Home      Discussion      Topics      Dictionary      Almanac
Signup       Login
Poverty of the stimulus

Poverty of the stimulus

Discussion
Ask a question about 'Poverty of the stimulus'
Start a new discussion about 'Poverty of the stimulus'
Answer questions from other users
Full Discussion Forum
 
Encyclopedia
In linguistics
Linguistics
Linguistics is the scientific study of human language. Linguistics can be broadly broken into three categories or subfields of study: language form, language meaning, and language in context....

, the poverty of the stimulus (POTS) is the assertion that natural language
Natural language
In the philosophy of language, a natural language is any language which arises in an unpremeditated fashion as the result of the innate facility for language possessed by the human intellect. A natural language is typically used for communication, and may be spoken, signed, or written...

 grammar is unlearnable given the relatively limited data
Underdetermination
In scientific theory, underdetermination refers to situations where the evidence available is insufficient to identify which belief we should hold about that evidence...

 available to children learning a language, and therefore that this knowledge is supplemented with some sort of innate linguistic capacity. As such, the argument strikes against empiricist
Empiricism
Empiricism is a theory of knowledge that asserts that knowledge comes only or primarily via sensory experience. One of several views of epistemology, the study of human knowledge, along with rationalism, idealism and historicism, empiricism emphasizes the role of experience and evidence,...

 accounts of language acquisition
Language acquisition
Language acquisition is the process by which humans acquire the capacity to perceive, produce and use words to understand and communicate. This capacity involves the picking up of diverse capacities including syntax, phonetics, and an extensive vocabulary. This language might be vocal as with...

 and is usually construed as being in favor of linguistic
Linguistics
Linguistics is the scientific study of human language. Linguistics can be broadly broken into three categories or subfields of study: language form, language meaning, and language in context....

 nativism
Psychological nativism
In the field of psychology, nativism is the view that certain skills or abilities are 'native' or hard wired into the brain at birth. This is in contrast to empiricism, the 'blank slate' or tabula rasa view, which states that the brain has inborn capabilities for learning from the environment but...

.

Nativists claim that humans are born with a specific representational adaptation for language that both funds and limits their competence
Linguistic competence
Linguistic competence is the system of linguistic knowledge possessed by native speakers of a language, it is in contrast to the concept of Linguistic performance, the way the language system is used in communication...

 to acquire specific types
Linguistic typology
Linguistic typology is a subfield of linguistics that studies and classifies languages according to their structural features. Its aim is to describe and explain the common properties and the structural diversity of the world's languages...

 of natural language
Natural language
In the philosophy of language, a natural language is any language which arises in an unpremeditated fashion as the result of the innate facility for language possessed by the human intellect. A natural language is typically used for communication, and may be spoken, signed, or written...

s over the course of their cognitive development and linguistic maturation. The argument is now generally used to support theories and hypotheses of generative grammar
Generative grammar
In theoretical linguistics, generative grammar refers to a particular approach to the study of syntax. A generative grammar of a language attempts to give a set of rules that will correctly predict which combinations of words will form grammatical sentences...

. The name was coined by Chomsky
Chomsky
Chomsky Khomsk ") is a Belarus'-origin surname, and may refer to:* Aviva Chomsky , American historian* Carol Chomsky , American linguist and wife of Noam Chomsky* Elsie Chomsky, American educator...

 in his work Rules and Representations. The thesis emerged out of several of Chomsky's writings on the issue of language acquisition
Language acquisition
Language acquisition is the process by which humans acquire the capacity to perceive, produce and use words to understand and communicate. This capacity involves the picking up of diverse capacities including syntax, phonetics, and an extensive vocabulary. This language might be vocal as with...

. The argument has long been controversial within linguistics, forming the backbone for the theory of universal grammar
Universal grammar
Universal grammar is a theory in linguistics that suggests that there are properties that all possible natural human languages have.Usually credited to Noam Chomsky, the theory suggests that some rules of grammar are hard-wired into the brain, and manifest themselves without being taught...

.

Summary


Though Chomsky and his supporters have reiterated the argument in a variety of different manners (indeed Pullum and Scholz (2002a) provide no less than 13 different "sub arguments" that can optionally form part of a poverty-of-stimulus argument), one frequent structure to the argument can be summed up as follows:
  • Premises:
    1. There are patterns in all natural languages that cannot be learned by children using positive evidence alone. Positive evidence is the set of grammatical sentences the language learner has access to, that is, by observing the speech of others. Negative evidence, on the other hand, is the evidence available to the language learner about what is not grammatical. For instance, when a parent corrects a child's speech, the child acquires negative evidence.
    2. Children are only ever presented with positive evidence for these particular patterns. For example, they only hear others speaking using sentences that are "right", not those that are "wrong".
    3. Children do learn the correct grammars for their native languages.
  • Conclusion: Therefore, human beings must have some form of innate linguistic capacity that provides additional knowledge to language learners.

For the argument


The validity
Validity
In logic, argument is valid if and only if its conclusion is entailed by its premises, a formula is valid if and only if it is true under every interpretation, and an argument form is valid if and only if every argument of that logical form is valid....

 of the argument itself is bitterly contested by constructionists. Constructionists are theorists who do not believe Chomskian arguments and believe language is learned through some kind of functional distributional analysis (Tomasello
Michael Tomasello
Michael Tomasello is an American developmentalpsychologist. He is a co-director of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.-Life:...

 1992). One problem in language is called the no negative evidence problem. This is basically that children cannot use only positive evidence to learn language. Constructionists stumble at this point whereas nativists simply use linguistic constraint theories (Baker 1979, Jackendoff
Ray Jackendoff
Ray Jackendoff is an American linguist. He is professor of philosophy, Seth Merrin Chair in the Humanities and, with Daniel Dennett, Co-director of the Center for Cognitive Studies at Tufts University...

 1975).

Several patterns in language have been claimed to be unlearnable from positive evidence alone. One example is the hierarchical nature of languages. The grammar
Grammar
In linguistics, grammar is the set of structural rules that govern the composition of clauses, phrases, and words in any given natural language. The term refers also to the study of such rules, and this field includes morphology, syntax, and phonology, often complemented by phonetics, semantics,...

s of human languages produce hierarchical tree structures
Tree structure
A tree structure is a way of representing the hierarchical nature of a structure in a graphical form. It is named a "tree structure" because the classic representation resembles a tree, even though the chart is generally upside down compared to an actual tree, with the "root" at the top and the...

 and some linguists argue that human languages are also capable of infinite
Infinity
Infinity is a concept in many fields, most predominantly mathematics and physics, that refers to a quantity without bound or end. People have developed various ideas throughout history about the nature of infinity...

 recursion
Recursion
Recursion is the process of repeating items in a self-similar way. For instance, when the surfaces of two mirrors are exactly parallel with each other the nested images that occur are a form of infinite recursion. The term has a variety of meanings specific to a variety of disciplines ranging from...

 (see Context-free grammar
Context-free grammar
In formal language theory, a context-free grammar is a formal grammar in which every production rule is of the formwhere V is a single nonterminal symbol, and w is a string of terminals and/or nonterminals ....

). For any given set of sentences generated by a hierarchical grammar capable of infinite recursion there are an indefinite number of grammars that could have produced the same data. This would make learning any such language impossible. Indeed, a proof by E. Mark Gold showed that any formal language that has hierarchical structure capable of infinite recursion is unlearnable from positive evidence alone, in the sense that it is impossible to formulate a procedure that will discover with certainty the correct grammar given any arbitrary sequence of positive data in which each utterance occurs at least once. However, this does not preclude arriving at the correct grammar using typical input sequences rather than particularly malicious sequences or arrive at an almost perfect approximation to the correct grammar. Indeed, it has been proposed that under very mild assumptions (ergodicity
Ergodicity
In mathematics, the term ergodic is used to describe a dynamical system which, broadly speaking, has the same behavior averaged over time as averaged over space. In physics the term is used to imply that a system satisfies the ergodic hypothesis of thermodynamics.-Etymology:The word ergodic is...

 and stationarity
Stationary process
In the mathematical sciences, a stationary process is a stochastic process whose joint probability distribution does not change when shifted in time or space...

), the probability of producing a sequence that renders language learning impossible is in fact zero.

Another example of language pattern claimed to be unlearnable from positive evidence alone is subject-auxiliary inversion
Subject-auxiliary inversion
In English, subject-auxiliary inversion occurs when an auxiliary verb precedes a subject. This is an exception to the English word order convention of subjects preceding their corresponding verbs...

 in questions, i.e.:
  • You are happy.
  • Are you happy?


There are two hypotheses the language learner might postulate about how to form questions: (1) The first auxiliary verb in the sentence (here: 'are') moves to the beginning of the sentence, or (2) the 'main' auxiliary verb in the sentence moves to the front. In the sentence above, both rules yield the same result since there is only one auxiliary verb. But, the difference is apparent in this case:
  • Anyone who is interested can see me later.
  1. Is anyone who interested can see me later?
  2. Can anyone who is interested see me later?


Of course, the result of rule (1) is ungrammatical while the result of rule (2) is grammatical. So, rule (2) is (approximately) what we actually have in English, not rule (1). The claim, then, first is that children don't see sentences as complicated as this one enough to witness a case where the two hypotheses yield different results, and second that just based on the positive evidence of the simple sentences, children could not possibly decide between (1) and (2). Moreover, even sentences such as (1) and (2) are compatible with a number of incorrect rules (such as "front any auxiliary). Thus, if rule (2) was not innately known to infants, we would expect half of the adult population to use (1) and half to use (2). Since that doesn't occur, rule (2) must be innately known. (See Pullum 1996 for the complete account and critique.)

The last premise, that children successfully learn language, is considered to be evident in human speech. Though people occasionally make mistakes, human beings rarely speak ungrammatical sentences, and generally do not label them as such when they say them. (Ungrammatical in the descriptive
Descriptive linguistics
In the study of language, description, or descriptive linguistics, is the work of objectively analyzing and describing how language is spoken by a group of people in a speech community...

 sense, not the prescriptive
Linguistic prescription
In linguistics, prescription denotes normative practices on such aspects of language use as spelling, grammar, pronunciation, and syntax. It includes judgments on what usages are socially proper and politically correct...

 sense.)

That many linguists accept all three of the premises is testimony to Chomsky's influence in the discipline, and the persuasiveness of the argument. Nonetheless, the APS has many critics, both inside and outside linguistics.

Against the argument


The soundness
Soundness
In mathematical logic, a logical system has the soundness property if and only if its inference rules prove only formulas that are valid with respect to its semantics. In most cases, this comes down to its rules having the property of preserving truth, but this is not the case in general. The word...

 of the poverty of stimulus argument is widely questioned. Indeed, every one of the three premises of the argument has been questioned at some point in time. Much of the criticism comes from researchers who study language acquisition
Language acquisition
Language acquisition is the process by which humans acquire the capacity to perceive, produce and use words to understand and communicate. This capacity involves the picking up of diverse capacities including syntax, phonetics, and an extensive vocabulary. This language might be vocal as with...

 and computational linguistics
Computational linguistics
Computational linguistics is an interdisciplinary field dealing with the statistical or rule-based modeling of natural language from a computational perspective....

. Additionally, connectionist
Connectionism
Connectionism is a set of approaches in the fields of artificial intelligence, cognitive psychology, cognitive science, neuroscience and philosophy of mind, that models mental or behavioral phenomena as the emergent processes of interconnected networks of simple units...

 researchers have never accepted most of Chomsky's premises, because these premises are at odds with connectionist beliefs about the structure of cognition.

The first and most common critique, is that positive evidence is actually enough to learn the various patterns that linguists claim are unlearnable by positive evidence alone. A common argument is that the brain's mechanisms of statistical
Statistics
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....

 pattern recognition
Pattern recognition
In machine learning, pattern recognition is the assignment of some sort of output value to a given input value , according to some specific algorithm. An example of pattern recognition is classification, which attempts to assign each input value to one of a given set of classes...

 could solve many of the imagined difficulties. For example, researchers using neural network
Neural network
The term neural network was traditionally used to refer to a network or circuit of biological neurons. The modern usage of the term often refers to artificial neural networks, which are composed of artificial neurons or nodes...

s and other statistical
Statistics
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....

 methods have programmed computers to learn rules such as (2) cited above, and have claimed to have successfully extracted hierarchical structures, all using positive evidence alone. Indeed, Klein & Manning (2002) report constructing a computer program that is able to retrieve 80% of all correct syntactic analyses of text in the Wall Street Journal Corpus using a statistical learning mechanism (unsupervised grammar induction) demonstrating a clear move away from "toy" grammars. In another study, a probabilistic type of computer without any programmed preconceptions about grammar at all were presented with lots of newspaper articles. Despite the fact that the scientists had censored all articles containing the sentence "colorless green ideas sleep furiously", the computer, after "reading" thousands of articles, deemed that sentence 10000 times more probable than a scrambled ungrammatical version. This proves that statistical analysis without preconceptions can reveal general grammatical rules at a humanlike accuracy.

There is also much criticism about whether negative evidence is really so rarely encountered by children. Pullum argues that learners probably do get certain kinds of negative evidence. In addition, if one allows for statistical learning, negative evidence is abundant. Consider that if a language pattern is never encountered, but its probability of being encountered would be very high were it acceptable, then the language learner might be right in considering absence of the pattern as negative evidence. Chomsky accepts that this kind of negative evidence plays a role in language acquisition, terming it "indirect negative evidence", though he does not think that indirect negative evidence is sufficient for language acquisition to proceed without Universal Grammar. However, contra this claim, Ramscar and Yarlett (2007) designed a learning model that successfully simulates the learning of irregular plurals based on negative evidence, and backed the predictions of this simulation in empirical tests of young children. Ramscar and Yarlett suggest that failures of expectation function as forms of implicit negative feedback that allow children to correct their errors.

As for the argument based on Gold's proof, it's not clear that human languages are truly capable of infinite recursion. Clearly, no speaker can ever in fact produce a sentence with an infinite recursive structure, and in certain cases (for example, center embedding
Center embedding
In linguistics, center embedding refers to the process of embedding a phrase in the middle of another phrase of the same type. This often leads to difficulty with parsing which would be difficult to explain on grammatical grounds alone...

), people are unable to comprehend sentences with only a few levels of recursion. Chomsky and his supporters have long argued that such cases are best explained by restrictions on working memory
Working memory
Working memory has been defined as the system which actively holds information in the mind to do verbal and nonverbal tasks such as reasoning and comprehension, and to make it available for further information processing...

, since this provides a principled explanation for limited recursion in language use. Some critics argue that this removes the falsifiability of the premise. Returning to the big picture, it is questionable whether Gold's research actually bears on the question of natural language acquisition at all, since what Gold showed is that there are certain classes of formal languages for which some language in the class cannot be learned given positive evidence alone. It's not at all clear that natural languages fall in such a class, let alone whether they are the ones that are not learnable.

Finally, it has been argued that people may not learn exactly the same grammars as each other. If this is the case, then only a weak version of the third premise is true, as there would be no fully "correct" grammar to be learned. However, in many cases, Poverty of Stimulus arguments do not in fact depend on the assumption that there is only one correct grammar, but rather that there is only one correct class of grammars. For example, the Poverty of Stimulus argument from question formation depends only on the assumption that everyone learns a structure-dependent grammar.

See also


  • Educating Eve: The 'Language Instinct' Debate
    Educating Eve: The 'Language Instinct' Debate
    Educating Eve: The 'Language Instinct' Debate is a book by Geoffrey Sampson, providing arguments against Noam Chomsky's theory of a human instinct for language acquisition. Sampson explains the original title of the book as a deliberate allusion to Educating Rita , and uses the plot of that play...

  • Empiricism
    Empiricism
    Empiricism is a theory of knowledge that asserts that knowledge comes only or primarily via sensory experience. One of several views of epistemology, the study of human knowledge, along with rationalism, idealism and historicism, empiricism emphasizes the role of experience and evidence,...

  • Government and binding
  • Innatism
    Innatism
    Innatism is a philosophical doctrine that holds that the mind is born with ideas/knowledge, and that therefore the mind is not a 'blank slate' at birth, as early empiricists such as John Locke claimed...

  • Nature versus nurture
    Nature versus nurture
    The nature versus nurture debate concerns the relative importance of an individual's innate qualities versus personal experiences The nature versus nurture debate concerns the relative importance of an individual's innate qualities ("nature," i.e. nativism, or innatism) versus personal experiences...

  • Plato's Problem
    Plato's Problem
    Plato's problem is the term given by Noam Chomsky to the gap between knowledge and experience. It presents the question of how we account for our knowledge when environmental conditions seem to be an insufficient source of information. It is used in linguistics to refer to the "argument from...

  • Principles and parameters
    Principles and parameters
    Principles and parameters is a framework within generative linguistics in which the syntax of a natural language is described in accordance with general principles and specific parameters that for particular languages are either turned on or off...

  • Psychological nativism
    Psychological nativism
    In the field of psychology, nativism is the view that certain skills or abilities are 'native' or hard wired into the brain at birth. This is in contrast to empiricism, the 'blank slate' or tabula rasa view, which states that the brain has inborn capabilities for learning from the environment but...

  • Rationalism
    Rationalism
    In epistemology and in its modern sense, rationalism is "any view appealing to reason as a source of knowledge or justification" . In more technical terms, it is a method or a theory "in which the criterion of the truth is not sensory but intellectual and deductive"...

  • Tabula rasa
    Tabula rasa
    Tabula rasa is the epistemological theory that individuals are born without built-in mental content and that their knowledge comes from experience and perception. Generally proponents of the tabula rasa thesis favour the "nurture" side of the nature versus nurture debate, when it comes to aspects...

  • Colorless green ideas sleep furiously
    Colorless green ideas sleep furiously
    "Colorless green ideas sleep furiously" is a sentence composed by Noam Chomsky in his 1957 Syntactic Structures as an example of a sentence that is grammatically correct but semantically nonsensical. The term was originally used in his 1955 thesis "Logical Structures of Linguistic Theory"...



External links