This applet demonstrates capture of the diffusive filling-in process. It emulate the experiment of Paradiso and Nakayama (1991), where a large target disk is briefly flashed on the screen and followed by a masking ring, which is smaller than the target. They found that for certain stimulus onset asynchronies the target center, inside the ring, never seemed to look as bright as the target outside the ring. They suggested the ring was blocking a filling-in process from the edges of the target disk to its interior.

This demo allows you to see a version of this phenomenon. The target and mask durations (60 milliseconds) are longer than in the original experiment, but the effect remains. The target-mask sequence it looped for 6 seconds, after which you can vary the interstimulus interval (ISI) between target and mask (and between mask and target in the loop). Press "j" to decrease the ISI and "k" to increase the ISI by 10 milliseconds. Multiple presses of j or k between loops will change the ISI an amount equal to the number of presses. Press the space bar to start the presentation loop for another 6 seconds at the chosen ISI.

Make several different observations.