Quick Answer: In the early 1980s, the MPAA ratings were G, PG, R and X. The PG-13 rating came about in response to parents’ outrage over movies like Indiana Jones and the Temple of Doom (1984) and Gremlins (1984), which were misleadlingly marketed as tame, kid-friendly entertainment. Steven Spielberg, director of Temple of Doom, claimed in 2004 that “I created the problem, and I also supplied the solution… I invented the [PG-13] rating.” Spielberg also likened the PG-13 rating to putting “hot sauce” on a movie to entice teenage audiences. In recent decades, PG-13 has become the target for studio blockbusters that aim to reach wide audiences and earn high box office returns.

A quick glance at the list of highest-grossing films in recent years reveals well-known titles like The Hunger Games: Catching Fire (2013), The Avengers (2012) series, Harry Potter and the Deathly Hallows - Part 2 (2011), The Dark Knight (2008) and, of course, Avatar (2009). If you pay attention to the beginnings of movie trailers, you probably know each of these flicks is rated PG-13 in the Motion Picture Association of America (MPAA) rating system. In fact, eight of the 10 highest-grossing films of the last 10 years were all rated PG-13. It seems clear that this particular mix of consonants and odd numbers is a studio’s golden ticket to box office success.

But how did the PG-13 rating come about? It didn’t have anything to do with superheroes or teen-friendly action movies. It had more to do with Steven Spielberg and a weird combination of still-beating hearts and exploding monsters. The PG-13’s origin story began in 1984 when Steven Spielberg’s Indiana Jones and The Temple of Doom (1984) hit the big screens. Parents brought their kids to theaters hoping for wholesome family entertainment. After all, the Indiana Jones prequel was billed as “suitable for kids” and “a triumph of escapist entertainment for all ages.”

Most importantly, the film was rated PG. In the early 80s, there were only four ratings in existence: G, PG, R and X. Parents assumed PG meant a movie was appropriate for children, but, unfortunately for a generation of traumatized kiddos, that wasn’t always the case. Since there was no middle ground between PG and R, the MPAA often had a hard time deciding which rating an edgy film might earn. And some of their decisions were, well, questionable.

Take Poltergeist (1982), a PG film co-written and produced by Steven Spielberg in which a guy tears off his own face. Despite that grisly scene, parents still trusted Spielberg enough to drop their kids off at Temple of Doom. Little did they know, their kids were in for nearly two hours of monkey brain buffets, child beatings and people falling into rock crushers, not to mention the infamous sacrifice scene wherein an evil sorcerer reaches into a guy’s chest, pulls out his beating heart and lowers the screaming victim into a lava pit.

Parents were not pleased. Reviews were mixed, with many commenting on the movie’s non-stop thrills which felt somehow empty and unsatisfying. (Variety called the film a “letdown” that used endless action “to exhausting a numbing effect.” The New York Times called it “exuberantly tasteless” and “endearingly disgusting.”) The heart scene was especially disturbing to young audiences, leading to complaints and demands that the MPAA get stricter about doling out the PG label.

Even so, the MPAA didn’t move fast enough to do anything about Gremlins (1984), released two weeks later. Directed by Joe Dante and — once again — produced by Spielberg, this horror-comedy was promoted like an E.T. (1982) clone, with heavy emphasis on the adorable Gizmo and not so much attention on the nasty gremlins. According to Dante, people thought they were taking their kids to see “a cuddly, funny animal movie.” It’s pretty understandable some adults got upset, especially when Billy Peltzer’s mom (Frances Lee McCain) dispatches a bunch of monsters with a food processor and a microwave.

Audiences had finally had enough. Parents complained to theaters and the MPAA, demanding somebody fix this cinematic situation. And who should save the day but Steven Spielberg? “I created the problem, and I also supplied the solution… I invented the rating,” Spielberg told the Associated Press in 2004. The man behind Poltergeist, Temple of Doom, and Gremlins decided it was time for a new rating, something to live in the netherworld between PG and R. According to Today, Spielberg contacted Jack Valenti, the head of the MPAA, and suggested they create either a PG-13 or a PG-14 rating.

Valenti conferred with the various guilds, studio heads, the National Association of Theater Owners and several religious organizations before finally settling on PG-13, choosing 13 as an age, according to AP, “when most kids knew the difference between fantasy and reality, and had more independence from their parent.” Thanks to the new rating, young kids were kept out of films that were too scary or too bloody, unless their parents tagged along. The first film released with a PG-13 rating was Red Dawn (1984), which was quickly followed by movies like Dune (1984), The Flamingo Kid (1984), and Johnny Dangerously (1984).

Whether PG-13 made cinema a safer place or has corrupted the art of moviemaking is a subject up for debate. Despite offering some warning to parents, the idea of PG-13 represents a strong attraction to young viewers. As Today wrote in 2004, “instead of being solely an extra warning to parents, as it was originally conceived, it has evolved into the preferred rating of studios and filmmakers. As Steven Spielberg told The Associated Press recently, PG-13 puts ‘hot sauce’ on a movie in the viewer’s mind.” In recent years, the mainstream allure of PG-13 is so strong that no movie in another ratings category can hope to equal the big bucks attainable by a PG-13 studio flick.

While the early PG-13 movies were considered rough and raw (at the time, Red Dawn was hailed as “the most violent movie ever made,” averaging 134 violent acts per hour, or 2.23 per minute. Adam Arseneau of DVD Verdict wrote that it “often feels like a Republican wet dream manifested into a surrealistic Orwellian nightmare”), over time the average PG-13 movie has become more violent. A 2013 study reported that PG-13 movies were even more violent than R-rated movies of the 1980s. Meanwhile, in today’s movies, sex and language are more strictly controlled by the MPAA, with even limited amounts of either often leading to R ratings, while early PG-13 movies were allowed more profanity and nudity.

Today’s box office statistics underline the reality that the majority of PG-13 movies today are geared toward the lowest common denominator, designed above all to attract wide audiences. This video by GoodBadFlicks points out that quite a few films that would work better as R-rated movies — Alien vs. Predator (2004), The Expendables 3 (2014), and Terminator Salvation (2009) — were toned down to earn a PG-13, for the explicit purpose of attracting teenagers and earning more money.

While Star Wars (1977) and Jaws (1975) might’ve created the summer blockbuster, Temple of Doom and Gremlins created a world where lucrative tent-pole movies can thrive, for better or for worse.