I'd like the title of the short story by Flannery O'Connor in which a man thinks he is engaging in friendly conversation only to find that his responses are used as data in an article published in a psychology periodical.
This looks like the beginning of The Violent Bear It Away:
The old man was in a position to know what his ideas were. He had lived for three months in the nephew’s house on what he had thought at the time was Charity but what he said he had found out was not Charity or anything like it. All the time he had lived there, the nephew had secretly been making a study of him. The nephew, who had taken him in under the name of Charity, had at the same time been creeping into his soul by the back door, asking him questions that meant more than one thing, planting traps around the house and watching him fall into them, and finally coming up with a written study of him for a schoolteacher magazine.