Humans Matched by Chimprehension

A chimpanzee has thrown doubt on the idea that only human brains are specially adapted to process speech.

The appropriately-named Panzee, now aged 25, is able to make out 128 different spoken words, even when the words are distorted or incomplete.

Panzee was raised by humans since she was eight days old, and has always been spoken to as if she were human. As well as being able to recognize the 128 words and point to a corresponding symbol on a lexigram board, she appears to understand their meaning and can use the board to communicate.

A team from Georgia State University, where Panzee lives, decided this made her an ideal test subject for research into understanding of speech. They played a series of 48 words to Panzee and gave her four options to choose the right answer from. The testing involved distorting the words in two ways: making them very husky (noise-vocoded synthesis) and reducing them to just three tones (sine-wave synthesis.) The researchers also asked 32 humans to take the same tests.

Science magazine has an audio link of the two techniques being applied to the word apricot. Fortunately they used the American English pronunciation: the British English variant of “ape-ri-cot” might have caused more confusion!

In the noise-vocoded synthesis test, Panzee scored 55% correct (significantly above the 25% that would have been expected by simply guessing), while the humans as a group achieved a 70% success rate. In the sine-wave synthesis test, Panzee matched the 40% score of the humans.

What this means is open to dispute. The Georgia researchers believe there is no doubt over the theory that human speech recognition skills developed through a brain adaptation only came when chimps and humans went their separate evolutionary ways. However, other researchers argue the results aren’t conclusive, noting that only have a vocabulary of 128 words makes the task of distinguishing between them far easier.

(Image credit: Carolyn Richardson/Division of University Relations/Georgia State University, via Science)

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