How does giving denjuu preferred items work?

[spiffles]

I know that in some calls we get nice info about what items some denjuu like. My first thought was that they meant items that you're supposed to use in evolution so you'll receive a lot of exp, but then I also remembered that there is a "gift" mechanic, where you can simply give an item to a denjuu as a gift (kinda like held items in Pokemon I guess). So I'd like to ask, what is the effect if you give a denjuu an item they're said to like, if any at all?