why do we have a blind spot

There are grizzled heroes and sleek assassins in movies who don t have metaphorical blind spots. They do have literal ones, though. Because of the way the eye is constructed, every human being does. For the most part, the human eye gives the brain an accurate picture of what s going on in the world. There are limitations. Although many birds and insects can see ultraviolet, and some creatures can see infrared, humans are stuck looking at so-called visible light only. This cuts down human s view of the world, not letting them see the urine trails left behind by some mammals, and not letting them fully appreciate the colors of certain flowers, which have evolved to put on quite a show in ultraviolet while remaining plain in visible light.

The human eye also can t distinguish between polarized and nonpolarized light, while many cephalopods and some birds can. Still, the eye sends back signals that let humans navigate through the world pretty successfully. Many assume that what they see is actually what s out there. That s not entirely true. Each human eye has a blind spot, and the brain sometimes has to fill in what is there by looking at the surrounding area. Light gets into they eye by passing through the pupil.

It hits the retina at the back of th eye. The retina is covered with light-sensing proteins. They relay what they sense to the optic nerve which carries the information back into the brain. The problem is, the optic nerve ends in the field of the retina itself. This is a little like having to plug the power cable for a TV directly into the screen. It creates a dark spot. Most of the time, the other eye will see what s happening in its partner s blind, but if the blind spots overlap while looking at a certain object, or if the person is only looking through one eye, the brain just fills in the spot looking at the surrounding picture.

There s a way to find your blind spot. Cover your left eye and look at the dot on the left in this image. Be aware of the cross on the right, but don t look at it - just keep your eye on the dot. Move your face closer to the monitor, and farther away. At some point, you should see the cross disappear. Stay at that point and close your right eye. Stare at the cross, and you should see that the dot has disappeared. It doesn t just happen with a white background. Try the same with colored paper, and your mind will fill in the background color of the paper when the mark gets in your blind spot.

You don t see as much of the world as you think. Via,
and. Anyone who knows how to drive will be familiar with the concept of a blind spot в a small area in the visual field of all vertebrates without vision. But did you know humans have an inbuilt blind spot, too? Light enters the eye through the pupil, before hitting the back of the retina. This information then needs to be transmitted to the brain. Therefore, the data needs a way out of the retina. It finds this exit route in the optic nerve, which is attached to the back of the retina.

The small circular spot where this cable connects to the back of your eye is lacking in light-detecting cells, creating a small gap in the visual field of each eye: the blind spot. В For the most part, the brain is clever enough at using information from its surroundings to fill in that gap. Itвs only when you cover one eye or if both blind spots overlap when looking at a single point, that it becomes apparent. Try it by looking at two crosses on a piece of paper. Focus your left eye on the right cross, and youвll see the left cross disappear. Voila в your blind spot.