Peter Tse , from Dartmouth College (USA) has get anether nice view for the classic afterimage optical illusion. If you haven’t encountered afterimage illusions before, I strongly recommend visiting Ilusiones opticas. So why is this illusion different? By using it, you can reveal if your brain predominantly sees horizontal or vertical lines! To begin, you’ll need to fixate the colored image (one on your left) by looking at the fixation spot for about 60 seconds. Now shift your eyes to the fixation spot surrounded by rectangular outlines. Which afterimage did you see first? You can manually shift which afterimage you experience by attending to one rectangle and then the other. If you attend to the vertical outline rectangle you will see the afterimage corresponding to it, and if you attend to the horizontal outline rectangle you will see the different afterimage corresponding to it. Now wasn’t this great?!