Playing by ear vs sight-reading (and at risk of repeating myself):

My godmother played the piano for the school assembly, but couldn't pick up tunes by ear; she said that if the hymn had four verses, she had to sight-read it four times. Conversely, and much to the annoyance of my piano teacher, I found my ear so much faster than my eye that I would hear the tune a few times, then play it from memory;* to this day I can't sight-read, only tease the dots out slowly from the stave and and memorise the tune. My godmother and I were each in awe of the other's skill.

* That's why I say I never learnt to play the piano; merely going to piano lessons is not at all the same thing. It didn't help that I was a lazy toad**, and found practice boring.

** Oi --- who said "What do you mean, *was*?"