Ternus Illusion

It involves the perception of rapid successive presentation of a sequence of three disks as a single, moving object.

The illusory effect is created by the close proximity and rapid succession of the disks, which leads to the perception of a single, continuous object in motion.

This illusion highlights the importance of the temporal aspects of vision in shaping our perceptions of the world around us.


Ternus Illusion
Ternus Illusion


Table of Contents

How does the Ternus Illusion work?

The Ternus illusion works by exploiting the way our visual system processes information over time.

When the three disks are presented rapidly in succession, the visual system integrates the information from each disk into a single, continuous object in motion.

This is because our visual system has a tendency to perceive smooth, continuous movement, even when the visual input is actually a series of discrete elements.

The effect is enhanced when the disks are close together and when the duration of their presentation is short, as this makes it more difficult for the visual system to process each disk as a separate, stationary object. T

he rapid presentation of the disks creates a temporal gap between their individual presentations, which is bridged by the visual system’s interpretation of a continuous object in motion.

In short, the Ternus illusion works by taking advantage of the visual system’s processing of temporal information, and the tendency to perceive smooth, continuous movement.

Versions of Ternus Illusion

The following is an alternate version of the Ternus Illusion with a slightly different speed. The second image shows both frames of the Ternus illusion simultaneously.


Ternus Illusion


Ternus Illusion


Illusions like the Ternus Illusion

The Ternus illusion is a motion illusion. It involves the perception of a single, continuous object in motion, even though the visual input is actually a sequence of three stationary disks presented rapidly in succession.

The illusion highlights the importance of the temporal aspects of vision in shaping our perceptions of the world around us and demonstrates how our visual system can create the perception of motion from rapidly presented, discrete elements.

Motion illusions are visual illusions that involve the perception of motion, when there is none or when the perceived motion is different from the actual motion.

Motion illusions can be created by a number of factors, such as changes in an object’s position over time, the interaction of moving stimuli with the visual field, or by conflicting depth cues.

These illusions demonstrate the brain’s ability to interpret motion and depth based on visual input, and the ways in which these processes can be influenced by the visual environment.

Some related illusions include the following:

The Stepping Feet Illusion is a visual illusion that involves an optical illusion of the apparent movement of a static image.



The kinetic depth effect refers to the perception of three-dimensional (3D) depth and solidity in an object that is produced by its motion, relative to the observer.



The spinning dancer illusion is a visual illusion that depicts a silhouette of a dancer spinning clockwise or counterclockwise. The direction of the dancer’s spin can appear to change depending on the viewer’s perception.


The beta movement illusion is a visual illusion in which a series of static images, such as a filmstrip or flipbook, appears to be in motion when viewed in rapid succession.


In Peripheral Drift illusions, the image or pattern appears to move or drift, even though it is actually stationary. This movement is caused by the brain’s attempt to interpret the image or pattern, which is often complex or ambiguous. The movement can be in any direction, such as horizontally, vertically, or diagonally.


Peripheral drift illusion jelly bean
From Wikimedia Commons


The rotating snakes is a peripheral drift illusion that consists of a grid of shapes, with some of them appearing to be rotating or undulating. The illusion is created by the interaction of the shapes with the neural processing of the visual system.


Rotating Snakes Autokinetic effect
A Version of Rotating Snakes


With Illusory motion, static image appears to be moving due to the interaction of color contrasts, shapes, and position



Troxler’s fading, also known as Troxler’s effect, is a phenomenon in which a stationary visual stimulus eventually disappears from perception, even though it is still present in the visual field.



Lilac-Chaser_Troxlers Fading

The stroboscopic effect is a visual phenomenon that occurs when a rapidly flashing light is used to illuminate a moving object.

The object appears to be frozen in a single position, even though it is in motion. This is because the flashing light is only on for a brief period of time, and the object is only visible when the light is on.

Stroboscopic effect


The Scintillating Grid Illusion, in which a grid of black and white squares appears to pulsate or “breathe” when viewed from the periphery of the image.



Simultaneous Contrast Illusion


The Motion Aftereffect (also known as the Waterfall Illusion) is a visual illusion experienced after viewing a moving visual stimulus, and then fixating on a stationary stimulus. The stationary stimulus appears to move in the opposite direction to the original stimulus.

For example, fixate on the moving image below for several seconds, then shift you gaze to another surface like a plain wall. You should still be able to see the motion on the static surface.


Motion-Aftereffect



The Café Wall Illusion is a visual illusion that is created by a grid of alternating light and dark horizontal and vertical lines. The lines appear to be bent or tilted, even though they are actually straight.


Cafe Wall Illusion



Discovery of the Ternus Illusion

The Ternus illusion is a visual illusion that was first described by the psychologist Paul Ternus in 1926.

Paul Ternus was a psychologist and a pioneer in the field of visual perception. He was born in Austria in 1883 and was best known for his work on visual illusions, including the Ternus illusion, which was named after him.

Ternus conducted a number of studies on visual perception, including the perception of motion and the integration of information over time. His work helped to establish the importance of temporal aspects of vision and laid the foundation for the study of motion perception in modern psychology.

In addition to his research, Ternus was also a talented teacher and was highly regarded by his students and colleagues. He made significant contributions to the field of psychology and is remembered today as one of the pioneers of visual perception research.

References and Resources

Check out our complete list of illusions.

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