Language and kids
Linguistics lecture #8
November 21, 2006
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Overview
• Why study children’s language?
• Evidence for innateness
• Modeling language acquisition
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Why study children’s language?
• Innateness can be studied by finding out
how much kids are born “knowing”
• Modularity can be studied by finding out
how language development relates to
general cognitive development
• Also, it’s cool!
- Kids develop language so easily, without any
explicit teaching, that linguists call it language
acquisition (acquiring), not language learning
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A critical period?
• Why is it so easy for babies and kids to
acquire a language, and so hard for adults?
• Maybe human brains develop by a
biological clock, so there is a critical
period of time when the brain can easily
acquire a language
• Some birds have a similar critical period for
acquiring their songs
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Innateness in speech perception?
• The hardest thing for an adult to learn is
phonology, including speech perception.
• Does this imply innateness?
• One way to find out is to test little babies:
Do they also show categorical perception?
• If they do, they probably did not have time
to learn it, so maybe they were born
“knowing” how to do it.
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But how can we “ask” them?
• Babies like to hear new things, so if they
recognize a change in speech sounds, they
suck faster, as measured by computer:
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Babies & categorical perception
• Even newborn babies (just a few hours old)
show categorical perception
• They perceive categories that may not be
used in their parents’ language
- Spanish babies perceive [pa] vs. [pha] even
though Spanish adults only use [ba] vs. [pa]
• They still must learn to focus attention on
the sounds important for their language
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What about words?
• Of course individual words are not innate,
and must be learned.
• But still, something must be innate about
the process of learning words. Do you
remember why?
• It’s because of the gavagai problem: people
seem to already “know” that names refer to
whole objects.
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Kids acquire grammar,
not language
• Babies and children don’t just memorize
phonological and syntactic atoms, but also
learn grammatical rules
• For example, kids are good at this test:
This is a wug.
Here are two more of them.
These are
two ______
wug[z]
wugs
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Is the “rule” concept innate?
• Of course kids have to learn the particular
rules in their parents’ grammar
• But do they have to learn the concept of
“rules”, or are they born expecting rules?
• In fact, kids seem to love rules, so much
that they use them even when their parents
don’t
• This is shown by U-shaped development
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U-shaped development
• Kids begin by imitating words: go - went
• Then they start to guess rules, and sometimes
go too far: go - goed
100% correct
go - went
eat - ate
talk - talked
2 years
go - goed
eat - eated
talk - talked
3 years
go - went
eat - eated
talk - talked
4 years ...
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Is there a biological clock?
• American and English kids start to overuse
rules like past tense (goed) around the age
of 3
• Deaf kids acquiring American Sign
Language start to overuse verb marker rules
and other rules around the age of 3
• Taiwanese kids start to overuse classifier
rules (兩個狗) around the age of 3
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Do parents teach grammar?
• Nobody teaches kids to say “goed”!
• Most parents don’t know enough linguistics
to teach grammar
(could you teach your kids the tone system in
Taiwanese?)
• Even when some parents do try to teach
grammar, the kids just ignore them!
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Want other one spoon, Daddy.
You mean, you want the other spoon.
Yes, I want other one spoon, please, Daddy.
Can you say “the other spoon”?
Other ... one ... spoon.
Say “other.”
Other.
“Spoon.”
Spoon.
“Other ... spoon.”
Other … spoon. Now give me other one spoon?
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Can cognitive development
explain language acquisition?
• Does language develop as an independent
module?
• Language development also requires:
- Theory of mind: the belief that other people
have minds like yours
- Object permanence: the belief that objects
continue to exist even when you don’t perceive
them
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Are these abilities also innate?
• At first, babies don’t act as if they have a
real theory of mind, but later they do….
But chimpanzees never seem to develop
much of a theory of mind at all!
• Piaget (皮亞傑) thought that object
permanence takes a long time to develop...
But more recent experiments show that very
young babies already have it!
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Modeling language acquisition
• Some models focus on innateness and
modularity, e.g. learnability theory
• Other models focus on learning from
experience and interaction, e.g.
connectionism
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Learnability theory
• This theory uses math to study innateness
• The focus is on how kids try to figure out
their parents’ grammar
• This task faces the problem of induction:
figuring out a general statement from a finite
set of data
How do kids take a finite set of sentences and figure
out an infinitely generative grammar?
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A formal example
• You’re a baby and you hear these sentences:
a … aa … aa … a … aa
• Suppose that you are born with no innate
expectations about language.
• Then you would have to consider both of
these possible grammars:
G = ({a}, {S}, {S  a, S  aS})
G2 = only a, aa are grammatical
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That won’t work!
• Suppose the correct grammar is G2, but you
guess G. Can you ever learn the right
grammar?
No. Both a and aa are grammatical by G, so why
change to G2?
• What if G is correct but you guess G2?
If you hear aaa, just change to G3; if you hear
aaaa, just change to G4; etc. How could you ever
conclude that the grammar was really G?
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A very different approach
• Some researchers argue against this
standard innateness-and-modularity view of
language acquisition
• They use connectionism to provide an
interactionist model of language acquisition
in which very little must be innate
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Rules or memory?
• Connectionism models memory and “rules”
the same way (remember 繩子  條?)
• So do kids really need to learn a “+ed rule”
(or a “個 rule”)? Maybe they just
generalize from memorized examples.
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Grammar = memorizing atoms?
• If so, the pattern of word learning should
match the pattern of syntactic acquisition
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What about the biological clock?
• Maybe the critical period exists because the
brain “gets too full” to learn a second
language perfectly
trynothing’s
learn
to learn
Chinese
English
innate
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Summary
• Experiments show that babies are born
“knowing” some things about language
• Kids acquire grammar; they don’t “learn
language” by simple imitation
• Learnability theory highlights the induction
problem, supporting innateness
• Connectionist models imply that innateness
and modularity may really be less important
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