We've had something of a dearth of memorable public-service announcements in recent years here in America. When was the last time something stuck with you or became part of our cultural memory like "This is your brain on drugs"? But in the UK, they try really hard to shock the hell out of you with PSAs, perhaps because they sometimes don't seem to get the difference between "memorable" and "effective." Take a look at this, which made the rounds yesterday. I'll talk in a moment about whether stuff like this actually works, but before you watch it, a warning: although it has only a bit of gore, you probably don't want to be raising a mug of hot coffee to your lips as it plays:
Clever, in that "We paid an elite ad agency half a million pounds to come up with this" kind of way. But it's far from the most horrifying PSA about automotive safety; for that, I'd nominate this Welsh PSA from a few years ago trying to discourage people from texting while driving, which vividly portrays not only the accident itself but the aftermath, even including the apparent death of a baby:
Now that is truly awful. But to get back to the first PSA, the message there is basically, "Boo!" Why they thought that would actually discourage people from getting behind the wheel after a few drinks is unclear. The anti-drunk-driving campaign of the 1980s was successful in large part because it joined the message about the dangers of drunk driving with a way people could avoid it, by introducing the concept of the designated driver, which ended up becoming a cultural norm. And this, it turns out, is central to the success of public health communication campaigns on topics like this one. Research has shown (here's a meta-analysis on this topic if you want to read more) that fear is actually quite useful, the more the better. But the message also needs to increase people's sense of efficacy, so that they have a way to resolve the fear through their actions. There are actually two kinds of efficacy that matter: self-efficacy, which is whether you believe you can successfully do whatever is being recommended ("Will I remember to bring a condom?") and response efficacy, which is whether you believe the recommended action is going to work ("Do condoms prevent transmission of HIV?").
If you succeed in making people afraid of something, like catching a terrible disease, they'll look for a way to handle the threat. But if you don't give them something they can do to alleviate the threat itself, they'll deal just with the fear they're feeling, by denying that they're vulnerable ("That'll never happen to me") or just trying not to think about it.
To return to that drunk driving ad, not only doesn't it suggest a way out, it's not even making you afraid—shock and fear are not the same thing, and once the shock wears off, it's gone. Obviously, every behavior you're trying to change is a little different, and some are easier to handle than others. Quitting smoking is very hard, while putting down your phone while you're behind the wheel is easy. But the British, it seems, are particularly enamored of PSAs that reach out from the screen and smack you across the face (here's a little round-up from BoingBoing). That doesn't mean they'll work, though.