Lets start with a research finding...

"In 2006, researchers at Lafayette College and Johns Hopkins University in a study found that left-handed men are 15 percent richer than right-handed men for those who attended college, and 26 percent richer if they graduated. The wage difference remains unexplained, and does not appear to apply to women"

Now for the new theory that possibly explains this reason.

Ok, firstly, take a look at this diagram (below) that I put together in a previous post... Left and Right Brain - Jung types



Now, Consider the left hemisphere of the brain controlling the right hand and the right hemisphere controlling the left hand/side of the body. From the previous post shown above Intuitive and Feeling is more predominant in the right hemisphere. (NB: S = Sensing, T= Thinking, N= Intuition, F= Feeling).

So, why does that make men earn more?

Well, If men have been competing with other men throughout the whole academic system on primarily left brain attributes even though their right brain is superior, then when do they make use of their right brain? Well, by applying Intuitive and Feeling to analytical vocations. That makes them far more able than pure left brainers in strategy and higher order conceptualisation.

Furthermore, the predominant use of left brain thinking even though they are right brainers means that they cross train their brain and likely grow greater connections between the two hemispheres (needs to be proven) and possibly explain why left handers have more distributive minds that make them less suitable for psychology tests.

Lastly, why does this theory then not hold true for women? If they are more right brained and undertaking analytical courses etc then you would expect they would have the same abilities to earn significantly more!

Well, according to Norman Geschwind "left handedness is a function of testosterone before birth. Higher amounts suppress growth of the left hemisphere and so more neurons migrate to the right hemisphere".

I'm not sure of the facts on female babies, but I believe that this effect has a different effect than just a pure imitation of female hemisphere orientation.