Your brain knows the key to “You are the Sunshine of my Life”.

Daniel Levitin, in “This is Your Brain on Music” has done studies and, apparently, our brains register the key when we hear a song on the radio (like in the old days) or on your iPod or whatever you listen to music on.
When you’re me and you attempt to sing a riff of that popular song as I did this morning to the one other person in my house, you or I would sing it in approximately the key that it is written in.

So I riffed it and Carol went to the piano and found I was in C. She said “I doubt it. Not many people write in C”. Googled it and Stevie does it in B. Only a semi-tone away – adjacent keys on the piano – no black key in between.

Interesting. To be further tested.