I have a friend who, when you're at the movies and something funny happens on screen, laughs and then looks at you to see if you're laughing. Which is one of those things that, once noticed, cannot be unnoticed.
You'll be sitting in a dark cinema, and something funny will happen on screen, and as you're laughing you'll be aware of his head turning, and his eyes training themselves on to you. It's unnerving. And it's also why I haven't seen a movie with this particular friend since 1998.
I also have a friend - I think we've all got one of these - who kind of taps you on the arm when he talks. It's a version of saying, "Hey, hey, listen to me", even if it's obvious that you are listening to him.
Conversations with this friend go something like this: "So I was trying to use miles to get an upgrade and" - tap tap - "I didn't have enough miles so" - tap tap - "I went up to the lady at the gate and I" - tap tap - "asked her if there was any room in business and she said" - tap tap - "that there wasn't."
Again, one of those things that you don't notice until suddenly you do. After which, it's impossible to do anything but silently count up the taps and become more and more irritated until you lash out suddenly and inappropriately at your now-baffled friend.
The tapper and the laugh-checker are doing personal audience management, and it's really no different, in a micro sense, from doing a focus group for a movie.
When a person taps your arm or checks your reaction, they're just doing a personal, individual kind of customer survey, as is done on certain websites. The only difference is you can't just click away from your friend who taps you.
I spend a lot of time when I'm shooting a television show watching the audience, which, if they noticed it, I'm sure would irritate them. And every filmmaker in the world uses whatever he or she can from the bag of tricks - explosions, music, camera angles - to tap the audience on the arm and say: "You with me? You're following this? You awake?"
Aspiring screenwriters spend a lot of time and money learning about - and fretting over - the time-tested structure of a film story.
Go to any bookstore in Hollywood and check out the screenwriting section and it's chock-a-block full of books promising to teach the foolproof structure for a hit movie or television show.
The pages are a blizzard of buzz- words: inciting incidents and rising action and plot-point pivots and act-two reversals, so many that it's tempting to think that this really is the solution, that there really is the simple formula to success.
Aspiring screenwriters are duped into believing that if they just figure out a story that hits all of those basic plot structure moments, their work is basically done. All that remains is collecting the giant cheque.
Maybe that's true. I don't know. I've been a screenwriter for more than 20 years, and the only thing I know for sure is we're all different. Sometimes at the movies my friend laughs and looks at me and I'm not laughing. Sometimes, no matter how often I get tapped on the arm, I mentally drift away while my friend is telling me the compelling story of his almost-upgrade.
Keeping someone's attention - which isn't just important to screenwriters, it's crucial for job-seekers, parents, teachers, and lawyers - is a complicated and often intuitive challenge. There aren't any shortcuts.
The only rule I really know, the only absolutely ironclad law you must follow is don't be boring.
When I stare up at the audience during a television show taping, what I tell myself I'm doing is paying attention to the laughs. But what I'm really doing is desperately trying to reassure myself that everyone up there is listening and engaged.
I can use whatever trick I know to delude myself that I can manage the audience, but I can't. I can only bore them or keep them interested.
Which is just one more way that what we worry about in show business, with our audience, and what we worry about in real life, with our loved ones, are exactly the same things.
The tricks we use in show business are often the same ones we use, judiciously, in our daily lives, to ask: "Hello? Are you listening to me? Do I have your complete attention?" And all we can hope, really, is that they love us enough to pretend that the answer is "Yes."
Rob Long is a writer and producer based in Hollywood. On Twitter: @rbcl