didn't they do some experiments with ... smarties? and the way that the kid's perceptions of what was in /their/ smartie tube affected what they believed about what was in everyone else's smartie tube, and how that changed with age? but I can't remember any details.

I cycled into a dog once (fortunately not hard. it ran off again apparently unhurt) when it failed to get out of my way as I was expecting it to. The two ladies walking it didn't seem remotely bothered.

This one? (Just googled for "smartie" and "experiment".) Apparently a 3-year-old, after finding out that a Smarties tube actually contains pencils, will immediately believe that his mother also knows it contains pencils. Whereas a 6-year-old will be able to comprehend the concept that he might know something his mother doesn't, and will therefore realise that unless his mother has also checked carefully she will still think the tube contains Smarties.