As a kid I found it interesting that people pretty much always crossed their arms and/or their legs when sitting on the ground in the same pattern.

After that re-trained myself a few times out of interest to do it the other way around, and one goes through the four odd phases of having to focus on it vs it just happening correctly without thinking about it.

From what I remember it could take 2-4 weeks before you would just do it both without thinking and correctly.