These so-called outliers were difficult to reconcile with the universal grammar that was built on examples from European languages.
Other exceptions to Chomsky’s theory came from the study of “ergative” languages, such as Basque or Urdu, in which the way a sentence subject is used is very different from that in many European languages, again challenging the idea of a universal grammar.
These findings, along with theoretical linguistic work, led Chomsky and his followers to a wholesale revision of the notion of universal grammar during the 1980s.
The new version of the theory, called principles and parameters, replaced a single universal grammar for all the world’s languages with a set of “universal” principles governing the structure of language. These principles manifested themselves differently in each language. An analogy might be that we are all born with a basic set of tastes (sweet, sour, bitter, salty and umami) that interact with culture, history and geography to produce the present-day variations in world cuisine. The principles and parameters were a linguistic analogy to tastes. They interacted with culture (whether a child was learning Japanese or English) to produce today’s variation in languages as well as defined the set of human languages that were possible.
Languages such as Spanish form fully grammatical sentences without the need for separate subjects — for example, Tengo zapatos (“I have shoes”), in which the person who has the shoes, “I,” is indicated not by a separate word but by the “o” ending at the end of the verb. Chomsky contended that as soon as children encountered a few sentences of this type, their brains would set a switch to “on,” indicating that the sentence subject should be dropped. Then they would know that they could drop the subject in all their sentences.
The “subject-drop” parameter supposedly also determined other structural features of the language. This notion of universal principles fits many European languages reasonably well. But data from non-European languages turned out not to fit the revised version of Chomsky’s theory. Indeed, the research that had attempted to identify parameters, such as the subject-drop, ultimately led to the abandonment of the second incarnation of universal grammar because of its failure to stand up to scrutiny.
More recently, in a famous paper published in Science in 2002, Chomsky and his co-authors described a universal grammar that included only one feature, called computational recursion (although many advocates of universal grammar still prefer to assume there are many universal principles and parameters). This new shift permitted a limited number of words and rules to be combined to make an unlimited number of sentences.
The endless possibilities exist because of the way recursion embeds a phrase within another phrase of the same type. For example, English can embed phrases to the right (“John hopes Mary knows Peter is lying”) or embed centrally (“The dog that the cat that the boy saw chased barked”). In theory, it is possible to go on embedding these phases infinitely. In practice, understanding starts to break down when the phrases are stacked on top of one another as in these examples. Chomsky thought this breakdown was not directly related to language per se. Rather it was a limitation of human memory. More important, Chomsky proposed that this recursive ability is what sets language apart from other types of thinking such as categorization and perceiving the relations among things. He also proposed recently this ability arose from a single genetic mutation that occurred between 100,000 and 50,000 years ago.
