Thumb twiddling

While it is an expression of at least a moderate amount of manual dexterity, thumb twiddling is frequently used as an example of a useless, time-wasting activity.

[1] Thumb twiddling can be used as a simple test for manual dexterity.

[2] Contra-rotation involves moving the thumbs in opposing directions.

While thumb twiddling comes naturally for almost everyone, it is extremely rare for people to be able to naturally contra-rotate their thumbs without spending a significant amount of time training the new technique.

[3] Typically, a person will get through a half rotation before both of the thumbs will inexplicably synchronize directions.