Role of transparency in the acquisition of inflectional morphology: experimental studies testing exponence type using artificial language learning

Agglutinating morphology has often been described as easier to learn than fusional morphology, in large part because it is more transparent (e.g., Brown, 1976; Goldschneider & DeKeyser, 2001; Igartua, 2015). Such claims mainly rest on data from natural languages, where transparency is often correlated with additional factors such as regularity, compositionality and frequency of morphemes in the system, making it difficult to quantify the effect of transparency alone. To address this issue, this thesis presents a series of artificial language learning experiments which make it possible to investigate the impact of transparency, and more specifically, separative exponence, on learnability in isolation. The artificial language instantiates a nominal paradigm with two binary features, CLASS and NUMBER, expressed through suffixes. In addition to controlling for factors like regularity, this paradigm size makes it possible to hold the number of morphemes to be learned constant. Transparency was manipulated between conditions by varying whether the morphemes exhibited one-to-one mappings between form and meaning (separative exponence, as in agglutinating systems) or one-to-many mappings (cumulative exponence, as in fusional systems). Experiments were conducted with three different groups of native speakers to represent different morphological techniques in the L1, namely native speakers of English (isolating), Turkish (agglutinating) and Spanish (fusional). This way, it was possible to test whether specific morphological experience from the L1 differentially influences the transparency benefit in the L2. Across all experiments, with over 600 participants in total, no learning advantage of the transparent condition over the non-transparent condition was found. Only a slight bias for form-meaning mapping transparency was revealed in participants’ error patterns. These results suggest that the role of transparency in the acquisition of morphology is more limited than commonly assumed and that it may be better understood as a benefit only in combination with other characteristics of morphological paradigms such as regularity, generalisability and frequency of morphemes.