Why Visual Illusions are Caused by Neural Processing, Not Psychological Processes
Introduction:
Visual illusions have long fascinated scientists and philosophers, with debates centered around whether they are a result of neural processing or more complex psychological processes. However, new research conducted by Dr. Jolyon Troscianko from the University of Exeter suggests that these illusions are primarily caused by limits in the way our eyes and visual neurons work, rather than deeper psychological factors.
Understanding the Nature of Visual Illusions:
Visual illusions occur when an object’s environment affects how we perceive its color or pattern. Until now, scientists have been divided on whether these illusions stem from neural processing in the eye and lower-level visual centers in the brain or involve higher-level thought processes such as context and prior knowledge.
Introducing the Model:
To shed light on this matter, Dr. Troscianko and his colleagues developed a model that proposes simple limits to neural responses as the explanation for visual illusions. The model takes into account the concept of “limited bandwidth” in neural firing rates and how humans perceive patterns at different scales. Additionally, it assumes that our vision functions optimally when observing natural scenes.
The Significance of Limited Bandwidth:
Our eyes send messages to the brain, which then causes neurons to fire at varying rates. However, there is a limit to how fast these neurons can fire. Previous research had not considered how this limit might impact our perception of color. The model developed by the researchers takes into account this “limited bandwidth” and suggests that it plays a crucial role in explaining visual illusions.
Predicting Visual Illusions:
Initially, the model was developed to predict how animals perceive color. Surprisingly, it was also able to accurately predict many visual illusions experienced by humans. This challenges long-held assumptions about the underlying mechanisms of visual illusions and suggests that simple limits in neural responses play a central role.
Exploring High-Contrast Images:
The research findings also provide insights into the popularity of high-definition televisions. These televisions produce bright white regions that are significantly brighter than the darkest black, approaching the contrast levels found in natural scenes. This poses a puzzle because evidence suggests that humans can perceive contrasts of only around 200:1 at a single spatial scale. Furthermore, the neurons connecting our eyes to our brain can only handle contrasts of around 10:1. Dr. Troscianko explains that the model shows how neurons with limited contrast bandwidth can combine their signals to allow us to perceive these immense contrasts, resulting in visual illusions.
Understanding Neuronal Capacity:
The model further reveals how our neurons have precisely evolved to utilize every bit of their limited capacity. For example, some neurons are highly sensitive to small differences in gray levels on medium-sized scales but are easily overwhelmed by high contrasts. On the other hand, neurons that encode contrasts at larger or smaller scales are much less sensitive but have a wider range of contrast perception, leading to strong black-and-white differences. This showcases how a system with severely limited neural bandwidth and sensitivity can perceive contrasts well beyond their inherent limitations, such as contrasts greater than 10,000:1.
The Implications of the Study:
The research conducted by Dr. Troscianko and his team challenges previous assumptions surrounding visual illusions. By establishing that these illusions are primarily a result of limits in neural processing, rather than complex psychological processes, the study contributes to our understanding of how our eyes and visual neurons work. Furthermore, it highlights the importance of considering neural responses and limited bandwidth in future research on visual perception.
Additional Piece:
Understanding the Complexity of Visual Perception
Visual perception is a remarkable aspect of human cognition that allows us to navigate the world around us. From recognizing objects to perceiving depth and color, our visual system processes an immense amount of information in a seamless manner. However, understanding the intricacies of visual perception is far from simple.
Neural Pathways and Brain Centers:
Visual perception involves complex interactions between our eyes, the optic nerve, and various brain centers responsible for processing visual information. The journey begins with light entering our eyes and being focused onto the retina. The retina contains specialized cells called photoreceptors that convert light into neural signals. These signals are then transmitted via the optic nerve to the visual cortex, where further processing occurs.
The Role of Neural Processing:
The research conducted by Dr. Troscianko and his colleagues emphasizes the importance of neural processing in understanding visual illusions. It suggests that these illusions arise from the limitations of neural responses rather than solely relying on higher-level cognitive processes. By considering the concept of limited bandwidth and how humans perceive patterns at different scales, the model provides valuable insights into the underlying mechanisms of visual illusions.
Practical Applications:
The findings of this study have broader implications beyond understanding the nature of visual illusions. They can potentially contribute to the development of technologies that enhance our visual experiences. For instance, high-definition televisions with their ability to create high contrasts pose a challenge to our visual perception. By understanding the limitations of our neural responses and the potential for visual illusions, designers and engineers can develop strategies to optimize visual experiences while minimizing undesirable effects.
Moreover, these insights can be integrated into virtual reality (VR) and augmented reality (AR) systems. By considering the principles of limited neural bandwidth, designers can create immersive and realistic visual experiences that align more closely with how our visual system processes information. This has the potential to revolutionize the way we interact with virtual environments, leading to more immersive and believable experiences.
The Complexities of Human Vision:
While the research conducted by Dr. Troscianko provides valuable insights into the neural mechanisms underlying visual illusions, it is important not to overlook the complexity of human vision. Our visual system evolved to adapt to the natural environment, where processing sensory information accurately and efficiently was crucial for survival. However, with the advent of modern technology and artificial stimuli, our visual system is constantly being challenged in unprecedented ways.
Understanding the limitations and capabilities of our visual system is an ongoing endeavor. By combining research in fields such as neuroscience, psychology, and computer science, we can continue to unravel the mysteries of visual perception. This knowledge can not only enhance our understanding of the human mind but also pave the way for innovative applications in fields such as healthcare, entertainment, and education.
In conclusion, visual illusions are primarily caused by limits in the way our eyes and visual neurons work, rather than complex psychological processes. The research conducted by Dr. Jolyon Troscianko and his colleagues provides valuable insights into the neural mechanisms underlying visual illusions. By considering the concept of limited bandwidth and how humans perceive patterns at different scales, the model developed in the study challenges long-held assumptions and sheds new light on the complexities of human vision. Understanding the intricacies of visual perception has immense practical implications, from optimizing visual technologies to creating more immersive virtual experiences. As we continue to delve deeper into the workings of our visual system, we unlock new possibilities for enriching our understanding of the world around us.
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Many visual illusions are caused by limits in the way our eyes and visual neurons work, rather than more complex psychological processes, new research shows.
The researchers examined illusions in which an object’s environment affects how we see its color or pattern.
Scientists and philosophers have long debated whether these illusions are caused by neural processing in the eye and lower-level visual centers in the brain, or involve higher-level thought processes such as context and prior knowledge.
In the new study, Dr Jolyon Troscianko, from the University of Exeter, co-developed a model that suggests simple limits to neural responses, not deeper psychological processes, that explain these illusions.
“Our eyes send messages to the brain causing neurons to fire faster or slower,” said Dr Troscianko, from the Center for Ecology and Conservation at Exeter’s Penryn Campus in Cornwall.
“However, there is a limit to how fast they can fire, and previous research has not considered how the limit might affect how we see color.”
The model combines this “limited bandwidth” with information about how humans perceive patterns at different scales, along with the assumption that our vision works best when looking at natural scenes.
The model was developed by researchers at the Universities of Exeter and Sussex to predict how animals see colour, but it was also found to correctly predict many visual illusions seen by humans.
“This throws up a lot of long-held assumptions about how visual illusions work,” said Dr. Troscianko.
He said the findings also shed light on the popularity of high-definition televisions.
“Modern high-dynamic-range televisions create bright white regions that are more than 10,000 times brighter than their darkest black, approaching the contrast levels of natural scenes,” added Dr. Troscianko.
“How our eyes and brains can handle this contrast is a puzzle because evidence shows that the highest contrasts we humans can see at a single spatial scale is around 200:1.
“Even more confusingly, the neurons that connect our eyes to our brain can only handle contrasts of around 10:1.
“Our model shows how neurons with such limited contrast bandwidth can combine their signals to allow us to see these huge contrasts, but the information is ‘compressed’, resulting in visual illusions.
“The model shows how our neurons precisely evolved to use every bit of capacity.
“For example, some neurons are sensitive to very small differences in gray levels on medium-sized scales, but are easily overwhelmed by high contrasts.
“Meanwhile, neurons that encode contrasts at larger or smaller scales are much less sensitive, but can function over a much wider range of contrasts, giving profound black-and-white differences.
“Ultimately, this shows how a system with severely limited neural bandwidth and sensitivity can perceive contrasts greater than 10,000:1.”
The article, published in the magazine PLOS Computational Biologyis entitled: “A Color Appearance Model Based on Efficient Coding of Natural Images.”
https://www.sciencedaily.com/releases/2023/06/230615183122.htm
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