Here's an interesting article abstract, Cooney, Boothby, & Lee, in the Journal of Experimental Psychology:
After conversations, people continue to think about their conversation partners. They remember their stories, revisit their advice, and replay their criticisms. But do people realize that their conversation partners are doing the same? In eight studies, we explored the possibility that people would systematically underestimate how much their conversation partners think about them following interactions. We found evidence for this thought gap in a variety of contexts, including field conversations in a dining hall (Study 1), “getting acquainted” conversations in the lab (Study 2), intimate conversations among friends (Study 3), and arguments between romantic partners (Study 4). Several additional studies investigated a possible explanation for the thought gap: the asymmetric availability of one’s own thoughts compared with others' thoughts. Accordingly, the thought gap increased when conversations became more salient (Study 4) and as people’s thoughts had more time to accumulate after a conversation (Study 6); conversely, the thought gap decreased when people were prompted to reflect on their conversation partners’ thoughts (Study 5). Consistent with our proposed mechanism, we also found that the thought gap was moderated by trait rumination, or the extent to which people’s thoughts come easily and repetitively to mind (Study 7). In a final study, we explored the consequences of the thought gap by comparing the effects of thought frequency to thought valence on the likelihood of reconciliation after an argument (Study 8). Collectively, these studies demonstrate that people remain on their conversation partners’ minds more than they know.
This is something I learned rather late in life. With some people (notably my wife and children, and certain of my colleagues) it is not necessary for me to repeat things that I feel haven't sunk in, because they will sink in later when people brood on them. For some of the people who have worked under me, the slightest criticism reverberates for days. Understanding this puts an obligation on us, as I see it, to choose our words carefully; they don't just pass through the air and disappear, but may linger for decades.