Long post on this fascinating subject...
I'm a lefty, as is my ex-husband, father of our four right-handed children. Hmmm.
Most lefties have to use scissors right-handed as that's how scissors are made. Same goes for most gadgets.
Thus, I had great trouble operating an expensive and supposedly foolproof tin opener. My son said, 'It's because you're left-handed....' and all became clear: I was working it backwards.
I read a fascinating pop psychology book some years back which demonstrated brain 'handedness' beautifully with a simple experiment.
(Basically, the brain is divided into left and right hemispheres, each of which has distinct characteristics. A person's 'handedness' is diametrically linked to the dominance of one hemisphere. With me so far? Good. So a left-handed person's RIGHT hemisphere is dominant, which is supposed to manifest itself in different thinking patterns from those of a righty.)
What you do is ask someone a simple question which has to be one of two types AND requires a moment's thought.
Type a- a factual question relating to the person's daily routine, e.g. 'where did you hang your coat last night?'
Type b- a subjective question, such as 'what is your second favourite colour?'
During the few seconds the person reflects on their answer, their eyes will drift toward the side of the brain which deals with that type of activity.
(So if I remember rightly, the reply to the coat question will be sought from the 'concrete thinking' LEFT side, and the second favourite colour will be found on the 'abstract thinking' RIGHT side. )
You can see them literally 'looking' for the answer!
I worked with young children when I read this book and it worked perfectly on them, over and over again.