Optical illusion facts for kids

An optical illusion (also known as a visual illusion) is when your eyes and brain see something that isn't quite real. It's like a trick played on your vision. What you see doesn't match what is actually there.

Our eyes gather information, and our brain processes it to create a perception of the world. Usually, this works perfectly. But with optical illusions, the brain's interpretation doesn't match the actual object or image.

What Are Optical Illusions?

Optical illusions happen because of how our brains try to understand what our eyes see. They show us images that look different from reality.

Different Kinds of Illusions

There are three main types of visual illusions:

• Literal optical illusions: These create images that are different from the objects themselves. Think of a picture that looks like one thing, but then you see something else hidden in it.
• Physiological illusions: These happen because of how our eyes and brain react to too much stimulation. This could be from very bright lights, strong colors, or certain patterns. It affects how we see size, position, tilt, or movement.
• Cognitive illusions: These are caused by our brain making quick, unconscious guesses about what we are seeing. Sometimes, these guesses are wrong.

How Our Brains Create Illusions

Many illusions can be explained by how our brain processes information from our senses. It tries to make sense of everything we see. A famous psychologist named Hermann von Helmholtz said that what we perceive is like an "unconscious guess" based on what our senses tell us and what we've learned before.

Another expert, Richard Gregory, explained that our brain makes a "hypothesis" or a best guess about what's out there. Sometimes, this guess isn't quite right, and that's when we see an illusion. His idea is that our perception is a mix of what our eyes see and what we already know or have experienced.

Researcher Mark Changizi thinks optical illusions happen because of a "neural lag." This means there's a tiny delay (about one-tenth of a second) between when light hits your eye and when your brain actually understands what it's seeing.

Changizi believes our visual system has learned to predict the future by a tiny bit. It tries to show us what will happen one-tenth of a second from now. This helps us do things like catch a ball or walk through a crowd without bumping into people. Illusions happen when our brain's prediction of the future doesn't match what's really there.

In simple terms, these ideas are similar. We don't just see things exactly as they are. Instead, our brains work quickly to figure out what we're looking at. This involves using our memory and logic. This process is usually very good, but it's not perfect. When it makes a mistake, we experience an optical illusion.

Images for kids

• 

  In this image, your brain creates a white triangle even though it's not actually drawn.

• 

  The two yellow lines look like different lengths, but they are actually the same!

• 

  The gray bar looks like it changes from light to dark, but it's all one color. The background makes it seem different.

• 

  These circles seem to move when you move your head while looking at the black dot.

• 

  Floor tiles at the Basilica of St. John Lateran in Rome. The pattern makes it look like there are three-dimensional boxes.

• 

  Gregory's categorization of illusions

• 

  In this animation, Mach bands make the edges of slightly different gray shades look more contrasting when they touch.

• 

  "The Organ Player" – Pareidolia phenomenon in Neptune's Grotto stalactite cave (Alghero, Sardinia)

• 

  This image can look like two faces or a vase, depending on what your brain focuses on.

• 

  This picture can be seen as either a duck or a rabbit.

• 

  The vertical line looks longer than the horizontal one, but they are the same length.

• 

  "Shepard's tables" deconstructed. The two tabletops appear to be different, but they are the same size and shape.

• 

  A visual representation of what an amputee with phantom limb syndrome senses.

• 

  Top-down processing involves using action plans to make perceptual interpretations and vice versa. (This is impaired in schizophrenia.)

• 

  An example of the hollow face illusion which makes concave masks appear to be jutting out (or convex).

• 

  An example of motion induced blindness: while fixating on the flashing dot, the stationary dots may disappear due to the brain prioritizing motion information.

• 

  Ambigram tessellation "Escher" using negative space to reveal letters upside down.

• 

  Lilac chaser: if the viewer focuses on the black cross in the center, the location of the disappearing dot appears green.

• 

  Motion illusion: contrasting colors create the illusion of motion.

• 

  Subjective cyan filter, left: subjectively constructed cyan square filter above blue circles, right: small cyan circles inhibit filter construction

• 

  Pinna's illusory intertwining effect and Pinna illusion (scholarpedia).(The picture shows squares spiralling in, although they are arranged in concentric circles.)

• 

  Optical illusion disc which is spun displaying the illusion of motion of a man bowing and a woman curtsying to each other in a circle at the outer edge of the disc, 1833

• 

  the full image]].

• 

  An ancient Roman geometric mosaic. The cubic texture induces a Necker-cube-like optical illusion.

• 

  The Spinning Dancer appears to move both clockwise and counter-clockwise

• 

  Forced perspective: the man is made to appear to be supporting the Leaning Tower of Pisa in the background.

See also

In Spanish: Ilusión óptica para niños