One is confirmation bias:
“the tendency to search for, interpret, favor, and recall information in a way that confirms one's preexisting beliefs or hypotheses.”
Watch a recent YouTube video shown above, with a tall geyser that confirms (based on our seeing Hollywood movies) - what should happen when a vehicle hits and breaks a fire hydrant just above sidewalk level. The video was made in Manhattan Beach, California.
But that’s just what happens with a wet barrel hydrant – a type used in Hollywood and other very warm places. It isn’t what happens in colder parts of the U.S. though where dry barrel hydrants are used. There usually will not be any geyer. Another YouTube video shows how dry barrel hydrants are made. The valve mechanism actually is located underground below the frost line. When the hydrant is hit above ground, the long rod which operates that mechanism just detaches.
Now that I’ve mentioned fire hydrants, you will start seeing them, and have another bias – the frequency illusion:
“The illusion in which a word, a name, or other thing that has recently come to one’s attention suddenly seems to appear with improbable frequency shortly afterwards.”
If you live in a city or town, then fire hydrants really are all around you. But you probably were not paying any attention to them. There are Clow brand hydrants at both ends of the block my house is on. Within walking distance in other housing developments there also are Mueller and Waterous brands.
Over two decades ago I looked at a “traffic hydrant” which was designed so the ground level flange connection would break away rather than the hydrant body. That design used four necked down bolts which unfortunately corroded severely from road salt. When the hydrant valve was opened one day, the bolts failed and the body flew upward like a rocket. On January 25, 2015 I blogged about A simple prop made from PVC water pipe fittings.
This post was inspired by the May 23, 2018 Saturday Morning Breakfast Cereal comic strip about the frequency illusion.