My nipples can get erect through touch, and especially (this is when they get the most erect) when I'm cold all over. But to my surprise if I use an ice cube on the nipple or areola it will not get erect at all, even though before hand it really feels like it will do. But it will feel pleasurable though.
I've always had the impression that ice would be the thing to get your nipples the most erect, and I'm sure this is the case with most people.
So it's very strange how even though my nipples can get erect from other ways (it's not like they just don't work at all), ice does absolutely nothing.
Ice touch light touches squeezes - all arouse my nipples. And my nipples will send my body into orgasm mode.