What's the Latest Development?
In general, it seems, we're pathetically obedient to signs, lining up where we're told to, walking where we're told to walk, just because it's printed on a sign. Studies suggest 'invoking norms' is a very effective tactic: to get people to reuse hotel towels, tell them lots of other guests do so. And specificity matters: asking hikers to keep to the footpath to preserve particular trees is better than asking them to protect the forest, which, in turn, is better than 'save the planet. Most intriguing, though, are those studies that demonstrate how often signs have the opposite effect from that intended.
What's the Big Idea?
A problem with controlling people's behaviour that goes far beyond signage is that to persuade people not to do something, you first have to raise the issue, thereby increasing its salience in their minds. The same hazard blights personal efforts at habit change: go on a diet, and suddenly you're thinking about food all the time. (That's why the best way to eliminate bad habits is to replace them with specific new habits.) Sometimes the best solution to a problem is to forget you had one. Whereas a notice just reminds you to notice.