Mom followed up her "I learned about Joy when I was a kid" story with an "I learned about yeast in the ninth grade" story:
While at a friend's house (note a recurring theme here?) they decided to make some bread for her friend's family. Mom's friend had watched her mom make bread lots of times. They also decided that instead of making one batch, they should double it.
Her friend's mom came home to a table full of bread dough that needed to be taken care of.
Mom is careful with her yeast measurements now.