Optical Illusions - Fine Arts Center (2024)

James Turrell, Alta (Pink)as part of “Cosmic Wonder” at San Francisco’s Yerba Buena Center, 1968. This piece shows how Turrell challenges the viewer into questioning whether that is justlight or something more physical, even something that you could potentially touch.

Many of James Turrell’sworks attempt to make light, something wholly non-physical, cross the standards boundaries of perception into an almost physical and material realm. The dramatic color and light saturation that dominate his pieces suggest an entirely new way of experiencing light that goes beyond the mere visual sense. Turrell’s undergraduate background in psychology has informed his works through their ability to challenge standard modes of perception.

An example of a literal optical illusionwhere the image created is differentfrom the objects. It is seeingan imagethat you normallywould not see in that context.

But what are optical illusions? Here’s a real life example of optical illusions by Mike Hewson, a public art commission in New Zealand that pays homage to the Christchurch Normal School, a building slated for demolition after the 2011 earthquake. Can you tell which type(s) of optical illusions Hewson is working with from the three categories below?

Types of optical illusions
Literal, physiological, cognitive

An example of a physiological optical illusion, which are most commonly characterized by the afterimages after looking at bright lights. This type of repeating or intense stimulus leads us to falsely perceive movement or repetition. Jeremy Hinton created this illusion around 2005 — if you stare at the center cross for about 20 seconds, then you see three things: (1) a gap running aroundthe circle of lilacs, (2) a green disc that joins the running purplelilacs, and (3) the green disc moving in the circular pattern and thelilac discs disappear(image source).

20th Century Analytic philosopher Ludwig Wittgenstein’s famous duck-rabbitpicture to demonstrate the distinction between “seeing as” and “seeing that”or, anexample of a cognitive visual illusion. There is nocorrect answer towhether thisis a drawingof a duck, or a rabbit. Cognitive illusions are a resultof ourconceptions and assumptions about the world, which we impose upon visualstimuli. This can lead to four types of cognitive illusions: ambiguous illusions,distorting/geometrical-optical illusions, paradox illusions, or fictions(image source).

Types of cognitive optical illusions
Ambiguous, distorting, paradox, fiction

The most common interpretation of the Necker Cube, an ambiguous cognitive illusion (image source).

A less common but equally plausible conception of the faces of the Necker Cube.

The Necker Cube is a well known example of an ambiguousillusion. The arrangement of the lines themselves are ambiguous, meaning nothing in the lines themselves suggest for the lower left face to be the “front” face. Computers do not have the same consistency as humans do in seeing this “front” face, rather, they see other interpretations with equal frequency.

The full moon illusion, a distortingcognitive illusion.

“The Café Wall” as n example of a geometricdistorting cognitive illusion becauseof the arrangement of the lines andshading that make it seem like the lines are not straight when in fact they are.

Distorting illusionsare some of the most common because they happen in everyday life as well as in geometric/artistic constructions. The photo on the left of the moon illustrates how our eyes are not equipped to see the true size of the moon, rather it depends on where the moon is in the sky. When directly overhead, the full moon looks much smaller than when it’s on the horizon. The psychological reasons behind this phenomena are still being debated.

The Penrose Stairs, an example of paradox cognitive illusion. This 2-dimensional depiction of a staircase has a 90º turn to form a continuous loop, where you would not get any higher or lower whichever step you take (image source).

Paradox illusionsare caused by images that cannot exist in real life, but our minds accept them, at least at first, to be convincing. The Penrose’s, father Lionel and son Roger, (no relation to Spencer and Julie Penrose) invented the most famous paradox illusion of the Penrose Stairs.


Fictionillusions occur most commonly in hallucinogenic drug users, schizophrenics and others with disorders that cause hallucinations. These illusions are perceived only by the subject, and not anyone else.

To see more examples of how our eyes can trick us, here’s an online gallery of more optical illusions.

Or, visit Convolutions, the first exhibition in our new Permanent Collection series, Raiding the Crates.Permanent collection works presented inConvolutionswere chosen in response to the upcomingJames Turrell and Scott Johnsonexhibitions.You’ll find some challenges to your visual perception by the likes of Larry Bell, Oskar Fischinger, Adam Fuss, and many more!

July 14–Sept. 30, 2012