At a museum’s busy entrance, visitors passed through a low-sensitivity metal detector. The device had bright blue lights, and it flanked the left and right side of a wide passage.

A uniformed guard, over and over, shouted the phrase, “If I don’t stop you, keep walking. If I don’t stop you, keep walking!”

The guard was clearly annoyed that people kept stopping in front of the metal detector, awaiting instructions and causing backups.

Unfortunately, most people have been conditioned to wait. At places where security is tight, metal detectors are single-use only. You wait your turn. You wait until the agent beckons you. If you walk through too early, you’re scolded and told to wait.

The museum guard was fighting years of conditioning.

Since the system wasn’t intended to prompt visitors to pause, a better design would have blended the detection elements with the architecture or kept them hidden.

People naturally do what they’ve learned to do. Good design encourages the appropriate behavior.