THE ROUGH GUIDE TO PSYCHOLOGYfocused on. So if the child glances at Ruby the dog, the parents tend to
go “Ooh, there’s Ruby the dog, say ‘hello Ruby’”, and so on. Then the child
reaches for a ball: “There’s your ball, darling. Do you want your ball?”
Taken together it can seem as though these conditions provide an ideal
learning environment for children to acquire their native language.
ACQUIRING THE RULES
And yet, while this might well be true for vocabulary, psycholinguists
have known for some time that the spoken language children are
exposed to is not sufficient for them to learn all the rules of grammar.
In the formal jargon, this is known as the “poverty” of the linguistic
input. Psychologists have pored over transcripts of children and parents
talking to each other, and while the latter do occasionally correct their
children’s grammatical errors, they don’t do it nearly often or systemati-
cally enough to explain how children are able to perfect their language
as effectively as they do. What’s more, the children’s errors – for example
over-generalizing the rule of applying an “s” to make a plural – have been
found to continue beyond the period when the adults were vigilant in
providing corrections. These observations about the poverty of the feed-
back have been combined with other observations about the constraints
of the world’s languages – what the pioneering linguist and intellectual
Noam Chomsky called a “universal grammar”. It’s not the case that just
anything goes. Instead, all languages seem to share key grammatical
commonalities, even if these are tweaked slightly from one language
to another. For example, most experts agree that all human languages
contain nouns (dissenters from this view highlight a handful of excep-
tions, including Straits Salish, a North American indigenous language).
Taken together, this evidence is used to argue that human infants come
with a language-faculty built in – what Chomsky called a language acqui-
sition device (LAD).
Chomsky’s idea is that on hearing language spoken, various gram-
matical switches or “parameters” are pushed one way or the other as the
child adjusts to its native tongue. Consider word-order. In English, the
rule is subject-verb-object, whereas in Japanese it is subject-object-verb.
The child’s “language instinct”, to borrow the title of Steven Pinker’s
best-selling book, means that their brain recognizes the importance
of word order and other rules in language. Repeated exposure to the
subject-verb-object or other convention then tunes this particular gram-
matical parameter in the child’s brain.