Hemispheric Asymmetry in Global and Focal Processing of Navon Figures in Older and Younger Adults: Behavioral Evidence From a Monocular Viewing Paradigm
Samantha H. Penhale, David B. Burtis, Liliana Salazar-Bejarano, Kenneth M. Heilman, Damon G. Lamb, John B. WilliamsonBackground:
Hemispheric lateralization plays a central role in attentional processing, with relative left-hemisphere advantages for linguistic and focal information and right-hemisphere advantages for visuospatial and global processing. Hierarchical Navon figures provide a useful method for examining interactions between focal and global attention and hemispheric specialization. Monocular viewing, which biases visual input to the contralateral hemisphere, has been proposed as a method to modulate attentional processing. However, its influence on attentional level and stimulus-type interactions in healthy adults remains unclear.
Objective:
To examine how attentional condition (focal vs global), stimulus type (letter vs shape), and monocular viewing eye (left vs right) influence reaction times during a hierarchical figure task.
Methods:
Fifty-four healthy, right-handed adults ages 18–86 years completed a choice reaction time task using hierarchical Navon figures (letter “A,” triangle, or both stimuli) under left- or right-eye monocular viewing. Linear mixed-effects models were used to test main effects and interactions.
Results:
Participants responded faster in focal than global conditions, and faster to the letter than the triangle. Focally presented letter stimuli elicited the fastest responses. In dual-stimulus trials, responses were faster when letters were focal and triangles global, particularly under right-eye viewing. Age was associated with slower reaction times overall, but there was no significant difference in pattern.
Conclusion:
Stimulus characteristics influenced attentional response speed, with focal verbal information eliciting the fastest responses, particularly during right-eye viewing. This is consistent with relative left-hemisphere advantages for focal and language processing. Findings suggest attentional specialization persists across adulthood despite generalized age-related slowing.