One of my pet peeves in books (and other media) is dumb characters. I like smart people. I know that writing smart people is a challenge because it’s harder to get them in trouble or to keep their plans from working the first time. Unless you’re really good at finding motivations for smart people to do dumb things or unless you create really difficult circumstances, if your characters are smart, you get the world’s shortest story. If the characters in your horror story don’t go alone into the dark basement, the story never goes anywhere.
But it’s incredibly painful to read a story that relies upon the characters being too stupid to live to have a plot. I recently read one that shall remain nameless in which the heroine piled stupid thing on top of stupid thing. There was one toward the end that was a gray area, an action I’d put in the category of “stupid good,” where it might have been considered the right thing to do, but it also put a lot of other people in danger and could have ruined things for a lot of people, all to help people who wanted to harm the main characters. I might have been more forgiving of that one if the heroine hadn’t already betrayed all the people who had helped her. She thought she was doing the right thing then, too (though it was mostly to benefit herself), but the person she betrayed them to was practically twirling his mustache, he was so obviously evil, and he even expressed opinions that made it clear he meant harm, and meanwhile she had made zero effort to find out what was really going on with the people who were helping her before she spilled it all to Snidely Whiplash — only to find out about thirty seconds later that she was entirely wrong about everything. And this was after she’d been foolishly naive and careless near the beginning of the story in a way that led to her being in a predicament. This chick was just careening through life, causing chaos every step of the way, but the author wrote her as though she was super intelligent and careful, and the character who criticized her rashness was later said to be wrong and made to apologize.
And then the next book I picked up had another idiot character. It’s got a romantic triangle, where the heroine is horribly torn between the guy who just ditched his long-term girlfriend, has confessed that he cheated on her, has admitted he’s just looking to fool around now rather than get into a real relationship, and is flirting heavily with the heroine’s friend, who has a boyfriend, and the guy who has helped her out of a number of predicaments, actually listens to her and pays attention to what she wants, and lives in the place she wants to open a business. Not that she’s obligated to be into a guy who’s nice to her, but she is into him. She’s just torn because she got a crush on guy #1 years ago and decided then that she wanted him when he was free, and now he is, so she feels obligated to go for him, even though she knows he’s bad news and she really likes guy #2 better. That’s definitely Too Stupid To Live territory. You’re allowed to change your mind, especially when it’s just a promise you made to yourself (that’s another pet peeve of mine: the plot that revolves around a character doing something they know is a bad idea that they don’t even really want to do because they promised themselves years ago that they’d do it).
There’s a really fine line between letting your characters make mistakes and making them be stupid. Smart people can do dumb things, but you’ve got to motivate it. I tend to write stubborn characters (gee, I have no idea what I might be drawing upon there), since smart people often have a tendency to feel like they can figure things out for themselves and go it alone, and that can get them in trouble when they overestimate their abilities and hate to admit when they don’t know something. There’s also perfectionism, which might lead to waiting too long to act if they’re waiting until everything is perfect. You can also come up with emotional blind spots, where they’re bright about everything except that one thing that’s their weakness.
In the book I’m working on, I’m trying to make the heroine fallible, and it helps that she may be smart, but she’s entirely lacking in information because she’s essentially a foreigner in an unfamiliar culture she knows nothing about, and based on that lack of knowledge she misjudges a lot of people and situations. She rushed into something based on ideals and assumptions and realized she was in way over her head. There are things she misses because that sort of thing isn’t at all important to her, and she doesn’t realize that those things are very important where she is. Since the whole book is from her point of view, the reader is seeing her perspective but may get the sense that she’s misjudging things. I hope that works to build a little dread while still making it clear why she sees things the way she does.