Colorless green ideas sleeping furiously (long)

[Subbarao Kambhampati <rao@parichaalak.eas.asu.edu>]

[[Okay--I am in one more of my compulsive writing modes. This is
probably palatable to only those one or two hearty souls who have the
time to read my long mails.]]

As I mentioned in the class today, for the longest time, and by that I
mean, until well into late 50's, the conventional scientific wisdom
was that infants come into this world with a "Tabula Rasa" (blank
slate) mind, and pick up everything by learning (supervised or
reinforced) and observation. The reigning doctrine was
"behaviorism"--you can condition/reinforce any behavior into any
organism. To behaviorists, children were but cuter (pavlovian) rats,
and language acquisition was no different than a acquisition of maze
following skills. B.F. Skinner was the leading exponent of behaviorism
and was, in early fifties, writing book after book expounding on how
behaviorism can explain all sorts of human behavior.
[Skinner was such an ardent behaviorist that there was even an
apocryphal urban legend that said he raised his own daughter in a
"skinner box" to test his behaviorism hypotheses--see
http://www.snopes.com/science/skinner.htm ]

 When Skinner came around to applying behaviorism explanations to
language acquisition and wrote the book on "Verbal Behavior", it was
expected to further shore up the behaviorism doctrine, and become a
classic. What became a classic instead is a critical scholarly 1959
"review" of the book by a then little-known linguist named Noam
Chomsky (
http://cogprints.ecs.soton.ac.uk/archive/00001148/00/chomsky.htm ).

 Chomsky essentially killed the book as well as much of the euphoria
of behaviorism by an arugment that has since then come to be known as
the "poverty of stimulus" argument.  He said that behaviorism and
stimulus/response reinforcement does not quite explain how it is that
children seem to be able to generate sentences that they have never
heard of. In other words, there are not enough examples (hence a
poverty of "stimuli") for the children to learn entire
language--grammar and sentences together (even for children--such as
mine--with overly talkative parents ;-) [You note that the argument
that something cannot be learned is being done in terms of the 
the inordinate number of examples needed to learn it. We will see in
the class that difficulty of learning tasks is measured in terms of
"sample complexity".]

 As an alternative explanation, Chomsky cited his own work on
"generative grammars"--a set of grammar rules that can generate
"grammatically correct" sentences from a language. He said that it
must be the case that children come into the world with grammar rules
already in their head. Since the grammars of different world languages
are different, he posited that the children come into this world with
a "universal" grammar. Using the language being spoken around them,
they then set the "parameters" (or knobs, if you will) on their
universal grammar such that it becomes customized to the specific
language environment they are in.  Once they have the customized
grammar, they then are in the business of learning word sense (or
semantics). "Colorless green ideas sleep furiously" is one of
Chomsky's famous examples, which he uses to show that even small kids
with limited vocabularies can tell automatically whether a sentence is
grammatically correct.  [Even here, in learning semantics, children
come into the world with pretty strong biases--including the so-called
"whole object hypothesis". If I point towards a big moving bus and say
"Bus", the kid hypothesizes that the whole big thing is called
bus--not just the wheels, or the hubcaps, or some subset of the
parts. Pretty strong bias, come to think of it--what if I said
"Driver" pointing towards the driver side of the bus?]

Chomsky of course went on to become the demi-god of cognitive science
in general, and mathematical linguistics in particular (and you
obviously heard of him in your CSE 355, when you probably learned
about the Chomskian hierarchy of languages--which is in terms of their
grammar complexity). A lot of research has been done since Chomsky's
original work, to shore up the support for the universal grammar
hypothesis.  It is so much of an accepted fact (dogma) now that it
(universal grammar) in turn is seen as yet another evidence that all
humans evolved from a common set of ancestors--as against evolving
separately and independently (the "Lucy" theory,
http://www.pbs.org/wgbh/evolution/library/07/1/l_071_01.html ; by the
way Don Johanson, who found Lucy skeleton in Ethiopia, is right here
at ASU--check out http://www.asu.edu/clas/iho/dcj.html ). The basic
argument is that the rank similarity of the human languages cannot be
explained without it. (Of course, there are much stronger arguments
for the common ancestor theory--including the fact that we are all
same species--any man from anywhere in the world can mate with any
woman from anywhere in the world and produce healthy offspring).

So that is some of the background on the universal grammar. By the
way, note that none of the above says that conditioning will not be
effective in changing ones behavior--you probably saw the recent press
accounts of the infamous Wendell Johnson orphan stuttering experiments
(http://www.jsonline.com/news/nat/jun01/stutter11061001.asp). All
Chomsky's argument says is that conditioning and reinforcement are
only part of the story and cannot alone explain language acquisition;
evolution did a whole other part too.

Now for a couple of references. Probably the best-written lay-person
book on human language acquisition is Steven Pinker's "Language
Instinct"(http://www.amazon.com/exec/obidos/tg/detail/-/0060976519/104-1220170-3641559).
A very nice and eminently watchable 3-part PBS series on language
acquisition is "Human Language"
(http://equinoxfilms.home.mindspring.com/HLseries.html). 

That is all for now. Now for more important things like Seinfeld rerun
already in progress.

Rao

Epilogue/Postscript: These days of course, a search on Chomsky on the
web is more likely to turn up references to his political views than
his linguistic ones. He is sort of a one-man vocal and loyal
opposition for many of the US government policies. For example, he
wrote one of the first dissenting "non-party line" opinions of the
9/11. Whether I agree with him or not, I am grateful that there is
someone unafraid of speaking his mind--especially in these days of
hyper-patriotism, where FBI thinks it normal to monitor you because
you are against war, and your freedoms are being re-defined as the
ones Ashcroft hasn't yet gotten around to excising into the "Patriot
Act".

----------------
  "I simply want to tell you that there are some men in this world who
 were born to do our unpleasant jobs for us. Your father's one of
them."
 [..] "I always thought Maycomb folks were the best folks in the world,
least that's what they seemed like."
 "We're the safest folks in the world" said Miss Maudie. "We're so
rarely called on to be Christians, but when we are, we've got men like 
Atticus to go for us."

        --Miss Maudie and Jem talking about Atticus Finch, as 
           Scout and Dill look on..