TIME-COURSE OF SENSITIVITY CHANGES AS ATTENTION SHIFTS TO AN UNPREDICTABLE LOCATION

Shifting visual attention is often described as analogous to a spotlight moving through empty space between locations. In the present experiment, a peripheral precue summoned attention to an initial location, and 200 ms later a second peripheral cue appeared beside one of two possible second locations, each 14-degrees away from the initial location. The target was twice as likely to appear at the location that had been indicated by the immediately preceding cue as at the location that had been previously cued or that would be cued. Fine-grained temporal analyses indicated that, as attention was shifted, sensitivity to information at the second location gradually increased while sensitivity at the first location simultaneously decreased. Average sensitivity over the two locations during the shift remained significantly greater than average sensitivity immediately following the initial precue. In contrast, an attentional "spotlight" moving from the first to the second location would produce a decrease in average sensitivity to its initial level while the spotlight was between locations.