I finished a book by Joe Navarro where he points out which nonverbal gestures may be related to negative emotions and which are generally related to positive ones.

I found it fascinating but I doubt the validity and applicability of such information. The author is a former FBI agent and the book was coauthored by a psychologist. It often cites individual studies to back up the information, but I know that doesn't necessarily amount to much without knowledge of the studies' methodologies and possible biases. I prefer extensive meta-analyses with adequate vetting standards, Cochrane style. The book has a lot of anecdotes from Navarro's career that relate to the various gestures.

Now, the book does make clear some things to keep in mind before reading into someone and jumping into conclusions as to what they may be feeling. Individual gestures can mean one thing or another, but they can also bear absolutely no relevance to a person's emotional responses. First you need to establish what the author calls a "baseline" for a specific person, so basically how that person habitually communicates with the body. Then you look for changes to that baseline that may indicate emotional responses to stimuli. These changes in body language should be noted in clusters, so you don't just pick out isolated gestures that may really mean anything: maybe they're crossing their arms not because they got defensive but because they're feeling cold, maybe they're scratching their face not to pacify against stress but simply because of an itch, or maybe they placed their handbag in between you and themselves not as a blocking behavior against you but because that was the most convenient place to put the bag. You get the idea. It's easy to feel too confident in your ability to read someone and then make inaccurate judgements because certain things happen to fit your narrative about what's going on in another person's head. That's a whole pitfall of cognitive biases that someone reading a book like this may easily fall into.

Another thing is that people are wired to interpret body language anyway, and trusting your gut feeling in interactions with others may be more accurate than any conscious effort to read people. Unless you're autistic I guess.

I'm under no illusion that I can now read people's minds. Rather, my biggest takeaway from the book is to make sure my body language is congruent with my thoughts and feelings. I mean, throughout my life I've had a bit of trouble communicating whether I'm comfortable, interested, having fun, etc. If I'm at a party and I'm having a good time, or I'm talking to someone and agree with what they're saying, I want them to know I feel that way in that situation. The book has made me aware of a bunch of the mixed messages I've been sending out, sometimes giving people the impression that I'd rather be somewhere else when in fact that wasn't true at all. Since reading the book I've been more open with my body and face, and more congruent with my verbal and nonverbal expression. This has made me feel more comfortable in social settings.

There are other books like this by "body language experts" as well. My main concern is whether it's all BS, a pseudoscience peddled by conmen to sell books and whatnot. From all my googling I've only managed to discover that reading into so called microexpressions (a topic focused on by the likes of Paul Ekman) is unproven and not backed by scientific research, and that people, even so called experts, who think they're good at detecting lies through reading body language are actually no better at it than anyone taking a wild guess. I thought Navarro's book did a pretty good job of avoiding wild claims, but I wonder if any of it is actually applicable at all.

I listened to an audio version of a similar book, by a different FBI agent (Jack Schafer), but with the same psychologist co-author. Same conclusion: there are plenty of ways you could be sending off the wrong signals and not realizing it. This seems neither controversial nor revolutionary to me.

If you really care what people think about you when they look at you, probably the only way to get better is to do what actors do, and practice in front of a mirror.

Truth. I'm naturally inexpressive and unexcitable. I've spent hours practicing simple things like smiling and making pleasant faces so people aren't put off by my uninterested or even angry appearance (see: resting ***** face). It's especially important when dealing with customers/clients.