Abstract: Three functional magnetic resonance imaging (fMRI) experiments were conducted to investigate three issues regarding the impacts of heterogeneity along the task-relevant and the task-irrelevant dimensions upon the efficiency in visual search. The first concerns the neural basis of the interaction between target-presence and the homogeneity along the task-relevant dimension. The second is about the behavioral consequences and the neural correlates of processing heterogeneous distracting information along task-relevant and –irrelevant dimensions. The third is about the common and specific brain mechanisms underlying the interactions between target-presence and the homogeneity along task-relevant and -irrelevant dimensions in feature search vs. conjunction search.

Key words: visual search, feature search, conjunction search, selective attention, task-relevant dimension, task-irrelevant dimension, fMRI