And I didn't say they necessarily were a different form of the same thing. The term "hallucination" covers a wide spectrum. It could conceivably include many different things.
Here's an analogy. The
Stanley Steamer lacked a characteristic that's shared by virtually every other automobile: an internal combustion engine. However, because it had four wheels, ran on roads rather than tracks, and carried a small number of passengers, I would still call it an automobile.
When trying to decide what a vehicle is, it wouldn't be valid to say "it's steam powered, therefore it's a locomotive and not an automobile." It's the thing's other characteristics that define what it is, even though (in the days before diesel locomotives, anyhow) it would have been a good rule of thumb that steam powered vehicles were generally locomotives and internal combustion vehicles were generally cars.
Just as the type of engine doesn't define whether or not a particular vehicle is an automobile, I don't think that whether or not something is a hallucination is defined by which parts of the brain light up on an MRI when the person is experiencing it. The defining criterion is whether it's a perception that's not reflective of an actual external stimulus.
No - you can use statistical methods to come up with a
hypothesis test to determine whether the variation you're interested in is a result of random chance or whether it indicates a real correlation.
You may have the advantage of me - I did say "without looking at the studies you mentioned."