I was using my soldering iron and unplugged it before I left the room. I stepped outside the door and thought: "Have I really unplugged it?" I stepped back in again and saw at a glance that I had:
And then I wondered when how had the concept of "unconnected" gotten into my brain, and how could I at a glance see that the soldering iron was unconnected. Somewhere in my brain the concept of unconnected was recognized as being active when shapes from my eyes we transmitted and interpreted.