For every 500 smoking scenes a child saw in PG-13 movies, his or her likelihood of trying cigarettes increased by 49%.

CNN: Should smoking trigger an R rating?

Smoking in PG-13 films -- including background shots and other passing instances -- was just as strongly linked with real-world experimentation as the smoking in R-rated films.

CNN: Should smoking trigger an R rating?

It's an open secret that some naturally PG movies have an element or two thrown in to earn a PG-13, so teenagers aren't scared off.

WSJ: Roger Ebert on Movie Ratings

This could create incentives for game developers to PG-13-ify their releases in much the same way NC-17 ratings have placed a ceiling on the kind of content we can see at the theatre.

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In the study, the relative handful of smoking scenes in G- or PG-rated movies didn't appear to influence a child's likelihood of trying cigarettes.

CNN: Should smoking trigger an R rating?

As for the rest of the franchise, Indiana Jones and the Temple of Doom was never a great sequel (although the fourth film made it look brilliant), but it was revolutionary in opening up the PG-13 rating.

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"Dan in Real Life" is rated PG-13 and runs 98 minutes.

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Scenes of smoking have become increasingly rare in non-R-rated movies, according to the MPAA. Of the movies portraying smoking in recent years, 72% were rated R, 21% were rated PG-13, and 6% were rated PG.

CNN: Should smoking trigger an R rating?