10 Everyday Optical Illusions

Here are 10 everyday optical illusions.

Though it’s often said that ‘seeing is believing,’ our eyes aren’t always all that reliable a source.
Here are 10 everyday examples of the optical illusions and visual trickery they’re vulnerable to.
Number 10. Optical Speed Bars. A number of states have taken to painting short, perpendicular lines along both the median and shoulder strips as a way to make drivers slow down. They’re spaced to give a motorist the impression that they’re accelerating in hopes that they’ll respond by tapping the brakes. 
Number 9. Curveballs. It turns out they don’t really plummet toward the ground at the last second. Between the very fast spinning of the ball and its arched trajectory, the batter’s eyes and brain just get tricked into thinking it’s gone haywire. As the ball moves in and out of central and peripheral areas of vision, the mind just gets a little flipped out. 
Number 8. Sidewalk Chalk Art. For decades, English street artist Julian Beever has been entertaining and confounding people with his amazing perception-manipulation skills. His works transform pavement and concrete into realistic looking swimming pools, lakes, and even entire streetscapes. 
Number 7. Upstairs-Downstairs Cat. The picture sparks much debate about whether the cuddly feline is walking up the stairs or down them, but confirmation either way has proven elusive. As the photo lacks sufficient orientation information, it really comes down to whether one interprets the gray area at the top as a floor or a ceiling.
Number 6. Pigeons’ Backwards Head Bobs. Slow motion video has revealed that the birds actually do no such thing. Their heads only move forwards, and they do so to get an advanced take on their surroundings. Once their bearings have been established, the body catches up with the head. No bobbing, just somewhat awkward walking. 
Number 5. Creepy Glances In Paintings. There really are portraits that seem to have moving eyes, but the explanation is more scientific than supernatural. If the subject is looking straight ahead, our brains will always interpret the gaze as looking at us, even when it’s viewed from a different angle. 
Number 4. Motion-Induced Blindness. If one stares at an image that contains a fixed central point and moving parts along the edges, the bits that are in motion will eventually vanish. This is largely due to the brain needed more processing power to fixate on the stationary object thereby limiting its peripheral abilities at that time.
Number 3. Giant moons. Logically, we know that the moon doesn’t grow, nor does it really get that much closer to Earth. What makes the satellite appear so large at times is unknown, but could be related to our ingrained ideas about perception and where the moon is sitting on the horizon at the time. 
Number 2. The Wagon-Wheel Effect. That’s the name for the phenomenon that makes car tires in movies look like they are turning backwards, even though the vehicle is moving forward. It happens when the frames filmed per second are at odds with the tire’s rotations per second. As not all of tire’s positions are captured, when the film is played back, it doesn’t always appear to be moving as it should. 
Number 1. Contrast in Shadows. When our eyes detect a shadow, our brains know the affected area is darker, but compensates by lightening it up, oftentimes too much. This can result in objects that are gray appearing white. 
Which optical illusion do you think is the trickiest?