Apparent motion, sometimes called the phi phenomenon, is the visual illusion of motion created by the rapid presentation of a sequence of still images. It is based on the idea that our eyes and brain perceive a series of still images as a continuous stream of motion. Phi phenomenon is technically a specific case of apparent motion observed when two nearby stimuli are presented in alternation with a relatively high frequency.
The phi phenomenon is the basis for the stroboscopic effect, it is the illusion of motion created by the rapid succession of still images that makes the stroboscopic effect work, where the object appears to be frozen in a single position, even though it is in motion.
The phi phenomenon has been studied extensively in fields such as psychology, neuroscience, and cognitive science, and it continues to be an important area of research today.
Table of Contents
- How does Apparent Motion work?
- Versions of Apparent Motion
- Illusions like Apparent Motion
- Discovery of Apparent Motion
- References and Resources
How does Apparent Motion work?
Apparent motion, also known as the phi phenomenon, works by taking advantage of the way our eyes and brain process visual information. The human visual system is designed to detect and respond to movement, and it does this by constantly analyzing the images it receives from the eyes.
When a sequence of still images are presented in quick succession, the visual system perceives the images as a single object moving from one position to another. This is because the visual system is constantly analyzing the images, and it uses the information from one image to make predictions about the next image. When these predictions are confirmed, the brain interprets this as a single object moving.
The speed of the apparent motion is determined by the rate at which the images are presented. The faster the rate, the smoother the apparent motion will appear. The brain also uses other cues such as brightness, size, and color to determine the apparent motion.
The phi phenomenon is based on the idea that our eyes and brain perceive a series of still images as a continuous stream of motion, this is the basis for the stroboscopic effect, where the object appears to be frozen in a single position, even though it is in motion, and it is also the basis for motion picture and animation, where a series of still images are projected in rapid succession to create the illusion of motion.
The Related and Often Confused Illusory Motion
Note that sometimes apparent motion is used to refer to illusory motion which is when static image appears to be moving due to the interaction of color contrasts, shapes, and position.
Illusory motion, also known as motion illusion, is the perception of movement in a static image or pattern.
This can occur when the brain is presented with a series of static images that change over time, or when certain visual patterns are arranged in a specific way.
The brain interprets these as if they are moving, even though the image or pattern itself is not actually moving.
There are several theories that try to explain the underlying mechanisms of illusory motion.
One theory is that it is a result of neural adaptation, where the visual system becomes adapted to certain stimuli and continues to respond as if they were present even after they are removed.
Another theory is that it is a result of the brain’s tendency to perceive patterns and to fill in missing information, known as Gestalt principles.
Versions of Apparent Motion
The following are some other examples of Apparent Motion
“phi phenomenon”
“phi phenomenon”
Illusions like Apparent Motion
The following are some illusions related to Apparent Motion
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.
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.
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.
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.
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.
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.
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.
These illusions are usually caused by the way our eyes process visual information and the way the brain interprets it. They can also be caused by the interaction of different visual elements, such as lines and angles, in the image. They are often used in research on visual perception and the neural basis of perception.
Discovery of the Apparent Motion
The phi phenomenon was first described by the German psychologist Max Wertheimer in 1912.
He observed that if two lights are turned on and off in quick succession, the brain perceives them as a single light moving back and forth. This is the basic principle behind motion pictures and animation, where a series of still images are projected in rapid succession to create the illusion of motion.
The phi phenomenon, also known as apparent motion, was first described by the German psychologist Max Wertheimer in his 1912 paper “Experimental Studies of the Perception of Movement.” In this paper, Wertheimer described a series of experiments in which he used a sequence of still images to create the illusion of motion, and he noted that the brain perceives these images as a single moving object.
Wertheimer’s work on the phi phenomenon was groundbreaking and had a significant impact on the field of psychology, particularly in the area of perception. His findings helped to establish the Gestalt school of psychology, which focuses on the way the brain organizes sensory information.
Wertheimer’s work on the phi phenomenon also laid the foundation for the study of motion perception and animation and helped to pave the way for the later development of motion pictures and television.
It’s worth noting that the phi phenomenon was also independently studied by other researchers such as Kurt Koffka and Wolfgang Köhler, who were also part of the Gestalt school of psychology and they made contributions to the field as well.
References and Resources
Check out our complete list of illusions.