Suggested reading: http://en.wikipedia.org/wiki/Visual_cortex#Function “Conceptually, this retinotopy mapping is a transformation of the visual image from retina to V1. The correspondence between a given location in V1 and in the subjective visual field is very precise: even the blind spots are mapped into V1.”
We can easily reject the Cartesian theater notions, but there are still “paintings” of images in our brains.
“This pattern of belief is very hard to justify from a Bayesian perspective. It is just the same hypothesis in both cases. Even if, in the second case, I announce an experimental method and my intent to actually test it, I have not yet experimented and I have not yet received any observational evidence in favor of the hypothesis.”
Always consider the source.
It is the same hypothesis, but if the person telling the story is unknown to me at the outset, then the credibility of the source rises with test plans, as follows.
After the just-so story: This could be any crank making up stories to sell an idea.
After hearing of a possible test: If this person has taken the time to work out how they would test it, then my confidence is significantly increased. They’ve just set themselves apart from the pure story-tellers.
After looking at the thoroughness of their proposed tests: Confidence rises if they’ve shown a willingness to consider lots of ways that their story and testing could be wrong or misleading. Evidence of familiarity with and adherence to scientific methodology does increase credibility.
After hearing that they are committed to performing their tests: Confidence increases a little more. Not much, but a little.
Sure, these increases in confidence are small—tiny compared to the boost from actually performing even one of the tests—but they are not zero.
If I’m already familiar with the story-teller, and have some prior opinion of their experience and capability, then you’re right: hearing about the tests shouldn’t affect my confidence.