Baboons can learn to tell the difference between real four-letter words and nonsense combinations of letters. And once they figure out the patterns, these monkeys can guess with impressive accuracy whether a new word is real or fake.
Because baboons can’t actually read, a new study supports the theory that the brains of our primate ancestors held the necessary hardware for understanding written words long before humans evolved. Only after we starting writing and reading about 5,400 years or so did we apply our object-recognition abilities to letter symbols.
And even though we think of letters as sound units that allow us to piece words together, the new findings suggest that our brains may also view written letters like the legs on a table or the wheels on a car. Each part fits together to create an object that we recognize as a whole.
Eventually, the findings might weigh in on debates about how best to teach children to read.
“Obviously, we are using letters to get from the printed to the spoken form, and it is absolutely essential for kids to learn that this has to happen, but that’s only part of the story,” said Jonathan Grainger, a cognitive psychologist at CNRS, a national research center in Marseille, France. “The other reason we use letters in the very first phases of learning to read is that we’re basically doing what we do with ordinary everyday objects – using object parts to reconstruct the whole identity.”
“We can now look at what happens when baboons are learning words and also associating them with meaning,” he added. “We have a new paradigm that needs to be explored.”
In a large enclosure about 30 miles from Marseille, resident baboons can enter small testing booths whenever they feel like it. Inside, a computer scans a microchip embedded in each animal’s arm and launches the appropriate experiment.
For the new study, six baboons spent about six weeks learning to recognize four-letter English words on a computer screen. In 100-round trials, words came up one at a time on the screen. After tapping the word, baboons touched either an oval to indicate that it was a real word or a plus sign to signal a nonsense word.
Within each trial, a single word would come up again and again, intermixed with real words that the baboon had already learned as well as fake words. All of the words, both real and fake, contained three consonants and one vowel. For each correct answer, baboons received a food reward.
By the end of the training period, which included about 50,000 trials for each animal, all of the baboons had learned to recognize at least 81 words at an accuracy rate of about 75 percent, the researchers report today in the journal Science. One animal learned more than 300 words.
Once the baboons had boosted their vocabularies, further testing showed that the animals could often tell whether a word they had never seen before was real or fake. The more similar the fake word was to actual words, the more likely the animals were to guess that it was real, suggesting that they had learned to recognize patterns of letters that often show up in the English language.
The baboons in the experiment were not actually reading, nor did they understand that what they were looking at had symbolic meaning, said Michael Platt, a neurobiologist at Duke University in Durham, North Carolina.
Instead, the baboons’ ability to recognize letter patterns suggests that, when humans started reading and writing, they probably tapped into already existing brain circuitry that developed to recognize visual patterns.
Along with other research, the findings support a theory that alphabets look the way they do because their shapes are easily recognized by these brain systems. One implication is that dyslexia, at its root, might be a kind of visual disorder.
The baboons “certainly seem to be capable of forming some sort of statistical sense of what kinds of orders letters go together into four-letter long English words,” Platt said. “This is suggesting that there is perhaps a very fundamental operation going on that is shared between humans and non-human primates in terms of being able to learn visual patterns. In this case, the visual patterns serve as a means of communication.”