Type of Display: This test shows motion blur on common LCD displays, and other sample-and-hold displays that do not flicker. If you are using LightBoost, temporarily turn off LightBoost. Adjust brightness to 100% during this test to prevent PWM artifacts from showing up during this test.
Explanation: You are witnessing motion blur caused by persistence instead of pixel transitions (GtG): This is motion blur caused by the motion of eye-tracking. This also affects AMOLED displays (Article: Why Do Some OLED's Have Motion Blur?). Your eye tracking causes the vertical lines in each refresh to be blurred into thicker lines, filling the black gaps. Short-persistence displays (such as CRT or LightBoost) eliminate this motion blur, so this motion test looks different on those displays.
WARNING: This animation should not be viewed by persons suspectible to epilepsy.