If you need it proven
There's a person with a IQ of 48 where 75 is considered borderline cognitive function
And here is some other evidence: the fact this happened
"I'm late to this party but I had a friend who for whatever reason was trying to guess my brother's middle name.. I gave her the hint "his middle name is the same as my Grandpa Tom's first name" and she got all huffy and said "I DON'T EVEN KNOW YOUR GRANDPA TOM!"
And besides I'm so dumb I dont even know how to reply