Suzanne E. Welcome 1, Laura K. Halderman 1, Janelle Julagay 1, Christiana Leonard 2, & Christine Chiarello 1 1 University of California, Riverside 2 University of Florida A Factor Analytical Approach to Hemisphere Differences in Lexical Processing Suzanne E. Welcome 1, Laura K. Halderman 1, Janelle Julagay 1, Christiana Leonard 2, & Christine Chiarello 1 1 University of California, Riverside 2 University of Florida Participants 200 university students – 100 female, 100 male – 14% non-right handed – 18 to 34 years of age Divided Visual Field Tasks Word Naming (2 separate occasions) Nonword Naming Masked Word Recognition Lexical Decision Semantic Decision Category Member Generation Verb Generation Analysis Techniques Reaction time and accuracy scores for each VF and each task were submitted to factor analysis using an oblique rotation Asymmetry indices for each dependent variable and each task were submitted to factor analysis using an oblique rotation Methods Results Conclusions Most studies of asymmetries in word recognition have used relatively small samples and a small number of tasks to investigate quantitative hemispheric differences in specific processes Biological Substrates for Language Project takes a multivariate approach to determine whether task structure differs between hemispheres Previous studies investigating correlations between asymmetry measures have used single, relatively simple measures of visual word recognition (Boles, 1998; Hellige, et al., 1994) Biological Substrates for Language Project investigated whether tasks tapping into differing aspects of visual word recognition load on different factors Previous factor analytic approaches investigating hemisphere differences have examined the factor structure of asymmetry scores (Boles, 1998; Boles, 2002) This study investigated whether scores from each VF load on the same factor If hemispheres differ in how information is processed, factor structure should differ between hemispheres If hemispheres differ primarily in efficiency of the same process, the factor structure should not differ between hemispheres Introduction References This research was supported by NIH grant DC Factor 1 Variables Std Reg Coeffs Factor 5 Variables Std Reg Coeffs Factor 6 Variables Std Reg Coeffs Word Naming 1 LVF Word Naming 1 RVF Word Naming 2 LVF Word Naming 2 RVF Masked Word Rec. LVF Masked Word Rec. RVF Lexical Decision LVF Lexical Decision RVF Semantic Decision LVF Semantic Decision RVF Nonword Naming LVF Nonword Naming RVF Verb Generation LVF Cat. Generation LVF Cat. Generation RVF Asymmetry for making single correct response Accuracy of generating one of many alternatives Accuracy of category generation Separate VF Scores Factor structure differs between dependent variables -For reaction time, factors appear to discriminate between tasks that rely on phonological decoding, tasks that require semantic generation and tasks that require binary decisions -For accuracy, factors appear to discriminate between tasks that allow only a single correct response and tasks that allow multiple correct responses Factor structure appears to be largely similar in the LVF and RVF -Suggests that hemispheres differ primarily in efficiency of processing, not type of processing done Asymmetry Indices Factor structure differentiates between tasks that allow multiple responses (Verb and Category Generation and Nonword Naming) and tasks that do not (Word Naming, Lexical and Semantic Decision) Factor structure from asymmetry scores is not mirrored in factor structure from separate VF scores A number of task asymmetries did not load significantly on either factor Perhaps reflects the fact that asymmetry scores are less reliable than individual visual field scores Suggests that individual visual field scores may convey information that asymmetry scores do not For reaction time and accuracy scores for both visual fields on each task, a six- factor solution was obtained which accounted for 86.9 percent of the total variance. Separate factors were obtained for accuracy measures and reaction time measures. Interpretations of each factor are given beneath the factor loadings. Boles, D.B. (1998) Relationships among multiple task asymmetries: II. A large-sample factor analysis. Brain and Cognition, 36, Boles, D.B. (2002) Lateralized spatial processes and their lexical implications. Neuropsychologia, 40, Hellige, J.B, Bloch, M.I., Cowin, E.K. Eng, T.L., Eviatar, Z., & Sergent, V (1994) Individual variation in hemispheric asymmetry: multitask study of effects related to handedness and sex. Journal of Experimental Psychology: General, 123, For asymmetry indices, a two-factor solution was obtained which accounted for 88.5 percent of the total variance Factor 1 Variables Std Reg Coeffs Factor 2 Variables Std Reg Coeffs Word Naming 1 Acc. Word Naming 1 RT Word Naming 2 Acc. Word Naming 2 RT Lexical Decision Acc. Lexical Decision RT Semantic Decision Acc Verb Generation Acc. Cat. Generation Acc. Nonword Naming Acc Asymmetry for making single correct response Asymmetry for making one of several correct responses Factor 2 Variables Std Reg Coeffs Factor 3 Variables Std Reg Coeffs Factor 4 Variables Std Reg Coeffs Word Naming 1 LVF Word Naming 1 RVF Word Naming 2 LVF Word Naming 2 RVF Nonword Naming LVF Nonword Naming RVF Verb Generation LVF Verb Generation RVF Cat. Generation LVF Cat. Generation RVF Masked Word Rec. LVF Masked Word Rec. RVF Lexical Decision LVF Lexical Decision RVF Semantic Decision LVF Semantic Decision RVF Latency of phonological decoding Latency of semantic generation Latency to make binary decision REACTION TIME FACTORS ACCURACY FACTORS