I'm not entirely sure about this, but I'll bite. here's an example, I'm 90% sure that learning to drive stick improved my quality of driving overall. One of my friends even remarked that I was driving a lot smoother, namely the braking and acceleration rates. It effectively stamped the model of the car engine switching through gears into my brain that carried over even when driving automatic. I always felt more in tune with cars thereafter and naturally drove the car with gears in my mind, translating to smoother takeoffs and, well I use to gear down with standard; I miss that functionality driving automatic.
I tried dvorak once and tried hard to grapple it. While trying out the new layout I was very conscious of using the home row - for eventual maximal speed. As a side effect of learning it, I ended up with much better adherence to good typing when having to return to qwerty.
I know some instruments, and I'm fairly sure that as I learn to play new ones.. working on guitar and lyra right now.. generalizations and cross applicative senses of things form such as chord theory, rhythms and melody, moods of music..
As for numpads.. It would be best to only ever have one layout.. right?