At least some birds can learn a pattern once proposed as unique to the grammars of human languages, say researchers.
Starlings trained in a lab have learned to distinguish between sounds strung together like a laundry list and those with nested, or recursive, elements, according to Timothy Q. Gentner of the University of California, San Diego.
Human languages make ample use of recursion. A simple sentence, "Scientists argue about languages," can expand quickly as the speaker tucks in subordinate bits within the basic framework. For example: "Scientists, who have passionate opinions, argue about languages, of which there are many."