Mark Liberman at Language Log has been investigating the “chin flick” gesture that Antonin Scalia recently used (and explained as meaning “I could not care less”). His latest post quotes an e-mail from Adam Kendon, “one of the world’s foremost authorities on the topic of gesture”; Kendon, in turn, quotes “Andrea de Jorio, whose La mimica degli antichi investigata nel gestire napoletano from 1832 is rather comprehensive regarding Neapolitan gesture” (I saw a reprint of this book, which is fascinating and enlightening—there should be such books for all cultures) as saying the gesture is a simple negative. This is backed up by “two local Procidanians” (Kendon is on Procida at the moment), but “if you ask someone from the more northerly parts of Italy about this gesture they are likely to say that it means ‘I don’t care’ or ‘It does not bother me’—and they do tend to suggest that it is a rather rude gesture.” In southern Italy and Sicily, the gesture frequently accompanies a backward toss of the head, and Kendon adds the following parenthetical remark:
As to the gesture of negation in which you push the head back, this is still used even today in Southern Italy and Sicily, and is almost certainly very old. It is distributed in those parts of the Mediterranean that were, in antiquity, occupied by Greeks [see Gerhard Rohlfs "Influence des élements autochones sur les langues romanes (Problèmes de gógraphie linguistique). Actes du Colloque International de Civilisations, Littératures et Langues Romanes. Bucherest: Comission nationale roumaine pour l'Unesco, Actes du Colloque international de civilisations. 1959/1960. 240-247 and see also Peter Collett and Alberta Contarello "Gesti di assenso e di dissenso" in Pio Enrico Ricci Bitti, ed. Comunicazione e gestualità. Milan: Franco Agneli, 1987, pp. 69-85]
I myself saw the head-toss used routinely not only in Greece but in Turkey (which of course was Greek before the Battle of Manzikert in 1071) and I believe also in Syria. It’s amazing how persistent such nonverbal signifiers can be.