Optical Illusions: How Does Our Brain Trick Us?

The way our visual perceptions work, and the illusions we experience, have been the subject of debate for a long time. Some argue that these illusions are caused by complex psychological processes, while others maintain that they result from limitations in our eyes and visual neurons. However, a new study published in the journal PLoS Computational Biology provides evidence supporting the latter theory.

The study, conducted by Dr. Jolyon Troscianko of the University of Exeter in collaboration with researchers from the University of Sussex, presents a novel model suggesting that visual illusions can be explained by constraints in neural responses rather than deeper psychological processes. According to Dr. Troscianko, the neurons in our eyes and brain have a limit to how quickly they can activate, which affects the way we perceive color.

Revealing the magic of visual illusions

The model combines the concept of the neurons’ “limited bandwidth” with information about how we perceive patterns at different scales. It also assumes that our vision works best when dealing with natural scenes. Initially, the model was designed to predict how animals perceive color, but it was also found to be capable of predicting many visual illusions observed in humans.

These findings challenge some previous assumptions about how visual illusions work. For example, they raise the question of how our eyes and brains can handle the high contrast of high-definition televisions, which create bright white regions contrasted with deep blacks. According to Dr. Troscianko, humans can perceive contrasts of only around 200:1 at a single spatial scale, while modern televisions reach contrast levels of up to 10,000:1. This raises a puzzle about how our visual system can handle such contrasts.

The proposed model reveals that neurons with limited contrast bandwidth can combine signals to allow us to perceive these enormous contrasts. However, this information is “compressed,” giving rise to visual illusions. Neurons specialized for different contrast scales have different levels of sensitivity and different capacities for handling high or low contrasts. In this way, our visual system has evolved to make the most of its capacity and perceive contrasts greater than 10,000:1.

This study demonstrates how much of the appearance of color and visual illusions may be attributed to simple mechanisms developed for the efficient coding of natural images. The results also provide a solid basis for modeling vision in both humans and other animals. Understanding how our visual perception works and the limitations inherent in it helps us appreciate the complexity of our visual system and how we interact with the visual environment around us.

These discoveries have important implications in various fields, from cognitive psychology to display technology. By better understanding how our visual perceptions are formed and how illusions can arise from neural limitations, we can develop more sophisticated technologies that adapt to the capabilities and limitations of our visual system. In addition, these findings open new avenues of research into visual perception and the way we interact with the visual world around us.

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A model of colour appearance based on efficient coding of natural images: