Morphological Structure and Hemispheric Functioning: The Contribution of the Right Hemisphere to Reading in Different Languages Zohar Eviatar University of Haifa Raphiq Ibrahim University of Haifa and Rambam Medical Center This study examined the relationship between morphological structure of languages and performance asymmetries of native speakers in lateralized tasks. In 2 experiments, native speakers of English (concatenative morphology stem plus affix) and of Hebrew and Arabic (nonconcatenative root plus word-form morphology) were presented with lateralized lexical decision tasks, in which the morpho- logical structure of both words and nonwords was manipulated. In the 1st study, stimuli were presented unilaterally. In the 2nd study, 2 stimuli were presented bilaterally, and participants were cued to respond to 1 of them. Three different indexes of hemispheric integration were tested: processing dissociation, effects of distractor status, and the bilateral effect. Lateralization patterns in the 3 languages revealed both common and language-specific patterns. For English speakers, only the left hemisphere (LH) was sensitive to morphological structure, consistent with the hypothesis that the LH processes right visual field stimuli independently but that the right hemisphere uses LH abilities to process words in the left visual field. In Hebrew and Arabic, both hemispheres are sensitive to morphological structure, and interhemispheric transfer of information may be more symmetrical than in English. The relationship between universal and experience-specific effects on brain organization is discussed. Keywords: language morphology, Hebrew, Arabic, lexical decision, interhemispheric integration Half a century of intensive research has revealed that although the left hemisphere (LH) is dominant for most language functions in 99% of right-handers and in the majority (65%) of left-handers, there is widespread variability in the linguistic abilities of the right hemisphere (RH). This variability has been noted in studies of the disconnected RH in split-brain patients (see Zaidel, 1998, for a review); in case reports of the reversal of laterality patterns in aphasia; and in cases of recovery of function believed to reflect RH compensation for a severely damaged LH (Kinsbourne, 1998). It has been suggested (e.g., Kinsbourne, 1998) that the language potential of the RH may be genetically underdetermined and that it may be subject to factors in embryogenesis or postnatal experi- ence. Much research has been done looking at the effects of biological variables, such as sex and handedness (e.g., Eviatar, Hellige, & Zaidel, 1997), on individual differences in patterns of hemispheric specialization. The research reported here focuses on the effects of a specific kind of postnatal experience, specifically, on the structure of the language that the individual uses. The last few years have seen a large number of studies exploring RH involvement in the processing of discourse aspects of lan- guage. Much of this interest is based on the findings from meta- bolic imaging studies that have revealed extensive RH activations while people are performing linguistic tasks (see Bookheimer, 2002, for a review). Faust et al. have examined RH involvement in syntactic processes (e.g., Faust, Bar-Lev, & Chiarello, 2003). The general findings have been that although the RH is sensitive to message-level processes, all the effects of syntactic manipulations are stronger in the LH. The role of syntactic processes is to compute the structural and thematic relationships between the words in the sentence, so it makes sense to assume that the more highly a language is inflected, the closer the interaction of these syntactic processes is with lexical representation. Thus, the manner in which words are represented in the mental lexicon has impli- cations for the mechanisms involved in comprehension of the message level of sentences. When these underlying representations differ among languages, is it the case that the relative involvement of the cerebral hemispheres differs as well? Brain imaging studies examining the processing of morpholog- ical aspects of language performance have tended to focus on regions of interest in the LH (e.g., Lehtonen, Vorobyev, Hugdahl, Tuokkola, & Laine, 2006). Studies examining Indo-European lan- guages have focused primarily on the representation of morpho- logical knowledge, testing dual-route models versus connectionist, single-route representations in English (e.g., Devlin, Jamison, Mat- thews, & Gonnerman, 2004; Joanisse & Seidenberg, 2005; Tyler, Stamatakis, Post, Randall, & Marslen-Wilson, 2005; Vannest, Polk, & Lewis, 2005), or on the separability of morphological processing from other aspects of word processing in morphologi- cally richer languages, such as German (e.g., Longoni, Grande, Hendrich, Kastrai, & Huber, 2005) and Italian (Marangolo, Piras, Galati, & Burani, 2004). Studies examining morphological pro- cessing in non-Indo-European languages with rich morphological structures have shown RH involvement in word perception, though the RH was not sensitive to inflectional morphological manipula- Zohar Eviatar, Psychology Department and Institute for Information Processing and Decision Making, University of Haifa, Haifa, Israel; Ra- phiq Ibrahim, Learning Disabilities Department, University of Haifa, and Cognitive Neurology Unit, Rambam Medical Center, Haifa, Israel. This research was supported by Grant 53/2000 from the Israel Founda- tion Trustees to Zohar Eviatar and Raphiq Ibrahim. Correspondence concerning this article should be addressed to Zohar Eviatar, Psychology Department and Institute of Information Processing and Decision Making, Haifa University, Haifa 31905, Israel. E-mail: zohare@research.haifa.ac.il Neuropsychology Copyright 2007 by the American Psychological Association 2007, Vol. 21, No. 4, 470 – 484 0894-4105/07/$12.00 DOI: 10.1037/0894-4105.21.4.470 470