Re: The Poverty of the Stimulus

From: E.J.Fletcher (
Date: Thu Apr 18 1996 - 23:04:21 BST

Evidence suggests that all languages are founded around a 'structure'
which is innate and common to all humans; as such, mankind possesses
some form of linguistic system which enables distinction between
'grammatical' and 'ungrammatical' phrases from birth. (The term
'grammatical', in this context, refers to whether a vernacular phrase
conforms to these innate, and universal, rules of grammar).

"It holds that beyond the peripheral processing mechanisms, there are
innate ideas and principles of various kinds that determine the form of
the acquired knowledge, in what may be, a rather restricted, and highly
organised way. A condition for innate mechanisms to become activated is
that appropriate stimulation be presented". Chomsky (1965).

 Therefore it is thought that, from birth, the infant is equipped with
a fixed, comprehensive 'database' of universal grammatical rules, from
which are extracted those which are appropriate to his language.
Chomsky terms the 'database' "Universal Grammar" (UG), and the
selection process, which occurs on exposure to a language, "parameter
setting". Evidence for the existence of this innate structure is
supported by the theory's ability to explain how language develops
under the "poverty of the stimulus".

 The stimulus is, in effect, the information that the child can
extract from the surrounding environment concerning language. The child
might gain information about grammatical structure through a process of
listening and attempted interaction, in which trial-and-error, and
feedback from others in the environment, would allow learning to occur.
This would require the child to be exposed to both grammatical and
ungrammatical phrases (or negative evidence). The distinction between
correct and incorrect syntax could then be made. However, the child
never hears or produces fundamentally ungrammatical phrases. This
makes the feedback and trial-and-error methods void, as they rely on
both positive and negative stimuli. Infringements of universal grammar
would therefore have to exist for universal grammar to be learnt in
this way. As such the stimulus is 'impoverished', or incomplete.

 Then what explanation can be given for the child's ability to
learn language? The only possible explanation is that the underlying
principles of language exist within the mind before birth. "What the
stimulus lacks is produced by the organism from its inner (genetically
endowed) resources" Chomsky (1980). Approaches to language which do not
consider this to be the case e.g. empiricism, must provide evidence
which shows the existence of both positive and negative stimuli within
the child's environment; and in doing so, show the poverty of the
stimulus to be a fallacy. Lauria's 1975 belief that such an internal
system of grammatical explanation could not exist, as "Universal
Grammar makes a postulate out of a problem", is thus ill- founded.
Although UG is based on something that has not been proven , evidence
may be presented in the form of the poverty of the stimulus, to suggest
that such a faculty exists. "...What we can try to do is to find
properties for which it is very implausible to assume that everyone has
had relevant experience" Chomsky (1983). Ironically, Lauria
continues by saying "...all further study in the area can lead us
nowhere". This indeed may be accurate, as UG, whose existence is
suggested through the poor nature of the stimulus, appears to fulfil
all the criteria for language acquisition. However if the stimulus
(i.e. the total of all the linguistic information which the child
receives) was shown to be less impoverished (i.e. the stimulus was
shown to provide enough information for learning to occur solely
through exposure to the language, without a inherent linguistic
structure) Chomsky's theory of Universal Grammar would be made
redundant. This is not the case: the stimulus may be shown to be poor.
The linguistic information the child receives from social interaction
is limited. How can such a limited input be manipulated to form such a
developed array of linguistic skills? Furthermore, the accuracy of the
stimulus may also vary, as the child may be exposed to errors made by
the speech community. Surely the child would be tempted to generalise
mistakes and over apply rules? Confusion over rules should occur where
the child over generalises. A child exposed to both "the cat seems to
be asleep" and "the cat seems asleep" would presumably believe that "to
be" may be dropped from the phrase. However, should this be applied to
the sentence "the cat seems to be sleeping", the result would be
ungrammatical. i.e. "the cat seems sleeping". Distinctions between
nouns and verbs may also be expected to become confused in a similar
way. e.g. when presented with the following stimuli,

          'Andrew hates flies.' 'Andrew hates dogs.' 'Andrew flies',

the child should consider 'Andrew dogs' as grammatically correct. It is
extremely unreasonable therefore to assume that every child will make
these mistakes and proceed to have them corrected by the speech
community. Children do not receive negative evidence as they do not
make the initial errors. If the stimulus is impoverished in this
manner, the most plausible explanation for language acquisition points
to the existence of a pre-programmed linguistic system in the mind;
whereby some form of mental process eliminates what seem to be
'logical' grammatical rules. The child later uses this innate source of
knowledge as a foundation from which to expand his linguistic capacity.
Trial-and-error, and feedback from others, allow innate grammatical
rules to be utilised with newly learnt rules. For example, the child
may learn, through trial-and-error, that phrases can be linked by the
word 'and'. The word "and" did not pre-exist within the mind, it had to
be learnt. However the grammatical structure in which the learnt word
becomes applied is inherent.

 The stimulus may be shown to be impoverished in several ways. Firstly,
the amount of input (linguistic information) the child receives from
the speech community is too impoverished to explain the child's vast
linguistic capacity. Similarly, how can an adult's ability to use
words in an infinite number of ways, be explained by the mimicry and
correction of a limited number of phrases experienced within his
lifetime? This would again rely heavily on the existence of negative
evidence. It seems that if the acquisition of grammar occurred in this
fashion another problem would immediately arise: who in the speech
community could have gleaned enough information to provide adequate
correction for others? It would seem almost impossible for the child to
receive information in this manner. Assuming that 'negative evidence'
is unobtainable, what prevents the child from creating too large a
language? After all it would be assumed that without negative stimuli,
i.e. without some form of correctional restraint, the child would
assume ungrammatical phrases to be correct. For the same reason that
ungrammatical phrases are never heard, the child never produces an
ungrammatical phrase. i.e. an internal system of grammatical rules must
presumably exist. It would be expected therefore that errors in speech
rarely occur. Pinker (1984) suggests that "errors occur between 0.1%-8%
of the time in three year olds...the opportunity for making errors is
more than 90% of the time". Furthermore if correction of such errors
was solely dependent on reaction from the primary care givers, learning
would be an arduous process. Feedback in the form of parental reaction
has been shown to be ambiguous, and difficult for the child to
understand. Active verbal interaction and feedback from others in the
environment also appear to be of little importance, as a child who was
unable to speak was shown to be able to understand complicated
sentences without difficulty. Stromswold (1994).

 Secondly the quality of the grammatical information presented to
the child is impoverished, not in the sense that it is degenerate (i.e.
the stimulus is poorly formed containing errors such as unfinished
phrases, impromptu pauses, and slips of the tongue) but that the
stimulus itself is of poor quality. i.e. it does not contain all the
information needed for all the principles of grammar to be acquired by
the child. Thus even motherese, simplified 'baby talk' is impoverished:
and perhaps is even harder for the child to comprehend than the
language from which it is derived. Motherese may neglect grammatical
rules and impoverish the stimulus for language acquisition still
further, despite being grammatically correct 99.93% of the time. This
form of parent-child communication still fails to provide a stimulus
which is rich enough to provide an adequate base for language

 Surprisingly bi-lingual language acquisition in children occurs with
little confusion. A distinction between two languages is created in the
absence of information to instruct the child to keep their varying
grammatical structures separate. The stimulus is impoverished as it
does not provide enough information for the acquisition of grammar to
occur. One would naturally expect the child to generalise the
grammatical rule within each of the separate language. It would also be
reasonable to assume that the generalisations produced in one language
would be drawn across into the other language. However once again this
does not occur. Children have the capacity to learn the nuances of
grammatical language without instruction or environmental input. This
suggests an inherent grammatical system. Even severely retarded
children, whose ability to acquire language from the speech community
is by nature impaired, show the ability to utilise inborn grammatical

  In conclusion the stimulus may be shown to be impoverished,
in that the examples which the child would need to observe to allow him
to learn grammatical rules are incomplete. i.e. negative evidence is
missing. For the stimulus to be sufficient, negative and positive
evidence is required. Evidence suggests that such ungrammatical phrases
do not exist as the speech community do not produce them. Furthermore,
why is it that the child does not over generalise, or indeed over
generate rules?

 The poverty of the stimulus naturally calls for an explanation of
how the grammatical rules of language are acquired. Chomsky provides an
answer to this through his assumption that "what the organism lacks is
produced from its inner (genetically endowed) resources". The poverty
of the stimulus has thus been instrumental in providing strong evidence
for Universal Grammar.


 Best, J.B. (1995) Cognitive Psychology Minneapolis: West Publishing

 Botha, R.P. (1989) Challenging Chomsky: The Generative Garden game.
Oxford: Basil Blackwell Ltd.

Cook. Chomsky's Universal Grammar.

 Stillings, N.A., Weisler S.E., Chase C.H., Feinstien M.H.,
Garfield J.L., Rissland E.L. (1995) Cognitive Science.
Cambridge Massachusetts: MIT Press

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