Not all information relayed by a person is anecdotal. There are ways of gathering formal accounts. An anecdote is an informal account. Many NDE reports, for example, are informal.Don't you think that modern neuroscience is based off of anecdote? I poke your brain, you tell me how you feel. Me telling you how I feel is anecdotal; I have an experience that is only accessible by myself. If you refuse to accept my experiences as nothing more than anecdotal, then the experiment cannot be done. I remember reading an article by a gentleman that was asked to think of something. He decided to screw around with the experimenters and think of something else. The FMRI showed that his patterns were identical to those who had followed the experimental protocol ( I'm paraphrasing the story here a bit, but it's somewhere on the old forum ).
Of course it's possible for subjects to screw around with psychology experiments. As we advance our understanding, we should be able to detect this more and more.
~~ Paul