I also remember reading the experiment with people with Alzheimer's. I remember it like this:

1) they showed them six paintings to order by how much they like them: #1 to #6;

2) then they told them they can take one of the paintings #3 or #4 (of course they took #3);

3) later (when the patients forgot everything), they were asked to order the six painting again... the painting #3 usually moved to a somewhat better position, and #4 to somewhat worse position.

So the lesson seems to be that when we actively accept (or reject) something, our brain adjusts to perceive that thing as better (or worse). This is not the same as rationalitazion, because it is not a bullshit you tell yourself when asked; this is a genuine change in preferences.