Video: Stare hard. What happens to the yellow dots?
If dots on a screen are surrounded by certain types of moving pattern, fixing your eyes on one of the dots can make the others disappear.
This illusion, called motion-induced blindness, was discovered 20 years ago but psychologists are still trying to understand why it happens. One possible explanation is that our visual system receives so much information at any given moment that we cannot process it all, so we remain unaware of it.
Now Erika Wells and Andrew Leber from the University of New Hampshire have come a step closer to the answer after investigating how two different moving backgrounds affect the illusion.
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In one version, fixed dots are surrounded by pixels that all move in the same direction. In the other, the background elements move randomly in different directions (see video above). Until now, most research has focused on the first set-up, says Wells, but by comparing the two versions the team are gaining new insights.
They found that that the illusion was more pronounced, and the yellow dots disappeared more readily, when the background pixels moved randomly. This could be because different parts of the visual cortex process these two types of motion.
鈥淚ncoherent motion is processed lower down in the visual cortex than coherent motion,鈥� Wells says. 鈥淚t may be that the signals coming from the early visual areas are 鈥榥oisier鈥�,鈥� she says. Noisier signals arriving in higher visual areas may be harder to interpret, distracting the brain from the target and so making it more difficult to detect.
Read more: Moving illusions: Brain-tricking motion