INTERVIEWS
Human Language Acquisition:
More Than the Ability to Speak
An Interview with Professor Laura-Ann Petitto
BY
EVE RUSSELL ’05
Psychology
Courtesy Laura-Ann Petitto
Challenging the prevailing theories of
language acquisition, Dr. Laura-Ann Petitto has
spent the last twenty years demonstrating that
language is neither a uniquely human nor a
strictly vocal faculty. Her work with chimpanzees
in the 1970’s explored the extent to which animals can (and cannot) acquire aspects of human
language and lead her toward the field of human
language acquisition. Her research is directed to
uncovering the biological mechanisms and environmental factors that determine how our
species acquires language as well as how language is organized in the brain. Dr. Petitto’s studies have graced the covers of both Nature and
Science with news that the babbling stage of language acquisition is also exhibited by deaf babies
through their hands similarly to the vocal babbling of hearing babies. She has done extensive Professor Laura-Ann Petitto
work with both deaf children and their use of
at all. I was an undergraduate at Columbia
sign language as well as bilingual children and
University and there was a little sign up in the
the cognitive, social and linguistic impact of
cafeteria that said ‘research assistant needed,
bilingual language exposure. Dr. Petitto joined
course credit granted’ at which point I said ‘hmm
the Dartmouth faculty during the fall of 2001 in
that sounds fun I’ll just go and see what that is”.
the departments of Education and Psychological
When I showed up at this professor’s door, he
and Brain Sciences. She is currently teaching
looked very breathless and disheveled and he
undergraduate courses in both language acquisibeckoned me into an inner chamber of his office.
tion and child development.
Then he opened another door and he pushed me
through and closed the door behind me. I
turned, and there on the floor was a baby chimER: How did you become interested in lanpanzee. I immediately fell to my knees and the
guage acquisition and child development?
chimpanzee, who I had perceived to be quite agitated, stopped being agitated, approached me
LP: I had a fascinating introduction into child
and started grooming me. At this point over a
language, which actually didn’t involve children
PA system, that I had not been aware of, the professor yelled out “you are on the project”. I had
been initiated onto a research project that was
attempting to teach sign language to a baby
chimpanzee. At the time our question was
whether all aspects of human language are
learned by a child entirely thorough environmental input, or if there are some things about
language that you cannot teach…that are under
biological control and part of our unique genetic makeup.
ER: Had there been other studies of chimpanzees prior to yours?
LP: When we began that study there had been
other language projects in existence for ten years.
This was the early 70’s, the chimpanzees from the
60’s had spectacular claims made about their
communication capacities. While they were very
strong claims, [from] the video tapes that were
released it looked [like] the animal was under
quite severe reinforcement contingencies where
they had lots of food rewards…[they had] basically shaped the animal to imitate and to do what
the teacher was doing. As in all scientific projects, we wanted to attempt to replicate this type
of study to see if in fact if language in apes was
true of all chimpanzees. This was a normal
process in science, we were replicating a study,
but we also wanted to go beyond by keeping a
large corpus of data and records commensurate
with the ones that were being kept for child language.
ER: What was involved in studying your chimpanzee, Nim Chimpsky?
LP: My job was to live with him, talk to him, and
take him through the day in the same way that a
mother takes her young baby through that child’s
day. Naturally, I talked about things in my world.
I signed to him in the loving exuberant way that
a parent would talk or sign about the world
around them. The hope was that this chimpanzee would become part of our social fabric,
would want to sign because we signed, would
emulate the life of a child, and would learn language. We were trying to make available to that
chimp what a human child has to see if development would parallel or be different and our goal
was to see not only the similarities, but also any
differences. We were very excited about any
potential differences because we were hopeful
that they would teach us which aspects of human
language were potentially part of our genetic
makeup.
Courtesy Laura-Ann Petitto
ER: What part of your research inspired you
the most?
LP: My interest really crystallized in working
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with Nim. I was absolutely tantalized by the
things that this chimpanzee couldn’t do. One of
the things that was really intriguing was that we
gave this chimp a way to bypass his inability to
speak, we gave him language on the hands. . . Yet,
there were still aspects of human language he
couldn’t grasp. When I went to the child language literature to give me insight, to help me
understand what is it that he did not have, the
prevailing view of the time was that children
learn language because of the ability to speak.
They hit the milestones of language because it is
reflecting the rate at which they get control over
the mouth muscles. Similarly, it was said that the
child begins to speak whole words because that
is reflecting the rate at which the child gains
more control over its perceptual world, the ability to discriminate sounds, the ability to segment
the stream, the ability to find the words in a
stream of speech. All the eggs had been put in the
basket of speech and I had reason to be suspicious of that. My suspicion, [was] that what
makes you and I special is not that we can speak,
but there was something else up in our heads
that [permits] us to engage in language. I
thought natural sign languages would provide us
a test case, that this would be a unique microscope to shine on the human brain that would
teach us what about language that is unique.
The existence of these natural languages allowed
me to ask whether or not language was unique
because we can perceive and produce sounds or
was there something else about language.
Perhaps that the brain had specialization for the
capacity to perceive patterns and their regularities and distributions or that the real essence of
human language is something else because we
were only shining light on the mechanism for
talking. That work with the chimp was pivotal in
implanting me in a research trajectory. I left the
project being absolutely certain that Noam
Chomsky was right, that aspects of human lan-
guage were part of our biological makeup. I left
the project convinced that what makes our
species special is not just our ability to talk. I
also left with a passionate interest in sign languages because I perceived immediately their
value as spectacular research tools, their value to
provide a window into the brain. . . If you take a
deaf child, stripped of speech and who is going
to acquire a language not based on speech but
based on the hands, what would happen in the
course of development if the organism did not
have the development of the oral-facial region,
didn’t have the development of the ears? The
existing view would predict that a child who did
not have accesses to that type of information
would acquire language in a deviant way when
they had the ability to control, hear and produce
speech. I had reason to be suspicious of that so I
began a trajectory of studies that asked of the
human brain: is it dedicated exclusively to sound
and the maturation of our ability to produce and
hear sound or is there anything else that evolution afforded us with that aids us in the task of
acquiring and using language.
ER: Would you identify that as the focal point
of your research?
LP: By asking that question I have been able to
discover processes in acquisition that are normal
but don’t rely on sound. Deaf children still
acquire language on identical milestones and
timetables as hearing children. These children
(who are neurologically healthy) when exposed
to signs from birth, even without the maturation
of the oral-facial region, achieve every milestone
in human language acquisition on their identical
timetable. The only way that the milestones of
spoken language and sign language could be the
same is if the brain has a common mechanism
that treats these two different modalities equally
and also has the capacity to see the invariants in
the patterns within the different modalities.
There was something about the brain that could
abstract away from the tongue and the hands
and none the less see that the nature of the patterns coming in was the same.
ER: Do deaf children develop language on the
same timetables?
LP: Yes, signing children at seven months have
the equivalent of reduplicative babbling. At ten
months, they have the equivalent of variegated
babbling and at 12 months they have jargon babbling. I am not being metaphorical; it is literally
the same thing. In seeing this kind of convergence, of deaf children acquiring sign language
at the same timetables as hearing children
acquiring speech, lead me to a new hypothesis.
Originally I thought that it was the same mechanism that was driving these two. Then I moved
to the level of reasoning where I thought that it
must be the same tissue, the same mechanism. I
did brain scanning studies at the Montreal
Mentological Institute and . . .found not only is
sign language processed in the left hemisphere
but we did not [previously] know how specific . .
. linguistic functions were processed at specific
brain sites. It turns out that they are bang on, not
close to it but the same tissue. We went to the
brain tissue that was universally regarded as
being the exclusive bastion of sound production,
unimodal. We went to Heschel’s Gyrus, the primary auditory cortex called A1 and we went to
A2, which is the Superior Temporal Gyrus, the
secondary auditory cortex. That tissue is highly
sensitive to syllabic units, phonetic organization
and rhythmic alternation. If it is truly sound tissue, I said let’s test it. If it is only sound tissue
then phonology in sign language shouldn’t be
there, but if it is not dedicated absolutely to
sound but to the patterns that got pressed into
sound (to something more abstract like the
phonological organization or maximal contrast)
then the tissue should turn up. We used Positron
Emission Tomography (PET scanning) and we
co-registered every individual’s PET scan with
their MRI so we could identify the brain tissue
relative to a very highly specific path. Our question was is the brain activation identical for the
linguistic functions that we see in spoken language at the identical sites and what we found is
that there is no difference in brain matter
because the hearing tissue is not just for hearing.
ER: To what extent do your studies with animals parallel patterns in human language
development? Do chimpanzees show similar
developmental stages in language acquisition?
LP: They do not show similar developmental
stages in language acquisition. There is no point
in human development when you can take a
chimpanzee and hold it up to the same continuum - a chimpanzee is never like a child at 11
months old . . . Chimpanzees are born different
from us and they never intersect that continuum
at any point in their development. Nim’s system
was non-malleable – [his] communicative repertoire at three days old was the same as it was at
six years old. Our human construct of development could not be placed on him.
ER: Why did you choose to come to
Dartmouth?
LP: There were three factors. I came to
Dartmouth because I thought that it was physically beautiful. I was introduced to the student
body who are fascinating and really nice people
and thirdly, I found a remarkable collegiality
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among the professors. I found an interdisciplinary and raw commitment to knowledge that I
had not seen anywhere else.
ER: In what research projects are you currently involved?
LP: We have a lovely palette, we are combining
basic research for advancing our knowledge
about fundamental parts of the brain and how
the brain is built, with basic research that can be
applied right here in the classroom to impact
children’s lives as quickly as possible by working
with the school systems to figure out when to
expose children to bilingual education in different cultural contexts . . . We are following, very
enthusiastically, bilingual studies trying to find
out when is the optimal age of exposure. We are
looking at new findings that are showing that
bilingual children are smarter. We are doing collaborative research with another team in Boston
to show that bilingual children have spectacular
ability to switch attention, that their attention
mechanisms are more facilitated, more
advanced. We are [also] looking at multiple edu-
cational implications with our findings . . . and
realizing that bilingual children are not delayed,
they are not confused. In fact, they are less confused if exposed earlier on in life. Other projects
have to do with the very specific timing of how
the neural strip is tuned.
ER: Are Dartmouth students involved in this
research?
LP: Yes! Dartmouth students are helping me and
I could not do a thing without them- I am so
lucky. They are interested, they are committed
and involved in every aspect of the research. We
are together . . . it is a real family in the lab. It is
a teaching context and a learning context and
there would be no lab without them.
ER: How have you integrated your research
interests into the classroom?
Courtesy Laura-Ann Petitto
LP: It is seamless. There can’t be teaching without a person who is asking some kind of question. Research is just asking questions and the
process of getting information. I don’t know
how you can stand up
in a classroom if you are
not intimately involved
in that material and
part of the group who
are
finding
those
answers. I couldn’t get
up there and tell my
class about language
acquisition or child
development if I had no
contact with the organism or was never
involved in the process
of asking questions.
ER: What plans do you have for the future?
LP: One of the things that I hope to do here is to
build a center, at Dartmouth, called the “Center
for the Improvement of Children’s Lives.” It is
going to bring together in a very formal, tangible
way people who do basic research on things that
are immediately relevant to a child’s life like
reading, language acquisition, cognitive development, moral development. [I want] to bring
these people in contact with the clinician or
pediatricians to get these people in a conversation. I want to bring in the parents and get
everyone involved and working together.
Sometimes findings in scientific literature do not
get put into practice for 20 years – I want to
bridge that time. This whole movement is a wave
of the future [started at Harvard], it is part of a
trilogy called “The Mind, Brain and Education”. I
see no reason why I can’t start that mind, brain
and education center at Dartmouth. I want to
wed these traditionally separate and non-communicating disciplines together formally to
impact educational policy in the United States.
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