Southeast Asian writing systems: a challenge to current models of visual information processing in reading

Abstract

The focus of this chapter is on reading non-Roman writing systems, in particular Thai and Chinese, and on how it can enhance our understanding of the reading process in general. A specific focus is on the visual information processing aspects of reading and on the computational modelling of these processes. It will be argued that the focus of current modelling efforts on Roman-derived alphabetic writing systems has limited the generality of the resulting models. Two research issues will be addressed: (1) the effective targetting by the eye of words in an unspaced writing system and (2) the parallel processing of more than one word in a fixation. The former issue poses serious problems for all current models of eye movement control in reading, while the answer to the question posed by the latter issue can, arguably, be found by looking to data from Chinese readers. READING SE ASIAN SCRIPTS 3 SE Asian writing systems: a challenge to current models of visual information processing in reading Introduction The focus of this chapter will be on how the study of reading non-Roman writing systems, in particular Thai and Chinese, can enhance our understanding of the reading process in general. A specific focus will be on the visual information processing aspects of reading and the computational modelling of these processes. I will argue that while the almost exclusive focus of current modelling efforts on Roman-derived alphabetic writing systems has made the modelling enterprise tractable, it has also given rise to models of limited generality. Before describing in more detail current approaches, I will provide a short introduction to the phenomenon of eye movements in reading and an overview of issues relating to writing systems and their relevant features from a reading perspective. Eye movements in reading A reader's eyes move along a line of text in a sequence of fixations separated by jumps called saccades. Reading, therefore, takes the form of a series of snapshots during which textual information is acquired. During one such snapshot the recognition of a single English word of average length takes about 100 ms (Rayner & Pollatsek, 1989). From the pioneering research of McConkie, Kerr, Reddix and Zola (1988), it emerged that the effective target of a given eye movement is the centre of the to-be-fixated word. The goal of eye movements in reading appears to be to attain an optimal viewing position READING SE ASIAN SCRIPTS 4 (OVP) on a word, which, if successful, facilitates its rapid recognition (O'Regan, 1990). In reality, fixation locations are normally distributed with means somewhere between the beginning and the centre of the word. This latter position is referred to as the preferred viewing location (PVL; Rayner, 1979). The eye frequently undershoots or overshoots the optimal position or even the word boundary with the consequence that extra fixations and/or movements back to previously fixated words may be needed (Nuthmann, Engbert, & Kliegl, 2005). An important question for eye movement control models in reading is what factors determine the target of a new fixation. The results of computer modelling by Reilly and O'Regan (1998) suggested that the decision might be a rather low-level one. Their simulation results indicated that the default target for the eye is the next most visually salient word to the right of the current fixation, but within a limited window of words. They argued that higher-level processes intervened only if there were comprehension difficulties. All current accounts of word targetting in reading assume that the writing system serves up unambiguously delineated word “blobs” that act as targets for the saccade programming mechanism. This solves several problems at one fell swoop. There is no need, for example, to invoke a word segmentation algorithm to extract the individual words for targetting. However, it raises the question of what happens when the words in a writing system are not so conveniently delimited. What strategies do readers adopt when reading unspaced writing systems such as Thai or Chinese? READING SE ASIAN SCRIPTS 5