Even two-year-old kids understand grammar

Children as young as two years old understand basic grammar rules when they first learn to speak and are not simply imitating adults, a new study has claimed.
Researchers from the University of Pennsylvania also applied the same statistical analysis on data from one of the most famous animal language-acquisition experiments and showed that Nim Chimpsky, a chimpanzee who was taught sign language over the course of many years, never grasped rules like those in a two-year-old's grammar.
The study conducted by Charles Yang, a professor of linguistics in the School of Arts and Sciences showed that two-year-old children have very small vocabularies and thus don't provide many different examples of grammar usage.

"While a child may not say very much, that doesn't mean that they don't know anything about language.
"Despite the superficial lack of diversity of speech patterns, if you study it carefully and formulate what having a grammar would entail within those limitations, even young children seem very much on target," Yang said.
Yang found a sufficient number of examples of article usage in the nine data sets of child speech he analysed, but there was another challenge in determining if these children understood the grammar rules they were using.

"When children use articles, they're pretty much error free from day one," Yang said in a statement.

"But being error free could mean that they've learned the grammar of article usage in English, or they have memorised and are imitating adults who wouldn't make mistakes either," said Yang.
This model was able to differentiate between the expected diversity if children were using grammar, as compared to if they were simply imitating adults.
"When you compare what children should say if they follow grammar against what children do say, you find it to almost indistinguishable.
"If you simulate the expected diversity when a child is only repeating what adults say, it produces a diversity much lower than what children actually say," Yang said.

As a comparison, Yang applied the same predictive models to the set of Nim signed phrases, the only data set of spontaneous animal language usage publicly available.
He found further evidence for what many scientists, including Nim's own trainers, have contended about Nim: that the sequences of signs Nim put together did not follow from rules like those in human language.
Nim's signs show significantly lower diversity than what is expected under a systematic grammar and were similar to the level expected with memorisation.
This suggests that true language learning is - so far - a uniquely human trait, and that it is present very early in development.