Concave or Convex Illusion

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In this Concave or Convex Illusion the circles on the left all appear to be convex and all the circles on the right appear to be concave.

There is only one change in the circles that creates this effect. In all other ways, the circles are identical. The difference is in the shading. The circles on the left as light on top, while the circles on the right are light below.

If you are interested in learning more about this Concave or Convex Illusion, scroll down to read more about it.

Concave or Convex Illusion


Table of Contents

What is the Concave or Convex Illusion?

The concave-convex circle illusion is an optical illusion that makes it appear that two identical circles are different only by changing the way that they are shaded. In reality, the circle remains the same shape throughout the illusion.

The key is the shading a which creates a perceived change in curvature of the circles. It is a fascinating example of how our brain can be tricked by visual information and highlights the complexity of perception and interpretation of visual stimuli.

How does the Concave or Convex Illusion Work?

The concave-convex circle illusion works by taking advantage of the way our brains interpret visual information. When we look at the circles, our brains use various visual cues, such as shading and relative size, to interpret their shape and depth. As a result, our brains interpret the concave circle as having a greater depth than the convex circle.

It has been theorized that the light on top is consistent with the sun lighting objects from above, as such, our visual system perceives the shapes on circles on the left to be solid and therefore appear convex.

The concave-convex circle illusion is a great example of how our brains can be tricked by visual information, and it highlights the complex interplay between perception, cognition, and interpretation of visual stimuli.

Some Similar Illusions

There are many similar illusions that take advantage of the way our brains interpret visual information. Here are a few examples:

  1. The Penrose triangle: Also known as the “impossible triangle,” this illusion depicts a triangle that appears to be three-dimensional, but is actually impossible to create in real life.
  2. The Ames room: This illusion uses distorted geometry to make objects appear larger or smaller than they really are, and can create the illusion of people changing size as they move around the room.
  3. The Moiré pattern: This illusion occurs when two or more grids or patterns are overlaid on each other, creating a rippling or pulsing effect.
  4. The Shepard tone: This auditory illusion creates the impression of an infinitely rising or falling sound, even though the pitch is actually staying the same.
  5. The Necker cube: This illusion depicts a cube that appears to flip back and forth between two different orientations, even though it is actually stationary.

These illusions, and many others, demonstrate the remarkable ways in which our brains interpret and process visual and auditory information, and highlight the complexity of perception and cognition.

Discovery of the Concave or Convex Illusion

The concave-convex illusion origin is not entirely clear. It is likely that the illusion has been observed and studied by many people throughout history, as similar illusions have been documented in artwork dating back to the Renaissance period.

One of the most famous examples of the concave-convex illusion can be found in a drawing by the artist M.C. Escher, who is known for his intricate and mind-bending works of art. Escher’s drawing, titled “Convex and Concave,” features a series of interlocking figures that appear to shift in and out of concave and convex shapes.

While it is not clear who first discovered or documented the concave-convex illusion, it has been studied and analyzed by scientists and psychologists for many years. In recent decades, researchers have used advanced imaging techniques and brain imaging technologies to better understand how the brain processes visual information and creates illusions like the concave-convex circle illusion.


References and Resources

In addition to the Concave or Convex Illusion check out our complete list of illusions.