Tennis Ball Illusion

This is the Tennis Ball Illusion. It’s also known as the “curvature blindness illusion”.

You have to check out this video. The balls are all moving in a straight line.

If you are interested in learning how it works, scroll down after watching the video.

What is the Tennis Ball Illusion?
How does the Tennis Ball Illusion work?
Discovery of the Tennis Ball Illusion
References and Resources

What is the Tennis Ball Illusion?

In the Tennis Ball illusion, a series of balls or other objects appears to be moving in a straight line, but in fact, they are following a curved path. The illusion is created by manipulating the position and spacing of the balls, so that they create a series of curves that the eye has difficulty perceiving.

The curvature blindness illusion is thought to be related to the way that the visual system processes information about motion and curvature. The brain tends to interpret motion along the shortest possible path, or “geodesic,” between two points. However, when the spacing and arrangement of the objects is carefully manipulated, the geodesic path appears to be a curve, rather than a straight line.

The curvature blindness illusion is a striking example of how our visual system can be fooled into perceiving something that is not actually there. It also highlights the complex and often counterintuitive ways in which the brain processes visual information.

How does the Tennis Ball Illusion Work?

The “curvature blindness illusion” or the “tennis ball illusion” works by exploiting the way that the visual system processes information about motion and curvature.

When we see a series of objects moving, our brains tend to interpret the motion as happening along the shortest possible path, or “geodesic,” between two points. However, when the spacing and arrangement of the objects is carefully manipulated, the geodesic path appears to be a curve, rather than a straight line.

In the case of the tennis ball illusion, the balls are spaced and arranged in such a way that they create a series of curves, even though they are actually moving in a straight line. The arrangement of the balls is designed to be subtle enough that the eye has difficulty perceiving the curvature, but strong enough to create a convincing illusion of a curved path.

One theory behind the tennis ball illusion is that it is related to the way that the visual system processes information about edges and boundaries. When two objects are close together, they create a strong boundary that the visual system interprets as a curve. By carefully manipulating the spacing and arrangement of the objects, the illusionist can create a series of boundaries that suggest a curved path, even though the objects themselves are moving in a straight line.

The tennis ball illusion is a fascinating example of how our brains can be fooled by subtle visual cues. It also highlights the complexity of visual perception and the ways in which the brain processes information about motion, shape, and spatial relationships.

Discovery of the Tennis Ball Illusion

The tennis ball illusion is a relatively recent discovery and it is not attributed to a single individual. The illusion was first described in a scientific paper in 2005 by researchers Peter Thompson and Kyriaki Mikellidou at the University of York in the United Kingdom. However, it is possible that other researchers or illusionists may have discovered the phenomenon independently around the same time or earlier.

Since its discovery, the tennis ball illusion has become a popular topic of study among researchers interested in visual perception and cognition. It has also been featured in numerous public demonstrations and exhibitions, showcasing the ways in which our visual system can be fooled and deceived by subtle cues and manipulations.

Similar Illusions

There are many other visual illusions that are similar to the tennis ball illusion in that they involve manipulating visual cues to create misleading or counterintuitive perceptions. Here are a few examples:

The Müller-Lyer illusion: This classic illusion involves two lines with arrowheads at either end. One line appears longer than the other, even though they are actually the same length.

The Ponzo illusion: This illusion involves two horizontal lines of equal length that are superimposed on a set of converging diagonal lines. The top line appears longer than the bottom line, even though they are actually the same length.

The Ebbinghaus illusion: In this illusion, two circles are surrounded by circles of varying sizes. One circle appears larger than the other, even though they are actually the same size.

The motion aftereffect: This illusion involves staring at a moving object for a period of time and then looking at a stationary object. The stationary object appears to be moving in the opposite direction.

The color assimilation grid illusion: This illusion involves a grid of colored squares, where the colors of the squares appear to be influenced by the colors of the squares around them.

These illusions, along with many others, demonstrate the complex and often surprising ways in which the brain processes visual information. They have fascinated researchers and laypeople alike for centuries, and continue to inspire new insights into the nature of perception and cognition.