Although Psycho (1960) is likely the first film that comes to mind when one hears the name Alfred Hitchcock, it was actually the director's fiftieth.
Shot in less than three months with a tight budget and the less-than-prestige crew of Hitchcock's television series Alfred Hitchcock Presents, Psycho was nevertheless his most successful film at the box office: an innovative promotional campaign (requiring theaters not to allow patrons to enter after the show started, keeping the film's stars out of the public spotlight for fear they might let a spoiler slip) and shocking subject matter were key factors that brought about record attendance for the film's New York premiere and led to lines around the block as the release expanded.
Adapted from Robert Bloch's 1959 novel of the same name, Psycho starts out as the story of a young woman, Marion Crane (Janet Leigh) who steals $40,000 from her employer, hoping to pay off her boyfriend's debts so the pair can marry. This relatively uncomplicated dramatic thread breaks at the end of the film's first act as she stops at an out-of-the-way roadside motel and is murdered by its deranged proprietor, Norman Bates (Anthony Perkins), in perhaps the most famous death scene in all of film history. Hitchcock's attention then turns from horror to mystery as Marion's sister and boyfriend team up to solve her disappearance.
Certainly, not the first nor the last film to run afoul of Hollywood's self-censorship apparatus in its myriad forms (the Hays Code, the MPAA, etc.), Psycho rang in a new era of moral transgression in mainstream American film, paving the way for increasingly explicit depictions of sexuality and violence throughout the decade and beyond. With this in mind, it is no surprise that the film is often cited by critics as the prototype of the "slasher" subgenre of horror film, which includes franchises like Halloween, Friday the 13th, and Nightmare on Elm Street. Digging a few decades farther back into the history of film, however, leads us to what could more rightly be called the "grandfather" of slasher flicks: Robert Wiene's silent masterpiece The Cabinet of Dr. Caligari (1920). A prime example of the Expressionist movement in German cinema during the interwar years, the film served as the origin of much of the aesthetic still seen in horror films to this day.
Hitchcock himself was no stranger to Expressionism: his early work, especially films like The Lodger: A Story of the London Fog (1927), shows a clear influence in terms of both form and content from Caligari and those that followed; nearly 35 years later, Psycho is no exception. While shooting in black-and-white for Psycho was mainly a budgetary decision after he had been making color films for over a decade (beginning with 1948's Rope), Hitchcock utilized the medium to such great effect that it's difficult to even imagine Psycho in color. The constant interplay of bright light and dark shadow throughout the film serves to externalize the inner dichotomy of the characters - Norman Bates's internal version of his domineering mother, Marion Crane's moral turmoil - and recalls the hand-painted sets and unnatural lighting effects Wiene and his team had achieved on Caligari.
The camera placement and angles Hitchcock chooses too, often shooting at what is known as a "Dutch" angle, also common in German Expressionist film, where the camera is tilted such that it is not parallel with the horizon, serves to lend a sense of uneasiness and even dread to the picture as a whole; this again shows Caligari's influence as Wiene, restricted by the enormous weight and bulk of early film cameras, tilted the sets themselves instead of the camera. Doing so created an effect where buildings loomed over his characters to visualize their sense of dread of the killer.
Finally, while the film's treatment of mental illness will seem outdated and even problematic to us in 2021, its use of certain aesthetics to draw the audience into what could indelicately be called the "mind of a madman" synthesized Caligari's influence and contemporary trends in psychoanalytic theory into a portrayal that is more nuanced than might be expected from a 60-plus-year-old film. The psychiatrist's explanation of Norman's illness that comprises Psycho's final scene, perhaps a disappointingly blunt narrative instrument in a film that had previously left so much else to the viewer's imagination, echoes a similar twist at the end of Caligari - the narrator is revealed to be the inmate of an asylum, and the titular Doctor not an evil mastermind but his psychiatrist, who finally has understood the narrator's illness enough to cure him. In both films, and in dozens upon dozens of horror movies since, the true terror comes not from knife-wielding killers but from within ourselves and the fact that, as Norman Bates himself sums it up, "we all go a little mad sometimes".