Those tests could also depend on some third thing, such as not believing that you're visualizing a bright light. I can't see their methodology. "Here, we show that the imagery pupillary light response correlates with objective measures of sensory imagery strength." Really, objective measures of how bright an imaginary light is, how on earth do they think they can measure that!? Was it like "we gave them a sheet of paper where they had to score how bright a light they were imagining, and the sheet of paper objectively existed so it was an objective test"?

Well anyway the whole concept, and the science, seems like a giant troll.