Are spatial and dimensional attention separate? Evidence from Posner, Stroop, and Eriksen tasks

Do various operational definitions of visual attention tap the same underlying process? To address this question, we probed visual selective attention using orientation of attention, flanker, and Stroop tasks. These were embedded in combined designs that enabled assessment of each effect, as well as their interaction. For the orientation task, performance was poorer at unexpected than at expected locations. The flanker effects also differed across the two locations. In contrast, the Stroop effects were comparable at expected and unexpected locations. We conclude that spatial attention (tapped by the orientation and the flanker tasks) and dimensional attention (tapped by the Stroop task) engage separate processes of visual selection, both of which are needed in normal attention processing.