There is a trend in the scientific community to classify people as “right handed” or “non-right-handed”, with those who are ambidextrous or cross-dominant (doing some things better with one side and other things better with the other side) being considered non-right-handed along with lefties.
This fits in with the latest genetic research that indicates that there is a gene for right handedness, but none for left handedness. If you’re born with the right handedness gene, you’ll be right handed. If you’re born without it, you can go either way, and there’s a small chance that you’ll go both ways.
My guess is that PnL’s suggestion that lefties have an easier time learning ambidexterity may be true because left-handedness doesn’t appear to be genetically programmed. That might also mean that someone born without the gene, but who ended up as a right-hander, might have an easier time learning fine motor control with her left hand.
@dragonflyfaith
There does seem to be a significant link between ambidexterity and learning problems, including dislexia.