Vaid, 1983).
In terms of the stage hypothesis (Galloway & Krashen, 1980), there should be greater left hemisphere involvement in second language processing in the final stages of second language acquisition. However, there is some sense in which the Hong Kong Chinese-English bilinguals should not be considered as reaching the final stages of bilingualism. It is true that these undergraduates have reached some kind of plateau of accomplishment in their second language acquisition, somewhat comparable to that of many beginning foreign students found in American universities. There has been concern that a lot of findings in the bilingual lateralization literature are either nonsignificant or contradicting each other (Paradis, 1990). To a large extent, methodological problems (e.g., Fennell, Bowers, & Satz, 1977; Sussman, 1989) and the lack of comparability between studies have led to a feeling of absence of progress. Different studies can employ diverse types of bilingual subjects, acquiring their languages under different circumstances and in different manners, and the
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languages involved could be different. One alternative would be for different procedures to be used by the same investigators on the same type of subjects, to provide some in-depth picture of the situation. This article reviews a number of studies carried out by the author on Chinese-English bilinguals in Hang Kong, using bilateral and hemifield presentation, monaural and dichotic listening, as well as time-sharing tasks to look at various aspects of bilingual functioning and the possibility of a different lateralization pattern for the two languages involved. Other experimental studies as well as aphasia studies are also reviewed. Visual Studies Three separate studies have been conducted comparing the lateralization of Chinese and English functions in visual tasks (Hoosain, 1986, in press; Hoosain & Shiu, 1989), all using Chinese-English bilinguals at the University of Hang Kong described above. In the first study (Hoosain, 1986), high frequency two-character Chinese words and three-lettered English words were presented in a visual hemifield procedure, with items shown in the right or left visual field so that the sensory information is initially conveyed to the contralateral hemisphere. The two Chinese characters in each item, as well as the three English letters were aligned vertically. Each item was shown for 150 ms, and subjects were asked to produce the translation equivalent of each presented item (in Chinese or in English) in the other language as soon as possible. Response times for each translation and error rate were obtained. It took the subjects about a second to translate the high frequency words in the experiment. Response times were faster for items shown in the right visual field, for both Chinese and English words, although the differences did not quite reach statistical significance. However, error rates for translating both Chinese and English words were significantly smaller when the items were shown in the right visual field. It would seem that lateralization patterns for the translation tasks in the two languages are similar, both favoring visual information initially conveyed to the left hemisphere.
Hoosain and Shiu (1989) conducted a more purely visual study. Pairs of items were presented on the two sides of the fixation point simultaneously for 120 ms. Each item could be a high frequency two-character Chinese word, a high frequency four- letter and two-syllable English word, or a four-digit random number. The pair of items could be Chinese-Chinese, Chinese- English, or Chinese-number in these bilateral presentations. Error rates showed that, whether paired with another Chinese word, an English word, or a number, Chinese words were seen significantly better when shown in the right visual field. Similarly, English words (which were always paired with Chinese words) were seen significantly better when they appeared in the right visual field rather than the left. Thus, both languages indicated a left hemisphere superiority in visual processing. Hoosain (in press) tested right-handed and left-handed subjects, as well as handedness-switched subjects who were born left-handed but forced to switch their preferred hand to the right during childhood. They were shown common two-character
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Chinese words and three-letter English words, with constituent characters or letters aligned vertically. Exposure time was adjusted for each individual subject. For righthanded subjects, there was a significantly greater number who identified more of the words shown in the right visual field than those shown in the left visual field, similarly so for Chinese and English words. Although both left-handed subjects and handedness switched subjects identified more Chinese and English words presented in the right visual field compared with the left, the numbers were not significant. Thus, there was no cerebral lateralization difference between identifymg Chinese and English words. Both kinds of items showed a left hemisphere advantage, although it was significant only for the right-handed subjects. Left-handers are known to show a weaker left lateralization and it appears that handedness switched subjects function similarly to ordinary left handers. To summarise, in various experimental tasks involving visual perception of Chinese and English words, the Hong Kong Chinese- English bilingual undergraduates did not display any differential lateralization for Chinese compared to English. Incidentally, while there have been periodic reports that visual perception of Chinese words is more right lateralized than that of English, due to its ideographic characteristic, it is now quite clear that this is not a valid factor and universal perceptual factors such as exposure time and the quality of the sensory signal are responsible for such findings (Hasuike, Tzeng, & Hung, 1986; Ho & Hoosain, 1989; Hoosain, 1991a). There are a few other studies reported in the literature involving Chinese-English bilinguals in perception of Chinese and English words. Kershner and Jeng (1972) tested right-handed Taiwanese Chinese graduate students in the U S . They were shown Chinese and English words as well as geometric forms in hemifield or bilateral presentation. In the case of both Chinese and English words, subjects were able to write down what they had seen better when the items were shown in the right visual field. This pattern was obtained for the hemifield as well as the bilateral presentation procedures. For the geometric forms, performance was better when items were presented in the left visual field using the hemifield presentation procedure, although no significant difference was found with the bilateral presentation procedure. Hardyck, Tzeng, and Wang (1977) tested bilinguals who were fluent in reading Chinese and English. Single-character words and their English translation equivalents were used. No signifcant response time and accuracy results were found with these subjects when pairs of Chinese-Chinese, Chinese-English, or English-English items were presented either in the same hemifield or bilaterally, and subjects had to indicate whether items had the same physical shape or not, or whether they had the same meaning or not. Hardyck, Tzeng, and Wang (1978) used similar materials, but about 5 minutes after the tachistoscopic presentation subjects were asked to recall the items presented. There was a significant difference in recall performance in favor of Chinese words shown in the right visual field compared to the left, and there was a similar but nonsignificant difference for English. This was the first experimental study that provided indication of differential lateralization -- a weaker left lateralization for English.
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But this finding of Hardyck et al. should be evaluated in connection with their report that response times in the initial tachistoscopic presentation were faster for first language compared with second language words. Most of the bilingual subjects had Chinese as their first language, although a few had English as first language. Thus, the majority of the subjects actually spent more time with the English words than with Chinese words during initial presentation. The longer dwell times for English items also meant that there was a greater opportunity for interhemisphere commmunication in processing English items.
To conclude, experimental visual studies of Chinese and English with bilingual subjects do not point to differential lateralization for the two languages. The only exception (Hardyck et al., 1978), showing weaker lateralization for English, involves longer processing times. This issue will be discussed later. Auditory Studies Reports on auditory studies of Chinese-English bilinguals are rare in the literature. Hoosain (1984) performed a digit span test on Chinese-English bilingual undergraduates. The standard procedure for such tests was used, except that each set of random numbers, starting with a short sequence and ending with a sequence too long for the subject, was presented only to the right or left ear over a set of earphones. Also, both forward digit span and backward digit span were determined, for Chinese and for English. The digit spans obtained by this monaural procedure showed a significant right ear (left hemisphere) superiority for forward digit span in Chinese. No other condition showed any significant laterality difference, although there was still a nonsignificant right ear superiority for forward digit span in English.
On the face of it, this would be a second indication (apart from that of Hardyck et al., 1978) of weaker lateralization of English functions in Chinese-English bilinguals. The weaker lateralization for the backward digit condition (for both Chinese and English) can be considered in terms of the view that operations to produce backward digt sequences involve the right hemisphere more (Rude1 & Denckla, 1974). But the weaker lateralization for the forward digit span in English is reminiscent of the finding of Hardyck et al., only now in the auditory mode rather than the visual. The actual forward digit span for English was smaller than for Chinese, that is, subjects found memorizing English numbers more difficult. In the case of tachistoscopic presentation in the Hardyck et al. study, response times were longer for second language items (which was English for most of the subjects). Again, this means that weaker lateralization was found with the more difficult language. In a dichotic listening study (Hoosain, 1991b), Chinese- English bilingual undergraduates at the University of Hong Kong heard two groups of four common two-character Chinese words (or four common two-syllable English words), each group through one ear, using a set of earphones. The percentages of correct recall of Chinese items were 62.4% for those presented to the right ear and 43.3% for the left ear. Thus, there was a right ear or left hemisphere superiority effect. For English, the
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corresponding results were 49.0% and 34.3% respectively. Although the English performance was not as good as that for Chinese, there was a similar right ear, left hemisphere superiority effect. The two auditory studies provide mixed results for the differential lateralization hypothesis. The monaural study showed some indication of weaker lateralization for English, but then subjects found the English digit span test more difficult than Chinese. The dichotic listening study showed similar left lateralization for both Chinese and English, even though English words were more difficult to recall. Time-sharing Studies There are only a couple of studies using the time-sharing paradigm (Hoosain, 1990; Hoosain & Shiu, 1989). In both studies, undergraduates at the University of Hong Kong were asked to count backwards by 3's (e.g., to say "97, 94, 91, etc." when given "97") in either Chinese or English. They were also asked to perform a standard finger tapping test, with the right or left index finger. After baseline measures for these tasks were obtained, subjects were asked to simultaneously engage in finger tapping with the right or left hand and backward counting in Chinese or English. Finger tapping is controlled by the contralateral hemisphere. When compared with baseline tapping or counting scores, changes in the respective performances during the time-sharing trials would indicate the extent to which the right or left hemisphere is engaged in the backward counting task in either language.
In the time-sharing trials, there was an increase in backward counts performed but a decrease in the number of taps made, when compared with the respective baseline measures. The possibility that one of the concurrent tasks could be carried out better than baseline performance has been acknowledged (Kinsbourne & Cook, 1971), although there could also be some practice effect. In these two experiments, it appeared that subjects attended to the counting tasks more than to tapping during the time-sharing trials. This pattern was found in both studies. Hoosain and Shiu (1989) found that concurrent counting affected right-hand tapping (controlled by the left hemisphere) more than left-hand tapping, and similarly so for both languages. This indicated that both Chinese and English backward counting was lateralized in the left hemisphere. The effect of concurrent counting on tapping performance did not show any significant lateralization pattern. On the other hand, Hoosain (1990) found some indication of right hemisphere involvement in second language functioning. This time, the effect of concurrent counting on tapping performance did not show any significant lateralization pattern. But when subjects were counting in Chinese, improvement in counting was greater during tapping with the left hand rather than the right. When counting in English, improvement was greater during tapping with the right hand. This would suggest that the left hemisphere is more concerned with counting in Chinese and the right hemisphere more concerned with counting in English. This particular finding provided
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perhaps the strongest single indication of right hemisphere involvement in English functioning. Thus, the two time-sharing studies produced contradictory findings. In a review of the time-sharing paradigm, Sussman (1989) warned that concurrent tapping disruption rates can be affected by discrepant baseline tapping speed of the dominant and nondominant hands. But in the case of Hoosain (1990) we had a significant interaction effect of language and hand used on the enhancement of backward counting. In any case, the contradictory results from the above two studies, one showing left lateralization for both languages and one showing left hemisphere lateralization for Chinese but right lateralization for English, reminds us of the contradictory picture for bilingual laterality pointed out by Paradis (1990). There is also a question of the reliability of the time- sharing procedure. We had enhanced tapping in one study and enhanced counting in another, although identical procedures were used on similar subjects. Enhanced performance during timesharing, particular involving the hand contralateral to the language hemisphere, is seldom found (Kinsbourne & Cook, 1971). It might be noted that the Hong Kong subjects tend to have very high baseline scores in the first place, averaging over 110 taps with the right hand and 14 backward counts, in 20 seconds. The subjects in Hoosain (1990) had even better baseline Chinese backward counting, averaging 16.0 counts. Aphasia Studies There are about a dozen individually reported cases of aphasia in Chinese-English bilinguals in the literature. Although there are indications of intrahemisphere differences in locations for Chinese and English processes, there is no overall picture of differential lateralization for the two languages. The earliest reported case was that of Lyman, Kwan, and Chao (1938). A patient from Shanghai who was fluent in both Chinese and English had a large left occipito-parietal fibroblastoma. His Chinese as well as English speech and oral comprehension were good. He had some difficulties with reading English, but his reading of Chinese was very much worse. His written English was also better than Chinese. For a few decades, this study had a prominent position in the literature on Chinese aphasia and provided support for the idea of differential lateralization of the two languages of the bilingual. It is also consistent with greater ambilaterality for the second language of the bilingual. April and his colleagues (April & Tse, 1977; April & Han, 1980) reported on two cases of crossed aphasia in Chinese-English bilinguals living in New York. The two right-handed Chinese males had right hemisphere lesions resulting in aphasia. The first patient had his Chinese functions affected more than English, and it was suggested that the right hemisphere might be more involved with using an ideographic language. However, the second patient did not show any significant difference between Chinese and English performance. April and Han (1980) also reported that a review of unspecified numbers of Chinese patients in New York and in Taiwan did not indicate
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an incidence of crossed aphasia above the 4% from the European literature. While many of the Taiwan patients may not be Chinese-English bilinguals, the New York patients should most likely be bilingual. The actual number of cases that were examined was not reported by April and Han, but it was apparently enough to convince the authors to give up the idea of differential lateralization amongst the Chinese (although the authors focused on altered lateralization due to use of the nonalphabetic Chinese language rather than bilingual differential lateralization as such). T’sou (1978) reported on a female Chinese-English bilingual in Hong Kong with a left posterior temporo-parietal hemorrhage resulting in conduction aphasia. Both Chinese and English were affected, although there were some variations dueto language characteristics. Thus, she had problems particularly with the low falling tone in Cantonese, and mirror image reversal in English (saying instead of god).
In the above four cases, the patients were all Chinese dominant, although that of Lyman et al. was fluent in English. Rapport, Tan, and Whitaker (1983) studied a total of seven right- handed polyglots in Malaysia. All were fluent in English and at least one Chinese dialect, and in some cases English was the dominant language. Some also spoke Malay. Different combinations of the Wada test (with one or the other cerebral hemisphere being temporarily incapacitated), cortical stimulation (while subjects were engaged in object naming or silent reading), and clinical tests were carried out on the patients. Five of t h e seven patients had left and two had right hemisphere lesions. Rapport et a]. found no pattern of greater right hemisphere involvement in language functions, either for Chinese or for the other languages. There were two cases of weaker lateralization, with indication of right hemisphere involvement. But, in one case, the patient was a young female with a laterality quotient of +75. In the other case, the patient could have mixed cerebral dominance as a result of congenital vascular anomaly in the left hemisphere. All the patients were left hemisphere dominant for the languages or dialects tested. Cortical stimulation did provide evidence that different languages or dialects could occupy different loci within the same left hemisphere. The Chinese-English aphasia literature does not generally support a conclusion of greater right hemisphere involvement for the second language, or indeed greater right hemisphere involvement for either language. The two cases of crossed aphasia reported by April and his colleagues could well fall within the category of reports that are selective in favor of the unusual, and they were more than counterbalanced by the absence of a higher incidence of crossed-aphasia amongst Chinese patients reviewed in New York and in Taiwan. Unfortunately, the actual number of cases considered by April and Han (1980) is not known, although in the New York sample, it was from two hospitals over two years in the city, and one of the hospitals treats a large Chinese population. This would apparently amount to an unselected group study (Solin, 1989).
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Conclusion The available experimental and aphasia studies, on the whole, do not present a picture of any pattern of differential lateralization of Chinese-English bilingual functions. Even so, there are a small number of reports going against the trend that need to be considered. There are two experimental studies showing a weaker lateralization for English (Hardyck et al., 1978, Experiment 2; Hoosain, 1984). In both cases, performance for English items was poorer, with subjects requiring more response time and recalling fewer items respectively. There is indication that tasks based on visual information taking more than one second to complete tend not to obtain significant lateralization effects (Hoosain, 1991a). In these cases, interhemisphere communication probably plays a greater role and the quest for lateralization effect is doomed. A similar situation could be found where a more difficult task requires greater effort. Given that second language functioning tends to be poorer (slower, with smaller short-term memory capacity, etc.) for most bilinguals, there is a built-in bias for findings what could be taken as weaker lateralization of second language functions. These findings do not necessarily mean that the locus of processing has moved away from the left hemisphere, or that right-hemisphere based processes or strategies are dominantly being used for the second language. In the case of the time-sharing studies showing contradictory results (Hoosain, 1990; Hoosain & Shiu, 1989) further work needs to be done to clarify the reliability of the of the procedure, particularly in view of questions concerning the paradigm (Sussman, 1989). Out of the eleven cases of aphasia reported, only three were consistent with the hypothesis of differential lateralization as a result of Chinese-English bilingual experience. The two cases of crossed aphasia reported by April and his colleagues are offset by their own reference to larger samples of left lateralization for language. The case of Lyman et al. (1938) would have to remain in its place in the classical literature, without us knowing whether it was selected because of its unusual features (we do not even know the handedness of the patient). References Albert, M. L., & Obler, L. K. (1978). The bilingual brain: NeuropJychological and tieurolingubiic aspects of bilingualism. New York: Academic Press. April, R. S., & Han, M. (1980). Crossed aphasia in a right-handed bilingual Chinese man: A second case. Archives of Neurologv, 37, 342-346. April, R. S., & Tse, P. C. (1977). Crossed aphasia in a Chinese bilingual dextral. Archives of Neurology, 34, 766-770. Fennell, E. B., Bowers, D., & Sat& P. (1977). Within-modal and cross-modal reliabilities of two laterality tests. Brain and Language, 4,63-69.
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