[lloeki]

Exactly.

My car has every button and knob share the same design language but all subtly - or not so subtly - different so that the moment a control is touched there is zero ambiguity as to a) how to operate it and b) which one it is.

Appearance also comes into play as one doesn't necessarily have to _look straight at_ something to distinguish which is which or what the position is, merely it being somewhere in peripheral vision may very well give just enough clue so that you don't really have to take your eyes off of the road.