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Illusions Are in the Eye, Not the Mind
Illusions are in the eye, not the mind [exeter.ac.uk]:
Numerous visual illusions are caused by limits in the way our eyes and visual neurones work – rather than more complex psychological processes, new research shows [plos.org].
Researchers examined illusions in which an object's surroundings affect the way we see its colour or pattern.
Scientists and philosophers have long debated whether these illusions are caused by neural processing in the eye and low-level visual centres in the brain, or involve higher-level mental 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 – explain these illusions.
"Our eyes send messages to the brain by making neurones fire faster or slower," said Dr Troscianko, from the Centre for Ecology and Conservation on Exeter's Penryn Campus in Cornwall.
"However, there's a limit to how quickly they can fire, and previous research hasn't considered how the limit might affect the ways we see colour."
[...] "This throws into the air a lot of long-held assumptions about how visual illusions work," Dr Troscianko said.
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 over 10,000 times brighter than their darkest black, approaching the contrast levels of natural scenes," Dr Troscianko added.
"How our eyes and brains can handle this contrast is a puzzle because tests show that the highest contrasts we humans can see at a single spatial scale is around 200:1.
"Even more confusingly, the neurones connecting our eyes to our brains can only handle contrasts of about 10:1.
"Our model shows how neurones with such limited contrast bandwidth can combine their signals to allow us to see these enormous contrasts, but the information is 'compressed' – resulting in visual illusions.
[...] "Ultimately this shows how a system with a severely limited neural bandwidth and sensitivity can perceive contrasts larger than 10,000:1."
Journal Reference:
Jolyon Troscianko, Daniel Osorio, A model of colour appearance based on efficient coding of natural images [open], PLOS Comp Bio, 2023. DOI: https://doi.org/10.1371/journal.pcbi.1011117 [doi.org]
