Language module

This article is about the structure in the human brain. For the software design technique supported by some programming languages, see Modular programming.

Language module refers to a hypothesized structure in the human brain (anatomical module) or cognitive system (functional module) that some psycholinguists such as Steven Pinker claim contains innate capacities for language. There is currently ongoing debate about this in the field of cognitive science (psycholinguistics) and neuroscience (neurolinguistics).

Meaning of a module

The debate on the issue of modularity in language is underpinned, in part, by different understandings of this concept.[1] There is, however, some consensus in the literature that a module is considered committed to processing specialized representations (domain-specificity) (Bryson and Stein, 2001)[2][3] in an informationally encapsulated way.[3][4] A distinction should be drawn between anatomical modularity, which proposes there is one 'area' in the brain that deals with this processing, and functional modularity that obviates anatomical modularity whilst maintaining information encapsulation in distributed parts of the brain.[5]

No singular anatomical module

The available evidence points towards no one anatomical area solely devoted to processing language. The Wada test, where sodium amobarbital is used to anaesthetise one hemisphere, shows that the left-hemisphere appears to be crucial in language processing.[6] Yet, neuroimaging does not implicate any single area but rather identifies many different areas as being involved in different aspects of language processing (Raichle, 1998)[7][8] and not just in the left hemisphere.[9] Further, individual areas appear to subserve a number of different functions (Raichle, 1998).[10] Thus, the extent to which language processing occurs within an anatomical module is considered to be minimal. Nevertheless, as many have suggested,[11][12] modular processing can still exist even when implemented across the brain; that is, language processing could occur within a functional module.

No double dissociation – acquired or developmental

A common way to demonstrate modularity is to find a double dissociation. That is two groups: First, people for whom language is severely damaged and yet have normal cognitive abilities and, second, persons for whom normal cognitive abilities are grossly impaired and yet language remains intact.[13][14][15] Whilst extensive lesions in the left hemisphere perisylvian area can render persons unable to produce or perceive language (global aphasia),[16] there is no known acquired case where language is completely intact in the face of severe non-linguistic deterioration.[17] Thus, functional module status cannot be granted to language processing based on this evidence.

However, other evidence from developmental studies has been presented (most famously by Pinker[18]) as supporting a language module, namely the purported dissociation between Specific Language Impairment (SLI), where language is disrupted whilst other mental abilities are not,[19] and Williams Syndrome (WS) where language is said to be spared despite severe mental deficits.[20] More recent and empirically robust work has shown that these claims may be inaccurate, thus, considerably weakening support for dissociation. For example, work reviewed by Brock[21] and Mervis and Beccera[22] demonstrated that language abilities in WS are no more than would be predicted by non-linguistic abilities. Further, there is considerable debate concerning whether SLI is actually a language disorder or whether its aetiology is due to a more general cognitive (e.g. phonological) problem.[19][23][24][25][26] Thus, the evidence needed to complete the picture for modularity – intact language coupled with gross intellectual deterioration – is not forthcoming. Consequently, developmental data offers little support for the notion that language processing occurs within a module.

Thus, the evidence from double dissociations does not support modularity, although it should be noted that lack of dissociation is not evidence against a module; this inference cannot be logically made.

Lack of information encapsulation

Indeed, if language were a module it would be informationally encapsulated. Yet, there is evidence to suggest that this is not the case. For instance, in the McGurk effect, watching lips say one phoneme whilst another is played creates the percept of a blended phoneme.[27][28] Further, Tanenhaus, Spivey-Knowlton, Eberhard and Sedivy (1995) demonstrated visual information mediating syntactic processing. In addition, the putative language module should process only that information relevant to language (i.e., be domain-specific). Yet evidence suggests that areas purported to subserve language also mediate motor control[29] and non-linguistic sound comprehension.[30] Although it is possible that separate processes could be occurring but below the resolution of current imaging techniques, when all this evidence is taken together the case for information encapsulation is weakened.

The alternative

The alternative, as it is framed, is that language occurs within a more general cognitive system.[31] The counterargument is that there appears to be something ‘special’[32] about human language. This is usually supported by evidence such as all attempts to teach animals human languages to any great success have failed (Hauser et al. 2003) and that language can be selectively damaged (a single dissociation)[33] suggesting proprietary computation may be required. Instead of postulating 'pure' modularity, theorists have opted for a weaker version, domain-specificity implemented in functionally specialised neural circuits and computation (e.g. Jackendoff and Pinker’s words, we must investigate language “not as a monolith but as a combination of components, some special to language, others rooted in more general capacities”).[34]

The debate is ongoing.

See also

References

  1. ↑ Coltheart, M. (1999). Modularity and cognition. Trends in Cognitive Sciences, 3, 115–120
  2. ↑ Bryson, J. J. (2002). Language isn’t quite that special. Brain and Behavioral Sciences, 25 (6), 679–680
  3. 1 2 Fodor, J. A. (1983). The Modularity of Mind. Bradford Books. MIT Press, Cambridge, MA
  4. ↑ Flombaum, J. I., Santos, L. R., & Hauser, M. D. (2002). Neuroecology and psychological modularity. Trends in Cognitive Sciences, 6 (3), 106–108
  5. ↑ Calabretta, R., Di Ferdinando, A., Wagner, G. P., & Parisi, D. (2003). What does it take to evolve behaviorally complex organisms? BioSystems, 69, 245–262
  6. ↑ Wada, J., & Rasmussen, T. (1960). Intracarotid injection of Sodium Amytal for the lateralization of cerebral speech dominance. Experimental and clinical observations. Journal of Neurosurgery, 17, 266–282
  7. ↑ Martin, R. C. (2003). Language processing: Functional organization and neuroanatomical basis. Annual Review of Psychology, 54, 55–90
  8. ↑ Binder, J., & Price, C. (2001). Functional imaging of language. In R. Cabeza and A. Kingstone (Eds.), Handbook of Functional Neuroimaging of Cognition (pp. 187–251). Cambridge, MA: MIT Press
  9. ↑ Robertson, D. A., Gernsbacher, M.A., Guidotti, S.J., Robertson, R.R., Irwin, W., Mock, B.J., & Campana, E. (2000). Functional neuroanatomy of the cognitive process of mapping during discourse comprehension. Psychological Science, 11, 255–60
  10. ↑ Grodinsky, Y. (2006). The language faculty, Broca’s region, and the mirror system. Cortex, 42 (4), 464–468
  11. ↑ Pinker, S. (1997). How The Mind Works. Harmondsworth: Penguin
  12. ↑ von der Malsburg, C. (1995). Binding in models of perception and brain function. Current Opinion in Neurobiology, 5, 520–52
  13. ↑ Dunn, J. C., & Kirsner, K. (2003). What can we infer from double dissociations? Cortex, 39, 1–7
  14. ↑ Coltheart, M., & Davies, M. (2003). Inference and explanation in cognitive neuropsychology. Cortex, 39, 188–191
  15. ↑ Moscovitch, M. & Umiltà, C. (1990). Modularity and neuropsychology: implications for the organization of attention and memory in normal and brain-damaged people. In M. F. Schwartz (Ed.), Modular Deficits in Alzheimertype dementia. Cambridge, MA: MIT Press
  16. ↑ Goodglass, H., & Kaplan, E. (1972). The Assessment of Aphasia and Related Disorders. Philadelphia, PA: Lea & Febiger
  17. ↑ Levy, Y. (1996). Modularity of language reconsidered. Brain & Language, 55 (2), 240–263
  18. ↑ Pinker, S. (1994). The language instinct: How the mind creates language, pp. 37–43. New York: W. Morrow
  19. 1 2 van der Lely, H. K. J. (2005). Domain-Specific Cognitive Systems: Insight from Grammatical Specific Language Impairment, Trends in Cognitive Sciences, 9 (2), 53–59
  20. ↑ Bellugi, U.,Marks, S., Bihrle, A., & Sabo, H. (1988). Dissociation between language and cognitive functions in Williams syndrome. In D. Bishop and K. Mogford (Eds.), Language development in exceptional circumstances (pp. 177–189). London: Churchill Livingstone
  21. ↑ Brock, J. (2007). Language abilities in Williams syndrome: A critical review. Development and Psychopathology, 19, 97–127
  22. ↑ Mervis, C. B., & Beccera, A. M. (2007). Language and communicative development in Williams Syndrome. Mental Retardation and Developmental Disabilities Research Reviews, 13, 3–15
  23. ↑ Norbury,C., Bishop, D. V. M., & Briscoe, J. (2001). Production of English finite verb morphology: A Comparison of SLI and mildmoderate hearing impairment. Journal of Speech, Language and Hearing Research, 44, 165–178
  24. ↑ Leonard, L. 1998, Children with Specific Language Impairment. Cambridge, Massachusetts: MIT Press
  25. ↑ Bishop, D. V. M. (1994). Grammatical errors in specific language impairment: Competence or performance limitations. Applied Psycholinguistics, 15, 507–550
  26. ↑ Kail, R. (1994). A method for studying the generalized slowing hypothesis in children with specific language impairment. Journal of Speech and Hearing Research, 37, 418–421
  27. ↑ McGurk, H., & MacDonald, J. (1976). Hearing lips and seeing voices. Nature, 264 (5588), 746–748
  28. ↑ Carston, R. (1996). The architecture of the mind: modularity and modularization. In D. Green et al. (Eds.), Cognitive Science: An Introduction (pp. 53–83). Cambridge: Blackwell
  29. ↑ Heiser, M., Iacoboni, M., Maeda, F., Marcus, J., & Mazziotta, J.C. (2003). The essential role of Broca's area in imitation. European Journal of Neuroscience, 17, 1123–1128
  30. ↑ Saygin, A. P., Dick, F., Wilson, S. M., Dronkers, N. F., & Bates, E. (2003). Neural resources for processing language and environmental sounds: Evidence from aphasia. Brain, 126 (4), 928–945
  31. ↑ Rumelhart, D. E., & McClelland, J. L. (1986) PDP models and general issues in cognitive science. In D. E. Rumelhart, J. L. McClelland, and the PDP Research Group (Eds.), Parallel distributed processing: Explorations in the microstructure of cognition. Volume 1: Foundations. Cambridge, MA: Bradford Books/MIT Press
  32. ↑ Pinker, S., & Jackendoff, R. (2005). The faculty of language: What’s special about it? Cognition, 95, 201–236
  33. ↑ Pulvermuller, F. (2003). The Neuroscience of Language. On Brain Circuits of Words and Serial Order. UK, Cambridge: Cambridge University Press
  34. ↑ Jackendoff, R. & Pinker, S. (2005) The nature of the language faculty and its implications for evolution of language (Reply to Fitch, Hauser, & Chomsky) Cognition, 97 (2), 211–225, page 223

Further reading

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