- Email: [email protected]
The Loch Ness Monster approach to bilingual language lateralization: A response to Berquier and Ashton
BRAIN
AND
LANGUAGE
4,
534-537 (1992)
The Loch Ness Monster Approach to Bilingual Language Latera~ization: A Response to Berquier and Ashton MICHEL PARADE
To continue to search for a difference in language lateralization between bilinguals and unilinguals is at best a futile task in the face of all the clinical evidence to the contrary and inconsistent experimental findings. No amount of refining of dichotic, tachistoscopic, or concurrent task procedures, or statistical sophistication, is likely to tap the differential reliance on pragmatic cues that might very well exist in some nonbalanced bilinguals. o 1992 Academic FYES, hc.
Some folks believe that a certain lake in Scotland is inhabited by a dinosaur-like aquatic monster. Occasionally, some people have claimed to have seen the monster rising above the surface. The search for the Loch Ness Monster dates back to the 1200s and though it has intensified since the 1930s no one has yet been able to provide any evidence of its existence. That does not deter some people from believing that if they could only find better ways to search for the monster, they would eventually find it. Maybe if they tried glass-bottom boats at night with more powerful lights, or perhaps specially equipped submarines, or if they improved the power of the lens of their periscope or the size of their dragnet, or if they controlled for weather conditions and time of day . . . they might find it. Replace the Monster by differential language lateralization in bilinguals and you have the story of the search for the elusive difference that has been keeping experimental psychologists busy for the past quarter of a century, especially so since the seventies. Like the Loch Ness Monster, differential laterality is occasionally claimed to have been seen, under certain restricted conditions, but the purported evidence does not stand scrutiny; it either cannot be replicated or the reverse is found. Who knows? Perhaps if one tried laterality of gaze direction of bilinguals while listening Address all reprint requests to Michel Paradis at the Department of Linguistics, McGill University, 1001 Sherbrooke St. West, Montreal H3A lG5, Quebec, Canada 534 ~3-9~~~
$5.00
Copyright 6 1992 by Academic Press, Inc. All rights of reproduction in any form reserved.
NOTES AND DISCUSSION
535
to one or the other language, one might find a nonsignificant trend to report. So why quit indeed? To justify continuing the search for a phenomenon after years of failure to experimentally demonstrate its existence in the light of clinical evidence to the contrary (i.e. no higher incidence of crossed aphasia that would necessarily show up, as in the case of left handers-and there are at least as many bilinguals as left handers in the world), one must have good grounds to believe that the phonomenon exists but that, for some reason, we have failed to demonstrate it. At least there is a good reason to believe in the Loch Ness Monster; it continues to bring in tourists to the area. What is that compelling reason, be it theoretical or empirical, that drives psychologists to want to conduct yet more of the same kind of experiments to find something that the clinic says is not there? At least the Loch Ness Monster is good for business. What are tachistoscopic, dichotic listening, or tapping experiments in bilinguals intrinsically good for (once it has become obvious that they lead nowhere)? There was a time when it was legitimate to ask the question about differential lateralization in bilinguals. There was a hypothesis-r a number of hypotheses-to be tested. However, none has panned out. Clinical studies are unanimously consistent with the null hypothesis, namely that there is no difference in lateralization in bilinguals compared to unilinguals. The contradictory results of those experimental studies that do find a difference, in the face of all those that find none, strongly suggest that the paradigms that have been used are not valid to measure what they set out to measure: the degree of lateralization of language in bilinguals. To justify a scientific search for some phenomenon, one would preferably have to have a good reason, some motivated hypothesis, especially if all attempts at documenting the alleged phenomenon have failed. I do not wish to suggest that ANCOVA should or should not be used to parcel out differences in initial performance in the concurrent task paradigm. I was merely pointing out that one author who had claimed to have found a difference was not even sure that the paradigm-cumstatistics that he himself had used were valid. The pitfalls of statistical methods are indeed many and subtle. There is no reason not to compare inconsistent conclusions across studies using divergent procedures, whether or not various cortical and/or subcortical structures are involved, unless one independently determines which procedures to measure language lateralization are not valid, and unless one is able to propose some theoretical motivation for supposing that oral word representations should be less lateralized in bilinguals than in unilinguals, but not written word representations (or vice versa) or any other dimension. What needs justification is the assumption that some particular language variable (as opposed to all others) should be selectively prone to different hemispheric treatment in bilinguals relative to unilin-
536
NOTES AND DISCUSSION
guals. Moreover, since no statistically significant differential lateralization has been reported in numerous studies that used differing paradigms as well as different types of bilingual populations, failure to find a difference is not likely to be dependent on a specific paradigm or a particular bilingual subpopulation. Various paradigms (as well as methodological variations within the same paradigm) have led to contradictory results and progressively more restricted populations of bilinguals have been hypothesized to have less asymmetrical representation of language. What would be the theoretical significance of finding that 10% of bilinguals or less who are, say, females at the early stages of acquiring their second language in an informal environment after the age of 40, provided they are tested before breakfast while blindfolded, show a 1% difference against unilingual controls provided a particular statistical procedure is used-or more in keeping with the relevant literature, when a nonsignificant trend is reported? Berquier and Ashton, in a perfect illustration of this modus operandi, report that in one study using right hemisphere damaged patients “although no statistically significant difference in incidence of aphasia was found between monolinguals and bilinguals, a small subgroup of bilinguals with subcortical damage showed evidence of aphasia.” (Italics added) So what? What is the point of reporting a nonfinding, this time subsequent to subcortical damage? Do the authors wish to imply that the difference in laterality is no longer to be searched for in the cortex, but in the thalamus? Do they wish to introduce yet another restriction, namely that differential lateralization can only be demonstrated at the level of the thalamus? But then why, since there is no greater incidence of bilingual aphasia subsequent to a lesion there than anywhere else? (If that fails, one could, of course, continue to search for a difference at the level of the striatum, the internal capsule, and the white matter near the lateral ventricle. Indeed, why not?) What Berquier and Ashton are saying is that results reported so far are an artifact of the methodology used. I could not agree more. That is exactly my point. But which of the studies published to date used the right methodology? Those that are consonant with the clinical findings (i.e., half the studies, which find no difference), or those that do find some difference but contradict each other with respect to the relevant subpopulation and that are not consonant with clinical reports--and if so, which one(s)? One may safely assume that whatever the right hemisphere is doing in unilinguals, it will do in bilinguals too. The question is whether the RH in bilinguals does anything more or does it differently than in unilinguals. Joanette, Lecours, Lepage, and Lamoureux (1983) have indeed shown that in a number of unilingual right handers, subsequent to RH damage, some subtle deficits in phonology, morphology, syntax, or the lexicon
NOTES AND DISCUSSION
537
could be demonstrated with a standard aphasia battery. To that extent, we have good reason to expect RH involvement in bilinguals-but to that extent only. If the RH is likely to participate more, it is not in subserving the grammar, but in the pragmatic aspects of language use. The nonbalanced bilingual might have a tendency to rely more on pragmatic cues vs. morphosyntactic cues in deriving an interpretation for utterances in the weaker language than in the stronger language. No amount of refined dichotic procedures (that bear on syllables or digits) or improved tachistoscopic hemifield presentation (of wo&) or statistical sophistication is likely to tap that difference. To continue searching for a difference that has, for decades, eluded experimental psychologists (who used procedures whose validity and reliability are, of their own admission, at best questionable), and for which there is no shred of clinical evidence (in fact, all the evidence we have points to the contrary), simply does not seem to be a very efficient, productive way to do research. REFERENCES Berquier, A., & Ashton, R. 1992. Language lateralization in bilinguals: More not less is needed. A reply to Paradis (1990). Brain and Language, 43, 528-533. Joanette, Y., Lecours, A. R., Lepage, Y., & Lamoureux, 1983. Language in right-handers with right-hemisphere lesions: A preliminary study including anatomical, genetic, and social factors. Brain and Language, 20, 217-248.
AND
LANGUAGE
4,
534-537 (1992)
The Loch Ness Monster Approach to Bilingual Language Latera~ization: A Response to Berquier and Ashton MICHEL PARADE
To continue to search for a difference in language lateralization between bilinguals and unilinguals is at best a futile task in the face of all the clinical evidence to the contrary and inconsistent experimental findings. No amount of refining of dichotic, tachistoscopic, or concurrent task procedures, or statistical sophistication, is likely to tap the differential reliance on pragmatic cues that might very well exist in some nonbalanced bilinguals. o 1992 Academic FYES, hc.
Some folks believe that a certain lake in Scotland is inhabited by a dinosaur-like aquatic monster. Occasionally, some people have claimed to have seen the monster rising above the surface. The search for the Loch Ness Monster dates back to the 1200s and though it has intensified since the 1930s no one has yet been able to provide any evidence of its existence. That does not deter some people from believing that if they could only find better ways to search for the monster, they would eventually find it. Maybe if they tried glass-bottom boats at night with more powerful lights, or perhaps specially equipped submarines, or if they improved the power of the lens of their periscope or the size of their dragnet, or if they controlled for weather conditions and time of day . . . they might find it. Replace the Monster by differential language lateralization in bilinguals and you have the story of the search for the elusive difference that has been keeping experimental psychologists busy for the past quarter of a century, especially so since the seventies. Like the Loch Ness Monster, differential laterality is occasionally claimed to have been seen, under certain restricted conditions, but the purported evidence does not stand scrutiny; it either cannot be replicated or the reverse is found. Who knows? Perhaps if one tried laterality of gaze direction of bilinguals while listening Address all reprint requests to Michel Paradis at the Department of Linguistics, McGill University, 1001 Sherbrooke St. West, Montreal H3A lG5, Quebec, Canada 534 ~3-9~~~
$5.00
Copyright 6 1992 by Academic Press, Inc. All rights of reproduction in any form reserved.
NOTES AND DISCUSSION
535
to one or the other language, one might find a nonsignificant trend to report. So why quit indeed? To justify continuing the search for a phenomenon after years of failure to experimentally demonstrate its existence in the light of clinical evidence to the contrary (i.e. no higher incidence of crossed aphasia that would necessarily show up, as in the case of left handers-and there are at least as many bilinguals as left handers in the world), one must have good grounds to believe that the phonomenon exists but that, for some reason, we have failed to demonstrate it. At least there is a good reason to believe in the Loch Ness Monster; it continues to bring in tourists to the area. What is that compelling reason, be it theoretical or empirical, that drives psychologists to want to conduct yet more of the same kind of experiments to find something that the clinic says is not there? At least the Loch Ness Monster is good for business. What are tachistoscopic, dichotic listening, or tapping experiments in bilinguals intrinsically good for (once it has become obvious that they lead nowhere)? There was a time when it was legitimate to ask the question about differential lateralization in bilinguals. There was a hypothesis-r a number of hypotheses-to be tested. However, none has panned out. Clinical studies are unanimously consistent with the null hypothesis, namely that there is no difference in lateralization in bilinguals compared to unilinguals. The contradictory results of those experimental studies that do find a difference, in the face of all those that find none, strongly suggest that the paradigms that have been used are not valid to measure what they set out to measure: the degree of lateralization of language in bilinguals. To justify a scientific search for some phenomenon, one would preferably have to have a good reason, some motivated hypothesis, especially if all attempts at documenting the alleged phenomenon have failed. I do not wish to suggest that ANCOVA should or should not be used to parcel out differences in initial performance in the concurrent task paradigm. I was merely pointing out that one author who had claimed to have found a difference was not even sure that the paradigm-cumstatistics that he himself had used were valid. The pitfalls of statistical methods are indeed many and subtle. There is no reason not to compare inconsistent conclusions across studies using divergent procedures, whether or not various cortical and/or subcortical structures are involved, unless one independently determines which procedures to measure language lateralization are not valid, and unless one is able to propose some theoretical motivation for supposing that oral word representations should be less lateralized in bilinguals than in unilinguals, but not written word representations (or vice versa) or any other dimension. What needs justification is the assumption that some particular language variable (as opposed to all others) should be selectively prone to different hemispheric treatment in bilinguals relative to unilin-
536
NOTES AND DISCUSSION
guals. Moreover, since no statistically significant differential lateralization has been reported in numerous studies that used differing paradigms as well as different types of bilingual populations, failure to find a difference is not likely to be dependent on a specific paradigm or a particular bilingual subpopulation. Various paradigms (as well as methodological variations within the same paradigm) have led to contradictory results and progressively more restricted populations of bilinguals have been hypothesized to have less asymmetrical representation of language. What would be the theoretical significance of finding that 10% of bilinguals or less who are, say, females at the early stages of acquiring their second language in an informal environment after the age of 40, provided they are tested before breakfast while blindfolded, show a 1% difference against unilingual controls provided a particular statistical procedure is used-or more in keeping with the relevant literature, when a nonsignificant trend is reported? Berquier and Ashton, in a perfect illustration of this modus operandi, report that in one study using right hemisphere damaged patients “although no statistically significant difference in incidence of aphasia was found between monolinguals and bilinguals, a small subgroup of bilinguals with subcortical damage showed evidence of aphasia.” (Italics added) So what? What is the point of reporting a nonfinding, this time subsequent to subcortical damage? Do the authors wish to imply that the difference in laterality is no longer to be searched for in the cortex, but in the thalamus? Do they wish to introduce yet another restriction, namely that differential lateralization can only be demonstrated at the level of the thalamus? But then why, since there is no greater incidence of bilingual aphasia subsequent to a lesion there than anywhere else? (If that fails, one could, of course, continue to search for a difference at the level of the striatum, the internal capsule, and the white matter near the lateral ventricle. Indeed, why not?) What Berquier and Ashton are saying is that results reported so far are an artifact of the methodology used. I could not agree more. That is exactly my point. But which of the studies published to date used the right methodology? Those that are consonant with the clinical findings (i.e., half the studies, which find no difference), or those that do find some difference but contradict each other with respect to the relevant subpopulation and that are not consonant with clinical reports--and if so, which one(s)? One may safely assume that whatever the right hemisphere is doing in unilinguals, it will do in bilinguals too. The question is whether the RH in bilinguals does anything more or does it differently than in unilinguals. Joanette, Lecours, Lepage, and Lamoureux (1983) have indeed shown that in a number of unilingual right handers, subsequent to RH damage, some subtle deficits in phonology, morphology, syntax, or the lexicon
NOTES AND DISCUSSION
537
could be demonstrated with a standard aphasia battery. To that extent, we have good reason to expect RH involvement in bilinguals-but to that extent only. If the RH is likely to participate more, it is not in subserving the grammar, but in the pragmatic aspects of language use. The nonbalanced bilingual might have a tendency to rely more on pragmatic cues vs. morphosyntactic cues in deriving an interpretation for utterances in the weaker language than in the stronger language. No amount of refined dichotic procedures (that bear on syllables or digits) or improved tachistoscopic hemifield presentation (of wo&) or statistical sophistication is likely to tap that difference. To continue searching for a difference that has, for decades, eluded experimental psychologists (who used procedures whose validity and reliability are, of their own admission, at best questionable), and for which there is no shred of clinical evidence (in fact, all the evidence we have points to the contrary), simply does not seem to be a very efficient, productive way to do research. REFERENCES Berquier, A., & Ashton, R. 1992. Language lateralization in bilinguals: More not less is needed. A reply to Paradis (1990). Brain and Language, 43, 528-533. Joanette, Y., Lecours, A. R., Lepage, Y., & Lamoureux, 1983. Language in right-handers with right-hemisphere lesions: A preliminary study including anatomical, genetic, and social factors. Brain and Language, 20, 217-248.