question for people who play ukulele and guitar

the only string instrument I have ever played is Ukulele (only for a year or so). Just curious how do people switch back and forth playing something else like a guitar? Is it kind of like speaking multiple languages and your brain just switches over... or do you find yourself working hard to keep the different finger positions separate (as I understand it a C chord on a Ukulele is not going to be the same finger positions as a C chord on a guitar/banjo/mandolin/etc)