Duality of patterning

Duality of patterning refers to the ability of human language, both signed and spoken, to form discrete meaningful units (morphemes; cf. "Rules of word formation (morphology)") from discrete non-meaningful segments (phonemes; cf. "Sound/sign patterning (phonology)"). No naturally occurring system of animal communication exhibits this basic feature of human language. The best evidence for anything remotely resembling duality of patterning in primates comes from putty-nosed monkeys: troop leaders at times combine discrete leopard and eagle alarm calls (Lⁿ ≤ 3, Eⁿ ≤ 4) to elicit troop movement responses that differ from those to leopard or eagle alarm calls in isolation. In other words, individual alarm calls seem to be stripped of their intrinsic “meaning” when combined in this way.