4 Lexical Processing and Sentence Comprehension in Aphasia

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134 ZURIF, SWINNEY, GARRETTCONCLUSIONAt the outset of this chapter we distinguished between the approach takenhere and the more usual information processing analyses of language disorders.both share the usual assumptions: that the language faculty can be decomposedinto a set of processing components or modules, some of whichare disrupted by brain damage; that the spared components do not, themselves,perform differently when one or more of the other components arenot functioning normally; and that the pathological performance will providea basis for discerning which components or modules are disrupted(Caramazza, 1984). The difference between the two approaches turns onthe manner by which each isolates the modules of the system. Informationprocessing approaches to language disorder characterizations typically producemodules in line with relatively uncontroversial distinctions among informationtypes specified in linguistic theory. So, generally, there arephonological, syntactic, lexical, and semantic components-each, often,with its own buffer. To these constituents additional components and accessroutes are provided as needed whether to explain modality differencesin performance (auditory vs. visual input systems) or to account for linguisticallyrelated symptoms, such as the relative sparing of concrete as opposedto abstract nouns or of open-class items as opposed to closed-classitems (e.g., Coltheart, Patterson, & Marshall, 1980, chapters and referencestherein).By contrast, the approach exemplified by the two studies described inthis chapter is not one of isolating modules as a direct reflection of partitionsin linguistic theory, nor one of isolating modules (together with theirfunctional lesions) solely as a means of redescribing the patterns of sparingand loss in aphasia. Rather, the evidence for modules in the present analysesemerges as the consequence of charting mandatory operating characteristicsof the comprehension system. Thus, whatever the status ofclosed-class access, our demonstration of the impenetrability (autonomy)of lexical access in general is grounded in the finding that such access ismomentarily uninfluenced by context. And, to the extent that we haveshown that the agrammatic deficit is statable in terms of a disruption internalto this device and not to its absence-the module is not destroyed, itjust works abnormally-we have provided a more suitable framework forevaluating variability and imprecision in aphasic performance. By contrast,functionally excising one or another box in an information flow diagramdisallows any explanation for the often encountered pattern of suboptimalperformance that is, nonetheless, above chance.By not confusing modules with the linguistic objects they are intended toimplement, and by, instead, measuring and ensuring the degree of encapsulationof any particular device in terms of on-line operating characteristics,we lessen the distance between the science of cognitive psychology and
4. LEXICAL PROCESSING AND SENTENCE COMPREHENSION 135neuroscience-the distance between descriptions of the functional architectureof language and descriptions of its (presumably hardwired) neurologicalresources.ACKNOWLEDGMENTSThe research reported in this chapter was supported in part by NS 11408and NS 06209 to the Aphasia Research Center, Department of Neurology,Boston University School of Medicine, by NS 21806 to Brandeis University,and by a grant from the Sloan Foundation to the MIT Cognitive ScienceCenter.REFERENCESBadecker, W., & Caramazza, A. (1985). On considerations of method and theory governingthe use of clinical categories in neurolinguistics and cognitive neuropsychology: The caseagainst agrammatism. Cognition, 20, 97-125.Berndt, R. S., & Caramazza, A. (1980). A redefinition of the syndrome of Broca's aphasia:Implications for a neuropsychological model of language. Applied Psycholinguistics, 1,225-278.Bradley, D. (1978). Computational distinctions of vocabulary type. Unpublished doctoral dissertation,Massachusetts Institute of Technology, Cambridge, MA.Bradley, D., & Garrett, M. (1983). Hemisphere differences in the recognition of closed andopen class words. Neuropsychologia, 21, 155-160.Bradley, D., Garrett, M., & Zurif, E. B. (1980). Syntactic deficits in Broca's aphasics. InD. Caplan (Ed.), Biological studies of mental processes (pp. 269-286). Cambridge, MA:MIT Press.Caramazza, A. (1984). The logic of neuropsychological research and the problem of patientclassification in aphasia. Brain and Language, 21, 9-20.Coltheart, M., Patterson, K., & Marshall, J. (Eds.). (1980). Deep dyslexia. London:Routledge & Kegan Paul.Drenowski, A., & Healy, A. (1977). Deletion errors on "the" and "and": Evidence for readingunits larger than the word. Memory and Cognition, 8, 636-647.Egido, C., & Garrett, M. (1981). Frequency contrasts for open and closed class words on auditorylexical decision. Unpublished manuscript, Massachusetts Institute of Technology, PsychologyDepartment, Cambridge, MA.Fodor, J. (1983). The modularity ofmind. Cambridge, MA: MIT Press.Forster, K. 1. (1979). Levels of processing and the structure of the language processor. InW. Cooper & E. C. T. Walker (Eds.), Sentence Processing. Hillsdale, NJ: LawrenceErlbaum Associates.Friederici, A. D. (1983). Aphasics' perception of words in sentential context: Some real-timeprocessing evidence. Neuropsychologia, 21, 351-358.Garcia-Albea, J., & Sanchez-Casas, Y. R. (1983). Language processes: Comparative psycholinguisticstudies in word recognition. Final Research Report for the Joint Spanish NorthAmerican Committee for Cultural and Educational Exchange.Goodglass, H., & Kaplan, E. (1972). The assessment ofaphasia and related disorders. Philadelphia:Lea & Febiger.
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