There's a key scene at the beginning of this month's lacklustre superhero sequel Kick-Ass 2 in which Hit-Girl, the film's deadly teenage heroine, protests against a household swear jar recently installed by her legal guardian. It's a knowing callback to the first Kick-Ass, in which the same character – then just 11 years old – famously addressed a gang of villainous henchmen with a word borrowed from the vocabularies of Derek and Clive. With that in mind, the remainder of KA2 plays out as a tedious slog towards the inevitable reprise, which dutifully arrives in the film's final moments. Because we all know it ain't over til the little girl says "cunt".

Train Pulling Into A Station.

Ever since cinemagoers declared themselves too sophisticated for the simple thrills of Train Pulling Into A Station, filmmakers have sought out more and more extreme methods of shocking their audiences.

1939: Censors bend the rules and allow a single use of the word “damn” in Gone With The Wind – unprecedented in American cinema history. Photograph: Allstar/MGM/Sportsphoto Ltd./Allstar

The Cult director Tod Browning challenged taboo when he cast actors with actual physical deformities in his 1932 horror classic Freaks, much to the consternation of backers MGM. Test screenings were riotous: one audience member claimed the spectacle had caused her to miscarry, and sued the studio for damages.

1955: Naturist “documentary” The Garden Of Eden brings full-frontal nudity to British cinemas, under the pretext of offering educational value.

With the collapse of Hollywood's draconian Hays censorship code in 1968, the path was cleared for a wave of increasingly frank films throughout the 70s.

1971: The dreaded C-word gets its first ever big-screen airing, courtesy of noted obscenity connoisseur Jack Nicholson in Mike Nichols’ Carnal Knowledge. Photograph: Allstar/Cinetext/AVCO EMBASSY

Audiences eager for extreme violence could see The Last House On The Left; those in search of graphic sex could see Last Tango In Paris; and those of the Mary Whitehouse persuasion could see society going to hell in a handcart.

1972: John Waters’ Pink Flamingos traumatises audiences with coprophagia, crushed chickens and a “singing” anus miming the words to Surfin’ Bird. Photograph: REX/Everett Collection

Today, with the internet threatening to outpace Hollywood in the shock video stakes, movie makers have been growing more imaginative. Srdjan Spasojevic's infamous 2010 torture-porn effort A Serbian Film packed so many memory-searing horrors into its two-hour runtime that its plot synopsis read more like Vlad The Impaler's rap sheet.

2005: The Aristocrats, a documentary about the “dirtiest joke ever told”, becomes the first film to be rated 18 for swearing alone. Photograph: REX/c.ThinkFilm/Everett

But shock tactics aren't solely the preserve of horror directors and arthouse provocateurs any more – now they're frequently being employed to drum up interest in otherwise conventional studio blockbusters. Few were expecting the montage of debauchery that played out over the end credits of mainstream comedy The Hangover a couple of years ago, but by the time the threequel hit cinemas this summer, the graphic giraffe decapitation scene that opened the film barely raised an eyebrow.

“The showing of The Devils, Straw Dogs, Clockwork Orange, Oh! Calcutta and now Last Tango In Paris all produce a sense of outrage in people who know that life has more to offer than violence, promiscuous sex, drugs and pornography” - Mary Whitehouse, 1971. Photograph: Photoshot/Hulton Archive

It's easy to see how the ubiquity of such shock tactics ends up rendering them ineffective, especially in the age of the advance teaser trailer. I haven't seen the new Jennifer Aniston comedy We're The Millers yet, but I have been inundated with enough TV spots, YouTube pre-rolls and red-band trailers to know that the film's major set piece involves a tarantula bite to the scrotum. Once the actual movie comes around, the big surprise might be how little of a shock it actually holds.