Testing the queue signs

An original contemporary non-fiction-style account.

At the school fair we set up two queues for tickets, one for cash and one for card payments. The signs were hung above the tables, but parents joined whichever line seemed shorter. From the back of either queue, the words were hidden by the open gazebo flap. When we moved the signs onto poles beside the waiting area, people chose the correct line before reaching the desks. We had originally placed the instructions where they were easiest for us to see.

Explain why parents initially joined the wrong ticket queue.