Functional Biases in Language Learning: Evidence from Word Order and Case-Marking Interaction

Functional Biases in Language Learning: Evidence from Word Order and Case-Marking Interaction Maryia Fedzechkina (mashaf@bcs.rochester.edu) , T. Florian Jaeger (fjaeger@bcs.rochester.edu) , Elissa L. Newport (newport@bcs.rochester.edu) Department of Brain and Cognitive Sciences, University of Rochester Rochester, NY 14627 USA Abstract efficient information transmission (Cancho, 2006; Piantadosi, Tily, & Gibson, 2011) and that these properties reflect pref- erences of incremental production (Aylett & Turk, 2004; Jaeger, 2010). Why do languages share structural properties? The function- alist tradition has argued that languages have evolved to suit the needs of their users. By what means functional pressures may come to shape grammar over time, however, remains un- known. Functional pressures could affect adults’ production; or they could operate during language learning. To date, these possibilities have remained largely untested. We explore the latter possibility, that functional pressures operate during lan- guage acquisition. In an artificial language learning experi- ment we investigate the trade-off between word order and case. Flexible word order languages are potentially ambiguous if no case-marking (or other cues) are employed to identify the doer of the action. We explore whether language learners are bi- ased against uncertainty in the mapping of form and meaning, showing a tendency to make word order a stronger cue to the intended meaning in no-case languages. Keywords: Language acquisition; language universals; acqui- sition biases; word order; case-marking Further evidence for the idea that functional pressures may constrain the space of possible language structures comes from studies showing a strong correlation between the phe- nomena categorically required by the grammar in some lan- guages and speakers’ gradient preferences in other languages where the grammar allows choices. One example comes from the effects of animacy on word order. The animacy of the grammatical object is an obligatory determinant of word or- der in the ditransitive construction in Sesotho (Morolong & Hyman, 1977) and Mayali (Evans, 1997). The same factor influences speakers’ gradient preference between the two per- missible orders in ditransitive alternation in English (Bresnan, Cueni, Nikitina, & Baayen, 2007). Introduction In short, there is evidence (a) that grammatical constraints reflect gradient processing preferences and (b) that languages have properties that facilitate language use (processing and communication) compared to what would be expected if functional pressures did not affect the shape of languages over time. What remains unknown, however, is by what means functional pressures come to shape grammar over time and affect the transmission of language from generation to gener- ation. The two broad logical possibilities are that functional pressures throughout life affect language production in adults, causing them to subtly change the input provided to the next generation, or that functional pressures operate during lan- guage acquisition itself, biasing learners to deviate slightly from the input they receive. Despite the long history of these claims, direct tests of these two hypotheses have been rare. Despite a variety of obvious differences, languages show striking underlying commonalities at all levels of linguistic organization (Dryer, 1992; Greenberg, 1963). Such regular- ities have been the subject of a long-standing debate (e.g., Christiansen & Chater, 2008; Chomsky, 1965; Evans & Levinson, 2009): Are the observed phenomena shaped by linguistic-specific constraints on structure and acquisition, or do they result from cognitively and communicatively moti- vated constraints? The latter possibility is intriguing as it would reduce the number of linguistic-specific and hence ar- bitrary properties that need to be accounted for and would result in a more parsimonious explanation of cross-linguistic regularities. It has long been hypothesized that grammatical structures that reduce the complexity associated with acquisition or pro- cessing of language tend to persist diachronically and hence cross-linguistically (e.g., Bates & MacWhinney, 1982; Bever, 1970; Hawkins, 2004; Newport, 1981; Slobin, 1973). The hypothesis that pressures on language use over time affect what grammatical properties of a language survive is sup- ported by evidence that existing languages have properties that have relatively low average processing cost and high ef- ficiency of information transfer. For example, dependency length is known to correlate with processing difficulty. Evi- dence from English and German suggests that the average de- pendency length in these languages is close to the theoretical minimum and far below what would be expected by chance (Gildea & Temperley, 2010). Cross-linguistic evidence also suggests that languages have properties that are beneficial for We address the latter possibility, that functional pressures affect language acquisition, using an artificial language learn- ing paradigm in which we expose learners to experimen- tally designed miniature languages. Artificial language learn- ing studies have several properties that make them ideally suited for the current purpose. Generally, adult learners ac- quire the statistical patterns in the input and reproduce them with roughly the same frequency as the input – ‘probability- matching’ (Hudson Kam & Newport, 2009). However, some studies have shown that learners preferentially acquire typo- logically attested patterns (Finley & Badeker, 2008; Newport & Aslin, 2004; Tily, Frank, & Jaeger, 2011). When learn- ers deviate from the artificial language input they receive, their productions reflect typologically more frequent patterns