Cross-Language Influences on Morphological Processing

This thesis offers novel insights into visual word recognition, focussing on both within-language and cross-language morphological processing in seven chapters. While each chapter focusses on a specific aspect of morphological processing, all chapters investigate whether individual differences modulate morphological processing using the masked primed lexical decision task. Chapter 1 provides a brief general introduction to reading and bilingualism, highlighting the main paradigm, and models that have motivated this thesis. Chapter 2 provides a comprehensive review of empirical evidence comparing morphological processing within L1 and L2. It further examines cross-language morphological transfer studies and introduces a novel framework for bilingual lexical access.

The within-language section of this thesis (Chapters 3 and 4) investigates morphological processing within L1 and L2. It aims to tease apart the early potential contributions of semantics and orthography on morphological priming in a series of four within-language experiments. Chapter 3 reveals that L1 speakers exhibit sensitivity to the morphological structure in the initial stages of compound processing independently of semantics, while L2 speakers, particularly those with less language proficiency, employ a form-based processing approach. Analysis of individual differences further indicates that form priming varies as a function of L2 proficiency/exposure and is only observed in the group with lower language proficiency. Chapter 4 integrates the masked morphological priming paradigm with the transposed-letter (TL) priming paradigm, offering an innovative approach to explore the orthographic influences on affixed word processing in L1 and L2. This chapter finds robust morphological priming in L1 and L2; however; significant differences are observed with morphological TL primes: letter transpositions within the stem facilitate L1 reading processes, while those that span across stem and suffix do not. The chapter further shows that the L2 reading system is sensitive to precise letter position coding schemes, requiring exact orthographic word encoding. Analysis of individual differences reveals that transpositions across morphemes interfere with lexical access only for L1 readers with advanced spelling skills, and that participants with lower orthographic skills can identify complex words with cross-morphemic letter transpositions. In L2, the level of L2 exposure mediates the way bilingual individuals process complex words with letter transpositions. Specifically, within-morphemic letter transpositions could still facilitate stem activation in bilinguals with higher exposure.

The cross-language section (Chapters 5 and 6) extends the within-language focus to probe cross-language influences on morphological processing across diverse bilingual populations. It examines morphological transfer across a bilingual’s two languages and the  key variables that influence this transfer in a series of three experiments. Chapter 5 presents original evidence of cross-language morphological priming in non-cognate words among Turkish-English similar-script bilinguals. This effect is enhanced in bilinguals who acquired their L2 at an earlier age. Chapter 6 builds on this novelty by replicating the cross-language priming effect in French-English bilinguals. Comparing the size of affixed priming in Turkish-English and French-English bilinguals, it further reveals that the morphological complexity of the L1 modulates cross-language morphological priming. Finally, Chapter 7 synthesises the key insights from previous chapters and proposes potential future research directions in the field.