Mental Limp
Some people have a bit of trouble with very simple tasks, they don't listen well and are probably not gonna go far in life. While people with physical limps have a bit of trouble getting by in the world, they are lucky that society is there to help; those with the mental limp are fucked for life.
I had to walk the guy through how to use the word processor, every instruction was repeated 2 or 3 times to him, I swear he had a mental limp.