| Summary: | Navajo and Quechua, both morphologically rich languages, present an interesting testing ground for proposals regarding the acquisition of inflectional systems. Of particular interest for these languages is the development of the verb, which encodes not only tense, aspect, and number- /person-of- subject, but also such grammatical notions as transitivity, causation, modification and internal arguments. In fact, the complex verb forms which characterize these languages often constitute the entire VP or, indeed, the whole sentence. The languages are all the more fascinating because, typologically, the structure of the verbs in Navajo is roughly the mirror image of Quechua verbs: while complex Navajo verbs are formed by appending prefixes to the root or stem, Quechua verbs are formed entirely through suffixation. This is illustrated in the Navajo and Quechua equivalents of the English sentence, `They were feeding it to me, too': (1) a. Navajo: Shí - aɬdo' - shá - da - 'í - ø - ɬ - stood; me also for Pl obj subj CL impf stem:FEED b. Quechua: Mikhu - chi - sha - wa - rqa - n - ku - pis; EAT Caus Prog l obj Past 3 subj Pl Add. In the Navajo verb form, the disjunct prefixes (those furthest from the stem) include oblique object, adverbial, postposition, and plural, and the conjunct prefixes (those closest to the stem), the direct object, subject, and transitive classifier. The stem 'feed' occurs in final position and its form indicates imperfective aspect. By contrast, in the Quechua verb shown in (lb), the stem created by affixing the causative suffix to the root means 'cause to eat' or 'feed', and the final element, the Additive suffix, is an independent enclitic meaning 'also.' The morphemes occurring between the causative stem and the final enclitic are part of the inflectional set. In both languages, a verb must minimally consist of a root and a person-of-subject affix; that is, adult speakers do not produce bare verb roots or stems. However, in Navajo, the ordering of the prefixes in relation to the verb stem is quite rigid, whereas, in Quechua, some of the suffixes attached to the verb stem may occur in varied order. While the Quechua suffixes have unique and identifiable meanings, the rules for their combination often have no basis in semantics: they are idiosyncratic, including ordering restrictions which must be formulated as negative filters (Muysken 1986, Muysken 1988). Recent work by several researchers has yielded relevant, isolated proposals, many intended to enlighten the nativist-empiricist debate. For example, Hyams proposed the stem parameter, with two possible settings: a verbal stem is/is not a well-formed word (Hyams 1986a, Hyams 1994, Pizzuto and Caselli 1994). She further claimed that children set this parameter very early on. Assuming that Hyams' parameter is a valid constraint on verb formation, we would expect children acquiring morphologically rich languages never to produce bare verb roots or stems. In a number of studies on the acquisition of synthetic languages, the perceptual salience of particular syllables is cited as a vital cue in segmentation (Pye 1983, Aksu-Koç and Slobin 1985, Mithun 1989), with the phonologically most salient morphemes occurring at the periphery of words. We would therefore expect children to produce the inflectional morphemes first, before the derivational affixes found closer to the verb stem (Peters 1995). On the way to meaningful productivity, children acquiring morphologically rich languages may at first produce frozen chunks or amalgams of affixes, even splicing together different unanalyzed strings to form novel, sometimes ungrammatical combinations (Peters 1985 and elsewhere, Franco and Landa 1998, Rubino and Pine 1998). Finally, it has often been noted that children learning a variety of agglutinative languages may insert novel filler syllables into the affixal string, (e.g., Aksu -Koç and Slobin 1985, Saville-Troike 1996). Peters (1985 and later work) views the insertion of such "placeholder" syllables as further evidence of unanalyzed amalgams in child production. As illuminating as these studies may be, none presents a model for the acquisition of morphology as comprehensive as Pinker's (1984) proposal regarding the acquisition of inflectional systems through paradigm-learning. In the Introduction to the second edition (1996), Pinker later cites a number of studies confirming his original proposal. In developing the proposal, Pinker draws on observations of inflectional learning in a variety of languages, both his own and those of other researchers such as Slobin. This brings us to the aim of the present study: an exploration of the acquisition of verb morphology by children learning Navajo and Quechua in the context of Pinker's theory.
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