We literally don’t know what we communicate in important conversations:
What you say in a conversation — whether it’s on a first date, a job interview or pitching an idea — may be less important than how you say it. But the cues that may decide the outcome can be so subtle that neither person in the conversation is consciously aware of them. Whether or not you get the job, or the other person’s phone number, is very strongly influenced by unconscious factors such as the way one person’s speech patterns match the other’s, the level of physical activity as people talk, and the degree to which one person sets the tone — literally — of the conversation. .. The features he found that are highly predictive of outcomes, he says, "match the literature in biology about signaling in animals." … "Half of our decision-making seems to be predicted by this unconscious channel," … The strong correlations between unconscious forms of communication and the decisions that result strongly undermines people’s perception that they are making choices based on rational, conscious factors.
HT to Michael Bishop.