[SOUND] So the plan for this course is to look at these three topics.right. Age of acquisition, what Ribot termed the law of regression, or the fact that earlier learned memories are better preserved. Proficiency, what Petri's termed as familiarity, or the fact that things that are used more often are better preserved and then control. What Putzel termed as a fixation, or the ability to move flexibly from one language to the other. And these three topics continue to exist in the psychological, and the neuroscience literature today. And what we'll discuss in this course is, how these three topics exist in different domains. So, we'll begin for each one, right? With, so let's start with age of acquisition. Right? When something is learned. And we'll consider it, outside of language. Right? There are phenomena, that can be studied outside of language which involves learning things early or later in life. And we can discuss how those are different, how early and late learning is different, and what that might tell us about language, and how early and late language learning is different, regardless of bilingualism. And finally, how early and late second languages are different from each other. So we'll proceed that way. We'll then go on to talk about familiarity or proficiency. Or if you read the non language and literature expertise. Right? There's a large literature on expertise that's been, studied for many, many years, looking at things like chess or music or, sports. Different domains in which people become experts, and we want to uncover what's the difference between an expert and a novice, and so we'll discuss that literature. We'll then move up to what's the difference between someone who speaks a language, proficiently, or less proficiently, a single language. And then finally, how do first and second languages that are spoken proficiently or less proficiently, how are those represented in the brain? And finally we'll go to control, which again there is a large literature on what's called non verbal control. Right? Having to, to do different tasks, in real time that do not involve language necessarily. We'll then talk about verbal control, in which there are tasks that are done, for example the Stroop task is an example of verbal control that's been done a lot with monolinguals, in which people look at, a green word in red, font and they have to say the color of the font, not the color of the word. This creates a kind of interference when they don't match, the color and the font don't match, relative to when they do match. And so this is a form of verbal control. It's studied in the monolingual literature. And then, finally, we'll look at control within the bilingual literature. And some newer findings suggesting that bilingualism may serve as a form of brain training. That helps one to exercise the brain, because of the switching that occurs from one language to the other. The next thing we have to think about are the metaphors of the mind. Right, how do we think the mind works? One possibility is that we think it's like a computer. Right. This is called information processing. It was, a revolution in the 50s to start to think about the mind as a computational, machine. So, we could think of this as, it was called human information processing. Right. We were information processors. And I think there's nothing wrong with calling us information processors. That's not an incorrect statement. When we think about the mind, and we think about it as a computer, then, for example, let's take memory, right? If I want to remember what, something for a very long time, then it gets stored in some form of a hard disk. It's there forever, right? If I want to remember something temporarily, somebody tells me their name. Somebody tells me a phone number and I want to remember it. Then I have to keep it in some form of RAM. Right? So that's one metaphor of the mind. A second metaphor that we could use, is we could start to think about a linguistic metaphor. So, if we want to think of our language. Our language is composed of different pieces. Right? The sounds we use to compose the words. The words we use to compose sentences, if it's written language, the letters that are used to compose words, the words that are used to compose sentences. If it's an, a sign language, the hand movements that are used to compose, the different signs that are then put into sentences. And so it's always got this hierarchical structure, right, this layered structure as I mentioned, just a minute ago. And we can think about a linguistic analysis of the different pieces of language and concepualist, conceptualize it that way. A third possibility is to think of the brain and the mind, and think about different abilities being localized or represented in different parts of the brain. The brain is a complex machine, right And there are some aspects of our processing that are localized to specific places very close to specific places and there are other aspects that are handled by many different areas of the brain. Right so it's not exactly like we have a storage closet. In our brain, and there is one area that is magically assigned to one language versus another, or to one process versus another. There is a lot of cross talk between the different areas of the brain. So let me, let me end with some final introductory thoughts, the first thing I think we should take out of these cases is that language is not one thing. Right? It's, it's very complex, right? There are lots of different layers to language. We could think of the sounds that compose the words that if, for someone who is producing spoken language. In, in sign language, it would be the different pieces of hand movements that are used to compose words and sentences in sign language. We can start there. We could start with letters that compose words in written language. We can talk about words that compose sentences. And sentences that compose larger pieces of language, right? There's a hierarchical structure, such that there's small pieces that, each time, combine, to form larger and larger pieces. Now, language is a complex thing, and it develops over time. You know, lots of times, people ask me, you know, is it really hard to learn a language when, you know, you're 12 or 13? You know? It's so much harder to do that. You know, in my native language, I already knew it at 12 or 13. And I say okay that's fine and I agree at 12 or 13 someone who speaks, spoken a language for 12 or 13 years of their lives, speaks it quite well. But the question I always ask is, why do they continue having languages classes until their 18? If they already know the language, right? So language is a very complex thing. People have language classes they can have language classes till their 20s, 30s, they can go back and take language classes when they're much older, to learn how to write in a certain manner for business, for their work, right? So language is a very complex thing, it takes a very long time to develop. And there are lots of different layers to it. So I think we need to consider that, when we think about language development, and that it's a very long horizon. And how it gets put together, and falls apart can be quite complex, because of the complexity of developing the system that layers itself across time.