Hemispheric Asymmetry and Task Accuracy.

Interhemispheric asymmetry is a core feature of human brain organization, yet its functional relevance across cognitive domains remains incompletely understood. Using data from 989 participants in the Human Connectome Project, we examined patterns of functional asymmetry and their relationship to task performance across seven domains-motor, language, social cognition, relational processing, working memory, gambling, and emotion. An fMRI-derived asymmetry index was computed across 17 task contrasts and mapped onto the cortical surface. Both fMRI signal amplitude and asymmetry were positively associated with task accuracy across multiple networks and cognitive domains. These associations were strongest in language, frontoparietal, and dorsal attention networks during high-demand tasks, such as story comprehension, relational processing, and working memory. Partial least squares regression revealed that while amplitude was the more robust predictor of task accuracy, asymmetry contributed unique, complementary variance. These findings suggest that greater neural activation and stronger hemispheric differentiation jointly support better cognitive performance. Together, our results underscore the behavioral relevance of both fMRI signal amplitude and lateralization, offering new insights into the functional architecture and efficiency of the human brain.