1. Early Time Course Hemisphere Differences in Phonological & Orthographic Processes Laura K. Halderman 1, Christine Chiarello 1 & Natalie Kacinik 2 1 University of California, Riverside 2 University of California, Davis Introduction Chiarello (2003) has proposed that the cerebral hemispheres use different processing styles for linguistic information LH - processes information rapidly, quickly moving to a deeper level, discarding initial, more shallow representations RH - processes information more slowly, maintaining shallow representations of the information, even if no longer relevant Form-Specific vs Abstract Form (Marsolek et al., 1992) Word Length effects in RH (Lavidor & Ellis, 2002) This model did not specifically consider phonological processes in reading Research on split-brain patients has revealed little evidence for Grapheme-to-Phoneme Conversion processes in RH (Baynes & Eliassen, 1998 & Zaidel, 1985) GPC processes in the LH have been attributed to speech mechanisms being located in the same hemisphere Normal population studies have revealed mixed results Phonology No evidence for phonology in RH (Khateb et al., 2000; Crossman & Polich, 1988; Rayman & Zaidel, 1991) Used metalinguistic tasks - Rhyme Judgment Evidence for bilateral phonological processes (Chiarello et al., 1999; Coney, 2002; Weekes, 1999) Orthography Greater orthographic processes in the RH (Crossman & Polich, 1988; Marsolek, 1992) Orthographic facilitation in RH, but no phonological facilitation (Lavidor & Ellis, 2003) Lateralized Backward Masking Presentation of target beings initial processing which is interrupted by the pseudoword mask Similar masks reinstate some of the initial decoded properties of the target and facilitates identification Pattern mask restricts perception to the initial processed properties of the target and mask Participants are unaware of the nonword mask Predictions Left Hemisphere LH will show facilitation for orthographic condition at both SOAs LH will show facilitation for phonological condition at both SOAs Right Hemisphere RH will show facilitation for orthographic condition at both SOAs RH will not show facilitation for phonological condition However, if phonological processes are slower in the RH, facilitation may occur in the 50 ms SOA Backward Masking Methods Participants 96 Native English speaking undergraduates Right-handed Stimuli & Presentation 150 Experimental Trials Pseudowords matched for orthographic regularity using Bigram frequencies (Mayzner & Tresselt, 1965) Forced Choice items matched for frequency (Francis & Kucera, 1982) 30 ms & 50 ms SOAs Each component of the stimuli was presented for 30 ms or 50 ms Results 30 ms SOA - RT - Visual Field X Mask Type Conclusions When no pseudoword mask is presented, the RVF advantage is equal to the Unrelated pseudoword mask condition However, when a pseudoword mask sharing relevant orthographic or phonological information is present, the hemispheres differentially use the overlapping information to facilitate target recognition The LH is benefited most by overlapping phonology at the shortest SOA, while the RH is benefited most by orthography RH does not show access to phonology, but it does demonstrate greater orthographic facilitation than the LH at this early time course, an effect similar to Lavidor and Ellis (2003) These results suggest the LH is capable of generating a phonological representation of words very quickly, perhaps automatically The RH, on the other hand, is capable of generating an orthographic representation very rapidly which stands in contrast to general findings of slower, RH processes (Chiarello, 2003) O+P+O+P-O-P- boat BOTEBOTSNENE Mask Type Conditions 50 ms SOA - RT - Visual Field X Mask Type LH O+P+ < O+P- O+P- < O-P- RH O+P+ = O+P- O+P- < O-P- LH O+P+ = O+P- O+P- < O-P- RH O+P+ = O+P- O+P- < O-P- Simple Masking Experiment A second experiment was conducted using a similar paradigm to compare the effects of the pseudoword mask to a condition with no pseudoword mask All methods were repeated except no pseudoword appeared between the target and final pattern mask Only the 30 ms SOA was examined Participants - 48 Native English speaking, Right-handed undergraduates Results No pseudoword condition compared to pseudoword condition - 30 ms Significant RVF advantage NoMask condition interacts with O+P+ and O+P- conditions No interaction between NoMask conditon and O-P- condition This research was conducted under the support of the National Science Foundation grant BCS-0079456, granted to the second author.