Strange lights have been seen in that abandoned old house up the road. Local villagers have been disappearing, only to return a few hours later, tired and apparently unable to recall what has happened to them.
As the detective, what do you guess is the reason?
- Vampires are harvesting unsuspecting victims for blood?
- Aliens are abducting and experimenting on humans?
- An underground smuggling ring is taking the villagers' organs and selling them?
- It's an illegal brothel and the townsfolk are just too ashamed to admit it?
Well, chances are, it would all depend on the genre of story you were in.
While normally Genre Savviness is very much intended by the author, many works also exhibit an unintentional form of Genre Savvy — while characters might not necessarily think in terms of tropes, they will often be limited by the genre they inhabit. For example, characters in a science-fiction book will be quick to discard mundane or spiritual explanations for what they see, while characters in a detective novel will always disregard the possibility of suicide or accidental death.
Another term for this is "cover copy savvy" — the idea that the characters have already read the blurb on the back of the book or the DVD case and know what conventions apply to their universe. This term comes from the Slacktivist reviews of Left Behind, in which it's pointed out that no character in the books seriously considers the idea that the events of the series have any explanation other than a religious one.
This can sometimes overlap with the Anthropic Principle; many of the plots these characters are involved in wouldn't happen if they turned out to be wrong, after all.
This concept is subverted with Wrong Genre Savvy, where the character in question appears to have read the back cover of the wrong book.
It is averted at first in works that start realistically (such as the novels of Stephen King or the films of M. Night Shyamalan) where the characters act as though they're in Real Life, even after the appearance of zombies, aliens, ghosts, mad AIs, werewolves, wizards, miscellaneous Things Going Terribly Wrong, or other genre-defining speculative fictional things or events. (Truthfully, if you saw a bloodied man shuffling toward you, would you really find the nearest shotgun, or would you call an ambulance? Hopefully the latter unless he was really, really obviously zombified, because this is Real Life, which is by default Like Reality Unless Noted.)