Optical illusions, more appropriately known as visual illusions, involve visual deception.
Notice how the dots at the center of each intersection seem to shift between white and gray?
Like many optical illusions, different theories have been proposed to explain exactly why this happens.
Rob Patrick Robpatrick / Flickr CC
Our brains can’t tell.
In reality, the illusion occurs because our brains must attempt to construct space around the spinning figure.
The Ames room illusion works due to the trapezoidal shape of the room.
Mosso - http://www.flickr.com/photos/39325045@N00/355613728/
From the viewer’s perspective, it looks like a square room, leading to the size distortion.
The small figure is, in reality, standing at a greater distance than the larger figure.
Which line is longer?
Fibonacci / Wikimedia Commons
In reality, they are exactly the same length.
This optical illusion occurs because people view the scene from a linear perspective.
When you look off into the distance, objects seem closer together as they become further away.
Wikimedia Commons
This illusion may occur due to the angle of the shorter lines compared to the long lines.
This causes the brain to perceive depth where there is none.
It is created by thebrain filling in gapsin order to perceive a more complete whole.
Fibonacci / Wikimedia Commons
According to theGestalt law of closure, we tend to see objects close together as a related group.
Which line is longer?
Both are the same length.
This phenomenon is known as theMuller-Lyer Illusion.
A few different explanations have been proposed to explain how it works.
Why does this happen?
geloo, modified by Kendra Cherry
An afterimage can occur when you stare at something for a long period.
This optical illusion works becausephotoreceptors in the eyebecome overstimulated and fatigued from staring at the image.
Because they lose sensitivity, you end up seeing negative afterimage briefly when you move your eyes.
Takeaways
These 10 optical illusions are just a sampling of the different visual illusions that exist.
Such illusions can be helpful for learning more about how the brain works.
The three main types of optical illusions are physiological illusions, cognitive illusions, and literal illusions.
These include auditory illusions, sensory illusions, olfactory illusions, and tactile illusions.
2021;21(5):26. doi:10.1167/job.21.5.26
Ross Lab.Making sense of the Hermann Grid illusion.
Glover EM, Lauzon O.Using a contrast illusion to teach principles of neural processing.J Undergrad Neurosci Educ.
2018;17(1):A81A88.
Qian K, Mitsudo H.Eggs illusion: Local shape deformation generated by a grid pattern.J Vision.
2016;11(7):e0159228.
2016;11(7):e0159228.
doi:10.1371/journal.pone.0159228
Bertamini M.Lilac chaser illusion.
In:Programming Visual Illusions for Everyone.
2017:153-161. doi:10.1007/978-3-319-64066-2_14
Todorovic D.What are visual illusions?*Perception.
2020;49(11):1128-1199. doi:10.1177/0301006620962279
American Psychological Association.Zollner illusion.
Sakiyama T, Sasaki A, Gunji YP.Origin of Kanizsa triangle illusion.
2014;26(8):1871-1882. doi:10.1162/jocn_a_00590
American Psychological Association.Afterimage.
Bachy R, Zaidi Q.Troxler fading, eye movements, and retinal ganglion cell properties.Iperception.
