A 2011 study from the UCSD psych department revealed that spoilers don’t really end up spoiling movies for you; in fact, knowing the twist ahead of time may actually cause you to enjoy the film more.
Essentially, some researchers assigned a number of books to two different groups of readers. One group was told the ending and the other gets to read the twists fresh. Across the board, those who had the book spoiled ahead of time actually rated it higher than those who were going in unaware.
Does this same principle apply to movies? Now You See It explores this question in detail in its latest video essay below.
For our purposes, the plot twist is defined as “a totally unexpected outcome to a story.” The funny thing here is, what we glean from this video is that a plot twist actually ends up working better when it’s not totally unexpected.
One of the most important principles of a good plot twist is that the “final payoff always matches the established logic” at the beginning of each story. The audience needs to be provided some information in the beginning so that by the time the payoff comes, it's satisfying because they’ll have been playing a game of trying to guess the twist during the entire time in between.
Hitchcock once said, "In order to get suspense you provide the audience with a certain amount of information and leave the rest of it to their own imagination."
"Psycho" Credit: Universal
It just seems like lazy writing when a twist does indeed come from completely out of nowhere. Sure, there is some shock value, but it is not earned and, as such, the feeling will only be fleeting. In the opinion of the essayist, “the best plot twist is the one that can create the biggest surprise without ruining the established logic.”
So to create a good plot twist, establish your story, give the audience some hints as to what could happen, and then come up with a story point that follows the rules of your narrative but is still completely unexpected. Or, to get stunningly academic, consider misdirection that adheres to your film’s verisimilitude.
Bringing things full circle back to the original UCSD study, you can test this theory on your own by looking at a film in terms of its rewatch value. A whole new form of entertainment shines through in a film with a good plot twist upon second watch, as you work to try and figure out all the hints the filmmaker has given you to lead you to discover the twist on your own.