A childhood belief about people

By the age of 4 or 5, I'd noted my parents were taller than my grandparents, and both were taller than my great-grandmother (whom I'd been told would soon die). I therefore concluded that people grew to a peak height at my parents' age, then progressively shrank thereafter. I assumed at the time that Great-Granny's 'death' would be a matter of her shrinking to nothingness in her bed. This latter part of the theory was revised after her funeral a couple of years later.