rock consciousness

A being (usually a human being) that has the amazing capability to consistently fail to understand any abstract concept, social cue, literary element, or hint within conversation. They seem to be so stupid that it prompts one to ask, “How did this person manage to get this far in life?”
Despite this, they carry on like anyone else would.

This customer had a rock consciousness. They complained that the food they were given didn’t look exactly like the picture on the menu.