Optical illusions

It is fascinating how the human brain works and how it interprets what colours, shapes and patterns it observes. Today I am going to talk about something that has always caught my attention. Optical illusions as research and as a tool for use in communication and interpretation.

Optical illusions are visual phenomena that play with human perception. In the context of visual arts and visual communication, these illusions can be powerful tools to create unique and surprising visual effects.

We might think that optical illusions are closer to cheap magic tricks than to the most revered works of art. This is a bit strange, considering that all works of art are, at heart, illusions in themselves. Rembrandt, Velázquez, Sorolla… these great painters were masters at applying their knowledge of light and perspective to make flat images appear three-dimensional.

There are certain conditions of colour, light, position, size or geometric shapes that can generate interpretations or concepts founded in our mind. In this article, we will look at three different types of optical illusions and what they can teach us about both art and the human brain.

Types of Optical Illusions

Optical illusions are also valuable from a scientific perspective. “The visual arts,” as a Scientific American article explains, “sometimes preceded the visual sciences in discovering fundamental principles of vision through the application of methodical, though perhaps more intuitive, research techniques. In this sense, art, illusions and visual science have always been implicitly linked“.

Let us look briefly at the different types, and subtypes, of optical illusions:

1.- Literal illusions:

The first and simplest type of optical illusion is the literal optical illusions, which describe images that can be seen in two different ways. My wife and mother-in-law is probably the most famous example of a literal optical illusion. Created by an unknown artist in the late 19th century, it shows a figure that, depending on the viewer’s focus, resembles either an old woman or a young woman. Another example might be All is Vanity. A black and white drawing from 1892 by Charles Allan Gilbert, which shows a woman applying make-up in front of a dressing table that also resembles a human skull.

Artistically, literal optical illusions can be used to establish a connection between two different ideas or objects. My wife and mother-in-law connects youth with old age and ugliness with beauty. All is vanity could be said to comment on pride and narcissism.

From a scientific point of view, these optical illusions provide insight into the nature of human perception. When Harvard psychologist Edwin Boring came across My wife and mother-in-law on a postcard, he was very surprised by people’s reactions. Some saw the young woman first, while others saw only the old woman. Some took seconds to see both, others had to struggle for minutes.

Boring conducted some experiments with the illusion and was not disappointed with what he found. In general, he found that younger participants were more likely to see the younger woman first. The older ones were more likely to see the older woman. In other words, you could say that our age influences the way we see the world.

2.- Physiological illusions:

The second type, physiological optical illusions, overstimulate the human brain with more light, shapes or colours than it is able to process. Such as kinetic illusions, which are images that use sensory overload to create the illusion of movement, first mentioned by Aristotle.

Many known physiological optical illusions were not created by artists, but by scientists. Mackay’s Rays, the work of neurologist Donald M. Mackay, presented in 1957, show a dense cluster of radial lines. When the eye is held in the centre of this cluster, the white space between the lines appears to change and glow. This induces an illusory perception of these rays when looking at the right image with the letter ‘F’. Another example is the Hermann Grid. A black and white grid in which grey dots seem to appear at intersections when there are none.

As physiological optical illusions are not representational, they did not appear in art history until the 1960s, when the optical art movement (op-art) emerged. The 1965 exhibition at the Moma in New York, entitled “The Responsive Eye ’, explored various optical illusions, which involved the viewer as never before.

Are physiological optical illusions created by the eye or by the brain? Researchers were unsure until Xoana Troncoso published a paper. In it, they argued that these illusions could be caused by small involuntary eye movements that occur when we fix our gaze on something, shifting our peripheral vision and thus creating the impression of movement or brightness.

3.- Cognitive illusions:

The third and most complex type of optical illusion are the so-called cognitive optical illusions. These not only deceive the eyes, but also the brain. Unlike psychological illusions, whose effects are quick, instinctive and without much thought, cognitive illusions require considerable effort to understand.

These illusions arise through interaction with assumptions about the world, leading to “unconscious inferences”. An idea first suggested in the 19th century by the German physicist and physician Hermann von Helmholtz. Helmholtz explained that our minds make assumptions about the environment around us and thus give rise to unexplained events.

Some of the best examples of cognitive optical illusions were created by the Dutch artist M.C. Escher. It is impossible not to mention Escher and his impossible drawings that baffle us precisely because they seem possible. Taking advantage of the logic of light and the viewer’s perspective, the artist is able to conceal his illusions.

M.C. Escher’s impossible drawings are not only artistically impressive. They also interest philosophers, who use them as visual analogies to understand and deconstruct paradoxes. Such as the so-called “Liar’s Paradox“, which poses the unanswerable question of whether or not a liar is telling the truth when he tells you he is lying.

Within cognitive illusions there are four subgroups:

• Ambiguous illusions: these are images that shift in the viewer’s perception. These illusions are called impossible images. Impossible in the sense that no two things can exist in the same image. A famous example is Necker’s cube or Rubin’s vase.

• Paradoxical illusions: these are illusions that are paradoxical in their existence. They are impossible objects in the sense that physics and three-dimensional space cannot explain how these objects are possible. Have you ever seen the staircase that never ends, or the Penrose triangle?

• Distorting illusions: also known as geometric optical illusions. They distort size, length, curvature and position to create an image that appears contorted. Examples are the coffee wall illusion, the Müller-Lyer illusion, Hering’s illusion, Ponzo’s illusion, Sander’s illusion, White’s illusion and many others.

• Fictional illusions: the viewer mentally creates an object that does not actually exist in the image. According to Piper Gourley, a fictional illusion exists entirely and exclusively as a product of the mind.
  
  Examples of such illusions are the Kanizsa triangle and the subjective Necker Cube. These three images show a star, a cube and a triangle that do not actually exist.

Explanation of cognitive illusions:

To make sense of the world it is necessary to organise incoming sensations into information that is meaningful. Gestalt psychologists believe that one of the ways in which this is done is by perceiving individual sensory stimuli as a meaningful whole.

In addition, Gestalt theory can be used to explain many illusions such as the illusory contours in the Kanizsa Triangle. The brain has a need to see simple familiar objects and has a tendency to create a ‘whole’ image from individual elements.

However, another explanation of the Kanizsa Triangle is based on evolutionary psychology and the fact that in order to survive it was important to see shape and edges. The use of perceptual organisation to create meaning from stimuli is the principle behind other well-known illusions involving impossible objects. Our brain makes sense of shapes and symbols by putting them together like a jigsaw puzzle, formulating what is not there for what is believable.

Artists who have worked with Optical Illusions:

Conclusion.

As we have seen, an optical illusion consists of deceiving the eye by taking advantage of the way in which the eyes and the brain work together to interpret the visual stimuli in our environment.
Many artists have created truly amazing works by using these optical illusions to great effect. Optical illusions can be beautiful works of art, but they can also be useful for learning more about how our minds work.

Hi, I’m Roberto Vidiella.

I am the founder and Creative Director of VIDI. I am passionate about graphic design, and through this blog, I try to deepen my knowledge and share what I have learned during my career. If you leave me a comment, you help me to keep learning and improving, and I’m really excited about it!