(n) lack of sensibility, Example:there was a dullness in his heart; without him the dullness of her life crept into her work no matter how she tried to compartmentalize it.
n. The state of being dull; slowness; stupidity; heaviness; drowsiness; bluntness; obtuseness; dimness; want of luster; want of vividness, or of brightness. [ Written also dulness. ] [ 1913 Webster ]
And gentle dullness ever loves a joke. Pope. [ 1913 Webster ]