The Effect of Reading Direction on Sentence Processing: An Investigation Using Cross-Linguistic Comparisons and Non-Invasive Brain Stimulation

Abstract

Whether language affects cognition and, if so, to what extent has been a long-standing debate. Extensive research found linguistic effects on cognition, with some evidence suggesting that features of a writing system can also impact cognitive functions. Specifically, the effects of reading direction on language processing have been reported. Several theories were proposed to explain the emergence of this effect. The Spatial Agency Bias model (SAB; Suitner & Maass, 2016) suggests the effect derives from reading-direction-congruent attentional allocation and word order flexibility, while the Pragmatic Relevance (PR) account (Halicki et al., 2021) claims it is influenced by sentence voice. Chatterjee (2010) further argues that this effect develops to enhance processing efficiency. However, existing literature on the cognitive effect of reading direction is limited, and the proposed theories lack experimental support. This thesis aimed to bridge these shortcomings by testing the effect of reading direction on language processing and investigating the effect's underlying mechanisms and purpose. In Chapter 2, we examined the effect of reading direction in the context of sentence production. We tested speakers of languages with opposite reading directions, using mouse tracking to address the SAB model. The results indicated an effect of reading direction on sentence production but did not provide support for the SAB model. In Chapters 3 and 4, we examined the effect of reading direction on simple sentence comprehension, and the SAB and PR theories. Chapter 3 used eye-tracking and active and passive stimuli to compare English and Arabic speakers. We found no effect of reading direction for simple sentence comprehension or support for either theory. Chapter 4 compared speakers of four languages with different levels of word order flexibility. It revealed limited support for the effect of reading direction but no support for the SAB model. In Chapters 5 and 6, we examined the effect of reading direction on complex sentence comprehension to assess its role in processing efficiency and to test Chatterjee's hypothesis. We also employed eye-tracking to test the SAB's applicability to complex language. In Chapter 5, we tested English and Arabic speakers and found that reading direction did not affect complex sentence comprehension despite differences in the first location of fixation between the groups. In Chapter 6, we tested English speakers and used non-invasive brain stimulation to disrupt their left-to-right attentional allocation. Among participants with lower phonological skills, we observed an effect of stimulation and a trend towards an effect of reading direction on complex sentence comprehension. Overall, based on all conducted experiments, we report an effect of reading direction on sentence production but a less pronounced effect on sentence comprehension. Furthermore, our findings predominantly fail to support the current theories regarding the effect of reading direction on cognition.

Date of Award	2 Oct 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Gorana Pobric (Main Supervisor) & Johan Hulleman (Co Supervisor)