Eye movements when reading spaced and unspaced Thai and English: A comparison of Thai–English bilinguals and English monolinguals Heather Winskel a, * , Ralph Radach b , Sudaporn Luksaneeyanawin c a School of Psychology, University of Western Sydney, P.O. Box 1767, Penrith South, NSW 1767, Australia b Department of Psychology and Florida Center for Reading Research, Florida State University, 1107 W. Call Street, Tallahassee, FL 32306-4301, USA c Center for Research in Speech and Language Processing (CRSLP), Chulalongkorn University, Phaya Thai Road, Pathumwan, Bangkok 10330, Thailand article info Article history: Received 4 June 2008 Revision received 27 June 2009 Available online xxxx Keywords: Reading Thai Interword spaces Eye movements Bilinguals abstract The study investigated the eye movements of Thai–English bilinguals when reading both Thai and English with and without interword spaces, in comparison with English monol- inguals. Thai is an alphabetic orthography without interword spaces. Participants read sen- tences with high and low frequency target words embedded in same sentence frames with and without interword spaces. Interword spaces had a selective effect on reading in Thai, as they facilitated word recognition, but did not affect eye guidance and lexical segmentation. Initial saccade landing positions were similar in spaced and unspaced text. As expected, removal of spaces severely disrupted reading in English, as reflected by the eye movement measures, in both bilinguals and monolinguals. Here, initial landing positions were signif- icantly nearer the beginning of the target words when reading unspaced rather than spaced text. Effects were more accentuated in the bilinguals. In sum, results from reading in Thai give qualified support for a facilitatory function of interword spaces. Ó 2009 Elsevier Inc. All rights reserved. Seen from a dynamic visuomotor perspective, continu- ous reading involves two concurrent streams of processing. The primary stream is the processing of written language, where the acquisition of orthographically coded informa- tion feeds into the construction of a cognitive text repre- sentation. At the same time, the targeting and timing of saccadic eye movements serve to provide adequate spa- tio-temporal conditions for the extraction of text informa- tion. Research into the architecture and dynamics of information processing during reading has entered a new stage with the recent development of complex theories and computational models (see Engbert, Nuthmann, Richter, & Kliegl, 2005; Reichle, Rayner, & Pollatsek, 2003, for seminal discussions). However, the focus of these theoretical developments and the underlying empirical research has been on Indo-European languages such as English and German and relatively little work exists on reading of non-Roman scripts. In this context, Thai is par- ticularly interesting as it has an alphabetic orthography, but does not naturally have interword spaces. Spacing effects in Roman scripts Visuomotor control in reading involves both spatial and temporal aspects. During each fixation it must be decided when and where the saccadic movement is to be executed. A large body of research has shown that eye movement control in alphabetic writing systems is largely word based. When a word is selected as the target for the ensu- ing saccade, a movement is programmed that aims at posi- tioning the eyes at an ‘‘optimal viewing position” (OVP) (O’Reagan, 1990) close to the word center. However, due to visuomotor constraints, the actual landing positions of incoming initial saccades tend to peak at locations further to the left, between the word beginning and word center (McConkie, Kerr, Reddix, & Zola, 1988; Radach & McConkie, 0749-596X/$ - see front matter Ó 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jml.2009.07.002 * Corresponding author. Address: 31 Douglas St., Richmond, NSW 2753, Australia. E-mail address: h.winskel@uws.edu.au (H. Winskel). Journal of Memory and Language xxx (2009) xxx–xxx Contents lists available at ScienceDirect Journal of Memory and Language journal homepage: www.elsevier.com/locate/jml ARTICLE IN PRESS Please cite this article in press as: Winskel, H., et al. Eye movements when reading spaced and unspaced Thai and English: A comparison of Thai–English bilinguals and English monolinguals. Journal of Memory and Language (2009), doi:10.1016/j.jml.2009.07.002