A study conducted when Koko was 15 years old was designed to see how accurately Koko understands spoken English, specifically the smallest units of speech sound or phonemes. Dr. Penny Patterson showed Koko sets of flash cards with photos of various objects that differed by just one phoneme, and then asked her for one of them by name. For example, one set of cards required that Koko distinguish between honey, money, bunny and funny. The results, summarized below, were presented to the American Society of Primatology in June, 2007.

As a subject in a longitudinal language acquisition project, Koko communicates using sign language, which she learned through the simultaneous communication of spoken English and American Sign Language (ASL). To test her understanding of spoken English she was presented with pictures representing words taken from her vocabulary (55 sets of 2, 3, or 4) that differed by one phoneme, either vowel or consonant, in the initial, medial, or final positions. Koko was able significantly to discriminate phonemes in a linguistic context (78.2%). Koko's scores were best when tested for final word sounds (100%) and when offered 4 words per test item (90%). Her poorest performance was with medial consonant word sounds when offered only 2 words per item (55.6%).

These results suggest that motivational as well as perceptual factors may have played a role in test performance. Nevertheless this finding indicates phoneme discrimination ability in a gorilla and supports the theory that speech perception evolutionarily preceded speech production.

The presentation was during a session entitled Learning, Cognition and Language, grouped with other talks related to these headings. For example a talk in the same session showed long-term memory capabilities of captive chimpanzees who not only remembered the location of 20 different hidden food rewards, but also prioritized the locations by food quantity, type, and proximity. It was fascinating to see what other researchers are doing to show the amazing cognitive abilities of non-human primates.

Our research focus at the next few conferences will shift to promoting two-way communication with gorillas and other non-human great apes as a form of enrichment and a husbandry aid. We have been working on developing technology to aid institutions who wish to expand on the natural ability of apes to gesture by teaching them to communicate with their keepers. Stay tuned for updates.

Dr. Christa Nunes
Associate Director of Research

(Note: The above presentation was given by Dr. Christa Nunes, based on results collected by researchers: May Goodreau, Christine Tam and Dr. Penny Patterson (Director of Research).)