Okay, welcome back. The third module, seventh unit of this course. Last time I left off by characterizing this general pattern that behavioral [UNKNOWN] is observed when they collect developmental data. That if there is a shared environmental influence, what you seem to see over time As an individual age, is that shared environmental influence declines while genetic influence is increased. And the question is, why does that pattern obtained? In this third module, I'm going to give the behavioral genetic Conceptualization of, of for it, that developmental pattern, and it's, based on the notion of Gene-Environment Correlation. A concept that I introduced earlier in the course, but in this module we're going to look at it more in depth. So what is Gene-Environment Correlation? Well strictly speaking, Gene-Environment Correlation, is nothing more than a statistical correlation. Between a genetic effect and an environmental effect. That makes it seem like a rather dry mathematical abstract concept. In fact, the notion of gene-environment correlation is psychologically rich. And it's psychologically rich because behavioral geneticists have characterized Three mechanisms by which genetic factors and environmental factors can come to be correlated with one another. And I'm going to go through each of these, at this point. The first behavior geneticist called passive gene environment, or G-E correlation. Passive G-E correlation arises because parents who transmit genes that might promote the development of a particular trait are likely to also create a rearing environment that promotes the development of that same trait. And thereby induce a correlation between the genes they transmit. In the environment they shape or create for their children. So, for example, if you considered a high ability parent to the extent that ability, general cognitive ability is a heritable trait, and hopefully at this point, you would agree that it-, to some extent is, then a high ability parent Will be transmitting genes to his or her children that would promote the development of high-ability. But also, that parent is likely to value high-ability activities and is likely therefore to create an environment that fosters the intellectual development of his or her children. So the genes here she's transmitted become correlated with the environment she or she provides with the child. And behavioral geneticists call this passive, because the child herself or himself really has no role, it just happens. It's something that the parents essentially enforce. The other types of G-E correlation, the individual involved plays a much more prominent role. The second type of G-E correlation is called reactive, gene-environment correlation. And what reactive G-E correlation recognizes is that the environment, the social environments We all experience are in part a reflection of our own behavior and to the extent our behavior is genetically influenced. Then our environments become correlated with our genes because our behavior illicits certain reactions from others. And, again, if our behaviour is genetically influenced, those reactions become correlated with our genes. So, a simple illustration of this. The environment that a crying, colicky baby will experience is going to be fundamentally different from the environment that a happy baby experienced. A laughing baby. Why? Well because this baby is going to elicit different reactions from its parents, from its relatives, from its siblings, from its caretakers than this baby. And those reactions that we elicit from others Probably shape our personalities, our psychologies. So, in part to the extent that being crying, and colicky versus happy, and easygoing reflects underlying genetic factors. This induces a correlation between our genes. And the environments we experience. Another example, a child who's impulsive and inattentive is going to illicit much different reaction from his or her's teachers, parents, and peers at school. Than a child who's conscientious, and turns in all their school assignments on time. So to the extent to which your impulsive versus nonimpulsive reflects in part underlying genetic factors. Then the experiences that we illicit from others by engaging in impulsive behaviors will become correlated with those genes. That's called a reactive G-E correlation. The third type of G-E correlation is called an active G-E correlation. And what active G-E correlation recognizes or acknowledges is that we all to some degree, some more than others, but to some degree, we all shape the environments we experience. We shape those environments by choosing what we decide to do. And again, we're not totally free to do that, and some of us for various reasons, maybe economic reasons, have greater independence in making those choices. But all of us, to some degree, do decide what we're going to do. And those decisions are probably influenced by our abilities, by our interests, by our values, and to the extent our abilities, our interests, and our values are genetically influenced. Then our genetic factors are going to be correlated to the environments we experience. So for example, some of us were going to go to the library and study on a, on a Thursday night, whereas others are going to go to the pub and drink. Those are choices we make. Well you might not be totally free to make those choices, but clearly if you're going to spend a lot of time in the library, you're going to, experiencing a different world. Then if you spend most of your time in a pub. And certainly those experiences are going to shape your pyschology. And to the extent that our abilities and our personality shape our decisions as to wheater or not to study, or drink. Then genetic factors are going to influence the environments we experience. That's called an active G-E correlation because we're, the individual him or herself, is actively shaping the environment he or she experiences. We know that G-E correlation is pervasive. And we know it's pervasive because if we look at lifestyle or environmental measures in twins, Inevitably on those environmental measure monozygotic twins are more similar than dizygotic twins. Now there are many, many illustrations of this I've kind of selfishly, egotistically use one that of a study I recently did with my colleagues in Denmark where we took a large sample. Was almost 4000 pair of middle-aged Danish twins, and we looked as six different lifestyle factors. So these are middle age individuals, no, no, no they're not living together anymore, and all I'm are reporting here are the mz and dz correlations for both men and women. Whether or not you smoke, you drink, whether or not you eat a lot of vegetables or fruits, how physically active you are, how intellectually active you are, how socially active you are. You're not totally, not every individual is totally free to make these choices. But to some degree, we all have some influence on the experiences that we have. And when we have those influences, what we find is, inevitably, monozygotic twins are more similar than dizygotic twins. Monozygotic twins experience more similar environments than dizygotic twins. Why? Because they choose to experience more similar en, environments. That there is a G-E Correlation. Well, why is this important? There's three reasons, that G-E correlation is important in psychology or behavioral genetics. The first, that I've listed here, I'm actually going to take up in the next module. The notion of gene correlation is fundamentally important to understanding parent offspring resemblance. And that's something that I'm going to go into detail in the next module. Second and I mentioned this very early on in the course, but I want to return to it here. Is that, for behavioral, behavioral traits are really fundamentally different. When we're talking about the genetics of them, then physical traits. Because for behavioral traits, one mechanisms of genetic influence, Is G-E correlation. I want to relate this back to a study I talked about when we talked about general cognitive ability. And we found out that general cognitive ability is much less heritable if you grow up in an impoverished environment than in an economically enriched environment. Now, it's not like there are genes that are active and expressed when you grow up in a rich environment and those genes are somehow turned off in an impoverished environment. That probably isn't why the heritability of general cognitive abilities is higher here than there. The reason it's probably higher here than there is that, one thing an impoverished environment does. Is it removes, to a certain degree, an individual's ability to shape his or her environment, to allow them to make choices that would allow them to fully develop their genetic talents. The heritability of general cognitive ability is probably low in an impoverished environment because you're breaking up this active gene correlation. That you're not allowed, or you have a diminished capacity to choose the activities that would allow you to fully those genetic talents. So that's a very fundamental and important way by which genes can influence behavioural differences. The environments we choose. The last thing, and I'm going to touch on it here before wrapping up this module, is that, this is how I got going on this notion of gene correlation, it really helps us understand developmental changes in heritability. In that shared environmental influence. And the theorists that have done most to explain how G-E correlation and help us understand those changes in, in heritability. Are two researchers Sandra Scarr, who's a very prominent development psychologist and behavioral geneticist, and Kathleen McCartney Who's a, a prominent developmental psychologist, they actually is currently the president of Smith College out of Massachusetts. And what they argued is that, that pattern of shifting heritability in shared environmental influence is really reflecting a different pattern of GE correlation. Passive G-E correlation they argued, declines with age. In a decliance with age because earlier in life, your parents have a big say on the environments in you're experience. If you think about an infant, the parents almost define the environment for an infant. But as you get older, parents lose more and more control And you take over more control. So the declining shared environmental influence in this scheme is hypothesized to reflect a diminishing impact that parents have in controlling the environment of the children they rear. What accounts for the increased inheritability? Well the complimentary developmental trend, that is as you get older, your parents are losing control, but you are taking control. Again the notion isn't never that you will have complete control over your experiences, but certainly a 25 year old has much more say over the experiences he or she will have than will a, a five month old. And as you get older, the decisions you make about what you're going to experience are going to reflect in part your personality, your abilities, things that are genetically influenced. Inducing an active G-E correlation that is hypothesized to be the basis for increasing heritability. Finally in their scheme, reactive g correlation the, the environments that we create by eliciting reactions from others by our behaviour. In this scheme that's thought to actually be relatively constant in its impact across development. But the shared environmental influence. Reflecting a decline in passive G-E correlational effects. The increase in heritability, and the increase in the importance of active G-E correlation. Next time, we'll take up the notion of how behavioural geneticists view family socialization processes. Because really the behavioural genetic finding of little shared environmental influence seems to fly in the face of the notion that we're socialized by the families we are reared in. Thank you. [SOUND] [BLANK_AUDIO]
