Human language system dissected: endless language proficiency
Human language is the most powerful communication system evolution has yet produced, but it is also immensely complex. Traditionally, its study has been primarily the domain of linguists. By also contributing expertise from other disciplines, scientists have gained innovative insights into language. That extends from the genes and the brain to social interaction and linguistic structures.
Text: Elke Veldkamp
'A characteristic of human language is that it is unique in its complexity and has a great deal of variation,' says Peter Hagoort. He is professor of cognitive neuroscience at Radboud University and initiator of the Language in Interaction consortium. Scientists have spent ten years studying all the different sub-areas of the human language system. 'We have a fixed repertoire of sounds and words. This allows us to create an infinite number of new combinations of messages that are still understood by the receiver. Our human brain allows us to do this. At the same time, human language comes in many variations: more than six thousand languages are spoken worldwide.
Never worked together before
The research uses knowledge from linguistics, but technological advances in the field of computing power and computer models mean that there are now many more options for studying language. Hagoort: 'We can now build advanced calculation models for language processing. Thanks to neuroimaging , we are able to study the neural basis of the language-proficient brain. And genetic sequencing provides insight into the influence of your genes.' In the first phase of the broad research programme, only proposals could be submitted for research involving collaboration between people who had never done so before and had never published together. 'That's how we got partnerships that wouldn't have come about otherwise.'
Everything we know about language
'We have learned a lot since the start in 2012,' says Hagoort. As an example, he cites the new knowledge about the variation in language areas in the brain and the insight that areas other than those of Broca and Wernicke (areas known to be responsible for language production, ed.) also play a role in language use. A more technical innovation concerns the human cerebral cortex, which consists of six layers. It is difficult to get a good picture of those layers separately and to see which activity takes place on which layer. We were the first to succeed in this, including for reading and language processing.'
In addition to scientific insights, the consortium has also delivered practical tools, such as an app with speaking exercises for patients with aphasia and the reading program Letterprins, to promote the reading skills of children in group three. Not to mention a book: Human Language . 'Everything we currently know about language has been brought together in this book, supplemented by contributions from other language experts. It has since grown into an important reference work.'
Customised language map
A common assumption is that the language areas in the brain look and function the same in everyone. But our brains differ enormously, according to large-scale research. So different people learn a language in different ways, according to neuroscientist Stephanie Forkel.
'We now have a fantastic assessment to determine someone's language skills. For example, one person is good at learning a new language, while the other has great speaking skills.' The four-hour assessment was carried out by more than a thousand test subjects. Subsequently, an MRI brain scan of the areas relevant to language skills was made of 204 test subjects. 'We then manually studied how those areas and the interconnections differ from person to person. The idea is that the differences in the physical brain correspond to the differences in language skills.'
According to Forkel, it is already clear that there are large individual differences between the language networks in people's brains. Ultimately, this should result in personalised language maps on an individual level. 'So if you have a certain type of connections in your brain, you will soon know which way of learning is appropriate. For example, we might be able to tailor language learning programs. Or people who need to learn to talk again can help with a therapeutic learning method that suits them specifically.'
Talking with your hands helps
If you are in a noisy environment and you want to tell someone something, it is better to support your story with hand gestures. This has emerged from research by cognitive neuroscientist Linda Drijvers.
Drijvers conducts research into language as a multimodal phenomenon, i.e. the simultaneous use of speech and gestures. 'Spoken language is not only something you hear, but also something you see. Its importance is often underestimated.' Among other things, she had test subjects watch videos with a lot of background noise, in which people pronounce verbs that express an action and make hand movements to do so. Drijvers looked at the brain waves in those parts of the brain where visual and motor information, as well as language information, are processed. 'When hand movements helped to recognise language, we saw that the brain areas for sight and for language and meaning became extra active, but also the part in the motor brain areas for understanding hand gestures.'
Drijvers studied both people who were spoken to in their mother tongue and people who were not. Both groups benefited from hand gesture support. When the noise became heavier, people who were not spoken to in their native language benefited less from hand gestures in understanding the sounds. 'That also corresponded with less activity in the brain areas for hand motor control.' According to Drijvers, the research shows that it is important to pay more attention to visual expressions, such as gestures, when communicating. 'Hearing tests, for example, are purely auditory, they do not measure how we perceive language in reality.'
Unique connections between language areas
What makes it possible for us humans to learn and use a language that animals cannot? Research by Vitoria Piai, Joanna Sierpowska and Katherine Bryant shows that humans have unique connections between the language areas of the brain.
"We know that there are two areas in the cerebral cortex of the temporal lobe—just before and behind the ear—that are important for our language ability," said Vitoria Piai, a language psychologist and principal investigator. 'In our study, we looked at how unique these areas are from a clinical perspective: if there is brain damage in the temporal lobe, we know that a patient's use of language is affected. We then looked at whether those spots differ in the brains of chimpanzees. In terms of brain structure, chimpanzees are very similar to humans, but they cannot communicate with language as we do.'
The study compared 50 human brain scans with 29 chimpanzee brain scans. Piai: 'In the human brain we clearly saw a pattern of connections between the posterior part of the temporal lobe and the frontal and parietal lobes. And we didn't see that in the brains of chimpanzees. That suggests they are crucial for us to be able to use language. We also saw the reverse: within the temporal lobe of chimpanzees we found unique connections that humans don't have.'
The research helps to increase understanding of the brain. 'We now have a better understanding of why brain injury in those areas has such serious consequences. That is, for example, relevant knowledge for operations on the brain, but also to be able to provide more accurate prognoses to patients.'
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