The addition of -ity to an adjective results in a shift of stress to the antepenultimate syllable; that is, words in -ity are stressed on the last syllable before the -ity, even in cases where this syllable is part of another suffix (as in words in -ability and -icity).
adjective, dumber, dumbest. 1. lacking intelligence or good judgment; stupid; dull-witted. 2. lacking the power of speech (offensive when applied to humans): a dumb animal.
By trying so hard, smart smart really misses the point. Smart dumb is The Fugs, punk rock, art schools, Gertrude Stein, Vito Acconci, Marcel Duchamp, Samuel Beckett, Seth Price, Tao Lin, Martin Margiela, Mike Kelley, and Sofia Coppola. Smart dumb plays at being dumb dumb but knows better.