Ability to identify colours not defined by language

London: The human ability to categorise colours may be independent of language, according to a case study on a 54-year-old French-Portuguese man who specifically lost his ability to correctly name colours after suffering a stroke. The ability of the man, identified as RDS, to categorise colours based on hues has remained intact since he suffered the stroke in 2014.

The case study, published in the journal Cell Reports, looked at how language influences human thinking. For centuries, philosophers have tried to understand if learning the names of objects was important for categorising them. "We perceive colours as continuous. There is no sharp boundary between, say, red and blue. And yet conceptually we group colours into categories associated with colour names," said Paolo Bartolomeo, a neurologist at the Brain and Spine Institute in Salpetriere Hospital in France. Many scientists, according to the study, believe that the names of different colours are stored in the human brain's left hemisphere, and for categorising colours, one is dependent on brain activity in that region.

However, the RDS case study suggests that colour categorisation is distributed across both hemispheres of the human brain. In the study, RDS was asked to identify same-category colours in viewing discs. These contained two colours from the same category, such as indigo and blue, or from different categories like brown and red. RDS was also asked to name 34 colour patches that were presented on a computer screen, of which eight were achromatic -- white, black and grey -- and 26 were chromatic. He was able to name all colours normally before the stroke. However, post the brain injury, an MRI scan revealed a lesion in the left region of his brain.

To ensure that RDS' brain was not an abnormal case, the researchers compared the functioning of his unaffected brain regions to that of the same areas in healthy subjects, and developed a non-verbal test to categorise colours. "Our result -- that his colour categories were independent from language -- could be generalised to healthy adults," Bartolomeo said. The researchers noted that the lesion could have severed RDS's memory of colour names from his visual perception of the colours.

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