The effectiveness of contingency-specific and contingency-nonspecific prompts in controlling bathroom graffiti.

The team taped a small sign inside public bathroom stalls.

The sign asked people not to write on the walls.

They counted new marks each day, took the sign away, then put it back again.

When the sign was up, graffiti almost stopped.

When the sign came down, scribbles came right back.

The sign acted like a switch for clean walls.

Dunlap et al. (1991) saw the same on-off effect with parking. Their sign warned, “concerned citizens are watching,” and illegal parking dropped by half.

Hsieh et al. (2014) kept the effect for months. A simple sign in a hospital kitchen kept dishes put away four months later.

All three studies show a posted prompt can control adult behavior in the real world, even without rewards or penalties.

You can stop problem behavior before it starts. Tape a short, polite sign near the spot where the behavior happens. Watch for a week, then remove it. If the problem returns, put the sign back. You just ran an ABAB probe with zero training time and no tokens.