stupidity vs dullness

stupidity and dullness both are nouns.

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

As nouns, dullness is a hyponym of stupidity; that is, dullness is a word with a more specific, narrower meaning than stupidity:

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