Editing Language acquisition (section)

===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>