A delayed induced-motion illusion.

We report a striking visual illusion which involves an induced motion that is delayed in time. An observer visually tracks a moving target in the neightborhood of a fixed target. The fixed target appears to be entrained by the moving target and appears to follow its movements after a lag of 0.33 second. A series of experiments showed that while the illusion depends on low background salience it obtains with both smooth and oscillatory motion in all directions including depth, under monocular and binocular viewing, in the absence of vestibular and kinesthetic motion cues or eye movements, and under a wide range of relative and absolute target luminance and position. The strength of the illusion and the magnitude of the induced movement's delay seem not to depend on any of the above factors. The illusion, by resisting a peripheral explanation, may provide some clues to central perceptual processing. In addition, we suggest the possibility that errors of judgment based on the nonveridical perception of motion displaced in time may play a role in nighttime automobile and aircraft accidents.