In college, I dated a guy who had a fish tank full of piranhas. It was so cool! He would go get a bunch of feeder fish and dump those poor little guys in the tank full of piranhas.
One time, I watched. I will never forget it.
The piranha didn't do anything at first. They just swam to the middle of the tank and let the goldfish swim around them.
Piranha, "Hey, guys, we won't hurt you, we are your friends."
Goldfish, "Do ta do ta do, I am swimming, I am swimming, do de do la la."
After the stupid goldfish were completely used to the piranha, sensed no harm and were completely comfortable, one of the piranha opened its mouth.
It just opened its mouth, that's it. It didn't move or anything.
A goldfish swam right in.
Chomp! The piranha bit it almost in half. The startled goldfish quickly swam away. Yes, it swam away, almost chomped in half. The back half was hanging on by a thread.
The piranha didn't move. It just closed its mouth again and stayed right there in the middle of the goldfish.
Goldfish, "Whew!" Then a few seconds later, "Do te do, la, la la, swimming."
The piranha opened its mouth again. Having learned nothing at all, that goldfish swam right into its mouth again.
The piranha didn't let the goldfish swim away again a second time.
Will the goldfish ever learn?