OK. So far we've spent a lot of our time talking about the origins of behavior. And so we've talked about the genetic component of behavior. And we've talked about the environmental component of behavior. And we've talked about how you can tease apart both of those influences and try to come up with some statistical models for their relative influence. But today I want to push past that. And I want to talk about the function of behavior. Because behavior, really, at a high level, is a homeostatic mechanism. And so when I say "homeostasis," what I'm referring to is the maintenance of a constant internal condition. And so we're defining behavior as the coordinated internal and external response of an organism or groups of organisms to their environments. So really, behavior is functioning in the big picture in a homeostatic sense in the realm of adaptation. So the field that's concerned with this functional study of behavior, especially the study of animal behavior in a natural environment, is ethology. So ethology. And really, ethology centers on the observations of these animal behaviors. So we call these observable behaviors overt behaviors. And I want to clarify here, because sometimes "overt" is used to describe something that's like hyper obvious or extremely exaggerated. And I'm just using the word to mean observable. So simply observable. But behavior gets further broken down from here, so further broken down past overt into, generally, three psychological categories. So we have innate behavior. We've got learned behavior. And we've got complex behavior. And we're going to see how these categories contribute to the adaptive value of behavioral traits. So first up, we have innate behavior. And when I say "innate behavior," I'm talking about behavior that's genetically programmed. So that's a DNA, because this is genetically programmed. And generally speaking, innate behaviors are going to share some characteristics. And to save a little bit of time, mostly so you don't have to watch me write all day, I've gone ahead and pre-written out this list. But we're going to go through this list of shared characteristics of innate behaviors. So first up we have inherited. And what I'm saying when I say "inherited" is that innate behaviors are encoded by DNA. And they're going to be passed to offspring, so inherited. And then next on the list we have intrinsic. And "intrinsic" means that these innate behaviors are present in an animal even if it were to be raised in isolation. So you can think back to that example that we used in a previous video of the barrel boys. And we said that these boys were raised in complete isolation in a barrel, but they still had some behavioral traits that were specific to humans. They still breathed like humans. And they still urinated and they pooped like humans. And we would say that those behavioral traits are intrinsic. And they're innate. And so further down the list, innate behavioral traits are stereotypic. And what that means is that they're performed the same way each time. So they're stereotypic. And innate behaviors are also inflexible. And that means that they're not modified by experience. Again, these are innate, inside you, not modified by experience. So they're inflexible. And lastly, we say that innate behaviors are consummate. And what I mean by "consummate" is that they're fully developed right away. So at their very first performance of these behavioral traits, they're fully developed. These aren't influenced at all by experience. So because these innate behavioral traits are encoded by DNA, they're subject to genetic change through mutations and recombination and natural selection, just like any physical trait would be. And so as a particular example, my wife is currently pregnant. And like many pregnant women in the first couple months of pregnancy, she experiences a lot of nausea. So here's my wife. And I will try not to let her know that I'm drawing her like this figure. But this is her. And she's pregnant. And she's experiencing a lot of nausea. And actually, a study in 2004 suggested this nausea encourages women to avoid bitter and strongly flavored and novel food, and that this innate trait might have had an adaptive role in the past in natural selection by helping women to avoid toxic foods in the most critical period of prenatal development. But in general, these innate behaviors are thought of as programmed. And they usually fit into one of three categories, the first being reflexes. And reflexes are really the most basic innate behavior. And they involve a reflex arc. But what you see is a preprogrammed, automatic, near instantaneous response to a stimuli involving a sensory nerve and a motor nerve. So I'll draw a brain to represent the central nervous system and the spine. And what you have, essentially, is a sensory nerve responding to some stimulus and a motor nerve effecting a preprogrammed, near instantaneous response to that. And this is just a looped response that doesn't require even any thinking. And a great kind of classic example is the knee-jerk reflex. And when you go to the doctor office, he may hit your knee with a little hammer. And he's eliciting your knee-jerk reflex. But reflexes are one of the categories of these preprogrammed, innate behavioral traits. So the next category would be orientation behaviors. And these are the behaviors that are involved in regulating us spatially in our environment. And again, these are preprogrammed. And so these are automatic responses to the stimulus that come packaged in our DNA. And one example of this would be kinesis. And kinesis involves our change in speed or the change of rate in turning. So change in speed would be orthokinesis. And a change of rate in turning would be klinokinesis. But this is in response to a stimulus. So you can imagine tripping on a sidewalk and your body naturally changing the speed of your fall or momentum. And that would be kinesis, an example of kinesis. And the next one would be taxis. And what taxis is, is a movement towards-- so a movement towards would be positive taxis-- or a movement away from, and that would be negative taxis. But movement towards or away from a stimulus. And so an example of this that you're probably actually quite familiar with would be insects and light. So let me draw a light bulb. And if I draw a little moth, you've seen what happens to them near light. They are just automatically attracted to that light source, sometimes to their demise if it's a bug zapper. But this is an example of phototaxis. They are moving automatically towards this stimulus. And that is an innate behavior. And then lastly, we have this category of innate behavioral traits called fixed action patterns. So I'll abbreviate that as FAP. And so a fixed action pattern would be a sequence of coordinated movements that are performed without interruption. So very similar to a reflex, but this time involving coordination of multiple movements. And an example of this would be a praying mantis. So this is my praying mantis. And any prey-sized movement that a praying mantis experiences within striking distance initiates a strike. And once that strike is initiated, it involves multiple movements. So it's both of its arms and its back. But once initiated, it can't be changed or redirected at all. And so that's a classic example of a fixed action pattern. And is that third category of these innate behavioral traits. And so we have these innate behavioral traits that are functioning towards our adaptation so that we can maintain our homeostasis. But also we have learned behavioral traits. And so learned behavioral traits are those persistent changes in our behavior that result from experiences. And so much like innate behavioral traits, learned behavioral traits have some kind of general trends to them. And I've written them down as well to save a little bit of time, but we'll go through them. And the first characteristic of learned behavioral traits are that they are non-inherited. So where innate traits were inherited and they were programmed into DNA and passed to offspring, these are non-inherited So they're acquired only through observation or experience. And then below this, we have extrinsic. Again, what "extrinsic" means is that these are absent in animals raised in isolation from others. So maybe an example of this, in that barrel boy example that we've been using, would be social skills. Social skills are a behavioral trait that would be absent in these boys that were raised in isolation inside these barrels. So that's an extrinsic, learned behavioral trait. And then moving down the list, we have a permutable. And so "permutable" means that this is a pattern or a sequence that can change over time. So you can think of this as changeable. But then we have adaptable. And I've drawn a little asterisk here with adaptable, because I don't mean to say that innate traits don't contribute towards our ultimate adaptation. But this is talking specifically about the trait. So this actual trait is adaptable. So it's capable of being modified. And it's suited to changing conditions. But that's adaptable. And then last but not least, learned behavioral traits, generally speaking, are progressive, which means that they're subject to improvement or refinement through practice. But there's going to be an entire playlist that focuses on the adaptive value of behavioral change in learning. And that would be a great place to start exploring the concepts of habituation, classic versus operant conditioning, and latent learning, and imprinting. But it's important to briefly mention that learning plays a big role in the adaptive value of behavior. So again, behavior at a bird's eye view focuses on homeostasis, right here, and has primarily an adaptive role. And then the last thing I want to do in this video is one more time tie in the relationship between genes and environment in adaptation. And that fits nicely into the last category of overt behavior, which is complex behavior. So like just about everything in psychology that we've studied, although we introduced the ideas in absolute terms, so we introduced innate and we introduced learned, ultimately we tend to reveal that most ideas fit into a spectrum. And so really, most behavior is actually somewhere between innate and learned. And as an example, let me draw an insect. The ability of an insect to fly, it starts off as innate. All these insects, they're born with their wings. And they have this innate ability to fly. But eventually, through learning, the insect becomes more efficient in their abilities of flight. And so this flight trait, its adaptive role is ultimately further accentuated. So it starts off as innate, but it's accentuated through learning. And this would be a complex behavior. But we've come from studying the relative role of genes and environment in forming behaviors. And now we can see that same relative role of genes and environment in contributing ultimately to the adaptive role of these behaviors.