I started thinking about this (see below, for background on this phenomenon). Why have I been convinced that 'pigeon' is spelled 'pidgeon' when it turns out not to be? I have a possible error theory. I lecture on philosophy and film, with an SF focus. And I always teach Forbidden Planet - sort of a silly one, yeah. But a classic. And I really like Walter Pidgeon as Morbius. I think I tend to think about Walter Pidgeon, and read things about the film in which his name appears, more often than I think about pigeons, and see texts with the word 'pigeon' in it. Maybe, like the good doctor, I am not as smart as I think, and should get out of the house more often.