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Mental Modules

Many scientists, such as cognitive scientist Steven Pinker, argue for the existence of mental modules in the brain that govern specific intellectual abilities. This view replaces the idea of a "general intelligence" or "general problem-solving capacity" with more specific segments of the mind that are primed to deal with certain aspects of the world.

The Grammar Module

In his book Words and Rules, Pinker postulates a grammar module within the brain that specifically prepares brains for the acquisition of grammatical rules, such as adding an 's' to make a word plural. In this view, brains are primed to acquire natural language with all its many rules of morphology and syntax; brains also possess a mental dictionary for storing vocabulary, as well as irregular verb forms and pluralizations, idiomatic expressions, and other linguistic idiosyncrasies that cannot be derived from ordinary grammatical rules.

According to Pinker, the grammar module is set up to receive input from the mental dictionary and apply rules for inflection, pluralization, etc. to make the word fit its desired usage in a sentence. For example, if someone wished to observe that it was hot outside, the grammar module would be responsible for putting the words in the proper order - so he says It is hot out, not Hot it out is - and for properly conjugating the verb, preventing errors such as It be hot out. Similarly, if the sentence to be said was Those shoes are mine, it is the mental grammar that would make the noun shoe plural, pair the pronoun those and the verb are with the plural noun shoes, and use the proper possessive form mine instead of my.

These functions make the mental grammar an extremely powerful device for communicating useful information comprehensible to both speaker and hearer. For this effective communication to be possible, common conventions of grammar must be shared - a person who constructs his sentences with the pattern SUBJECT-VERB-DIRECT OBJECT, such as The girl watered the plant, will utterly confuse someone who constructs his sentences with the pattern DIRECT OBJECT-VERB-SUBJECT, making the previous sentence equivalent in his mind to The plant watered the girl. For this reason, grammatical conventions must be determined and standardized within a language; these standards will be picked up and internalized by babies and toddlers who are "stocking" their mental grammars with the rules that apply to their specific language. This topic will be covered in further detail in Language Acquisition.

The Mental Dictionary

The powerful idea that drives the grammar module is the mental dictionary, which contains an entry for every word, expression, and irregular form known to a given individual. Obviously the specific entries differ between an English speaker and a Russian speaker, but the principle is identical in each case - all the vocabulary known to a person is stored in a specific "memory bank" where it can be accessed by the grammar module whenever the person needs to form grammatical sentences.

In this way, the mental dictionary is the raw material from which the grammar module fashions intact, grammatically correct sentences. Many times a mental dictionary alone is enough to deduce the meaning of an ungrammatical string of words; for example, most people have a good idea of what sets of words such as red car blue car bang might mean - namely, that an accident occurred involving a red car and a blue car colliding. This might have been the way that early speakers of proto-language communicated - they may have designated sounds to represent objects, and only later developed a consistent grammatical structure and the mental equipment to follow it.

The mental dictionary also contains information such as idiomatic expressions whose meanings cannot be predicted using ordinary rules of grammar and syntax. Some English examples include She has a bee in her bonnet (she is irritable), The little boy cried his eyes out (he cried a lot), and He was beating around the bush (he avoided getting to the point). None of these phrases has a meaning that can be predicted from the meanings of the individual words composing it, and therefore these expressions and their meanings must be included in one's mental dictionary.

The same reasoning applies to irregular verbs and pluralizations. It cannot be deduced from normal English grammatical rules that the past tense of go is went, not goed. Therefore the mental dictionary entry for the verb go includes a notation that indicates its irregular past-tense form. This goes for plural nouns as well - a note in the dictionary keeps most English speakers from calling a group of first-graders childs instead of children. These notations must be commonly referenced in order to override the prevailing regular rules; children, who have had less exposure to regular grammar and are still developing their dictionaries and modules, sometimes say things like goed and childs because their notations have not yet been reinforced enough times. Even adults sometimes make mistakes with common irregular verbs and nouns when speaking quickly or when paying little attention. Finally, there are verbs like thrive and stride whose irregular past tenses, thriven and stridden, are used quite infrequently; thus thrived and strided are more likely to be written and accepted than the more frequent form goed.

Phrase Construction and Recursion

The grammar module and mental dictionary combine to create a very powerful phenomenon called recursion, defined by Pinker in Words and Rules as "a procedure that invokes an instance of itself, and thus can be applied, ad infinitum, to create or analyze new entities of any size" (p.294). It is recursion - the ability to embed types of phrases and clauses inside one another - that gave all grammatical systems their true expressive power.

A phrase is a group of words with a logical meaning, but not possessing a subject and predicate: on the roof, sitting with my dog, and dedicated to reason. A clause is a set of words that does have a subject and predicate; it can be a complete thought but is not necessarily so: I slept, after the man ate dinner, and because we left early are all clauses. While these types of constructions are useful in themselves and in combination, their expressive power multiplies manyfold when embedded with recursion.

Recursion is the ability of the mental grammar to assemble a phrase such as on the roof and then embed it in another phrase, as in the fat cat on the roof. This phrase, with its embedded structure, can then be added into a clause: while the fat cat on the roof slept. Finally, this clause - composed of two phrases, a verb, and a conjunction, or connecting word - can be used in a sentence, as in Mice invaded the cellar while the fat cat on the roof slept. Only with recursion can we produce such sentences, and we can employ it to create much more complicated ones as well: While I read the book that I borrowed from my friend last week, my cat dozed in a sunny spot on the floor, oblivious to the noise of the construction crew working on a new house across the street.

When demonstrated in this way, recursion seems to be an extremely complicated device, and many people have wondered why it evolved in the first place. However, it is wise to remember that not all recursive sentences are long and convoluted; recursion allows such normal and simple-sounding constructions as the dress she wore, the mayor of the city, and I know he's here. These sorts of constructions were surely quite valuable to our hunter-gatherer ancestors, who probably had reason to say the meat I had, the chief of the tribe, and I think they came - all of which are grammatically identical to the examples given above.

Looking Further: Links and References

The following links and references are useful in the study of the production of language via the grammar module and the mental dictionary.

• Books
  • The Language Instinct by Steven Pinker
  • How the Mind Works by Steven Pinker
  • Words and Rules by Steven Pinker
  • Darwin's Dangerous Idea: Evolution and the Meanings of Life by Daniel C. Dennett (see ch. 13)

• Websites
  • Chapters 3 and 8 of The Language Instinct by Steven Pinker
  • Language Miniatures - collection of language essays by William Z. Shetter

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