People often send us papers and data via Twitter that they believe rule out a radical, non-representational theory of cognition. Because I have yet to agree about any of these studies, these people then often ask in exasperated tones 'well, what would you accept as evidence?'.
My current best answer is "about 20 years of hard work".
When you study perception, your goal is to control the flow of information going into the system so that you can measure the resulting behaviour and evaluate how that information is being used. There are two ways to do this, one (sometimes) used by me, one used by, well, everyone else. In this post I'm going to compare and contrast the methods and describe why the perturbation method is what we should all be doing.
The standard method is to present experimentally isolated cues and test whether people can detect those cues. The perturbation experiment presents a 'full cue' environment but selectively interferes with the link between a single variable and the property it might be information about. These two different methods lead to very different ways of thinking and talking about perceptual abilities.