Control of the location and extent of visual attention

Purpose. The spotlight metaphor of visual attention suggests shifts of the location attended, and the zoom-lens metaphor suggests changes of the spatial extent attended. The purpose of the study is to examine how one controls the attention center and extent. Experiment. We compared the attention center and extent among conditions with different attention states required, measuring spatial tunings of contrast sensitivity while the observer was tracking a moving object (Shioiri et al, 2002). The observer tracked a target rotating apparently either in the clockwise or counter-clockwise direction around a fixation point in an ambiguous apparent motion display. The display consisted no net motion energy in either direction so that attentional facilitation on contrast sensitivity was isolated from any influences of low-level motion signals. Measurements of sensitivity at variable locations would provide the spatial tuning of attentional facilitation. To investigate whether the observer can adjust his/her attention state to cover possible probe locations with tracking the target, we used various sets of probe locations used in a session. Experiment 1 used probe sets with different ranges centering at the tracked disk, and Experiment 2 used probe sets with the same range centering at different locations relative to the tracked disk. In each session, the observer had knowledge of the possible flash locations. Results and Discussions. In Experiments 1, the sensitivity function peaked near the target position while the spatial extent of the function tended to increase with increase in the probe location range. In Experiments 2, the sensitivity function peaked also near the target position instead of the center of the probe location range. These results suggest that the spatial extent of attention can be varied centering at a location, but attention cannot be divided into two locations at least in our experimental condition.