Global-local interference modulated by communication between the hemispheres

Three experiments examined whether interhemispheric interaction modulates s elective attention in a same-different version of D. Navon's (1977) global- local paradigm. In Experiments 1 and 2, interhemispheric interaction reduce d interstimulus interference produced when two stimuli matched at a preassi gned level (e.g., local) but differed at the irrelevant level (e.g., global ). This effect was greater for stimuli made of a few large elements than fo r those made of many small elements. Experiment 3 demonstrated that (a) the ability of interhemispheric interaction to reduce interstimulus interferen ce is not constrained by hemispheric differences for global and local proce ssing and (b) interhemispheric interaction does not strongly modulate intra stimulus interference produced when the forms at the preassigned (e.g., loc al) and irrelevant (e.g., global) levels differ within an individual stimul us. These findings indicate that interaction between the hemispheres is a n eural mechanism that may aid selective attention.