I can close my eyes and imagine a red cube with a yellow star on it. Although I don't literally see it -- if there was a red cube with a yellow star on the inside of my eyelids, I'd know the difference -- I can experience it in much the same way as if I was seeing it.
I can do much the same thing with sound, imagining (say) the sound of a bird, or of a bell ringing.
But I can't imagine any tastes, or smells. I know what cinnamon smells like: if several spices were placed in front of me, I could readily identify the cinnamon. But I can't call a familiar smell or a taste to mind in the same way I can call a familiar sight or sound to mind.
I don't think it's merely a memory thing. Even if I've never seen the box, I can still imagine it. I can imagine the sound of a bird tweeting in a large echoing hall, even though I've never heard it. But I can't synthesize unknown smells or tastes in my imagination in the same way I could unknown sights or sounds. I don't think I'm unusual in this respect (correct me if I'm wrong).
Are there any theories as to why this is?