The ability to create and understand speech makes people unique. But not only humans, also monkeys and dogs can learn words. So where does it lie, the crucial difference to our human language?? And how does this medium develop, in which we speak and write, think and write poetry??
By Angela Friederici, Michael Skeide and Verena Muller
The universal nature of language development – from the crying and babbling phase to the acquisition of first words and syntactic rules to the processing of complex sentence structures – can be marveled at especially in children: effortlessly, every child can learn any language in the world into which he or she is born.
Language is what makes a person. Although some would reply at this point that other living beings also communicate with each other. Agree. In fact, different species can exchange information with each other in a variety of ways. They can even learn individual symbols or words as designations for different things and objects. Especially dogs and apes show impressive abilities here. What they learn in the process, however, is an association between a particular abstract symbol or acoustic word form and an object, for example, the term "car" and an actual passenger vehicle. So they acquire each "word" individually by association.
So learning words is not what human language is all about. What is it then? It is the gift of combining words according to certain rules. Because loosely strung together words do not yet make a language. Only when they are joined together according to a fixed set of rules do they produce a meaning. Human apes, on the other hand, are not able to learn grammatical rules that correspond to those of a language.
For example, let’s take a list of words. Sleeping, green, colorless, angry, idea. Combined according to the rules of German grammar, we might get the sentence "Colorless green ideas sleep furiously." . Although this sentence is grammatically correct and can be processed, because it follows the rules of language. But it does not make sense. Because it is not only important in which order we string the words together. How we interpret them is also crucial. The sentence structure, the syntax, is thus only one aspect of the language. Equally important is the meaning of the individual words, the semantics. With a few small changes, we can thus also give meaning to this sentence: "Still somewhat colorless green ideas sleep furiously in my head" for example. How each person interprets this sentence depends in turn on his or her individual knowledge of the meaning of words, which he or she has stored in his or her so-called mental lexicon of the brain.
From babble to complex sentences
With the help of a brain scanner dummy, a young test subject prepares for an experiment. Michael Skeide, a scientist at the Children’s Language Laboratory of the Max Planck Institute for Human Cognitive and Brain Sciences, trains the girl in advance to ensure that everything goes smoothly during the real measurement.
© MPI for Human Cognitive and Brain Sciences
Despite these apparent limits given to our language by this set of rules, the abundance of possibilities to conjure language out of words is inexhaustible. As impressive as this infinity is, however, the path that our language system passes through in the brain to reach full maturity also seems long. For as delighted as parents are when their little one speaks the first words – whether "Ma-Ma" or "Pa-Pa" – it also becomes clear at that moment what quantum leaps it must master in order to later understand and interpret complex sentences. Some of these leaps are achieved in no time at all, for others it takes many years.
For example, even three-year-olds have an extensive vocabulary pool and can understand simple sentences without any problems. "The fox chases the hedgehog," for example. The little ones reach a real hurdle, however, when the sentence deviates from its simplest structure. For example, if you want to emphasize that it is the hedgehog and not a bird that the fox is chasing, you change the statement accordingly: "The fox is chasing the hedgehog". Misunderstandings are inevitable. For young speakers still unconsciously rely on the assumption that the subject, the hunting fox, comes before the object, the hunted hedgehog, in the sentence. On the other hand, children already register unconsciously that the article "the" somehow does not fit the subject, and does not belong at the beginning of the sentence. Only the adult brain can process the changed sequence of sentence components with ease.
Why is this so? Why is it that, on the one hand, we can already distinguish vowels from each other in the womb, but on the other hand, at the age of seven at the earliest, we can understand grammatically more demanding sentences, even if they are composed of simple words??
The brain also needs to mature
In short: Good things take time. The brain and its individual areas responsible for language mature at different rates. Some areas only gradually condense their network to other regions, so that they can then exchange information faster and more effectively.
One area that is bursting with activity from the very beginning, even before birth, is the so-called Wernicke’s region in the left temporal lobe of the cerebrum, which matures very early in development. From a very early age, this brain region not only helps us to distinguish between sounds such as "ma" and "pa" at top speeds of 0.2 to 0.5 seconds. It also decides for us whether a string of syllables is a word at all and thus worthy of further attention. Even simple sentences consisting of a few words can already be processed here. Until about the age of three, the Wernicke region is the epicenter of our language.
It is only from this age that a second central speech region gradually joins in: Broca’s region in the frontal area of our cerebrum, which is primarily dedicated to processing more complicated language. It receives the pre-sorted information from the temporal lobe and gives an overall meaning to the words strung together individually. Separate pieces of raw information are used to build meaningful sentences. As the neurons here also become more and more wired, even more complicated formulations become easy for us with increasing age.
We can therefore increasingly compensate for the increased difficulty of complex sentences by activating Broca’s area more strongly than with simple sentences. But this is not the only reason: The connecting pathway between the two main players in language processing, Wernicke’s and Broca’s regions, also plays a crucial role. This bundle of nerve fibers, the fasciculus arcuatus, takes a particularly long time to be fully functional. The reason: It slowly forms a thick layer of myelin around each of its fibers. This may take many years, but it is all the more effective in the end. Like the plastic around the copper wire of an electric cable, myelin ensures that electrical signals are transmitted with as little loss as possible and at high speed. Recent research has shown that the thicker the myelin layer around these high-speed cables, the faster difficult sentences are processed. As a result, it is not until around the end of puberty that more complicated formulations can be processed just as quickly as simple ones – regardless of whether the hedgehog is the first or last object in the sentence.
Watching the brain speak
We owe these findings in large part to one thing: the new technical innovations of recent years, especially functional magnetic resonance imaging (fMRI). Through it, we can almost watch the brain speak. By taking advantage of the different magnetic properties of oxygen-poor and oxygen-rich blood, the method shows us activated brain areas flooded with oxygen. This was a big step, because until then, conclusions about the functioning of our thinking organ could be drawn mainly from the example of patients with specific failures – and the examination of their brains after their deaths.
And even after developing these new methods, until recently they were almost exclusively limited to studies with adults. For meaningful recordings, it is crucial that the test subjects do not move their heads during the speech test in the tomograph. Something that children are known to find particularly difficult. Nevertheless, we at the Max Planck Institute for Human Cognitive and Brain Sciences have succeeded in developing methods that allow us – even in three-year-olds – to look into the child’s brain as it processes language. Our idea: Combining the pleasant with the useful. We practice keeping still with the little ones, for example, by showing them a cartoon in advance, which they can watch without interruption if they keep their heads still while watching it. And if the cartoon is exciting, this works.
Language development – a universal program
How universal this biological program is – from the crying and babbling phase to the acquisition of first words and syntactic rules to the processing of complex sentence structures – can be marveled at especially in children: effortlessly, every child can learn every language of the world into which it is born. After birth, it is initially open to any language, but then specializes according to the respective linguistic environment. In the first months of life, all children worldwide recognize phonetic differences in the same way, regardless of whether they are important in their native language or not. Later, they can only distinguish those that are relevant in their own native language. A famous example is the difference between the speech sounds "r" and "l", which is crucial in German to separate "Rast" from "Last", but not in Japanese. Therefore, Japanese people lose the ability to distinguish these speech sounds. In other languages, in turn, other sounds are without meaning, so that these are also lost.
The medium in which we speak, read and write, think and write poetry, email and tweet is ultimately a specifically human natural and cultural product of complexly interconnected neuron bundles. A bundle that develops according to a predefined biological program, but clearly develops under the influence of the cultural environment in which we grow up and live. Only if we look at both, the scientific and the spiritual aspect, a deeper understanding of language becomes possible.