Article curated by Ginny Smith
Language is a vital part of being human, and some argue it is what sets us apart from other animals. But plenty of mysteries remain. Why do children find it so easy to learn a language, but many adults struggle? And do any animals have true language?
The evolution of human language
No one really knows how human language first evolved, but many theories have been suggested. One idea is that calls and gestures transformed over time into complex communication as the environment became more complex. Those who could communicate in this way were more successful, and so the ability was selected for.
However there is no real proof for this theory. Instead, it may be that language was a by-product of another adaptation, rather than something that evolved independently itself. It may simply be that as our brains evolved to be better at complex tasks like making tools, the structures for communication came into being, and so language appeared.
Even within each theory there are disagreements. If language did evolve, how and why? One idea is that it started as a way for mothers to reassure their babies when they had to put them down, because our lack of hair meant babies could no longer hang on to their mother's backs like infant monkeys do. Or did it evolve to help lubricate the complex social structures of early humans and ensure altruism was reciprocated and bonds were formed? There is even disagreement over whether it initially evolved from gestures that had meaning, or whether it originated with calls like those of other animals. These are just a few of the leading theories, but unfortunately, there is little evidence to go on, as speech doesn’t fossilise! Sadly, it is possible we will never know how our ancient ancestors sounded when they first began to speak.
Learning to speak
Learning language requires complex processing, and anyone who has tried to learn a foreign language as an adult will testify that it isn't easy. Yet young babies seem to handle it with little difficulty. This has led to the idea that infants' brains are somehow primed to learn language, but that as we grow, this ability disappears, or at least reduces.
The time during which you can learn something is known as a 'Critial Period', and they are relatively common in the animal kingdom. For example, a newly hatched chicks will imprint on the first suitable moving stimulus they see after hatching. If they don't imprint in the first 14-16 hours, the opportunity has passed, and they will never imprint on anything. The evidence in humans is limited, but it does seem that for some aspects of language, there is a window after which the opportunity for learning has passed. One of the strongest pieces of evidence comes from the few examples of feral children, raised with very little human interaction. The most studied case was of Genie, who was kept tied to a chair in a silent room for most of the first 13 years of her life. When she and her mother finally escaped, she spoke only a few words, and couldn’t chew or straighten her arms and legs. However with help she rapidly begin acquiring new vocabulary, and stringing together pairs of words. It seemed the critical period theory was in trouble- it was possibly to learn language after early childhood. But, unfortunately, her progress didn’t continue. She remained stuck at this stage, and was never able to grasp grammatical rules or put together whole sentences. So for grammar, at least, this supported the critical period hypothesis. But cases like this are rare, and it is impossible to say whether her years of abuse were part of the problem.
Further evidence comes from the difficulty of learning a second language later in life, and the fact that it is nearly impossible to produce a native-sounding accent if you start speaking the language after childhood. We also know that children who suffer damage to the language areas of their brain often recover language much better than adults with the same damage, suggesting their brains are more flexible.
Now, most scientists talk about sensitive periods rather than critical periods- times when our brains are more ready to absorb new information. This doesn’t mean we can’t do it at other times, but during these sensitive periods learning is easier and faster.
Language in the brain
We know that our brains are able to change throughout our lives- the networks of neurons can grow, and new connections can be formed or lost. One of the reasons scientists believe children are so good at learning languages is that their brains are more plastic, meaning they can change more easily. We don't know what changes in the brain as we age to put the breaks on this learning ability, but by understanding more about it we may be able to find a way to extend the flexibility as we grow and age.
Historically, researchers have identified 2 main brain areas to be vital in language processing, through studies on people with damage to these areas. These are in the left hemisphere of the brain in most people and are called Wernicke's and Broca’s areas, after the people who discovered them.
Wernicke’s area is involved in speech production, and is vital for the meaning of words. Patients with damage to this area have difficulty understanding words, but seem to speak fluently and easily. However, their words will lack meaning. Broca’s area is linked to the grammar and syntax of speech- damage to this areas leads to hesitant, stumbling speech, and an inability to use grammar to understand a sentence, even when the meanings of the words are understood.
Recent imaging studies, however, suggests speech processing may not be quite as neatly divided between these areas as previously suggested, but spread over a wide network of cortical areas. The initial studies on damage to Wernike's and Broca's were in patients who also had damage to other regions, but this wasn't initially taken into account. We now know that patients with more focused lesions don't show the same level of difficulty with speech. Exactly how these different regions are involved, and whether our speech ability is distributed across them or whether certain roles are focused in certain areas remains to be seen.
Even in healthy people, sometimes the language areas of our brain can play tricks on us. Tip of the tongue syndrome is a common occurrence when you ‘know’ the word you are searching for, but can’t seem to access it. It gets more common as people age and occurs more frequently in people who are bilingual, mostly when they are speaking their second language.
One theory is that the cues to the word you are searching for have caused you brain to recall another, similar word, which then blocks access to the word you want. Another idea is that the activation level of the word is strong enough for you to detect it is there, but not strong enough to access it directly. We know that people store memories in different ways, such as through motion, sound, colour or touch. This means we can sometimes find it difficult to "translate" a word from memory that hasn't been used in a while- this could be another explanation for Tip-of-the-tongue syndrome. Storing memories in varied ways allows us to pack more information in, but sometimes makes it harder to unravel when we need it
Do animals have language?
Animals certainly communicate- some using sounds, and others using body language, pheromones or even electricity. But does any of this actually constitute language? The first step in language is to associate sounds or signs with objects, and some wild animals do this. Vervet monkeys, for instance, have a different call when warning of an eagle than a snake. But to constitute proper language, there also needs to be syntax or grammar. This set of rules allows words to be combined into an infinite number of meaningful phrases and sentences. This seems to be something unique to humans- no wild animals have yet been found to use grammar. But that doesn't mean they definitely don't- it could just be their form of language is so different from our own we aren't able to recognise it.
This article was written by the Things We Don’t Know editorial team, with contributions from Ginny Smith, and Cait Percy.