Humans have motion-induced blindness (just stare at the flickering green dot in the middle for 10 sec)
The Yellow dots will seem to disappear as you stare at the green one.
Note: In this demonstration the observer focuses at the flickering green dot in the middle. After about 10 seconds, the observer sees one, two or all three of the static yellow dots arranged at the corners of an imaginary equilateral triangle disappear and then reappear. These disappearances and reappearances continue at random for as long as the observer cares to look.