Back when I was studying the psychology of deceiving and getting deceived, my colleagues and I did some research in which we asked people to tell us, in detail, about the most serious lie they ever told to anyone and the most serious lie anyone ever told them. (You can read some of their stories here.) It will not surprise you that more serious lies were about affairs than anything else. There was a certain theme I found intriguing in the stories of the people whose partners were cheating on them - they suggested that once they became certain that their partner was cheating, all sorts of things seemed to fall into place. It was as if they "knew it all along," but had not let themselves acknowledge what was going on until they had to.
There was no way to know from that study alone what was actually happening. Did they just tell themselves that they knew it all along so they would not feel like complete and total dupes? Or at some level, did they really know?
People in close romantic relationships often believe that they know better than anyone else when their partner is lying. Sometimes they can even describe to you what they believe to be the tell-tale clues. But thinking that you can tell doesn't mean that you can tell. (In fact, in a review my colleagues and I did of all of the available studies of accuracy and confidence, we found that people who were confident about their judgments of deceptiveness were no more or less likely to be correct in their judgments than people who were not confident.)
The intuitive case for believing that you know when your partner is lying better than anyone else does is that you spend so much time with that person, and observe that person so carefully (at least in theory). Perhaps that greater exposure and experience could help if it were the only thing figuring into your insights into your partner's deceptiveness. But of course it is not. One of the most important additional factors is motivation. What would it mean to see through to the truth instead of the fantasy that your partner is selling to you? If you are worried that you might not like what you see, you may not be so great at all at recognizing what is right there in front of you.
In fact, a graduate student of mine a while back, Eric Anderson, did a clever dissertation (described here) in which he had people answer the dreaded question, "Do you think that person over there is attractive?" The romantic partners did worse at knowing whether the answers were truthful or deceptive than total strangers did. At some level, though, they did seem to know the truth. When they were asked indirect questions (for example, "did you get enough information from the person's answer?"), the partners were actually better than the strangers at distinguishing the lies from the truths. That is, they realized that they had not gotten enough information when their partner was lying (even though they didn't know for sure that their partner was lying) and they felt that they did get enough information when their partner was telling the truth.
Probably because of my interest in single life, I've always been more interested in what friends know and don't know than what romantic partners do. As friends get to know each other better, do they become more insightful about each other's honesty and dishonesty? My colleagues (Eric Anderson and Matthew Ansfield) and I assessed the deception-detection abilities of 52 pairs of friends when they had known each other for just one month, and then again about five months later. (The study is here.) When we just compared the deception detection accuracy of all 52 pairs the second time around to their accuracy when they only knew each other for a month, it looked like nothing happened. They got no better or worse over time.
As friendships progress, some of them deepen and others - well, they don't. We thought that might matter. So we looked separately at the pairs of friends who had become closer after five months, and those who had become less close. Now things started to happen. The friends who were becoming closer were also becoming better at separating each other's lies from their truths. Not so for the friends who were growing apart. They just became more distrusting overall. They became more inclined to believe that their friend was lying, even when that person was telling the truth.
The theme of today's "hot topic" is "friendships are complicated, too," so now let me introduce an intriguing complication. Does a friend's insightfulness depend on what it is that the other person is trying to hide?
It does indeed. In another study (also here), Weylin Sternglanz and I videotaped people as they honestly described experiences that had made them feel happy or sad or angry. They also described other experiences that made them feel happy or sad or angry, but they tried to conceal their true feelings rather than express them clearly. Close friends, less close friends, and strangers watched the tapes and tried to figure out how the people on the tapes really did feel.
When no one was trying to hide anything, the friends were always better than the strangers at knowing how the people on the tape really did feel. The closer friends were better than the strangers, and the less close friends were better, too.
If you want to test your psychological intuition, take a guess about the relative accuracy of the close friends, the less close friends, and the strangers when the people on the tape were trying to conceal negative feelings (sadness or anger). When you've told yourself your answer, then continue reading.
The people who did the worst at discerning how the people on the tape were feeling when they were trying to hide their sadness or their anger were the close friends. The close friends were even a shade worse at the task than the complete strangers. The people who did really well were the less close friends.
It will take additional research to nail down a definitive explanation for these results, so I'll just mention a few of the possibilities that Sternglanz and I considered. What if the feelings of sadness or anger had something to do with the friend? It might be more threatening to a closer friend than to a less close friend to realize that a friend is mad at you or disappointed with you. So if you are that closer friend, maybe you just don't see that negativity.
Or maybe closer friends are more inclined to allow one another a zone of privacy - maybe they can tell when the other person doesn't want to talk about something, and they leave it alone. Or maybe closer friends, if they recognized the anger or sadness, would feel more responsible for doing something about it than less close friends. If they don't want to do what it would take to deal with their friend's distress, then maybe the easy answer is not to recognize the distress. (That doesn't fit the ideal of the close friend, and it is not my preferred interpretation, but it is a possibility.)
The bottom line is that it is complicated with friends, as it is with lovers. Your special closeness and added experiences offer the potential to make you more insightful. That's just a potential, though. If you might not like what you see, maybe you just won't see it. There may come a time when denial is no longer an option. It is then that you may realize that, at some level, you knew it all along.