PSYCHOPHYSICAL ANALYSES OF THE SIZE EFFECTS OF SPATIAL ATTENTION ON FIGUREâ€“GROUND ASSIGNMENT
The figureâ€“ground assignment process is regarded as a preattentive process in hierarchal visual processing. However, some researchers have demonstrated that the spatial location of visual attention affects the figureâ€“ground process. In contrast, the relationship between figureâ€“ground assignment and the spatial size of attention has never been investigated. In this research, we psychophysically analyzed the effect of the spatial size of attention on the figureâ€“ ground assignment process. In our experiments, we measured the reaction time (RT) for identifying the edge shapes of the inner or outer regions contained in ambiguous figureâ€“ ground stimuli, using compounded letters to manipulate the size of the spatial attention. The results revealed that the RTs for inner edge shapes were faster than those for outer ones, followed by those for local letter discrimination. This indicates that local attention assigns the inner region as the figure, suggesting that the size of spatial attention affects figureâ€“ground assignment.