Be forewarned: There are spoilers ahead. But this article won’t reveal anything about current or upcoming movies that you haven’t already learned from the films’ trailers. That’s right — in a season of leaked footage and plot details, the biggest revelations are found in studio-sanctioned marketing. And the reasons for that might surprise you.

Did you know that Rachel McAdams is shot and killed at the one-minute mark of Southpaw? In the movie’s trailer, that is. In actuality she departs about a third of the way through the movie, but that plot turn ordinarily would have been considered spoilery enough to avoid giving away, especially with an actress of McAdams’ caliber and her prominence on the movie’s poster. Even Southpaw’s own director thinks the spot could have handled it without being so heavy-fisted. “I was concerned about [the revelation], for sure,” Antoine Fuqua (The Equalizer) tells EW. “I still am. And I spoke my mind about it.”

Fuqua is just the latest director this summer-movie season to voice disappointment about the trailer for his own movie. But he also points to the underlying motivation behind such a strategy. “The audience sometimes, I guess, needs a little bit more [plot], especially for this type of movie,” he says. “So I had to roll with it. I trust them, [Southpaw‘s distributor] the Weinstein Company.” (Southpaw opened at the box office to a better-than-expected $16.5 million.)

And he’s right to trust them. According to experts in the trailer-making business, the more audiences know, the likelier they are to go. “There was a lot of discussion internally whether to show the death of the wife,” says Matt Brubaker, president of theatrical at Trailer Park, the agency that edited the preview for Southpaw. “But it was decided to show more of the good, so to speak. People have felt burned in the past. If someone’s going to pay $20 to go on opening weekend to see this movie, they want to know that they are making a pretty good investment.”

And that is borne out in the rigorous focus testing that studios perform. “As much as people complain that trailers give away too much,” says Brubaker, “nine times out of 10, the more of the plot you give away, the more interest you garner from the audiences. Audiences respond to the trailers with more of the movie.”

“We prefer to be mysterious,” says Dan Asma, co-owner of trailer company Buddha Jones. “That’s what good marketing is. But what can we do when testing and focus grouping consistently say that numbers spike when you give away more of the story.”

Trailer maestro Mark Woollen, who cut acclaimed spots for The Social Network and Boyhood and the recent preview for Alejandro G. Inarritu’s Birdman follow-up The Revenant, also confirms that audiences prefer spoilers but suggests that there are signs of a generational split. He mentions an as-yet-unreleased trailer for an upcoming movie and points to the two opinions that emerged after it was focus tested by the studio. “Older audiences seemed to want more plot,” he says, “and younger audiences were like, ‘Nah, it’s cool.’”

Over-sharing in trailers can split both ways. The sight of Chris Pratt motorcycling alongside velociraptors gave Jurassic World director Colin Trevorrow qualms when the trailer debuted in November. “In my opinion, [the studio has] shown far more of this movie than I would ever have wanted,” he said.

And then there’s Terminator Genisys. Its trailer spoiled the twist that rebel hero John Connor (Jason Clarke) is a villain, leading director Alan Taylor to remark about “unpleasant conversations” between him and the studio executives. The box office returns on those two films muddy the argument even further. Jurassic World‘s plot revelations piqued curiosity to a $208 million opening; Terminator Genysis made one tenth of that in its first weekend.

Audiences also are quick to grumble when trailers are misleading. In 2011, a woman felt so bamboozled by the previews for the Ryan Gosling art house flick Drive (in part, she was expecting The Fast & the Furious) that she sued the distributors. And 2013’s dark family drama August: Osage County (like Southpaw, distributed by The Weinstein Company) elicited plenty of groans from audiences who thought they were seeing a comedy.

“That trailer pushed the comic aspects of the movie,” says Bill Neil, longtime trailer editor at Buddha Jones. “But it was a viable way to make people see the movie, even if it’s not nearly as funny as the trailer. And hopefully once they’ve seen it, well, maybe it’s not as funny as the trailer but its still fulfilling in another kind of way.”

Adds Asma from Buddha Jones, “And even if they’re not satisfied, they’ve already put down their money and put their butts in the seats. And the studio’s going to be very happy with that.​”

Directors such as Fuqua, Trevorrow, and Taylor have little to no say in the matter of trailers. Marketing consultation is written into the contract of higher ranking directors such as Christopher Nolan, for example, who has final approval of all footage used in his films’ trailers. And what studio exec would argue against him having that leverage? The spots for Inception, The Dark Knight Rises, and Interstellar are all considered marvels of restraint and tease — and each film rocketed to huge numbers when it opened at the box office.

As with Nolan, director Guillermo del Toro is heavily involved in the marketing process, according to agency Buddha Jones, who cut the full-length trailer for his latest, Crimson Peak (out Oct. 16). But compared to Nolan, he is on the other side of the spoiler debate. “Let me warn you,” a smiling del Toro told the audience at Comic Con in July, “for those who don’t like spoilers, there are spoilers.”

And let us warn you too: Jessica Chastain’s dark-haired spinster is revealed to be the film’s antagonist, a fact not confirmed until the movie’s third act. The bloody knife she is swinging through elevator bars at the end of the trailer sure does its job. It slices right through our expectations — and hurts so good. ■

(Additional reporting by Jeff Labrecque)