The quality of being mentally slow and limited(noun)
WordNet. Princeton University. 2010.
Use "slow-wittedness" in a sentence
""Forrest Gump" celebrates innocence and slow-wittedness -- not just as a handicap to be surmounted, but the key to worldly success."
"“Potter came in here to get it,” said Malfoy with ill-disguised impatience at the slow-wittedness of his colleagues. “so that must mean –”"
"Why do they even need to ponder the reasons for taking an extra team member to the boardroom, let alone to expose their slow-wittedness by asking, "Why would I want to do that Mr. Trump?""