Watching our 2 year old navigate the iPad has been amazing. She has a huge capacity to figure it out, play her favorite songs, run her favorite apps, etc.
Of course she does a lot better when there are pictures. An icon, no matter how small, gives her tons more benefit than just a text label.
But it's about the Nouns
But the biggest concept I've learned is the idea of nouns vs. verbs.
When language starts developing, you see thousands of nouns appear, before verbs really show up at all.
And even for adults, the best interfaces are made of simple nouns. Apps are nouns. One of the big splits between an early "technology" for "professionals" and "consumer apps" seems to happen at the point a UI gets noun-ized. A photo, a song, a file.
It's not a "workflow" or a "write down these steps." It's, that app, or, that icon. It's when you become a noun that your software takes a leap in usability.
In real life, our most important tools do things, so software designers try to emulate that. But the best-loved tools are also nouns. And those tools, those nouns, can only do a few things. You start a sentence with a noun, and it limits which verbs apply. So your brain is just faster this way.
It's what toddlers do, and it's the same with people bigger than two years old.
Your users aren't so smart that they want a workflow or a wizard or an action.
Instead, you should try to start with nouns.