dullness vs stupidity

dullness and stupidity both are nouns.

Word	Noun	Adjective	Verb	Adverb
dullness	Yes	No	No	No
stupidity	Yes	No	No	No

As nouns, stupidity is a hypernym of dullness; that is, stupidity is a word with a broader meaning than dullness:

dullness (noun)	stupidity (noun)
lack of sensibility	a stupid mistake
without sharpness or clearness of edge or point	a poor ability to understand or to profit from experience
the quality of lacking interestingness
a lack of visual brightness
the quality of being slow to understand