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gorilla sign language: DO ANIMALS HAVE LANGUAGE?
The American psychologist John Ridley Stroop devised his test in the 1930s to demonstrate the interference effect your brain experiences when linguistic information conflicts with information from other senses.
When you ignore color and simply read the words, you only need to use your language processing system, so it’s easy to say each word aloud. But when you try to say the color of each word, your brain’s executive system discerns a conflict between what your color processing modules are telling you and what your language processing modules are telling you about the meanings of the words associated with the colors. Two different kinds of information are entangled.
To sort out the conflicting information, you have to first suppress the meaning of each word normally associated with the sequence of letters. This takes some effort. Then you have to translate the color of each group of letters into the word with the meaning that matches the color. Only then can you say the correct word.
Primates such as gorillas, chimpanzees, and bonobos do not develop any kind of language-like communication system in the wild. They lack the language brain modules that humans are born with. However, in captivity, with much time and effort, trainers can get them to understand, in a rudimentary way, that arbitrary symbols represent objects. Apes can also “learn” elementary sign language and grammar-like rules, such as linking two symbols representing something different from either of the individual symbols. With about 30 years of patient training, a great ape can memorize a couple of hundred word meanings, and can almost acquire the language understanding of an 18-month-old human child. Bonobos fare somewhat better at “language learning” than chimpanzees.