I am interested in the history of (+). I am tracking the "evolution" of this
interaction idiom (and others) and the ways in which user mental models have
to adapt to such changes.
I think (+) first meant "expand" as opposed to (-) which meant "collapse."
In iTunes it means "Add Playlist" and this has been copied (very crudely) in
the Sony Reader eBook Library application. In the original iPhone/iPod Touch
Safari interface it meant "Add Bookmark" but after the January 2008 upgrade
it has been generalized to mean "Add Something."
I am not a long-time Mac user so I wonder if (+) has always been part of the
Apple lexicon, or if it is new. Also, has anyone on this list seen (or
created) different implementations/meanings of (+) in other products?