Do Innate Expectations About Causation Reflect "Universal Grammar?"

Many theorists insist that some kind of domain-specific language acquisition device underlies language learning (see, for example, the debate covered on Tuesday). One form of this argument, as laid out by Lidz & Gleitman (2004), suggests that children must have measurable expectations about language that hold across cultures, regardless of their actual language experience, because the action of a domain-specific language device constrains the kinds of languages that exist.

So, what evidence do Lidz & Gleitman use to support this assertion? They claim that the following "one-to-one" principle holds true across all human languages: "Every participant in an event as it is mentally represented shows up as a syntactic phrase in a sentence describing that event." In other words, if two entities are involved in some event, then there will be at least two syntactic phrases used to describe that event.

They also show that this principle is adhered to by home-grown sign language systems developed between deaf children and non-signing parents. Of course, this is not particularly strong evidence, since the non-signing parents could have intentionally incorporated the above principle into the make-shift language.

Lidz & Gleitman present slightly stronger evidence in their study of child speakers of Kannada, an Indian language in which a morpheme roughly equivalent to the English suffix "-ize" indicates causation. For example, one might say "John melt-ized the ice" to indicate that John caused the ice to melt. Critically, one can also just say "John melt-ized" in Kannada - so morphology, and not necessarily "transitive" syntax, is a more reliable marker of causation. Interestingly, Lidz & Gleitman interpret Kannada to violate the principle they claim is common to all languages, in which any statement with two objects has two syntactic phrases!

Disregarding that logical disconnect for the moment, the authors demonstrate that Kannada speakers tend to act out phrases with 1 syntactic phrase as non-causative, while those with 2 syntactic phrases are acted out as causative, regardless of the use of the "-ize" morpheme. This, they claim, shows that even children who speak Kannada maintain this internal mechanism for grammar that specifies causation involving two agents must have at least two syntactic phrases - in other words, the one-to-one principle.

There are such serious problems with this account that it appears somewhat incoherent.

1) First, if the one-to-one principle is innate, and language is a product of this innate mechanism, all languages should manifest it. Yet Kannada doesn't - isn't this prima facie evidence that no such innate mechanism is required?

2) Kannada uses syntactic structure to indicate causation less frequently and therefore less reliably than morphology. However, this does not mean that syntax's bearing on causation goes unlearned by Kannada children - therefore, their behavior could result from learning rather than the action of innate syntax-causation mechanisms.

3) Causative relationships might be mentally represented with more than one agent because that is "the way the universe works." This need not be innate, nor specific to language: things act upon other things, and it should not be surprising to see human behavior (even from the youngest infants, the most remote cultures, or the most exotic languages) correspond to this simple fact of life.

In summary, the case of Kannada and deaf children of non-signing parents does not unequivocally demonstrate that syntax-causation rules must be innate. First, if they were, one would not expect a language such as Kannada to exist, and second, the appearance of such rules might simply reflect more general processes of learning from the environment.

Related Posts:
Linking the Nativist and Empiricist Views of Grammar
Poverty of the Stimulus and the Power of Statistical Learning
A Presentation on the Self-Organizing Learning of Semantics
Machine and Human Learning of Word Meanings
Watching a Language Evolve Among Robotic Agents
Symbols, Language, and Human Uniqueness