The first few levels of the hierarchy, DH0, DH1, DH2, DH3, are not useless, if you’re concerned with getting to the truth efficiently. Pointing out that the author has no credentials in the area they are speaking in would allow people to limit their attention to credentialed speakers (due to bounded rationality). The senator example is similar—if you can’t listen to everything and have to prune someone, choosing to forgo listening to obviously biased speakers might be a reasonable choice.
DH2 and DH3 are sometimes valuable as well, because we can do some inference about the world, taking a piece of communication as evidence. For example, we may infer something about the author’s personality or beliefs from their tone; and then (bounded rationality again) decide whether to read further based on this (limited, probabilistic) estimate of the author.
Contradiction works similarly; it’s a performance, putting the reputation of the speaker behind the negated claim. If a third party hears a college freshman make a point, and the professor flatly contradicts it, then the third party may be able to decide who to believe, shortcutting detailed analysis (scarce processing again). In some cases, this kind of contradiction argument can even be supported solely on tone, without leaning on reputation. A scholarly-sounding contradiction to a casual claim may be sufficient to sway me in some situations—perhaps the stakes are low.
The first few levels of the hierarchy, DH0, DH1, DH2, DH3, are not useless, if you’re concerned with getting to the truth efficiently. Pointing out that the author has no credentials in the area they are speaking in would allow people to limit their attention to credentialed speakers (due to bounded rationality). The senator example is similar—if you can’t listen to everything and have to prune someone, choosing to forgo listening to obviously biased speakers might be a reasonable choice.
DH2 and DH3 are sometimes valuable as well, because we can do some inference about the world, taking a piece of communication as evidence. For example, we may infer something about the author’s personality or beliefs from their tone; and then (bounded rationality again) decide whether to read further based on this (limited, probabilistic) estimate of the author.
Contradiction works similarly; it’s a performance, putting the reputation of the speaker behind the negated claim. If a third party hears a college freshman make a point, and the professor flatly contradicts it, then the third party may be able to decide who to believe, shortcutting detailed analysis (scarce processing again). In some cases, this kind of contradiction argument can even be supported solely on tone, without leaning on reputation. A scholarly-sounding contradiction to a casual claim may be sufficient to sway me in some situations—perhaps the stakes are low.