Unveiling the Truth: The Role of Vision in Visual Illusions

by Mateo Gonzalez
visual illusions

According to a recent study led by Dr. Jolyon Troscianko from the University of Exeter, visual illusions primarily arise from the limitations of our eyes and neural processes, rather than complex psychological phenomena.

The University of Exeter conducted research that demonstrates how visual illusions are a result of the inherent constraints of our eyes and neural pathways, rather than intricate mental processes. The study’s model effectively predicts human visual illusions and elucidates our ability to perceive high-contrast images, such as those found on high-definition TVs, despite the limited bandwidth of our neurons.

Various visual illusions stem from the limitations in the functioning of our eyes and visual neurons, rather than more intricate psychological processes, as revealed by new research.

The study investigated illusions in which an object’s surroundings influence the perception of its color or pattern.

For years, scientists and philosophers have debated whether these illusions arise from neural processing in the eye and low-level visual centers in the brain or involve higher-level mental processes like context and prior knowledge.

The image above shows a bar in the center with the same shade of gray throughout, yet it appears lighter on the left and darker on the right due to the gradient in the background. This phenomenon, known as simultaneous contrast, illustrates how dark surroundings make objects appear lighter, and vice versa. (Image credit: Jolyon Troscianko)

In this recent study, Dr. Jolyon Troscianko from the University of Exeter collaborated on a model that suggests simple limitations in neural responses, rather than deeper psychological processes, account for these illusions.

Dr. Troscianko, from the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall, explained, “Our eyes communicate with the brain by regulating the firing rate of neurons—either faster or slower. However, there is a limit to the speed at which they can fire, and previous research has not considered how this limit might affect our perception of color.”

The model combines this notion of “limited bandwidth” with information on how humans perceive patterns at various scales, along with the assumption that our vision functions optimally when observing natural scenes.

The image above displays two gray bars in the center, with both bars having identical shades of gray. However, the bar on the left (surrounded by more black bars) appears darker. This contrasts with the example of simultaneous contrast mentioned earlier, as the darker surroundings now make the target seem darker. (Image credit: Jolyon Troscianko)

Initially developed to predict how animals perceive color, the model was also found to accurately predict numerous visual illusions experienced by humans.

Dr. Troscianko remarked, “This challenges long-held assumptions about the workings of visual illusions.”

Furthermore, the findings shed light on the popularity of high-definition televisions.

“Modern high dynamic range televisions produce bright white regions that are over 10,000 times brighter than their darkest black, approaching the contrast levels found in natural scenes,” added Dr. Troscianko.

Both cubes in the image above appear to have yellow and blue tiles on their top surfaces. However, the tiles that appear yellow on the left are, in fact, a gray color identical to the blue tiles on the right. Our model can help explain why objects appear to possess the same color despite changes in lighting and why such illusions make gray hues appear colorful. (Image credit: Jolyon Troscianko)

He continued, “How our eyes and brains manage this contrast is puzzling because tests indicate that the highest contrasts humans can perceive at a single spatial scale are around 200:1.”

“Even more perplexing, the neurons connecting our eyes to our brains can only handle contrasts of about 10:1.”

“Our model demonstrates how neurons with such limited contrast bandwidth can combine their signals, enabling us to perceive these substantial contrasts. However, the information becomes ‘compressed,’ resulting in visual illusions.”

“The model illustrates how our neurons have precisely evolved to utilize every ounce of their capacity. For instance, some neurons are sensitive to minute differences in gray levels at medium-sized scales but become easily overwhelmed by high contrasts. Meanwhile, neurons that code for contrasts at larger or smaller scales are far less sensitive but can operate over a broader range of contrasts, resulting in distinct black-and-white disparities.”

“In essence, this demonstrates how a system with severely limited neural bandwidth and sensitivity can perceive contrasts larger than 10,000:1.”

The paper, titled “A model of color appearance based on efficient coding of natural images,” was published in the journal PLOS Computational Biology, authored by Jolyon Troscianko and Daniel Osorio on June 15, 2023.

Reference: “A model of colour appearance based on efficient coding of natural images” by Jolyon Troscianko and Daniel Osorio, 15 June 2023, PLOS Computational Biology.
DOI: 10.1371/journal.pcbi.1011117

Frequently Asked Questions (FAQs) about visual illusions

What does the new study suggest about visual illusions?

The new study suggests that visual illusions are primarily caused by limitations in the eyes and neural processes, rather than complex psychological phenomena.

How were visual illusions previously thought to be caused?

There has been a long-standing debate among scientists and philosophers about whether visual illusions are caused by neural processing in the eye and low-level visual centers in the brain or involve higher-level mental processes such as context and prior knowledge.

What is the model developed in the study?

The study developed a model that combines the concept of “limited bandwidth” in neural responses with information on how humans perceive patterns at different scales, while assuming that our vision functions best when observing natural scenes.

What can the model predict?

The model not only predicts human visual illusions accurately but also provides insights into our ability to perceive high-contrast images and the phenomenon behind the popularity of high-definition televisions.

How do neurons with limited contrast bandwidth perceive large contrasts?

The study explains that neurons with limited contrast bandwidth combine their signals to perceive substantial contrasts, but the information becomes “compressed,” resulting in visual illusions. Neurons specialized for different scales exhibit varying sensitivity to contrast, contributing to black-and-white disparities in perception.

What implications does this study have?

The findings challenge previous assumptions about how visual illusions work and shed light on the limitations and mechanisms of human vision, color perception, and contrast processing. They have potential implications for fields such as visual neuroscience and sensory processing.

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JohnSmith83 July 13, 2023 - 3:18 pm

wow this study is really cool! it shows that visual illusions aren’t just in our mind but also in our eyes and brain! i always thought it was all in our head lol

Bookworm27 July 13, 2023 - 3:47 pm

intresting research! i always wondered how we see illusions and now they say it’s cuz our eyes and brain can only do so much. mind blowing stuff!

ScienceNerd42 July 13, 2023 - 4:20 pm

i always thought visual illusions were just in our mind. who knew our eyes and brain had limits too? this research shows there’s so much more to it than we thought. fascinating!

CrazyCatLady July 13, 2023 - 5:41 pm

visual illusions are wild! this study proves it’s not all in our heads but our eyes and brain play tricks on us too. i guess we can’t always trust what we see!

CreativeGrl July 14, 2023 - 5:57 am

this study is like mind blown! it shows how our eyes and brain work together to make us see things that aren’t really there. it’s like magic but in our own heads!


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