Modularity

History of the Modularity Construct

The idea that the brain is made up of separate components, each with its own particular job, dates at least to the earliest days of modern neurology, when Broca and Wernicke showed that damage to certain brain regions resulted in specific types of language impairments. But as understanding of the complexity of the brain has increased, simplistic ideas of “one structure, one function” are no longer tenable. While it is clear that certain brain regions have specializations, it is now understood that complex abilities such as language are widely distributed in diverse neural regions, within complex networks linking them. Thus, while modularity as a construct has a long history, in the decades since the 1980s, the term has been applied primarily to an abstract conception of mental processes rather than to highly localized brain regions with unitary functions.

The term modularity of mind stems from a work of that name by Jerry Fodor (1983); this work references neurology but is focused on philosophical argumentation as it pertains to psychology. Similar to theoretical linguists who used logic to develop nativist views of language, Fodor’s work centered on logical argumentation to support his proposal that the mind is organized via modules, which exhibit domain specificity, that is, each has specific tasks (e.g., language processing). Specialized modules are argued to account for the mind’s remarkable speed and smoothness in processing the array of complex information that constantly bombards it. Fodor further hypothesized that in order to achieve speed and efficiency, the modules would operate without conscious direction and automatically, with limited input from centralized processes. It is in this sense that Fodorian modules are “informationally encapsulated,” meaning that they do not draw on other information in the system, operating only on their specialized inputs. He did argue that they have specific neural substrates, although not necessarily narrowly confined within a brain region.

Some of the arguments for (and against) modularity of mind draw on evolutionary theory. Some evolutionary psychologists argue that modular minds will operate more rapidly and hence increase survival fitness. The opposite view is that evolution does not support sudden development of a novel system, but rather new abilities such as language are built on older ones developed for other purposes (i.e., exaptations). From this perspective, language is unlikely to be a genetically endowed, informationally encapsulated, domain-specific system, contra the modularists’ view.

Modularity and Language Disorders

Major arguments for modular organization of language relate to communicative impairments in development and in neurological disorders. So the fact that children with Williams syndrome have large vocabularies and elaborate sentence structure, but have visuospatial abilities within the range of moderate to severe intellectual disability, suggests a language module separate from their general cognition. Similarly, the pattern of language deficits seen in Broca’s aphasia, where damage to a specific region results in specific types of grammatical deficits, is argued to reflect the modular nature of grammar. Both these interpretations of the data have been challenged; a major critic of modular accounts, Elizabeth Bates, argued that these clinical examples were misinterpreted and their true nature not carefully described. She pointed out that children with Williams syndrome do exhibit language delays, and their language profiles are not so much spared as significantly different from those of children with typical development. Similarly, the notion that Broca’s aphasia results in specific impairment only in syntax is belied by findings that individuals with Broca’s aphasia can make subtle grammatical judgments. Ultimately, arguments for modularity from populations with communicative disorders—so-called double dissociation where language is seen as separate from cognition and vice versa—have foundered when the complex nature of language [Page 1183]and cognition in individuals with these disorders has been more carefully described.

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