I think we all do what they do, just aren't as aware of it; if you are working or studying you concentrate on your work or studies for a period and then concentrate on making lunch talking to someone, you are in the conversation, etc. They don't turn off and turn on, it's not discreet periods of time, what we say/do reminds them of other stuff, just like when we're talking to someone and think, "Gee, I'll have to tell Perna about this, I didn't realize Tigergirl was thinking the same thing as she was talking about just yesterday. . ."