Grist readers are familiar with the work of social psychologist Robert Cialdini (I’ve written about his work here and here and interviewed him here). He gave the opening keynote at the Behavior, Energy, and Climate Change Conference, and as usual, he was a veritable font of amusing and intriguing case studies.

Hotel towel signThe uninspiring message from my hotel.Photo: Dan McKayOne of his favorites — which I’ve mentioned before a few times — is about hotel towels. Specifically, it’s about those little signs encouraging hotel guests to hang their towels up rather than throwing them on the floor to be laundered.

Cialdini and his students have run several experiments with these signs. What they’ve discovered, unsurprisingly, is that the typical environmental appeal yields a fairly low level of compliance. What works a little better is a sign that plays on the principle of reciprocity: We the hotel have donated to an environmental organization in your name; will you help by hanging your towel?

Even better is a message that plays on “social evidence,” more colloquially known as peer pressure. The best performer is something like this: “75 percent of people who have stayed in this room hung their towels up to save water. Will you do the same?” That bumps compliance up by something like 20-30 percent from the baseline environmental message.

This experiment is as close to famous as a social science experiment can be; I’ve seen it referenced in close to a dozen popular sources. So after I heard it from Cialdini yet again, I thought, hey, I wonder what the sign in my hotel says?

Here it is:

SAVE OUR PLANET

Dear Guest,

Every day millions of gallons of water are used to wash towels that have only been used once.

YOU MAKE THE CHOICE

A towel on the rack means “I will use again.”
A towel on the floor means “Please replace.”

Thank you for helping us conserve the Earth’s vital resources.

I don’t think I’ve ever seen one of these signs use Cialdini’s more effective messaging. Basically hotels are leaving 20 percent water savings (for free!) on the table, all because they don’t bother to familiarize themselves with the most rudimentary social psychology relevant to their communications with their customers. Multiply that ignorance and neglect across a thousand other institutions across the country and you start to see both the potential and the challenge for behavior change as an energy strategy.

How about you? Ever seen a hotel towel sign about anything but SAVING OUR PLANET?