Learning unattested languages

Learning Unattested Languages Sara Finley (finleys@elmhurst.edu) Department of Psychology, Elmhurst College Elmhurst, IL, 60126, USA Abstract This paper demonstrates the role of morphological alternations in learning novel phonotactic patterns. In an artificial grammar learning task, adult learners were exposed to a phonotactic pattern in which the first and last consonant agreed in voicing. Long-distance phonotactics encoded as strictly piecewise languages suggest that first-last phonotactic patterns should be unattested in natural language. However, recent theories of morphologically induced phonological patterns predict that long-distance agreement between the first and last consonant of a word can occur when the agreement is induced as a morphological alternation. The results of two experiments support the prediction that first-last harmony patterns are more easily learned when morphological cues to the pattern are present. Participants only learned the first-last pattern when presented as a morphological alternation. Keywords: statistical learning, phonotactics, morphology. Introduction One of the major goals of generative linguistics is to explain the nature of language in terms of computational constraints on the cognitive capacity for human languages. Computational models of phonotactic patterns work to understand the restrictions that underlie the set of patterns that are possible in natural language and the set of patterns that are not possible. Recent work has argued that phonotactic patterns, defined as constraints on the co- occurrence of different sounds within a word, are subject to a very specific set of computational constraints (Heinz, 2007, 2011a, 2011b). In particular, it has been demonstrated that long-distance phonotactic patterns derived from consonant harmony can be simulated using strictly piecewise languages (Heinz, 2010; Heinz & Rogers, 2010; Rogers et al., 2010), a subset of regular languages. Computational models of phonotactic patterns raise three important questions for a theory of the cognitive science of language. First, is there a correlation between the patterns that are learnable and the patterns that can be generated by computational models? There is a prediction that any long- distance consonant agreement pattern that does not fall within the set of strictly piecewise languages should not be learnable. Second, do computational models of phonotactic patterns capture the intricacies of generative models of phonological representations? If morphological and syntactic constructions require more complex computational machinery to generate, then there is a question of whether patterns at the interface between phonology and morphology, and phonology and syntax are subject to the same computational constraints as purely phonotactic patterns (Heinz & Idsardi, 2011). Third, is there a way to reconcile apparent exceptions to general tendencies linguistic typology? Linguistic tendencies are typically proposed as opposed to universals because almost any ‘universal’ has exceptions (Evans & Levinson, 2009). These questions are particularly salient for a specific, hypothetical phonotactic pattern: first-last agreement (Lai, 2012). For the purposes of this paper, a first-last agreement pattern is any phonotactic pattern in which the first and last segment in a word must agree in terms of some phonological feature. For example, a first-last consonant voicing pattern requires that the first and the last consonant in a word share the same value for the feature [Voice]. In such a pattern, the word [boteg] would be a possible word because the first consonant ([b]) and the last consonant ([g]) are voiced, even though the medial consonant ([t]) is voiceless. However, *[boget] would not be a possible word because the first consonant ([b]) is voiced and the final consonant ([t]) is voiceless. First-last patterns are said to be unattested in natural language (Lai, 2012). One possible explanation for the failure to find a true case of first-last agreement is that such patterns can not be generated with a strictly piecewise grammar (Heinz & Rogers, 2010). If long-distance phonotactic patterns must be generated with a strictly piecewise grammar, patterns that fall outside of the cognitive constraints on phonological patterns may not be learnable. While purely phonotactic first-last patterns have not been described in natural languages, there are some possible cases of first-last agreement patterns when morphology is considered. A morphologically controlled phonological alternation is any sound pattern that occurs only in the presence of a specific morphological environment. For example, the alternation between /o/ and /e/ in ‘goose’ vs. ‘geese’ is induced by the alternation between singular and plural. Such morphologically controlled patterns may manifest as a first-last agreement pattern. For example, in Lokaa, a Benue-Congo language spoken in Nigeria, the future tense is marked with a low tone on the final syllable and a prefix containing a low tone (e.g., [na-a-fuka] ‘you will gather’). In this case, the first and last vowels of a word must agree in tone, but only in the future tense. (Iwara, Akinlabi, & Truckenbrodt, 2003). Finley (2009) accounts for this morphological alternation using morpheme-specific constraints that target specific edges of the word. Finley’s analysis suggests that morphologically controlled patterns, also referred to as ‘featural affixation’, are subject to different constraints than purely phonotactic patterns. The possibility that featural affixation can target the first and last element of a word leads to the prediction that long-distance