Interesting experiment, and I think this effect can quickly get reinforced by parents (or grandparents / other family). Your kid picks a book a few times, next

Interesting experiment, and I think this effect can quickly get reinforced by parents (or grandparents / other family). Your kid picks a book a few times, next thing you know the parents are emphasizing IS THIS YOUR FAVORITE BOOK? There's a themed birthday party with the characters. That becomes part of the child's identity. I've found it helps to not hold any of your kids preferences static. If they like something now, don't assume they will still like it 2 weeks from now. Consciously give them the space to change their mind.