A software engineer who helped develop the Mozilla Firefox internet browser says he’s just figured out he has an unusual brain quirk that makes him unable to visualize images in his mind.

Blake Ross, who is also the former director of product at Facebook, writes about his realization in a lengthy post on Facebook.

He explains he never understood that, when other people say they can picture a face or a location, they actually “see” it in their mind’s eye. That’s something he says he simply can’t do.

“I have never visualized anything in my entire life,” he writes.

“I can’t ‘see’ my father’s face or a bouncing blue ball, my childhood bedroom or the run I went on 10 minutes ago. I thought ‘counting sheep’ was a metaphor. I’m 30 years old and I never knew a human could do any of this. And it is blowing my goddamned mind.”

Ross says this mind-blowing revelation came to him recently, after he read an article in the New York Times about the brain condition “aphantasia.”

The article, from June, 2015, explained that researchers in England had recently discovered that certain people see nothing when asked to picture something mentally. Effectively, it’s as though their “mind’s eye” were blind.

He said the idea of “picturing” something as mundane as a red triangle makes no sense to him.

“I can’t even understand the question. I can think about the idea of a red triangle. But it’s blackness behind my eye,” he said.

What’s more, Ross says he almost never has dreams – or at least, never has visual dreams.

“I’ve had a couple dreams but there was no visual or sensory component to them,” he said.

That doesn’t mean, he said, that he can’t recognize people or places; he just can’t picture them. The researchers who identified aphantasia say it appears that the brain process of “putting a name to a face” is different from the process of “picturing” a face.

Ross says he has also realized that he can’t “hear” songs in his head. He says he recognizes the theme song to Star Wars, for example, but can’t actually hear the music in his head.

“And I’ve never had a song ‘stuck’ in my head,” he added.

Ross says he’s been asking friends and colleagues to better understand what their minds can do that he can’t.

In the process, he has stumbled on three other people who share his experience. Two are fellow software engineers, who have long shared a sense of “otherness” they could never pinpoint.

“We started a thread to compare our tics and quirks—it’s a lot of ‘YES!’ and ‘exactly!!’ and ‘Wow you too?’” he said.

“It’s the feeling of finding your people.”

Ross says, since his revelation, he’s gotten in touch with the British scientific team that first identified aphantasia, and wants to be part of their research.

“I’m looking forward to getting MRI results and funding future research,” Ross said.