Researchers from Johns Hopkins University studied a 60-year-old man known as RFS, who has a rare degenerative brain disease that prevents him from seeing numbers two to nine.

He would describe seeing one of these numbers as a tangle of black lines that changed every time he looked at it. He had otherwise normal vision, and had no problem identifying letters and other symbols.

The problem would happen before he knew which number he was looking at, which meant his brain had to at least know that numbers were in the same category before something could then go wrong; study author Mike McCloskey tells NR Times.

“It didn’t matter how we presented digits to him, they were always distorted,” says McCloskey, a researcher in the Cognitive Science Department at Johns Hopkins University.

The researchers didn’t know what they were looking for when they started working with RFS, as this specific pattern has never been recorded before. The closest recorded cases are of patients who see distorted faces.

The researchers, whose findings were published in the journal, ‘Proceedings of the National Academy of Sciences,’ also found that RFS couldn’t recognise anything placed near or on top of a number.

They recorded RFS’s brainwaves while he looked at a number with a face embedded on it, and found that his brain detected the face, even though he was unaware of it.

“In one experiment, we showed him a big digit with a face on top of it and recorded EEG signals to see how his brain responded to the face.

“Even though he couldn’t see the face at all, we could pick up a response in the brain 170 milliseconds after the face was presented.

“We saw a perfectly normal brain response to the face, which told us his brain unconsciously identified the face as a face, even though he wasn’t aware of it at all.”

In another experiment, they put words next to the numbers and told him a target word. When he saw the target word, his brain had a bigger response even though he said he couldn’t see the word. They also did tests where they placed a number in front of RFS and asked him to guess what a number was, to test implicit knowledge.

“Sometimes, blind people say they can’t see a light, but can often point to it accurately when forced to make a guess,” McCloskey says.

“We did that with him and saw absolutely no indication he had any implicit knowledge. He couldn’t tell us if numbers were the same or different, odd or even – yet the EEG showed his brain was responding.

The reason it could just be numbers that are affected, he says, is because evidence suggests the brain treats categories of things differently.

“Furniture, fruit and vegetables, for example, may be treated separately, so it’s possible for some areas to be affected and some not.”

The findings demonstrated that the complex processing needed to detect words, numbers and other visual stimuli isn’t enough to make a person aware of what they’re seeing.

“We can draw conclusions about what’s necessary for you to be aware of what you’re seeing. You’d think that, if the brain has done enough work on something to know it’s a face or a particular word, you’d be aware of it.

“These results tell us the brain can do an awful lot of processing on something you’re looking at without you being aware of it at all,” McCloskey says.

“Something else needs to happen after the brain has identified what it’s looking at before you become aware of it at all. ”

And the reason these findings apply to everyone else is because the researchers assumed RFS’s brain was the same as anyone else’s, except for this one thing that went wrong.

“In order to become aware of something, you have to do more than processing to allow you to identify what you see – we think this is true for everyone.”

As for RFS, who was a geological engineer, the story has a happy ending.

“Because RFS couldn’t see regular digits, this was a real problem for him. We created a new set of symbols for him for digits, to see if he could use those,” McCloskey says, as well as a calculator on his phone using the digits.

“He learned them very easily – we wondered if they’d get distorted for him but fortunately, they didn’t. He says he’s been using the symbols ever since – he uses them in his daily life and stayed in his job two years longer than he would’ve otherwise, because of them.”