Viestintä yleensä epäonnistuu, paitsi sattumalta (Communication usually fails, except by accident)Wiio's First Law
Wiio's Laws are unfortunately not generally well-known in English-speaking countries. Jukka Korpela provides an English translation of the laws and commentary on them, which is definitely worth reading.
I was reminded of them by some recent discussions, and so two related reasons for communication failure I want to highlight are privilege and "core assumptions".
Failure of communication due to privilege is commonplace, and the reason is probably sufficiently obvious to most readers that I won't spend much time on it. The nature of privilege is that it's difficult to notice when you have it, which makes it easy to assume everyone has it, which means that the usual pattern-recognition features of the brain go in the wrong direction.
This makes people immune to both anecdotal and systematic evidence. Anecdotal because the anecdotes, regardless of number, don't fit their personal experience, and so get written off as unusual occurrences rather than commonplace. Systematic because for any study you care to name, in any field beyond the highly obscure, there will be another study that contradicts it (and it doesn't matter if there's only a couple of contradictory studies to hundreds or thousands saying the same thing1).
Core assumptions are more generally important, though. The connection between core assumptions and privilege are many. You could define privilege entirely as a core assumptions problem, though to do so would ignore that fact that the core assumptions a person holds are often a consequence of their privilege: the whole thing is self-reinforcing.
I'm using "core assumptions" to mean the assumptions about the way that the world works that are so fundamental to a person's way of thinking that they're not (always) aware that they're making them.
For instance, a common (and generally harmless) core assumption is that effect follows cause, and not the other way round. If I attempt to present an argument that relies at some point on the cause being after the effect, regardless of how much evidence I provide that this was apparently the case, then if you share that core assumption you won't accept my arguments. If I hold the core assumption that cause and effect can come in either order, I probably also will find it difficult to understand why you don't accept my arguments. I've given you plenty of evidence that X happened because Y then happened; the fact that you consider this inconceivable will not occur to me. Almost everyone has been in plenty of discussions where the other party appears to accept all the evidence you present and then come to a diametrically opposed conclusion from it.
It's very difficult to have an ultimately productive discussion with someone whose relevant core assumptions are not compatible with your own.
Core assumptions aren't necessarily harmful - common ones like the nature of cause and effect, in fact, are generally helpful to the majority of situations because they provide a common basis for discussing the world2. The core assumptions linked to privilege, however, are harmful, because they make it difficult to get people to see the privilege.
Core assumptions aren't static - but if someone has a core assumption that is getting in the way of seeing privilege, it's very difficult to shift it. Conversely, if you can remove it, they might very quickly come the rest of the way into agreement on the basis of the evidence you've already provided.
So, the question is, how do you shift a core assumption? If you want to do this other than accidentally, the most important thing to do is to identify what the core assumption is. If you get this wrong, and argue against something that logically follows from the core assumption instead, then it will be an uphill struggle to get any evidence to stick.
Having identified it - and that's difficult in itself, because a person who doesn't consciously know they're making an assumption is unlikely to admit to it - you can then work directly on the assumption. Misidentifying it will often just lead to wasted effort.
(I'm writing this as applied to arguing against someone else's core assumption, but of course it applies without much modification to the extremely important task of identifying one's own privilege-influenced core assumptions so that you can stop assuming them and begin the long process of reconstructing your world view without them)
For instance, some people defending privilege will have the core assumption (and they might even be aware enough of it to state it explicitly):
"X and Y are different, and this explains differences in outcome without needing there to be discrimination"
There are studies carrying out controlled experiements to show that this isn't true, and discrimination is statistically visible across the population.
For other defenders of privilege, that won't be the core assumption. The core assumption will be "Y are inferior", and the assumption above will be a logical consequence of it. In that case the studies above will be useless. I'm not sure if there is anything that can be done to argue with such a plain assertion as a core assumption.
1 It's not necessarily true that the massively greater volume of studies is correct, because the studies are themselves made by researchers with varying degrees of privilege, and this can let core assumptions of the entire field be entirely wrong but remain unchallenged even in the face of strong counter-evidence. (e.g. most research on the "obesity epidemic")
2 There are of course plenty of core assumptions that are both extremely common and extremely harmful. "Gender is strictly binary and immutable", for instance. These core assumptions are very strongly self-reinforcing, because almost everyone acts as if it's completely and self-evidently true, which means most people never consider that it might not be (and dehumanisingly write-off any counter-examples).