Sound probably. But I doubt smell and taste would ever play large roles in UI design - it isn't a huge part of how we interact with the world aside from the obvious bits about eating.
Say I want to buy some flower for my spouse, at my the whims of my thoughts, a smattering array of flower images get into my head. I "wander" to the one I think my spouse would like, and when I feel like I want to smell it, I do. I'd then decide "Yes, buy it", and the order gets sent.