Introduction

1. Hemisphere differences in the time course of phonological and orthographic processes: A backward masking investigationLaura K Halderman & Christine ChiarelloUniversity of California, Riverside Introduction Results Conclusions • For reaction time, there was a significant 2(SOA: 20ms & 60ms) X 2(Visual Field) X 4(Mask Type) interaction: • F(3,138) = 2.72, MSE = 12573, p < .05 • Previous work has shown the cerebral hemispheres process words differently during pre-lexical moments of word recognition (Halderman & Chiarello, 2005) • RVF/LH - both orthographic and phonological processes are available, however by 30ms, phonological information leads to greater word recognition • LVF/RH - orthographic processing is more robust and enhanced, relative to the RVF/LH • Previous work did not include a condition where phonology was the primary source of similarity • SOA differences were absent possibly because SOA was treated as a between subject variable • Right Visual Field/Left Hemisphere • At 20ms, the effects of orthography and phonology were indistinguishable • O+P+ = O+P- and O+P+ = O-P+ • By 60ms, the effects of both orthography and phonology together were greater than the effects of orthography or phonology alone • O+P+ was faster than O+P- and O-P+ • Left Visual Field/Right Hemisphere • Results were consistent across SOAs • When orthographic similarity was present, phonological similarity did not improve performance • O+P+ = O+P- • However, when phonological similarity was present, orthographic similarity did improve performance • O+P+ was faster than O-P+ Methods Lateralized Backward Masking 20/60ms Discussion 20/60ms • At the shortest SOA, the effects of orthography and phonology are underadditive for the LH. However, the LH can very quickly reach a deeper representation that integrates both sources of information. • Orthographic processes are more effective than phonological processes for the RH. However, if the RH could not process phonology at all, the O-P+ condition should be equivalent to the O-P- condition, suggesting some phonological abilities 20/60ms 20/60ms 300ms ISI 4000ms Relatedness Conditions Acknowledgments This research was partially supported by NIDCD grant 5R01DC6957, awarded to the second author.