The Gestural Theory of Language The initial language in hominids was gestural, and communication using the hands was actual

The Gestural Theory of Language
    Good morning everyone. Today’s lecture is about the gestural theory of language. The idea here is pretty simple. The idea is that in hominids, the species whose descendents include us, initial language was gestural. Walking upright, bipedalism, freed the hands for communication, and communication using the hands was actually the first form of language.
     (1)We know, as I’ll show you in a minute, that sign languages can be very complicated, but sign languages have a limitation. In order to be able to communicate, you have to be looking at the signer. If you’re not looking at the signer, everything else is lost. That’s not true with sound. In sound you don’t have to be looking at the person, you can be in the dark and still have a conversation. One of the theories of the origin of language is that sounds were first associated with language because they drew attention to the signer. In this particular diagram this guy here, making noise, signals to the recipient that he’s about to say something incredibly significant with his hands, like "Look out, there’s a predator ahead. " That sound simply drew attention to the signing, sound took over. The gestures became vocal; they went from being hand gestures to being vocal, and were thus invisible.
     (2)What’s the evidence for this? Well, we have a large are group of human signers that use different languages. Here we use mostly American sign language in the United States, but there are a number of different sign languages that use gestures and are very capable of communication.(3)Sign languages meet all of the criteria for languages. They have large lexicons. There are a very large number of gestures. They carry meaning, and they’re grammatical. The order in which they’re made has a very profound significance in terms of their meaning.
     (2)(4)Another piece of evidence in favor of the gestural origin of sign language comes from a very interesting study on how we perceive sound. As I’ll show you in a minute, sound and visual information can be combined within the nervous system, where the meaning of both is the same and activates the same group of neurons. We can see this very profoundly in a phenomenon called the McGurk Effect.
    You’re going to see somebody speaking, and you will hear speech sounds. If you listen to these sounds with your eyes open, they will sound different from what you listen to with your eyes closed, but the guy is making the exact same sounds all of the time.(5)What’s different is that when you hear a sound together with a set of lip movements, it actually sounds different to you compared with what you hear by yourself. So here’s the McGurk Effect. Keep your eyes open for the first two sounds, close them for the second two sounds, and then open them again for the final two sounds.
    "Ba ba, ba ba, ba ba."
     (6)If your eyes were open the whole time, or closed the whole time, they’ll sound identical, but if you opened your eyes in the middle they’ll sound different. We think we hear what we hear, but apparently what we hear also depends on what we see when it’s a human speaker. This is a good example of the combination of visual input and of gestures.
     (7)At the level of the nervous system it turns out that there are nerve cells, there are neurons, that display the ability to respond to sound and also to respond to visual stimuli. These are called mirror neurons. In one case the sound is turned off, and in the other case the visual stimulus is turned off. In both each one of these little hash marks here represents one action potential—what you can see is that this neuron is excited both by the sight of ripping the paper and also by the sound of ripping the paper. The neuron, in a sense, represents paper ripping.
    If we go and map the occurrence of these mirror neurons in the brain of a rhesus macaque, so this is front and this is back,(8)what we see is that there are groups of mirror neurons, there are groups of neurons that are thought to be involved in language in humans, and they overlap.
This has actually been done. We have results of a study here in which they looked at the area of the hypoglossal canal. You can see that in humans you have the very big hypoglossal canal, particularly since our oral cavity volume is not so huge.
    But look, we completely overlap with chimps.(9)So while having a lot of axons may be necessary to innervate your tongue, it isn’t sufficient for the development of language. We’re looking for necessity and sufficiency. We can go back and we can take a look at all of these values in the fossil record. In fact there is no strong correlation between language itself, its emergence, and hypoglossal size.
    Okay. How about the way we create sounds themselves? How about the human vocal organ and the human vocal tract? In humans we can tell a lot about the speaker.(10)You can see this pretty clearly when we look at the fundamental frequency in hertz. Then what happens at the time of puberty is that it drops in both of them. The pitch of voice also carries communication significance, and that’s because the vocal folds thicken at puberty due to the action of sex hormones.
    One of the things we can look at is we can say okay, let’s look at the tongue and the larynx and the air sacs in humans and in species—non-human primates—and ask what’s going on. It’s actually kind of dangerous to have a descended larynx, it makes it much more likely that food will get stuck. It’s actually the origin of having to do the Heimlich maneuver. Once again, it might have been necessary but it’s not sufficient.
    All right. Today we discussed the gestural theory of language. I hope you will have a more clear understanding of it. Thank you very much!