Editing Language acquisition (section)

==General approaches==

A major debate in understanding language acquisition is how these capacities are picked up by infants from the linguistic input.<ref name="Kennison 2013">{{Cite book  | last1=Kennison | first1=Shelia M. | title=Introduction to language development | date =2013-07-30  | publisher=SAGE Publications  | location=Los Angeles  | isbn=978-1-4129-9606-8 | oclc=830837502 }}</ref> Input in the linguistic [[Context (language use)|context]] is defined as "All words, contexts, and other forms of language to which a learner is exposed, relative to acquired proficiency in first or second languages". [[Psychological nativism|Nativists]] such as Chomsky have focused on the hugely complex nature of human grammars, the finiteness and [[semantic ambiguity|ambiguity]] of the input that children receive, and the relatively limited [[cognitive abilities]] of an infant. From these characteristics, they conclude that the process of language acquisition in infants must be tightly constrained and guided by the biologically given characteristics of the human brain. Otherwise, they argue, it is extremely difficult to explain how children, within the first five years of life, routinely master the complex, largely tacit [[Grammar|grammatical rules]] of their native language.<ref name="Sakai, 2005">{{cite journal |last1=Sakai |first1=Kuniyoshi L. |title=Language Acquisition and Brain Development |journal=Science |date=4 November 2005 |volume=310 |issue=5749 |pages=815–819 |doi=10.1126/science.1113530 |pmid=16272114 |bibcode=2005Sci...310..815S }}</ref> Additionally, the evidence of such rules in their native language is all indirect—adult speech to children cannot encompass all of what children know by the time they have acquired their native language.<ref>{{cite book |doi=10.1017/CBO9780511803413 |title=Child Language |date=2006 |last1=Lust |first1=Barbara C. |isbn=978-0-521-44922-9 |pages=28–29 }}</ref>

Other scholars,{{who|date=December 2024}} however, have resisted the possibility that infants' routine success at acquiring the grammar of their native language requires anything more than the forms of learning seen with other cognitive skills, including such mundane motor skills as learning to ride a bike. In particular, there has been resistance to the possibility that human biology includes any form of specialization for language. This conflict is often referred to as the "[[nature and nurture]]" debate. Of course, most scholars acknowledge that certain aspects of language acquisition must result from the specific ways in which the human brain is "wired" (a "nature" component, which accounts for the failure of non-human species to acquire human languages) and that certain others are shaped by the particular language environment in which a person is raised (a "nurture" component, which accounts for the fact that humans raised in different societies acquire different languages). The as-yet unresolved question is the extent to which the specific cognitive capacities in the "nature" component are also used outside of language.{{citation needed|date=December 2024}}

=== Emergentism ===
[[Emergentism|Emergentist]] theories, such as Brian MacWhinney's [[competition model]], posit that language acquisition is a [[cognitive process]] that emerges from the interaction of biological pressures and the environment. According to these theories, neither nature nor nurture alone is sufficient to trigger language learning; both of these influences must work together in order to allow children to acquire a language. The proponents of these theories argue that general cognitive processes subserve language acquisition and that the result of these processes is language-specific phenomena, such as [[vocabulary development|word learning]] and [[syntax|grammar acquisition]]. The findings of many empirical studies support the predictions of these theories, suggesting that language acquisition is a more complex process than many have proposed.<ref>{{cite book|title=The Emergence of Language|publisher=Lawrence Erlbaum Associates|year=1999|isbn=978-0-8058-3010-1|editor=Brian MacWhinney|oclc=44958022}}</ref>

===Empiricism===

Although Chomsky's theory of a [[generative grammar]] has been enormously influential in the field of linguistics since the 1950s, many criticisms of the basic assumptions of generative theory have been put forth by cognitive-functional linguists, who argue that language structure is created through language use.<ref>{{cite book|title=Constructing a language: a usage-based theory of language acquisition|author=Tomasello, Michael|publisher=Harvard University Press|year=2003|isbn=978-0-674-01030-7|location=Cambridge|oclc=62782600}}</ref> These linguists argue that the concept of a [[language acquisition device]] (LAD) is unsupported by evolutionary anthropology, which tends to show a gradual adaptation of the human brain and vocal cords to the use of language, rather than a sudden appearance of a complete set of binary parameters delineating the whole spectrum of possible grammars ever to have existed and ever to exist.<ref name="Mameli 2011">{{Cite journal|last1=Mameli|first1=M.|last2=Bateson|first2=P.|date=Feb 2011|title=An evaluation of the concept of innateness.|journal=Philos Trans R Soc Lond B Biol Sci|volume=366|issue=1563|pages=436–43|doi=10.1098/rstb.2010.0174|pmc=3013469|pmid=21199847}}</ref> On the other hand, cognitive-functional theorists use this anthropological data to show how human beings have evolved the capacity for grammar and syntax to meet our demand for linguistic symbols. (Binary parameters are common to digital computers, but may not be applicable to neurological systems such as the human brain.){{citation needed|date=July 2012}}

Further, the generative theory has several constructs (such as movement, empty categories, complex underlying structures, and strict binary branching) that cannot possibly be acquired from any amount of linguistic input. It is unclear that human language is actually ''anything like'' the generative conception of it. Since language, as imagined by nativists, is unlearnably complex,{{citation needed|date=July 2012}} subscribers to this theory argue that it must, therefore, be innate.<ref>{{cite book |doi=10.1093/oxfordhb/9780199573776.013.10 |chapter=The Argument from the Poverty of the Stimulus |title=The Oxford Handbook of Universal Grammar |date=2016 |editor-last1=Roberts |editor-first1=Ian |last1=Lasnik |first1=Howard |last2=Lidz |first2=Jeffrey L. |pages=220–248 |isbn=978-0-19-957377-6 }}</ref> Nativists hypothesize that some features of syntactic categories exist even before a child is exposed to any experience—categories on which children map words of their language as they learn their native language.<ref>{{Cite book|title=The Cambridge Handbook of Child Language|last=Bavin |first= Edith L.|date=2009|publisher=Cambridge University Press|isbn=9780511576164|location=Cambridge|pages=15–34|oclc=798060196}}</ref> A different [[theory of language]], however, may yield different conclusions. While all theories of language acquisition posit some degree of innateness, they vary in how much value they place on this innate capacity to acquire language. Empiricism places less value on the innate knowledge, arguing instead that the input, combined with both general and language-specific learning capacities, is sufficient for acquisition.<ref>{{cite journal|last1=Tomasello|first1=Michael|date=2000|title=First Steps Toward a usage-based theory of language acquisition|journal=Cognitive Linguistics|volume=11|issue=1–2|pages=61–82|doi=10.1515/cogl.2001.012}}</ref>

Since 1980, linguists studying children, such as [[Melissa Bowerman]] and [[Asifa Majid]],<ref name="Majid Bowerman 2007">{{cite journal |last1=Majid |first1=Asifa |last2=Bowerman |first2=Melissa |last3=Staden |first3=Miriam van |last4=Boster |first4=James S |title=The semantic categories of cutting and breaking events: A crosslinguistic perspective |journal=Cognitive Linguistics |date=19 January 2007 |volume=18 |issue=2 |doi=10.1515/COG.2007.005 |hdl=2066/104711 |hdl-access=free }}</ref> and psychologists following [[Jean Piaget]], like Elizabeth Bates<ref name="Bates 2003">{{cite journal |last1=Bates |first1=Elizabeth |last2=D’Amico |first2=Simona |last3=Jacobsen |first3=Thomas |last4=Székely |first4=Anna |last5=Andonova |first5=Elena |last6=Devescovi |first6=Antonella |last7=Herron |first7=Dan |last8=Ching Lu |first8=Ching |last9=Pechmann |first9=Thomas |last10=Pléh |first10=Csaba |last11=Wicha |first11=Nicole |last12=Federmeier |first12=Kara |last13=Gerdjikova |first13=Irini |last14=Gutierrez |first14=Gabriel |last15=Hung |first15=Daisy |last16=Hsu |first16=Jeanne |last17=Iyer |first17=Gowri |last18=Kohnert |first18=Katherine |last19=Mehotcheva |first19=Teodora |last20=Orozco-Figueroa |first20=Araceli |last21=Tzeng |first21=Angela |last22=Tzeng |first22=Ovid |title=Timed picture naming in seven languages |journal=Psychonomic Bulletin & Review |date=June 2003 |volume=10 |issue=2 |pages=344–380 |doi=10.3758/BF03196494 |pmc=3392189 |pmid=12921412 }}</ref> and Jean Mandler, came to suspect that there may indeed be many learning processes involved in the acquisition process, and that ignoring the role of learning may have been a mistake.{{citation needed|date=February 2011}}

In recent years, the debate surrounding the nativist position has centered on whether the inborn capabilities are language-specific or domain-general, such as those that enable the infant to visually make sense of the world in terms of objects and actions. The anti-nativist view has many strands, but a frequent theme is that language emerges from usage in social contexts, using learning mechanisms that are a part of an innate general cognitive learning apparatus. This position has been championed by [[David M. W. Powers]],<ref>{{Cite book|title=Machine learning of natural language|last1=Powers|first1=David M. W.|last2=Turk|first2=Christopher.|publisher=Springer-Verlag|year=1989|isbn=978-0-387-19557-5|location=London; New York|oclc=20263032}}</ref> [[Elizabeth Bates]],<ref>{{cite book|title=A companion to cognitive science|author1=Bates, E|author2=Elman, J|author3=Johnson, M|author4=Karmiloff-Smith, A|author5=Parisi, D|author6=Plunkett, K|publisher=Blackwell|year=1999|isbn=978-0-631-21851-7|editor1=Graham, George|location=Oxford|pages=590–601|chapter=Innateness and emergentism|oclc=47008353|editor2=Bechtel, William}}</ref> [[Catherine E. Snow|Catherine Snow]], [[Anat Ninio]], [[Brian MacWhinney]], [[Michael Tomasello]],<ref name="=Tomasello, 2008" /> Michael Ramscar,<ref>{{cite journal |last1=Ramscar |first1=Michael |last2=Gitcho |first2=Nicole |title=Developmental change and the nature of learning in childhood |journal=Trends in Cognitive Sciences |date=July 2007 |volume=11 |issue=7 |pages=274–279 |doi=10.1016/j.tics.2007.05.007 |pmid=17560161 }}</ref> William O'Grady,<ref>{{cite journal |last1=O'Grady |first1=William |date=2008 |title=Innateness, universal grammar, and emergentism |url=http://www.ling.hawaii.edu/faculty/ogrady/Innateness,_UG,_Emergentism.pdf |journal=Lingua |volume=118 |issue=4 |pages=620–631 |doi=10.1016/j.lingua.2007.03.005 }}</ref> and others. Philosophers, such as Fiona Cowie<ref name="Cowie">{{cite book |last1=Cowie |first1=Fiona |title=What's Within?: Nativism Reconsidered |date=1999 |publisher=Oxford University Press |isbn=978-0-19-984952-9 }}{{page needed|date=December 2024}}</ref> and [[Barbara Scholz]] with [[Geoffrey Pullum]]<ref>{{cite book |last1=Scholz |first1=Barbara C |last2=Pullum |first2=Geoffrey K |chapter=Irrational nativist exuberance |pages=59–80 |editor1-last=Stainton |editor1-first=Robert J. |title=Contemporary Debates in Cognitive Science |date=2006 |publisher=Wiley |isbn=978-1-4051-1305-2 |author1-link=Barbara Scholz |author2-link=Geoffrey Pullum }}</ref> have also argued against certain nativist claims in support of empiricism.

The new field of [[cognitive linguistics]] has emerged as a specific counter to Chomsky's Generative Grammar and to Nativism.

====Statistical learning====
{{Main|Statistical learning in language acquisition}}
Some language acquisition researchers, such as [[Elissa L. Newport|Elissa Newport]], Richard Aslin, and [[Jenny Saffran]], emphasize the possible roles of general [[learning]] mechanisms, especially statistical learning, in language acquisition. The development of [[connectionist]] models that when implemented are able to successfully learn words and syntactical conventions<ref>{{cite journal |last1=Seidenberg |first1=Mark S. |last2=McClelland |first2=James L. |title=A distributed, developmental model of word recognition and naming. |journal=Psychological Review |date=1989 |volume=96 |issue=4 |pages=523–568 |doi=10.1037/0033-295X.96.4.523 |pmid=2798649 }}</ref> supports the predictions of statistical learning theories of language acquisition, as do empirical studies of children's detection of word boundaries.<ref name="Saffran 1996 1926–1928"/> In a series of connectionist model simulations, Franklin Chang has demonstrated that such a domain general statistical learning mechanism could explain a wide range of language structure acquisition phenomena.<ref>{{cite journal |last1=Chang |first1=Franklin |last2=Dell |first2=Gary S. |last3=Bock |first3=Kathryn |title=Becoming syntactic |journal=Psychological Review |date=2006 |volume=113 |issue=2 |pages=234–272 |doi=10.1037/0033-295x.113.2.234 |pmid=16637761 }}</ref>

[[Statistical learning theory]] suggests that, when learning language, a learner would use the natural statistical properties of language to deduce its structure, including sound patterns, words, and the beginnings of grammar.<ref name="Saffran, 2003">{{cite journal |last1=Saffran |first1=Jenny R. |title=Statistical Language Learning: Mechanisms and Constraints |journal=Current Directions in Psychological Science |date=August 2003 |volume=12 |issue=4 |pages=110–114 |doi=10.1111/1467-8721.01243 }}</ref> That is, language learners are sensitive to how often [[syllable]] combinations or words occur in relation to other syllables.<ref name="Saffran 1996 1926–1928">{{cite journal |last1=Saffran |first1=Jenny R. |last2=Aslin |first2=Richard N. |last3=Newport |first3=Elissa L. |title=Statistical Learning by 8-Month-Old Infants |journal=Science |date=13 December 1996 |volume=274 |issue=5294 |pages=1926–1928 |doi=10.1126/science.274.5294.1926 |bibcode=1996Sci...274.1926S |pmid=8943209 }}</ref><ref name="Graf Estes 2007 254–260">{{cite journal |last1=Estes |first1=Katharine Graf |last2=Evans |first2=Julia L. |last3=Alibali |first3=Martha W. |last4=Saffran |first4=Jenny R. |title=Can Infants Map Meaning to Newly Segmented Words?: Statistical Segmentation and Word Learning |journal=Psychological Science |date=March 2007 |volume=18 |issue=3 |pages=254–260 |doi=10.1111/j.1467-9280.2007.01885.x |pmc=3864753 |pmid=17444923 }}</ref><ref name="Lany 284–91">{{cite journal|last=Lany|first=Jill|author2=Saffran|date=January 2010|title=From Statistics to Meaning: Infants' Acquisition of Lexical Categories|journal=Psychological Science|volume=21|issue=2|pages=284–91|doi=10.1177/0956797609358570|pmc=3865606|pmid=20424058}}</ref> Infants between 21 and 23 months old are also able to use statistical learning to develop "lexical categories", such as an animal category, which infants might later map to newly learned words in the same category.  These findings suggest that early experience listening to language is critical to vocabulary acquisition.<ref name="Lany 284–91"/>

The statistical abilities are effective, but also limited by what qualifies as input, what is done with that input, and by the structure of the resulting output.<ref name="Saffran, 2003" /> Statistical learning (and more broadly, distributional learning) can be accepted as a component of language acquisition by researchers on either side of the "nature and nurture" debate. From the perspective of that debate, an important question is whether statistical learning can, by itself, serve as an alternative to nativist explanations for the grammatical constraints of human language.

==== Chunking ====

The central idea of these theories is that language development occurs through the incremental acquisition of meaningful [[chunking (psychology)#Chunking as the learning of long-term memory structures|chunks]] of elementary [[constituent (linguistics)|constituents]], which can be words, phonemes, or syllables. Recently, this approach has been highly successful in simulating several phenomena in the acquisition of [[syntactic category|syntactic categories]]<ref>{{cite journal|last=Freudenthal|first=Daniel|author2=J.M. Pine|author3=F. Gobet|year=2005|title=Modelling the development of children's use of optional infinitives in English and Dutch using MOSAIC|url=http://bura.brunel.ac.uk/bitstream/2438/731/1/oi-paper-all.pdf|journal=Cognitive Science|volume=30|issue=2|pages=277–310|doi=10.1207/s15516709cog0000_47|pmid=21702816|access-date=2 April 2009|author3-link=Fernand Gobet|doi-access=free}}</ref> and the acquisition of phonological knowledge.<ref>{{cite journal|last=Jones|first=Gary|author2=F. Gobet|author3=J.M. Pine|year=2007|title=Linking working memory and long-term memory: A computational model of the learning of new words|url=http://bura.brunel.ac.uk/bitstream/2438/618/1/DevSci_revised-final.pdf|journal=Developmental Science|volume=10|issue=6|pages=853–873|doi=10.1111/j.1467-7687.2007.00638.x|pmid=17973801|access-date=2 April 2009|author2-link=Fernand Gobet}}</ref>

Chunking theories of language acquisition constitute a group of theories related to statistical learning theories, in that they assume that the input from the environment plays an essential role; however, they postulate different learning mechanisms.{{clarify|reason=Different than what?|date=January 2020}}

Researchers at the [[Max Planck Institute for Evolutionary Anthropology]] have developed a computer model analyzing early toddler conversations to predict the structure of later conversations. They showed that toddlers develop their own individual rules for speaking, with 'slots' into which they put certain kinds of words. A significant outcome of this research is that rules inferred from toddler speech were better predictors of subsequent speech than traditional grammars.<ref>{{cite journal|vauthors=Bannard C, Lieven E, Tomasello M|date=October 2009|title=Modeling children's early grammatical knowledge|journal=Proc. Natl. Acad. Sci. U.S.A.|volume=106|issue=41|pages=17284–9|bibcode=2009PNAS..10617284B|doi=10.1073/pnas.0905638106|pmc=2765208|pmid=19805057|doi-access=free}}</ref>

This approach has several features that make it unique: the models are implemented as computer programs, which enables clear-cut and quantitative predictions to be made; they learn from naturalistic input—actual child-directed utterances; and attempt to create their own utterances, the model was tested in languages including English, Spanish, and German. Chunking for this model was shown to be most effective in learning a first language but was able to create utterances learning a second language.<ref>{{cite journal |last1=McCauley |first1=Stewart M. |last2=Christiansen |first2=Morten H. |title=Computational Investigations of Multiword Chunks in Language Learning |journal=Topics in Cognitive Science |date=July 2017 |volume=9 |issue=3 |pages=637–652 |doi=10.1111/tops.12258 |pmid=28481476 |doi-access=free }}</ref>

===Relational frame theory===
{{Main|Relational frame theory}}
The [[relational frame theory]] (RFT) (Hayes, Barnes-Holmes, Roche, 2001), provides a wholly selectionist/learning account of the origin and development of language competence and complexity. Based upon the principles of Skinnerian behaviorism, RFT posits that children acquire language purely through interacting with the environment. RFT theorists introduced the concept of [[functional contextualism]] in language learning, which emphasizes the importance of predicting and influencing psychological events, such as thoughts, feelings, and behaviors, by focusing on manipulable variables in their own context. RFT distinguishes itself from Skinner's work by identifying and defining a particular type of operant conditioning known as derived relational responding, a learning process that, to date, appears to occur only in humans possessing a capacity for language. Empirical studies supporting the predictions of RFT suggest that children learn language through a system of inherent reinforcements, challenging the view that language acquisition is based upon innate, language-specific cognitive capacities.<ref>{{cite book |editor1=Steven C. Hayes |editor2=Dermot Barnes-Holmes |editor3=Brian Roche |title= Relational Frame Theory: A Post-Skinnerian Account of Human Language and Cognition (Hardcover)|publisher= Plenum Press |year= 2001 |isbn= 978-0-306-46600-7 |oclc= 51896575}}</ref>

=== Social interactionism ===
{{Main|Social interactionist theory}}
Social interactionist theory is an explanation of [[language development]] emphasizing the role of social interaction between the developing child and linguistically knowledgeable adults. It is based largely on the socio-cultural theories of Soviet psychologist [[Lev Vygotsky]], and was made prominent in the Western world by [[Jerome Bruner]].<ref>Bruner, J. (1983). ''Child's Talk: Learning to Use Language''. Oxford: Oxford University Press.</ref>

Unlike other approaches, it emphasizes the role of feedback and reinforcement in language acquisition. Specifically, it asserts that much of a child's linguistic growth stems from modeling of and interaction with parents and other adults, who very frequently provide instructive correction.<ref>{{cite journal|last1=Moerk|first1=E.L.|year=1994|title=Corrections in first language acquisition: Theoretical controversies and factual evidence|journal=International Journal of Psycholinguistics|volume=10|pages=33–58|url=https://psycnet.apa.org/record/1996-30150-001|access-date=2019-08-29|archive-url=https://web.archive.org/web/20190829210059/https://psycnet.apa.org/record/1996-30150-001|archive-date=2019-08-29|url-status=dead}}</ref> It is thus somewhat similar to behaviorist accounts of language learning.  It differs substantially, though, in that it posits the existence of a social-cognitive model and other mental structures within children (a sharp contrast to the "black box" approach of classical behaviorism).

Another key idea within the theory of social interactionism is that of the [[zone of proximal development]]. This is a theoretical construct denoting the set of tasks a child is capable of performing with guidance but not alone.<ref>Vygotskii [Vygotsky], L.S. 1935. "{{lang|ru-Latn|Dinamika umstvennogo razvitiia shkol'nika v sviazi s obucheniem.|italics=no}}" In {{lang|ru-Latn|Umstvennoe razvitie detei v protsesse obucheniia|italics=no}}, pp. 33–52. Moscow-Leningrad: Gosuchpedgiz.</ref> As applied to language, it describes the set of linguistic tasks (for example, proper syntax, suitable vocabulary usage) that a child cannot carry out on its own at a given time, but can learn to carry out if assisted by an able adult.

=== Syntax, morphology, and generative grammar ===
As syntax began to be studied more closely in the early 20th century in relation to language learning, it became apparent to linguists, psychologists, and philosophers that knowing a language was not merely a matter of associating words with concepts, but that a critical aspect of language involves knowledge of how to put words together; sentences are usually needed in order to communicate successfully, not just isolated words.<ref name="Innateness and Language"/> A child will use short expressions such as ''Bye-bye Mummy'' or ''All-gone milk'', which actually are combinations of individual [[noun]]s and an [[operator (linguistics)|operator]],<ref>{{cite book|author= Fry, Dennis|year=1977|title=Homo loquens, Man as a talking animal|url= https://archive.org/details/homoloquensmanas00fryd|url-access= registration|publisher=Cambridge University Press|pages= [https://archive.org/details/homoloquensmanas00fryd/page/117 117]|isbn=978-0-521-29239-9}}</ref> before they begin to produce gradually more complex sentences. In the 1990s, within the [[principles and parameters]] framework, this hypothesis was extended into a maturation-based [[structure building model of child language]] regarding the acquisition of functional categories. In this model, children are seen as gradually building up more and more complex structures, with lexical categories (like noun and verb) being acquired before functional-syntactic categories (like determiner and complementizer).<ref>{{cite book|author= Radford, Andrew|year=1990|title=Syntactic Theory and the Acquisition of English Syntax|publisher=Blackwell|isbn=978-0-631-16358-9}}</ref>  It is also often found that in acquiring a language, the most frequently used verbs are [[irregular verbs]].{{Citation needed|date=September 2017}} In learning English, for example, young children first begin to learn the past tense of verbs individually. However, when they acquire a "rule", such as adding ''-ed'' to form the past tense, they begin to exhibit occasional overgeneralization errors (e.g. "runned", "hitted") alongside correct past tense forms. One influential{{citation needed|date=January 2020}} proposal regarding the origin of this type of error suggests that the adult state of grammar stores each irregular verb form in memory and also includes a "block" on the use of the regular rule for forming that type of verb. In the developing child's mind, retrieval of that "block" may fail, causing the child to erroneously apply the regular rule instead of retrieving the irregular.<ref>{{cite journal|vauthors=Marcus G, Pinker S, Ullman M, Hollander M, Rosen TJ, Xu F|year=1992|title=Overregularization in language acquisition|journal=Monographs of the Society for Research in Child Development|volume=57|issue=4|series=Serial No. 228|pmid=1518508|doi=10.1111/j.1540-5834.1992.tb00313.x|url=http://www.psych.nyu.edu/gary/marcusArticles/Marcus%20et%20al%201992%20SRCD%20Mono.pdf|pages=1–182}}</ref><ref>{{cite book|author1=Carlson, Neil  |author2=Heth, Donald|year=2007|title=Psychology the Science of Behaviour|publisher=Pearson Education:New Jersey}}</ref>

=== Merge (linguistics)-based theory ===
<!-- Maybe this is supposed to be a new section???  In any case, I did not understand this section, and suggest that someone familiar with the concepts and fluent in the English language review this. ~~~~ --><!-- This First sentence is too long.  -->
{{further|Merge (linguistics)}}
In bare-phrase structure ([[minimalist program]]), theory-internal considerations define the specifier position of an internal-merge projection (phases vP and CP) as the only type of host which could serve as potential landing-sites for move-based elements displaced from lower down within the base-generated VP structure—e.g. A-movement such as passives (["The apple was eaten by [John (ate the apple)"]]), or raising ["Some work does seem to remain [(There) does seem to remain (some work)"]]). As a consequence, any strong version of a structure building model of child language which calls for an exclusive "external-merge/argument structure stage" prior to an "internal-merge/scope-discourse related stage" would claim that young children's stage-1 utterances lack the ability to generate and host elements derived via movement operations. In terms of a merge-based theory of language acquisition,<ref>{{cite book|author1=Galasso, Joseph  |year=2016|title=From Merge to Move: A Minimalist Perspective on the Design of Language and its Role in Early Child Syntax|publisher=LINCOM Studies in Theoretical Linguistics 59}}).</ref> complements and specifiers are simply notations for first-merge (= "complement-of" [head-complement]), and later second-merge (= "specifier-of" [specifier-head], with merge always forming to a head. First-merge establishes only a set {a, b} and is not an ordered pair—e.g., an {N, N}-compound of 'boat-house' would allow the ambiguous readings of either 'a kind of house' and/or 'a kind of boat'. It is only with second-merge that order is derived out of a set {a {a, b}} which yields the recursive properties of syntax—e.g., a 'house-boat' {house {house, boat}} now reads unambiguously only as a 'kind of boat'. It is this property of recursion that allows for projection and labeling of a phrase to take place;<ref>{{cite book|author1=Moro, A.  |year=2000|title=Dynamic Antisymmetry, Linguistic Inquiry Monograph Series 38|publisher=MIT Press}}).</ref> in this case, that the Noun 'boat' is the Head of the compound, and 'house' acting as a kind of specifier/modifier. External-merge (first-merge) establishes substantive 'base structure' inherent to the VP, yielding theta/argument structure, and may go beyond the lexical-category VP to involve the functional-category light verb vP. Internal-merge (second-merge) establishes more formal aspects related to edge-properties of scope and discourse-related material pegged to CP. In a Phase-based theory, this twin vP/CP distinction follows the "duality of semantics" discussed within the Minimalist Program, and is further developed into a dual distinction regarding a probe-goal relation.<ref>{{cite book|author1=Miyagawa, Shigeru  |year=2010|title=Why Agree? Why Move?|publisher=MIT Press}}</ref> As a consequence, at the "external/first-merge-only" stage, young children would show an inability to interpret readings from a given ordered pair, since they would only have access to the mental parsing of a non-recursive set. (See Roeper for a full discussion of recursion in child language acquisition).<ref>{{cite book|author1=Roeper, Tom  |year=2007|title=The Prism of Grammar: How child language illuminates humanism|publisher=MIT Press}}).</ref> In addition to word-order violations, other more ubiquitous results of a first-merge stage would show that children's initial utterances lack the recursive properties of inflectional morphology, yielding a strict Non-inflectional stage-1, consistent with an incremental Structure-building model of child language.

Generative grammar, associated especially with the work of Noam Chomsky, is currently one of the approaches to explaining children's acquisition of syntax.<ref>{{cite book |author1=Lillo-Martin, Diane C. |author2=Crain, Stephen |title=An introduction to linguistic theory and language acquisition |publisher=Blackwell Publishers |location=Cambridge, MA |year=1999 |isbn=978-0-631-19536-8 |oclc=799714148 }}</ref> Its leading idea is that human biology imposes narrow constraints on the child's "hypothesis space" during language acquisition. In the principles and parameters framework, which has dominated generative syntax since Chomsky's (1980) ''[[Lectures on Government and Binding|Lectures on Government and Binding: The Pisa Lectures]]'', the acquisition of syntax resembles ordering from a menu: the human brain comes equipped with a limited set of choices from which the child selects the correct options by imitating the parents' speech while making use of the context.<ref>{{cite book |author=Baker, Mark Raphael |title=The atoms of language |publisher=Oxford University Press |location=Oxford [Oxfordshire] |year=2002 |isbn=978-0-19-860632-1 |oclc=66740160 }}</ref>

An important argument which favors the generative approach, is the [[poverty of the stimulus]] argument. The child's input (a finite number of sentences encountered by the child, together with information about the context in which they were uttered) is, in principle, compatible with an infinite number of conceivable grammars. Moreover, rarely can children rely on [[corrective feedback]] from adults when they make a grammatical error; adults generally respond and provide feedback regardless of whether a child's utterance was grammatical or not, and children have no way of discerning if a feedback response was intended to be a correction. Additionally, when children do understand that they are being corrected, they don't always reproduce accurate restatements.<!-- I changed "few" to "rarely", so that's the text that this "dubious" comment is referring to. ~~~~ -->{{Dubious|More than a few children can rely on corrective feedback|reason=Children can distinguish corrective feedback from other responses|date=May 2017}}<ref>{{cite journal |last1=Marcus |first1=Gary F. |title=Negative evidence in language acquisition |journal=Cognition |date=January 1993 |volume=46 |issue=1 |pages=53–85 |doi=10.1016/0010-0277(93)90022-n |pmid=8432090 }}</ref><ref>{{cite book |last1=Brown |first1=Roger |last2=Camile |first2=Hanlon |chapter=Derivational complexity and order of acquisition in child speech |pages=11–54 |editor1-last=Hayes |editor1-first=John R. |title=Cognition and the Development of Language |date=1970 |publisher=Wiley |isbn=978-0-471-36473-3 |oclc=577205221 }}</ref> Yet, barring situations of medical abnormality or extreme privation, all children in a given speech-community converge on very much the same grammar by the age of about five years. An especially dramatic example is provided by children who, for medical reasons, are unable to produce speech and, therefore, can never be corrected for a grammatical error but nonetheless, converge on the same grammar as their typically developing peers, according to comprehension-based tests of grammar.<ref>{{cite book|author=Lenneberg, Eric|year=1967|title=Biological Foundations of Language|location=New York|publisher=Wiley}}</ref><ref>{{cite conference|author=Stromswold, Karin|title=Lessons from a mute child|conference=Rich Languages from Poor Inputs: A Workshop in Honor of Carol Chomsky|location=MIT, Cambridge, MA|date=11 December 2009}}</ref>

Considerations such as those have led Chomsky, [[Jerry Fodor]], [[Eric Lenneberg]] and others to argue that the types of grammar the child needs to consider must be narrowly constrained by human biology (the nativist position).<ref name=Chomsky1975>{{cite book|author=Chomsky, N.|title=Reflections on Language|url=https://archive.org/details/reflectionsonlan00chom|url-access=registration|location=New York|publisher=Pantheon Books|year=1975}}</ref> These innate constraints are sometimes referred to as [[universal grammar]], the human "language faculty", or the "language instinct".<ref name=Pinker>{{cite book |author=Pinker, Steven |title=The Language Instinct: How the Mind Creates Language (P.S.) |publisher=Harper Perennial Modern Classics |year=2007 |isbn=978-0-06-133646-1 |oclc=778413074 }}</ref>

===Comparative method of crosslinguistic research===
The comparative method of crosslinguistic research applies the [[comparative method]] used in [[historical linguistics]] to [[Psycholinguistics|psycholinguistic]] research.<ref>{{cite book |last1=Pye |first1=Clifton |title=The Comparative Method of Language Acquisition Research |date=2017 |publisher=The University of Chicago Press |isbn=9780226481289}}</ref> In historical linguistics the comparative method uses comparisons between historically related languages to reconstruct a proto-language and trace the history of each daughter language. The comparative method can be repurposed for research on language acquisition by comparing historically related child languages. The historical ties within each language family provide a roadmap for research. For [[Indo-European languages]], the comparative method would first compare language acquisition within the Slavic, Celtic, Germanic, Romance and Indo-Iranian branches of the family before attempting broader comparisons between the branches. For [[Otomanguean languages]], the comparative method would first compare language acquisition within the Oto-pamean, Chinantecan, Tlapanecan, Popolocan, Zapotecan, Amuzgan and Mixtecan branches before attempting broader comparisons between the branches. The comparative method imposes an evaluation standard for assessing the languages used in language acquisition research.

The comparative method derives its power by assembling comprehensive datasets for each language. Descriptions of the [[Prosody (linguistics)|prosody]] and [[phonology]] for each language inform analyses of [[Morphology (linguistics)|morphology]] and the [[lexicon]], which in turn inform analyses of [[syntax]] and [[conversation]]al styles. Information on prosodic structure in one language informs research on the prosody of the related languages and vice versa. The comparative method produces a cumulative research program in which each description contributes to a comprehensive description of language acquisition for each language within a family as well as across the languages within each branch of the language family.

Comparative studies of language acquisition control the number of extraneous factors that impact language development. Speakers of historically related languages typically share a common culture that may include similar lifestyles and child-rearing practices. Historically related languages have similar phonologies and morphologies that impact early lexical and syntactic development in similar ways. The comparative method predicts that children acquiring historically related languages will exhibit similar patterns of language development, and that these common patterns may not hold in historically unrelated languages. The acquisition of [[Dutch language|Dutch]] will resemble the acquisition of [[German language|German]], but not the acquisition of [[Totonac languages|Totonac]] or [[Mixtec language|Mixtec]]. A claim about any universal of language acquisition must control for the shared grammatical structures that languages inherit from a common ancestor.

Several language acquisition studies have accidentally employed features of the comparative method due to the availability of datasets from historically related languages. Research on the acquisition of the [[Romance languages|Romance]] and [[North Germanic languages|Scandinavian]] languages used aspects of the comparative method, but did not produce detailed comparisons across different levels of grammar.<ref>{{cite book |last1=Clark |first1=Eve |editor1-last=Slobin |editor1-first=Dan Isaac |title=The Crosslinguistic Study of Language Acquisition, Volume 1: The Data |date=1985 |publisher=Erlbaum |isbn=0898593670 |pages=687–782 |chapter=The acquisition of Romance, with special reference to French}}</ref><ref>{{cite book |last1=Plunkett |first1=Kim |last2=Strömqvist |first2=Sven |editor1-last=Slobin |editor1-first=Dan Isaac |title=The Crosslinguistic Study of Language Acquisition, Volume 3 |date=1992 |publisher=Erlbaum |isbn=0805801057 |pages=457–556 |chapter=The Acquisition of Scandinavian Languages}}</ref><ref>{{cite journal |last1=Grinstead |first1=John |title=Subjects and interface delay in child Spanish and Catalan |journal=Language |date=2004 |volume=80 |pages=40–72 |doi=10.1353/lan.2004.0024 }}</ref><ref>{{cite journal |last1=Hoekstra |first1=Teun |last2=Hyams |first2=Nina |title=Aspects of root infinitives |journal=Lingua |date=1998 |volume=106 |issue=1–4 |pages=81–112|doi=10.1016/S0024-3841(98)00030-8 }}</ref> The most advanced use of the comparative method to date appears in research on the acquisition of the [[Mayan languages|Mayan]] languages. This research has yielded detailed comparative studies on the acquisition of phonological, lexical, morphological and syntactic features in eight Mayan languages as well as comparisons of language input and language socialization.<ref>{{cite book |last1=Pye |first1=Clifton |last2=Pfeiler |first2=Barbara |last3=Mateo Pedro |first3=Pedro |editor1-last=Aissen |editor1-first=Judith |editor2-last=England |editor2-first=Nora C. |editor3-last=Zavala Maldonado |editor3-first=Roberto |title=The Mayan Languages |date=2017 |publisher=Routledge |isbn=9780415738026 |pages=19–42 |chapter=Mayan language acquisition}}</ref><ref>{{cite journal |last1=Pye |first1=Clifton |last2=Pfeiler |first2=Barbara |title=The comparative method of language acquisition research: A Mayan case study |journal=Journal of Child Language |date=2014 |volume=41 |issue=2 |pages=382–415 |doi=10.1017/S0305000912000748 |pmid=23527489 }}</ref><ref>{{cite book |doi=10.1515/9783110923148.15 |chapter=Roots or Edges? Explaining variation in children's early verb forms across five Mayan languages |title=Learning Indigenous Languages: Child Language Acquisition in Mesoamerica |date=2007 |last1=Pye |first1=Clifton |last2=Pfeiler |first2=Barbara |last3=De León |first3=Lourdes |last4=Brown |first4=Penelope |last5=Mateo |first5=Pedro |pages=15–46 |hdl=11858/00-001M-0000-0013-1744-D |isbn=978-3-11-092314-8 }}</ref><ref>{{cite journal |last1=Pye |first1=Clifton |last2=Pfeiler |first2=Barbara |last3=Mateo Pedro |first3=Pedro |last4=Stengel |first4=Donald |title=Analysis of variation in Mayan child phonologies |journal=Lingua |date=2017 |volume=198 |pages=38–52|doi=10.1016/j.lingua.2017.07.001 |doi-access=free }}</ref><ref>{{cite book |last1=Brown |first1=Penelope |last2=Pfeiler |first2=Barbara |last3=de León |first3=Lourdes |last4=Pye |first4=Clifton |editor1-last=Bavin |editor1-first=Edith L. |editor2-last=Stoll |editor2-first=Sabine |title=The Acquisition of Ergativity |date=2013 |publisher=John Benjamins |isbn=9789027234797 |pages=271–306 |chapter=The acquisition of agreement in four Mayan languages}}</ref><ref name="Pye Pfeiler acquisition of extended ergativity">{{cite book |last1=Pye |first1=Clifton |last2=Pfeiler |first2=Barbara |last3=Mateo Pedro |first3=Pedro |editor1-last=Bavin |editor1-first=Edith L. |editor2-last=Stoll |editor2-first=Sabine |title=The Acquisition of Ergativity |date=2013 |publisher=John Benjamins |isbn=978-90-272-3479-7 |pages=307–335 |chapter=The acquisition of extended ergativity in Mam, Q'anjob'al and Yucatec }}</ref><ref>{{cite journal |last1=Pye |first1=Clifton |last2=Pfeiler |first2=Barbara |title=The acquisition of directionals in two Mayan languages |journal=Front. Psychol. |date=2019 |volume=10 |page=2442 |doi=10.3389/fpsyg.2019.02442 |pmid=31736835 |pmc=6839415 |doi-access=free }}</ref><ref>{{cite journal |last1=Pye |first1=Clifton |last2=Pfeiler |first2=Barbara |last3=Mateo Pedro |first3=Pedro |title=The acquisition of negation in three Mayan languages |date=2017 |journal=Estudios de Cultura Maya |volume=49 |pages=227–246|doi=10.19130/iifl.ecm.2017.49.771 |doi-access=free }}</ref><ref>{{cite journal |last1=Pye |first1=Clifton |title=The genetic matrix of Mayan applicative acquisition |journal=Linguistics |date=2007 |volume=45 |issue=3 |pages=653–682|doi=10.1515/LING.2007.020 |hdl=1808/17412 |hdl-access=free }}</ref>