text:  You know, how can we be sure? I mean, well, for a long time, we couldn't be sure. We had to sort of take someone's word for it, that that's what they were imagining, that's what their experience was like. But then I found this guy, Joel Pearson. I'm a professor of cognitive neuroscience at the University of New South Wales. Who sort of like stumbles into this way of showing that there really is a difference here. It was almost an accidental discovery. One day, he's in his lab. I was programming an experiment. He was playing around with this thing called binocular rivalry.