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{\LARGE Evaluating the CPH in L1A
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(with Insight from L2A)}
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{\Large 21.325}
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{\large Juliet C. Bourne
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December 16, 1991}
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{\ms Introduction}

The relative ease and uniformity with which children acquire their
native language has made language acquisition a popular topic of
research. One of the more controversial topics in language acquisition
research has been the Critical Period Hypothesis. Questions asked
include: Is there some period of time after which language acquisition
is no longer possible?  Can a conclusion relevant to language
acquisition be drawn from the non-linguistic, non-human appearances of
critical periods, such as the imprinting of ducklings or the learning of
bird-song? Or is the very idea of imposing a critical
period on language acquisition ridiculous?

The arguments for and against the Critical Period Hypothesis (CPH) are
restricted mainly to indirect evidence, since all normal children
acquire their mother tongue without problem. There is no direct
(ethical) way to study the effects on a child of not being exposed to
language within some hypothesized critical period.\footnote{Scientists
do not perform the same kind of experiments on humans as they do on
birds, for instance.} Thus, neurological and developmental evidence, as
well as what evidence is to be gotten from studying the language
acquisition of so-called ``wolf children,'' is used in evaluating the
validity of the CPH.

The arguments for the CPH involve neurological evidence of the decline
of the plasticity of the brain and of language recovery after brain
injury and evidence from the incomplete acquisition of language by
``wolf children.'' It has been asserted that the brain becomes ``rigid''
where language is concerned between 5 and 9 years of age.
\cite[53]{singleton} This is mainly concluded from studies of patients
suffering from brain lesions resulting in loss of speech and their
ability to recover speech.  When the injury is sustained early in life,
the chances of being able to ``transfer'' language to another part of
the brain, and thus recovering language, are better. Evidence such as
this has been used in support of the CPH by drawing the conclusion that
after a certain age the brain is no longer able to develop language.

Another argument for the CPH uses evidence from so-called
``wolf children.'' These are children who were either abandoned or
otherwise deprived of language at an early age and who were subsequently
discovered when they were near the age of puberty. Their acquisition of
language (or lack thereof) after discovery is of particular interest to
those holding the CPH to be valid. The fact that these children do not
ever fully acquire language seems to show that there is some sort of
critical period involved in acquiring language. Thus, this evidence
along with the neurological evidence is used to support the assertion
that there is a critical period in acquiring language.

The arguments against the CPH include disputing the evidence cited by
the supporters of the CPH as well as giving developmental evidence which
shows the acquisition of language skills continuing past the ``critical
period.'' In response to the neurological evidence, skeptics claim:
``The fact that different researchers have specified different ages as
marking the onset of a decline in cerebral plasticity specifically in
relation to language functions does not inspire confidence in their
assertions.'' \cite[53]{singleton} It also has been asserted that:

\begin{mq}

\noindent ``one can pose the question whether evidence concerning
compensation for damage to normal speech centres tells us {\em anything}
about putative maturational constraints on language acquisition where
these centres are entirely unimpaired.'' \cite[54]{singleton}

\end{mq}

\noindent Thus, the arguments using this neurological evidence in
support of the CPH are not considered convincing enough by skeptics.

As for the evidence involving ``wolf children,'' skeptics of the CPH
assert convincingly that the data collected from such cases could be
used both for and against the CPH. However, there are too many unknowns
in these cases, such as amount of exposure to language before discovery,
mental or physical trauma before discovery which could affect mental or
cognitive abilities, {\em et cetera}. Thus, arguments for or against the
CPH based on the cases of ``wolf children'' can never be completely
convincing or unequivocable.

In addition to disputing the arguments for the CPH, opponents of the CPH
present developmental evidence to further argue against the CPH. This
evidence includes the acquisition of language skills such as reading,
acquiring new vocabulary items, learning correct stress placement, {\em
et cetera}.  Since a person's vocabulary never stops growing, since a
person can learn to read and write late in life, and since language
skills generally improve with age, opponents of the CPH claim that the
idea that there is a time after which ``language acquisition'' ceases to
continue, or even just declines, is ridiculous.

One area of research that doesn't seem to be used directly in arguments
for or against the CPH for first language acquisition is second language
acquisition research. First and second language acquisition are
considered disparate.\footnote{As far as I can tell.} Evidence from L1A
is used in L2A, but not {\em vice versa}. Although first and second
language acquisition are necessarily distinct, it seems that a lot could
be gained from applying evidence from L2A to the CPH for L1A. Since it
has been shown that L2A is affected by the age of the beginning of
acquisition, studying why this is the case might have importance in L1A.

In this paper I will try to explore some of the evidence for and against
the CPH. I will mainly concern myself with evidence from
``wolf children'' and from the continuation of language development into
adult years. I will also try to show how evidence from L1A can (and
should) be used to shed some light on the CPH for L1A. From the
examination of arguments for and against the CPH, I hope to show that
there is a middle ground that is relatively unexplored in which
acquiring a first language after a ``critical period'' is related to
L2A.

\vspace*{.15in}
{\ms Wolf Children}

Since experiments in which children are intentionally deprived of
exposure to language are (hopefully) not done, direct evidence for the
existence of a critical period in the acquisition of native language is
not readily available. The most ``direct'' evidence is therefore taken
from the studies of wild or isolated children, so-called ``wolf
children.'' \footnote{This term probably comes from the fact that such
children were occasionally found living with wolves. In the case of
isolated children, this term does not really apply, since they were
``raised'' by humans.} These children were either abandoned or isolated
early after they were born and received no real language input until
their discovery. By studying how these children subsequently acquired
language, one can draw conclusions, if only tentative ones, about the
validity of the CPH. \footnote{By the very nature of these children's
circumstances and experiences, many factors are unknown or unclear, such
as previous exposure to language, mental and/or physical trauma, {\em et
cetera}.  Thus conclusions from these cases are, for the most part,
tentative.}

Throughout history there have been stories of ``wolf children.'' The
earliest documented case is from 1344 (first well-documented in 1702).
Granted, many of these have contained ``large elements of fantasy,'' but
that ``should not discourage us from seeking the kernel of truth in
these accounts.'' \cite[62]{malson} The oldest scientifically
well-documented case is that of Victor, ``the wild boy of Aveyron.''
Jean Itard was given control of Victor's education after his discovery
(and capture) at age 11 in 1799. Under Itard, Victor became somewhat
civilized, his cognitive abilities expanded somewhat, and he learned to
recognize and write words in order to communicate his wants and needs.
Unfortunately, Victor never learned to speak (other than a couple
mispronounced words) and, partly because of this, Itard stopped working
with him after 7 years. Victor never progressed further afterwards. Many
questions have been raised with respect to Victor's case, such as: Was
the reason that Victor never progressed very far in terms of
intellectual and linguistic abilities related to Victor's innate
(dis)abilities (i.e. was he mentally deficient in some respect?) or to
his experiences before or during his abandonment? \footnote{It is
suggested that a deliberate attempt was made on his life, as evidenced
by a large scar on his throat, which could have affected his abilities
and/or his mental state.} Due to these uncertainties, drawing convincing
conclusions from this case is impossible. In order to draw reasonably
convincing conclusions, cases in which more thorough knowledge can be
obtained about the children's past and physical and mental health must
be studied.

Two such cases come from this century: the case of ``Isabelle'' and the
case of ``Genie.'' Both were isolated children. Both were discovered and
subsequently acquired language. However, what is interesting to note is
that one was discovered early in life and the other was discovered just
past puberty. The difference in the ``end states'' of their acquired
language is striking and has implications for the CPH.

Isabelle was discovered in 1937 at the age of six and a half. She was
the daughter of a deaf-mute and ``mother and child lived most of the
time in a darkened room away from the rest of the family.''
\cite[191]{brown} At the time of her discovery, Isabelle ``had no speech
and made only a croaking noise'' \cite[191]{brown} and even though her
first IQ test score was very low, she was put into a program of speech
training.  Her speech and language progressed rapidly under this
attention:

\begin{mq}

\noindent ``Isabelle passed through the usual stages of linguistic
development at a greatly accelerated rate. She covered in two years the
learning that ordinarily occupies six years. By the age of eight and
one-half Isabelle had a normal IQ and was not easily distinguished from
ordinary children her age.'' \cite[192]{brown}

\end{mq}

\noindent This case seems quite remarkable in that Isabelle was
discovered at an early age, had no apparent mental defects, and, it is
reasonably certain, received no linguistic input until her discovery.
Conclusions drawn from this case, such as the conclusion that it is
possible to make up for six and a half years of being deprived of
language input, can be fairly convincing.

The other case is that of Genie. She was discovered in 1970 when she was
thirteen and three-quarters and she was subsequently admitted to a
hospital.  The facts of her life prior to her discovery seem to be:

\begin{mq}

\noindent ``... [F]rom the age of 20 months until shortly before admission
to the hospital, Genie had been isolated in a small room, tied into a
potty chair where she remained most or all hours of the day, sometimes
overnight. ... [T]he father's intolerance of noise of any kind kept any
acoustic stimuli which she received to a minimum. ... Genie was
physically punished by the father if she made any sounds.''
\cite[84f]{fromkin}\footnote{As cited by \cite[50]{singleton}}

\end{mq}

\noindent Medical examinations revealed no evidence of physical or mental
disease, and within a few weeks she was no longer as withdrawn as first
discovered. Tests revealed that Genie's knowledge of language was
limited to a few individual words.  Over the next two years, however,
she acquired comprehension of several different structures and, as
Curtiss {\em et al} report, ``her progress in the acquisition of
language, though slower than usual, paralleled that of normal
English-speaking children.'' \cite{curtiss} \footnote{As cited by
\cite[51]{singleton}} Genie's progress in speech production was also
slower, but approximately normal in other respects.  However, one
observation must be noted: she had certain ``syntactic-semantic
idiosyncrasies'' \cite[51]{singleton} such as ``interpreting simple NVN
sentences incorrectly.'' \cite{curtiss} \footnote{As cited by
\cite[51]{singleton}} So, it would seem that although she acquired
language, Genie did not fully acquire the English language, and the
native-like ability that that implies. Like the case of Isabelle,
conclusions from this case can be fairly convincing, even though full
extent to Genie's language input before discovery is not known.
\footnote{It has been mentioned that Genie received language input,
however limited, from her mother which could have affected her
subsequent acquisition. But this still wouldn't explain her linguistic
idiosyncrasies.}

So what is the significance of the differences between the cases of
Isabelle and Genie? The relevant differences are the ages of discovery
(and thus the beginning of rich linguistic input) and the apparent
``end-states'' achieved by both. Isabelle's exposure to language input
was well before the hypothesized ``critical period,'' whereas Genie's
was shortly after this critical period. Isabelle can be said to have
{\em fully} acquired English (i.e. she is not easily distinguished from
a native speaker), whereas Genie seems to have acquired a language very
similar to English, but not quite the native language of English. That
is to say, Genie seems to be somehow a ``second language learner'' of
English rather than a ``first language learner'' of English like
Isabelle. This conclusion has an important impact on the CPH: if the
same results and conclusions found in second language acquisition
research can be applied to first language acquisition, then a lot more
can be said about the CPH as it applies to first language acquisition.

\vspace*{.15in}
{\ms The Role of L2A Evidence in L1A}

Most of the research done in L2A seems to indicate that the age at which
one begins to learn a second language is an important factor in
determining how well one learns that language, or how ``complete'' their
acquisition is. Naturalistic immigrant studies (studies of immigrants
who learn a second language naturalistically, i.e. with no formal
training) show that the younger an immigrant starts to learn the second
language the more likely he or she is to acquire that language well
enough to be indistinguishable from native speakers. Although this fact
holds strikingly where the acquisition of phonology is concerned, it can
be observed in other areas, such as comprehension, as well. Studies that
demonstrate this fairly well are two done by Susan Oyama in 1976 and
1978. Both involved Italian immigrants who lived in New York City. She
tested them ``for degree of approximation to a native American English
accent and for proficiency in English listening comprehension.''
\cite[85]{singleton} She found that there was a very strong ``age of
arrival'' effect, with little ``length of residency'' effect, such that
``youngest arrivals perform in the range set by the controls, whereas
those arriving after about age 12 do not.'' \cite{oyama} \footnote{As
cited by \cite[86]{singleton}} Most of the immigrant studies which
controlled for age of arrival, length of residency, and amount of
exposure show this same effect. This seems to be strong evidence that
the younger one is, the easier one {\em fully} acquires a language.

While there are studies which seem to indicate the opposite of that
stated above, the majority of them seem to involve comparisons of second
language learners in formal education settings and their performance on
exams usually associated with formal education. In these kinds of
settings, the older learners will almost certainly do better than their
younger counterparts, who are not at the same level of cognitive
development. Younger children do not have the formal learning abilities
that would enable them to learn language in the largely artificial
setting of a classroom. As Singleton states:

\begin{mq}

\noindent ``[T]here are no real grounds for saying that the eventual
attainment of older learners is better than that of younger learners in
a formal learning situation if `eventual' is to have the same content as
in relation to naturalistic learning situation.'' \cite[121]{singleton}

\end{mq}

\noindent Thus, the conclusion to be drawn from second language
acquisition research seems to be that the younger one begins to acquire
(as opposed to ``learn'') a second language, the more fully one will
acquire it, and that the ``critical period'' for full (complete)
native-like acquisition seems to be in the early teens. The question of
Universal Grammar (UG) access in L2A is relevant to L1A which begins
past the ``critical period.'' If it can be shown that L2 learners do not
have the ability to ``start from scratch,'' one must ask how much of
this is due to the fact that they have already acquired a first language
and how much is due to the fact that some ``critical period'' has
passed. Recent L2A research has been exploring this possibility. However,
experiments which unequivocally show that the reason for incomplete
acquisition is the degradation of UG access are hard to design and the
results are sometimes hard to interpret. If it can be shown that access
to UG is no longer fully available after a certain age, then it can be
hypothesized that the reason L1A after this age is also incomplete is
because of the degradation of UG access.\footnote{Which seems to be a
reasonable amendment to the CPH.}

{\ms Language Development after the ``Critical Period''}

For both first and second language acquisition, it cannot be said that
the development of language stops at the end of the ``critical period.''
This is a major argument against the CPH. Studies done show that one
continues to acquire vocabulary, develop reading and comprehension
skills, and develop better writing and speaking skills. A review of such
studies in 1971 by John Carroll of the Education Testing Service
included studies of everything from vocabulary knowledge to listening
skills to ``skills in using the grammatical system.'' \cite{carroll}
However, the results of these studies are mainly used to determine how
to test and characterize language skills in such a way as to be able to
make comparisons between individuals, who invariably differ from one
another in this respect. The fact that there is such variation in the
level of attainment of language {\em skills} seems to indicate that the
acquisition of such skills is not universal, as opposed to the
universality of acquiring {\em language}.

Arguing against the CPH by pointing to the evidence that adults know
more vocabulary, write better, or are more ``linguistically''
sophisticated in general, does not effectively discredit the CPH since
language skills are not universal. Indeed, there are some children who
probably read better than their parents, as evidenced by the programs in
Cuba, Nicaragua, and the Republic of Somalia, which closed down the
schools so that children could teach their elders to read and write.
\cite[44]{bown}\footnote{As cited by \cite[79]{singleton}} However, the
adults thus being taught to read and write had undoubtedly already
acquired their native language and needed no help in that
respect.\footnote{The fact that in general one can learn to read and
write at any age indicates that there is no ``critical period'' for
developing those skills.} The usual variation in level of competence in
language skills between adults and children (i.e. with adults being more
competent than children) can be explained in terms of cognitive
abilities. It has been convincingly shown (by Piaget, for instance) that
adults are more capable of formal and abstract thinking than children
and thus are more likely to have a larger vocabulary (more concepts,
more subtle distinctions), to write better, to have better reading
skills, {\em et cetera}, all of which involve complex thought skills
which are not {\em exclusively} derived from knowledge of one's native
language.

So, just as one's mathematical skills develop once the counting system
is understood, so too one's language skills develop once one's native
language is acquired. Once the fundamentals are known, one can begin to
expand on them. Using the development of language skills past the
``critical period'' as an argument against the CPH does not make much
sense since the CPH is concerned with the acquisition of the
fundamentals, not with the abilities that are built on top of the
fundamentals. Thus, the arguments based on the studies described in
opposition to the CPH \cite{singleton} do not pose a serious threat to
the CPH.

\vspace*{.15in}
{\ms Conclusion}

Both L1A and L2A evidence seems to favor the CPH. In L1A, the cases of
children isolated from language show that when the process of first
language acquisition begins after a certain age, the language will not
be acquired to native-like levels. In L2A, numerous studies show that
the earlier the process of second language acquisition begins, the more
the acquired language approximates native-line fluency. Counter evidence
is derived mainly from studies of language acquisition occurring in
artificial environments where formal learning skills are needed to learn
the language. Such studies cannot discredit the CPH since they involve
cognitive ability differences between adults and children.

Since direct evidence for the CPH in L1A is very rare, L2A research
seems like the best alternative given that L1A and L2A seems to be
similar with respect to the CPH. If, for example, it is discovered that
access to the Universal Grammar decreases after a certain age and that
that is why younger and older L2 learners differ so much, then it could
very well be the case that this same decrease in access affects L1A in a
similar way. 

Finally, some people might argue that what is being described is not
really a {\em critical} period, but merely a sensitive period during
which language is acquired more efficiently. However, if one defines
language after this period never to be ``complete'' or acquired like
native speakers, then this period could be called critical. The next
step would then be to define what ``complete'' acquisition is and to
find a way to distinguish native speakers from those who have really
acquired the language well. But whether it is called a ``sensitive''
or a ``critical'' period, the hypothesis still provides a reason why
language acquisition is harder for adults than for children. (One of
the great mysteries of life.)

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