Term paper
Language and Brain
Proseminar ”Linguistically relevant films”
Anne Schröder
WS 02/03
Ronny Plontke
March 13, 2003
Ronny Plontke, Hohensteiner Str. 49, 09212 Limbach-Oberfrohna
7th semester, student of computer science
Chemnitz University of Technology
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Contents
1 Introduction
1
2 The human brain
1
2.1
Nervous system . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
2.2
Neurons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
2.3
Localization of language . . . . . . . . . . . . . . . . . . . . . . . .
3
3 Neural learning and language acquisition
4
3.1
Basics of neural networks . . . . . . . . . . . . . . . . . . . . . . . .
5
3.2
The human brain as self-organizing network . . . . . . . . . . . . .
5
3.3
Critical period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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4 Considerations regarding the films
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4.1
Greystoke – The Legend of Tarzan, Lord of the Apes . . . . . . . .
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4.2
Nell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
4.3
Nirgendwo in Afrika . . . . . . . . . . . . . . . . . . . . . . . . . .
10
5 Conclusion
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6 Bibliography
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II
1
Introduction
In this paper I will present an overview of the field of neurolinguistics, which means
the study of how the brain permits us to have language. I will analyze details of
human language acquisition and I will show the relevance of the topic on some
examples from the films we saw during the seminar Linguistically relevant films.
In in the beginning I will give a short survey of the human brain function. It
will lay the basic groundwork for the following explanations. Section 3 will give
an introduction to neural learning and consider the significant aspects for language
acquisition. Although it is rather theoretical it provides an essential approach to
my analyses regarding the films. In the last section I will evaluate films dealing
with the language acquisition topic in detail and I will illustrate my explanations
with relevant examples.
2
The human brain
2.1
Nervous system
The objects of study that must be linked in neurolinguistics are language and neural
components. Approaches to neurolinguistic studies are the localization of speech
relevant areas of the human brain and to find out about the connection how these
areas work together. Therefore I will reflect in the following paragraphs the most
important facts about the nervous system and the human brain. These explanations
are based on Obler and Gjerlow (13-36) and on the more comprehensive descriptions
in Calvin and Ojemann (15-90).
The human nervous system is composed of the central and the peripheral system. The peripheral nervous system is responsible for the regulation of vital body
functions such as breathing and temperature maintenance. For this reason it is
also referred to as automatic nervous system because it is functioning without our
conscious awareness. The central nervous system consists of the brain and the
spinal cord. Most crucial for neurolinguists is the brain itself, or more precisely, the
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outer surface of the cerebral hemispheres, the cortex. The center of human speech
and language processing has been localized in the cortex. The fact that language
is prevalently represented within the left hemisphere will be discussed below (see
2.3.1).
2.2
2.2.1
Neurons
The architecture of a single neuron
It is estimated that the human brain consists of 100 Billion (1011 ) neurons. This vast
number of networked autonomous units is responsible for the excellent intellectual
abilities of the human species especially in solving complex tasks.
Neurons are a specialized type of cells. They consist of a cell body and extensions
that connect it with other neurons. Figure 1 shows a single neuron. The dendrites
carry impulses toward the cell body, the cell body processes the input information of
all dendrites and the axon carries impulses away from the cell body. The connections
between the axons of the sending cells and the dendrites of the receiving cells are
realized by the so called synapses (Obler and Gjerlow, 14-16).
Figure 1: A neuron, Obler and Gjerlow (1999), 15
Information between cells is carried in form of electrochemical changes. In representational form the cell body can be seen as a function evaluating the input from
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the dendrites. Whenever a certain threshold value is reached the neuron fires a
signal to its adjacent cells via the axon connections.
The neurons are connected to a large and complex network. The design of this
network is the key to any kind of intelligence. A single neuron usually has 1000
connections to other neurons. Section 3 will show how the brain is able to represent
knowledge using this network structure. With regard to language it is in particular
interesting how the lexicon of one ore more languages and grammatical rules are
stored and whether there is a time limit in human life to acquire language.
2.3
2.3.1
Localization of language
Language within the left hemisphere
The human brain is split into two hemispheres. The left hemisphere controls any
muscular activity on the right side of the human body and the right hemisphere
operates vice versa. But how to localize the representation of brain centers for
speech and language? This search dates back to the early nineteenth century. Some
physicians observed that brain injured patients with damage on the left hemisphere
often lost speech or linguistic abilities while people with a lesion on the right side
did not lose this ability.
From the vantage point of the present the dominance of the left hemisphere for
language is largely uncontroversial. Today exist different test methods to prove the
localization of language within the left hemisphere for most people. Recent studies
estimate that 97% of the population has language represented in the left hemisphere
(Obler and Gjerlow, 28).
2.3.2
Cortical maps
The localization of the motor and sensor areas is easily possible, that means maps
are available that show which part of the cortex controls the movement of distinct
parts of the body. The localization of speech relevant areas on the cortex is more
difficult and might vary significantly for different people.
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Neurosurgeons have to detect speech relevant areas by using electrical stimuli
on the cortex before operating an patient in order to remove brain tissue to cure
epilepsy or brain tumors. An example of a so called cortical stimulation map 1 is
shown in figure 2. Whenever speech relevant areas on the cortex are stimulated,
the patient will be unable to name things he or she is shown, or he or she might be
unable to produce grammatically correct sentences. Damaging one of these areas
could mean the patient will become temporarily or permanently aphasiac.
Figure 2: Cortical stimulation map, Calvin and Ojemann (1994), 46
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Neural learning and language acquisition
This section explains how the human brain is able to process and to store information, especially language relevant data like the meaning of words and grammatical
rules. This topic is also exceedingly interesting for computer scientists and closely
related to artificial intelligence topics.
Considering linguistic topics, simulated neural networks are often used to represent grammatical rules in computers. They might even be the key to genuine
synthetic speech, both understanding as well as producing. I suppose the computer
scientist’s view on neural learning might be helpful to understand how information
1
A particular usage of cortical stimulation maps and its use for linguists is described in the
magazine Der Spiegel, 43/2002, 229-234.
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can be stored in the brain based on a neural network. Therefore I will concentrate
on basic structures of neural networks.
3.1
Basics of neural networks
Neural networks are self-organizing networks, wich means they are a certain kind
of a dynamic knowledge base. The network is learning through experiences, either
extern using the connected senses or intern by introspection. Consequently a neural
network without experience cannot represent any knowledge. Applied to language
acquisition that means language cannot be given by birth. The human genetic code
contains the speech-ability which will be gradually evolved by training the brain.
Neural learning is rather complex and productive. The neural network consists
of a set of independent units, the neurons (see also 2.2.1). Figure 3 shows how neural
networks can be simulated. Autonomous units (an ) are connected to a network. The
units have a number of assoziative input edges where each edge has a certain weight
factor (wij ). Units will send a signal to its subsequent neighbors, when the sum
of the weighted input edges exceeds a certain threshold level. Knowledge will be
represented through the resulting interactions in this balanced network.
Figure 3: Neural network simulation, Desnizza (2001), 119
3.2
The human brain as self-organizing network
Neural learning in the brain can be realized on the one hand by changing the network
structure, which will only take place in early childhood when new cell assemblies
can be formed, and by changing the edge weighting on the other hand. The neural
network in the human brain is formed by the genetic code acting as a framework,
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and by individual development. Long-term memory is either achieved by changes
on the synapses (more strength connections) or by changes of functional units (new
cell assemblies). A connection can become stronger when the same path is used
often, the other way round a connection that is rarely used will weaken.
Its complexity also explains why the human brain still can be superior to current
computer systems in solving difficult tasks. Computers are able to process lots of
uniform data really fast, but they get in trouble with an increasingly complex input.
3.3
Critical period
In the presentation The Critical Period in Language Acquisition it has been explained that the first language of a child must be acquired during a period between
18 month and early puberty to achieve proficient results. According to Mehler,
Christophe and Ramus (59-68) some evidence is given that first language learning
is qualitatively different from later language learning.
In reference to my explanations about neural learning I can accomplish these
theory. In early childhood the brain has an initial plasticity where new cell assemblies can be formed easily. This ability will be lost later in life when brain structures become less flexible. The learning process is gradually displaced to changes
on synapses than on creation of new functional units. First language learning will
form the necessary structures in the brain to represent the lexicon and grammatical
rules as well as the mental representation of symbolized words. Language relevant
knowledge is stored in form of mental maps on an linguistic meta-level where similarly and synonymously used words or rules are stored in the same local areas. As
a matter of fact this phenomenon can be observed when cortical maps are created
in neurosurgical operations (compare 2.3.2).
In addition this also explains why there is a greater risk of permanent aphasia
after a brain lesion as an adult. Whenever brain structures are damaged in early
childhood the brain is much more flexible to compensate language deficits.
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4
Considerations regarding the films
4.1
4.1.1
Greystoke – The Legend of Tarzan, Lord of the Apes
The story framework
The film Greystoke – The Legend of Tarzan, Lord of the Apes (1984) by Hugh
Hudson is an adaption of Edgar Rice Burrough’s novel Tarzan of the Apes (1914).
The linguistic significance of this film is based on the question whether a child that
got lost in the jungle and was raised up by apes far from any human contact can
acquire language when he or she meets another human by chance at the age of
twenty.
The story begins with two shipwrecked English nobles, the heir to the Earl of
Greystoke and his pregnant wife, who ran ashore on the West coast of Africa. Their
effort to survive in the hostile wilderness fails and ends in tragedy. When they die,
only their new born baby son is left. Alone in the jungle he gets adopted by an
anthropoid ape who has lost her own baby. The baby, Tarzan, grows up with the
apes and gets part of their community.
Despite the fact that he is far from any human contact Tarzan soon develops
a growing consciousness for his difference. When he finds the wooden hut of his
parents by accident he begins to realize that he is distinct from the apes. Examples
are the scene with the mirror as well as in scene when he finds the knife. Tarzan
with his given intelligence is able to use the knife to his advantage, although he has
never seen anybody using it before, whereas the apes are not able to use it. That
is why he is in the position to become the leader of the apes community after the
breathtaking fight with the ancestral group leader.
4.1.2
Linguistic relevance
The crucial scene in the film is when Tarzan eventually meets the Belgian explorer
Captain D’Arnot who gradually teaches him how to talk and to realize that he is
human. In this film Tarzans language acquisition progress might be more realistic
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than in Burrough’s original story, where Tarzan more or less embodies an autodidact, self-educated by the books found in the parental tree house. It is evident that
no human can learn how to read and to speak a language he or she never had heard
anyone speak. However, the plot about Tarzans language acquisition in the film has
some improbabilities and appears rather fantastic.
Regarding my explanations in the previous sections I must come to the conclusion that it must be impossible to learn human language in Tarzan’s position. If
he had been found at the age of four or five it would have been possible to teach
him language in the way it is shown in the film. Even then he would have to
struggle with irreparable deficits in language learning similar to children suffering
from speech disorder. Based on the fact that each neural network needs a training
phase to gain its experience it is possible to draw the conclusion that human beings
are only able to develop speech and language abilities when they hear other people
speaking. The age is a really important aspect, from my point of view I would say
that even the time before the first word is spoken in childhood is eminent. I suppose
grammatical structures are build in the brain before humans are able to speak the
first words themselves. When Tarzan has human contact at the age of twenty, the
development of linguistic structures in his brain was finished for a long time. That
means he would not be able to develop speech as illustrated in the film, where later
when he comes ’home’ back to England he even learns to speak French as a second
language, too.
According to section 3 about neural learning it is important to build up the
genetically allocated structures during childhood before the end of the critical period in language acquisition. Tarzan actually could not develop language because
the apes around him did not have human-like language. Tarzan was able to communicate with the apes and more than that, because of his human origin he could
produce more sounds than the vowels the apes were able to utter. The human
vocal tract is different from that of the apes. So it is incontestable that Tarzan
theoretically would be able to produce human words, but it would be limited to the
production of the sound.
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Due to the lack of first language acquisition in his childhood Tarzan did not have
the possibility to evolve sufficient structures for language in his brain. That means
in contrast to the film he will not be able to pick up human speech, especially he
will not be able to store the lexicon and grammatical rules.
4.2
Nell
The film Nell (1994) directed by Michael Apted is narrating the story of a woman
who was raised in the remote backwoods of North Carolina without human contact
except her speech-impaired mother. Because of a stroke Nell’s mother, Violet Kellty,
had been severely disabled physically and linguistically. Only one side of her face
was working for which reason she was not able to speak properly.
Nell who lived her entire life with her aphasiac mother did not acquire an understandable language. She is in her mid twenties when her mother dies. In that state
Nell is finally found by the local doctor Jerome Lovell. The plot is about Lovell’s
struggle against the authorities, represented by psychologist Dr. Paula Olsen. From
their point of view Nell is, due to the lack of English language, not competent and
capable of taking care of herself, so that her interests would be best served if she
was institutionalized. Dr. Lovell has three months to learn Nell language to show
that she can function in the outside world and to prove that she can survive on her
own.
After reading section 4.1.2 one could argue it must also be impossible for Nell
to learn English language as it is impossible for Tarzan. Nell grew up only in
contact with her twin sister, who died tragically in early childhood, and her aphasiac
mother, so that she has never learned to speak ’proper’ English. The difference is
that Nell actually has acquired a language during her childhood. She might speak
an unintelligible language but as Lovell and Olsen revealed, she speaks her own
fractured form of English. For this reason Nell’s age is not the determining factor
in that constellation.
Nell’s brain had the possibility to develop speech relevant structures during her
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childhood. Her mother talked to her in English, but she was not able to produce the
correct sounds because of her physical disability. Nell had acquired a ’strange’ form
of English as her own first language. One striking feature of Nell’s speech is that
she drops consonants (e.g. spea – speak, afe – after). Furthermore her language is
mixed with twin speech components. Jerry Lovell tries to adapt her language in
order to create a common basis for communication.
Because of her first language acquisition in childhood Nell has the means to
learn English language just like learning it as a second language. That learning
process is stated really realistically in the film. In fact, Nell’s problems are much
more located in her social incompetence due to her hermit life in the woods. The
film gives only a vague hint why her mother withdrew in the woods and became a
hermit. In the scene at the sheriffs office, Dr. Lovell reads a paper article submitted
via fax, reporting that Miss Kellty was raped after church two decades ago. This
could have caused an agoraphobia in her, so that she felt obliged to go in the woods,
and it might also be the clue why Nell was told never to go out in daylight.
In my opinion the film Nell has high linguistic relevance and potential. I was
deeply impressed by that film and found the plot really realistic. The language
acquisition topic can be excellently studied on that sophisticated case, whereas the
film is additionally dealing with the special twin speech topic and problems of social
competence.
4.3
Nirgendwo in Afrika
The two films in the preceding sections are most suitable two illustrate factors of
first language acquisition. To complete my explanations I will briefly summarize
some factors of second language acquisition, too. Therefore I will have a closer look
at the film Nirgendwo in Afrika (2001) by Caroline Link.
Whilst first language learning happens relatively unconsciously, second language
learning is much more influenced by different cognitive and affective factors. In the
film these factors can be evaluated regarding the characters of the Jewish emigrants
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Walter, Jettel, their child Regina and Süßkind. They all acquired German as their
first language before they emigrated to Kenya in order to escape the Nazi regime.
In second language acquisition the age is also an important factor, but it is not
as significant as it is in first language acquisition. It does not really exist a critical
period in second language learning. A reason for this might be that a second
language will be partially mapped on the existing mental structures in the brain.
Nevertheless late second language learners will have difficulties in pronunciation,
morphology and syntax, because the first acquired language will dominate the later
acquired ones. To develop good second language skills it is undoubtedly important
to start learning as early as possible (Mehler, Christophe and Ramus, 56/57). In
the film it can be seen that Regina has an advantage of her young age in learning
other languages. She relatively quickly adapts Swahili and furthermore she becomes
proficient in English within a period of about six to seven years.
In second language learning factors like motivation, intelligence and aptitude
are also relevant. This can be especially observed in the role of Jettel. She does
not have a certain speech aptitude and her motivation in the beginning of the film
is rather bad, as a result she does not make progress in second language learning.
When she finally gets aware of her situation, in the scene when Walter and she are
arrested separately by the English and therefore she had to shift for herself, her
motivation changed rapidly. From that point on she starts to learn English and
later she even learned Swahili.
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Conclusion
In this paper I discussed important aspects of the connection between language and
brain. I examined how language acquisition phenomena can be explained by neural
network behavior. In conclusion it can be noticed that the critical period in first
language acquisition is based on neurological reasons. Apparently these reasons do
not effect second language acquisition that much. The films give evidence of the
considered facts and provide an interesting and fascinating access to the topic.
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Bibliography
Obler, L. & Gjerlow, K. (1999)
Language and the Brain.
Cambridge University Press
Calvin, W. & Ojemann, G. (1994)
Conversation with Neil’s Brain.
Addison-Wesley, New York
Desnizza, Wolfgang (2001)
Neurowissenschaftliche Theorie des Sprachwandels.
Peter Lang – Europäischer Verlag der Wissenschaften, Frankfurt/M.
Mehler, J. & Christophe, A. &
”How Infants Acquire Language: Some Preliminary
Ramus, F. (2000)
Observations.” In: Marantz & Miyashita & O’Neil,
Image, Language, Brain. Papers from the first Mind
Articulation Project Symposium.
The MIT Press, Massachusetts Institute of Technology: 51-75
Thimm, Katja (2002)
”Geist unterm Messer.” Der Spiegel, 43/2002: 229234.
Hiermit versichere ich, daß ich die vorliegende Arbeit selbständig und nur unter Zuhilfenahme der angegebenen Hilfsmittel verfaßt habe. Alle wörtlich übernommen Aussagen
sind als Zitate eindeutig gekennzeichnet. Die Herkunft der indirekt übernommenen Formulierungen und Gedankengänge ist angegeben.
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