One person may think, for example, that by offering help to a colleague, she is coming across as generous. But her colleague may interpret her offer as a lack of faith in his abilities. Just as he misunderstands her, she misunderstands him: She offered him help because she thought he was overworked and stressed. He has, after all, been showing up early to work and going home late every day. But that’s not why he’s keeping strange hours; he just works best when the office is less crowded.

These kinds of misunderstandings lead to conflict and resentment not just at work, but at home too. How many fights between couples have started with one person misinterpreting what another says and does? He stares at his plate at dinner while she’s telling a story and she assumes he doesn’t care about what she’s saying, when really he is admiring the beautiful meal she made. She goes to bed early rather than watching their favorite television show together like they usually do, and he assumes she’s not interested in spending time with him, when really she’s just exhausted after a tough day at work.

Most of the time, Halvorson says, people don’t realize they are not coming across the way they think they are. “If I ask you,” Halvorson told me, “about how you see yourself—what traits you would say describe you—and I ask someone who knows you well to list your traits, the correlation between what you say and what your friend says will be somewhere between 0.2 and 0.5. There’s a big gap between how other people see us and how we see ourselves.”

This gap arises, as Halvorson explains in her book, from some quirks of human psychology. First, most people suffer from what psychologists call “the transparency illusion”—the belief that what they feel, desire, and intend is crystal clear to others, even though they have done very little to communicate clearly what is going on inside their minds.

Because the perceived assume they are transparent, they might not spend the time or effort to be as clear and forthcoming about their intentions or emotional states as they could be, giving the perceiver very little information with which to make an accurate judgment.

“Chances are,” Halvorson writes, “how you look when you are slightly frustrated isn’t all that different from how you look when you are a little concerned, confused, disappointed, or nervous. Your ‘I’m kind of hurt by what you just said’ face probably looks an awful lot like your ‘I’m not at all hurt by what you just said’ face. And the majority of times that you’ve said to yourself, ‘I made my intentions clear,’ or ‘He knows what I meant,’ you didn’t and he doesn’t.”

The perceiver, meanwhile, is dealing with two powerful psychological forces that are warping his ability to read others accurately. First, according to a large body of psychological research, individuals are what psychologists call “cognitive misers.” That is, people are lazy thinkers.