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Ruth Singer, a linguist at the Wellsprings of Linguistic Diversity Project of the Australian National University, realized this by chance, and wrote about receptive multilingualism at Warruwi Community recently in the journal Language and Communication. In 2006, for one of her trips for fieldwork on South Goulburn, Singer and her husband had a Toyota truck shipped from Darwin by boat. Though the island’s not very big, there aren’t many cars, so having one is a social lubricant. Singer and her husband became friends with a local married couple, Nancy Ngalmindjalmag and Richard Dhangalangal, who had a boat and trailer but no car, and the two couples ended up going fishing and hunting, and digging up turtle eggs on the beach. That’s when Singer noticed that Nancy always spoke to Richard in Mawng, but Richard always replied in Yolngu-Matha, even though Nancy also spoke fluent Yolngu-Matha.

“Once I started to work on multilingualism and tuned my ear into how people were using different languages,” Singer wrote in an email, “I began to hear receptive-multilingualism conversations all over Warruwi, like between two men working on fixing a fence, or between two people at the shop.”

There are a variety of explanations for this, Singer says. In the case of her married friends, Richard didn’t speak Mawng, because he wasn’t originally from Warruwi Community. If he did so, it might be perceived as a challenge to rules that exclude outsiders from claiming certain rights. Also, Yolngu-Matha has more speakers, and those speakers tend to be less multilingual than speakers of smaller languages.

More broadly, people at Warruwi Community avoid simply switching to a shared language because there are social and personal costs of doing so. Some families insist that their children speak only their language, usually their father’s. Languages are associated with particular pieces of land or territory on the island, and clans claim ownership of that land, so languages are also considered to be owned by clans. One can only speak the languages one has a right to speak—and breaking this restriction can be seen as a sign of hostility.

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Still, neither restriction applies to understanding a language—or as Nancy put it in an interview with Singer, to “hearing” it. Singer suspects that receptive multilingualism in Australia has been around for a long time. The phenomenon was noted by some of the earliest European settlers on late 18th-century expeditions into the Australian interior. “Although our natives and the strangers conversed on a par, and understood each other perfectly, yet they spoke different dialects of the same language,” one settler wrote in a journal.