SEX, HANDEDNESS,AND SPATIAL ABILITY AFFECT LATERALITY FOR MENTAL ROTATION

Spatial laterality refers to the localization of spatial processing within the right and left cerebral hemispheres. Although a left visual field/right hemisphere (LVF) advantage has generally been observed for spatial processing,observations of a right-visual field/left hemisphere (RVF) advantage and no visual field/no hemisphere (OVF) advantage have also been reported.The inconsistent research findings in spatial \nlaterality have been attributed to individual differences (e.g.,sex and handedness), although research in this area has been limited. Some evidence suggests that level of spatial ability may affect spatial laterality. For example, Voyer and Bryden (1990) reported a RVF advantage for participants with high spatial ability,a OVF advantage for participants with medium spatial ability, and a LVF advantage for participants with low \nspatial ability. The main purpose of this thesis was to replicate and extend Voyer and Bryden's findings. Two experiments were conducted. Level of spatial ability (low, medium,or high) for participants was determined by performance on a standard, paper­ and-pencil measure of mental rotation. The experimental task was a lateralized mental rotation task presented on a computer. Experiment 1 examined the performance of 52 right-handed undergraduate students. Right-handed males with low or high spatial \nability demonstrated a significant RVF advantage in performance on a lateralized spatial task. Experiment 2 examined the performance of 50 left-handed undergraduate students. Left-handed participants with low \nspatial ability demonstrated a significant RVF advantage in performance on a lateralized spatial task. Left-handed females, regardless of ability level, also demonstrated a significant RVF advantage in spatial \nperformance. Limited support was found for the notion that level of spatial ability affects spatial laterality in right-or left-handed males and females. Rather, the results could be attributed to the linguistic nature of the experimental stimuli, which engaged a left-hemisphere verbal processing strategy.