Most of us if not all have been involved in persuasive conversations where somewhere along the lines you realized there was more going on than a dispassionate assessment of justifications and evidences. However, how do we know that?
Before we answer that, we can say that most of us just realize from experience that what is said and what is understood is not always the same thing. People “interpret” what they hear, they read between the lines, they read body language and react sometimes in non-rational ways. Clear communication between and amongst those involved in a conversation is the anomaly.
A particularly glaring example might be trying to convince someone who is afraid of heights to stand close to you and at the edge of a reinforced glass enclosure to see the great view of the city below. You may even attempt to persuade the person to stand where you are because they are missing something that nobody would want to miss seeing. And, yet most of us can “read” their reluctance....
Those who suffer from this phobia may even give you a bunch of plausible “reasons” why they may not want to do so; some may admit they’re just afraid of heights. Others do not because there is a social stigma attached to irrational or non-rational behavior. You can get responses from those that range from, “I can see everything just fine from here,” or “...we’ve spent enough time up here and I’m ready to go.”
Further encouragements won’t help much in those sort of cases because there is something going on besides the rational assessment of the risk/reward for getting the nice view. There is some underlying and maybe not even fully realized by either party; we need to remember that it’s always possible a phobia prompts some to demur.
Those who study human behavior have suggested a myriad of “causes” for this kind of behavior including early child-hood experiences, pre-dispositions and emotional “wiring” and the like of that. There is the typical nature versus nurture debate about such things, but we need not enter into that here. All we need to recognize is that there is often more going on in forming people’s attitudes and behavior than meets the eye on the conscious level.
So the returning to the original question, how do we recognize that sort of non-rational part of the conversation?
For most of us it is observing people in relevant contexts where important clues and cues are “read” in people’s faces, tone of voice and body behaviors, in other words: body language. The reason for that working so well is that it is that it’s hard to long suppress body language. It can be disguised, but even then we subconsciously often notice that something is wrong.
Parenthetically, it should be noted that being directly involved in the exchange may not necessarily make one in a better position to read this. The reason for that is many people are not able to both think about what the other person has said, read their body language and put together their response without missing something.
Only the best of us do that well and even fewer regularly well, and that’s why many of us appreciate having a “silent” friend involved in the conversation but who watches and can give us feedback (either at a later time or very subtly) on how well we communicated and what cues we might have read incorrectly or missed.
That sort of feedback is crucial in learning to get better at listening and reading people’s response so you can address the real issues--even the non-rational ones in a way that is appropriate to that sort of concern. It would be a huge mistake to try to handle non-rational objections or concerns by ignoring them or merely appealing to rational justification.