Inter-hemispheric recruitment as a function of task complexity, age and cognitive reserve

In a behavioral divided visual field study, we investigated the efficiency of inter-hemispheric cooperation according to (1) task computational complexity (physical-identity versus name-identity letter matching), (2) age (younger versus older adults) and (3) educational attainment, used as a proxy for cognitive reserve. Overall, the results indicated a shift from within- to across-hemisphere processing advantage with increasing task complexity, suggesting that bilateral engagement leads to enhanced performance under high-demand conditions. This pattern was influenced by age, with older adults showing no within-hemisphere advantage in the simpler task and a greater across-hemisphere advantage in the more complex one, consistent with an age-compensatory view of inter-hemispheric recruitment. Moreover, for older adults, more years of education was associated with a weaker across-hemisphere advantage. Thus, we propose that cognitive reserve may account for bilateral engagement efficiency. Finally, the groups differed in terms of laterality effects, with only younger adults demonstrating a left visual field advantage in the name-identity task, lending some support to the right hemi-aging hypothesis