[Music] welcome back to the developmental psychology chapter in this chapter we'll be talking about the younger years of development in life primarily the time between conception until adulthood although it will speak about the later years of life a little bit after to get started with we're going to take a look at some of the definitions and general topics that are involved in developmental psychology developmental psychology is defined as the study of the physical cognitive and social changes that occur throughout the lifespan now as a psychology student you should recognize that whenever you see a psychologist make a definition that says the physical cognitive and social changes that they really means something else they're really saying everything we can think of because when you take a look at the aspects of physical development cognitive development and social development it fully encompasses all of psychology all of the basic physical development that occurs throughout your lifespan that affects how you're going to behave your cognitive aspects are really a very general category the term cognitive is a very broad category that includes all thinking and feeling and internal activities that you may not even be aware of and social of course includes all of the aspects of you interacting with others in the world so physical cognitive and social really means all of the things that you can think of the things that you're aware of today and all the things that you might be aware of tomorrow but always in every case for a project to be a developmental psychology project you have to study it over time time is the primary function in the field of developmental psychology that sets it apart from other fields of psychology everything in development is always studied over time typically it's studied over the course of years in which we're aware of change occurring say for example from five year-olds to 15 year-olds or from 20 year-olds to 50 year olds changes that occur over time are the purview of developmental psychologists now the term developmental psychology has traditionally referred to the time from conception through old age but it has started to imply the point from conception until adulthood so approximately age 20 lifespan development has been the term that has now become primarily used for referring to the entire life of an individual so if you were to take a class in developmental psychology next semester it almost certainly would include everything from conception to about early adulthood but if you were to take a lifespan development course it would include everything from conception up until old age now the field of developmental psychology was essentially around at the very beginning of the time of vaunt and the early labs in 1879 work was being done of the Veltman psychology back at that time and as you see in this graph there has been a continual increase in the amount of developmental psychology completed every decade and that number continues to rise one of the main issues from this figure that I want you to draw upon is the fact that there are too many articles written in developmental psychology each decade for any one person to realistically read every single article that is actually published which means if there's too much data for any one person to cover that requires people to specialize now and so you do consistently see that individuals in the field development are not generally generalists but they are specialists in particular areas of development such as educational development morality physical development other kinds of cognitive structures and so forth now let's take a look at a question related to the definition of developmental psychology which of the following is not a lifespan psychology experiment and the correct answer there is D vocabulary comprehension across cultures in this case vocabulary comprehension across cultures the comparative aspect across cultures does not involve an aspect of time if you take a look at answer a memory processes across adulthood simply tells you that you're going to look at things across time learning across pre-adolescence that is again telling you change over time in see comparing physical strength between young adults and the elderly certainly certainly implies time and II which is written a little bit more vaguely educational influences on intellectual development the term development there implies change across time so it also fits the basic definition of developmental psychology so looking at the number of words in the vocabulary of a child a five-year-old in London or Sydney Australia or Boca Raton Florida would be a comparison across cultures to see whether or not there was the same size English vocabulary in each of these three cultures now they get started with development I mentioned repeatedly that we would start at conception and conception has probably been taught to you in the past that one sperm and one egg create a single individual unless of course that fertilized egg splits and you wind up with identical twins but the story of one sperm in one egg is typically given throughout middle school in high school but the variation on that which is now known to occur which is the development of a chimera is part of a story that simply has not filtered down through the science books yet a chimera is an individual who has been created through more than one sperm or one egg and not in the traditional process of twins that we were talking about but rather in a unique fashion so for example chimeras are the name given to an individual that may have been created through two sperm reaching an egg at the point of conception and that actually both sperm cells get into the egg and form a completely healthy individual how you know an individual may have been created this way is that once you do a genetic test on that individual usually in adulthood you will find different DNA signatures in different sections of their body so unlike most of us we have the same genes no matter where in our body you draw the sample from hair skin saliva blood but for a chimera they will have one set of DNA in one portion of their body and another set of DNA and another location which parts of their body obtain which set of DNA appears to be completely random there's a lot of open questions about chimeras but at the at the current time it appears to be completely random another possibility for forming a chimera is to have a fertilized egg fused with an unfertilized egg so that during conception there may be two eggs available but only one becomes fertilized and then at a very early stage of development the fertilized egg bumps up against the unfertilized egg and so you wind up with a single individual that actually has different DNA as a result of the mixture of that sperm with the two separate eggs also occurring again in a very early stage of development two fertilized eggs my fused together so for example in a scenario in which fraternal twins would have been born there were two available eggs each one is fertilized by a single sperm and then the two fertilized eggs probably within the first two weeks after conception physically touch and then fuse into one single individual thereby giving multiple DNA signatures to the individual that is born and finally two embryos fuse together and in this scenario you have the latest stage possibility of having the individuals fuse together in cases where two embryos fully fuse together the individual who is born may never know their entire life that they were a chimera however in some cases the fusing is not complete and the partial fusing of two individuals together produce what's called conjoined twins which of the following reasons would ensure that the difficulty of determining the base rate of chimeras in the general population and the correct answer here is a you have to check every cell in your body to rule out that you're not a chimera the issue with Kaymer ism is that when an individual is born they don't show any immediate outward signs of being a chimera as a result people have typically found out that they have they are chimeras by accident typically through the use of genetic testing for completely different reasons other than trying to evaluate their status as a chimera so in genetic tests that are establishing paternity or genealogy sometimes lead to individuals finding out by accident that a hair sample or a blood sample from the same person indicated that they were two separate people and of course when those lab results come back indicating that the hair sample the blood sample came from two separate people but you know that it was your hair in your blood you find out that you're a chimera this process makes it extremely difficult to find out how many people are actually chimeras in the general population simply because as best we know now which portions of your body are taken over by one set of genes and which other parts are taken over by the other set of genes appears to be completely random so if you were to check to see whether you were a chimera you could do some simple genetic testing on yourself like comparing your saliva and your hair but if your saliva in your hair match genetically it would not rule out the fact that you were not a chimera because it might not be hair and saliva that are actually different it might be blood or skin or bone or just one particular internal organ like your kidney for example might have the separate set of genes from all the rest of your body as a result you would have to literally check a sample from every soft tissue and bone inside your body and that has two problems one it's going to be unethical because you're going to cause damage when you start taking tissue samples from the central nervous system which we've already established that in the neuroscience chapter that that damage will essentially be permanent also you're not going to be able to pull a sample from the inner ear bones from somebody's cochlea because they're too small and of course you'll also cause permanent damage there okay so even if you just ignore the whole ethical aspect of it currently the skill it would take to be able to draw samples from every cell in your body is really just not there and so you really don't have a very good scenario set up to evaluate the base rate of Kaymer ism so the estimates of Kaymer ism in the general population are typically made based upon the accidental discovery of individuals through the use of genetic tests for genealogy and medical purposes that simply occur randomly as a result there is a very loosey-goosey estimate of the rate of Kaymer ism in the general population which seems to be fairly low and approximately around one to two percent however the reason why I stay on this topic so long is because it actually has a substantial influence on work that you've already covered in chapter 3 on nature-nurture we talked about how the Pearson correlation coefficient establishes the degree of similarity between two individuals that have some amount of genetic or environmental similar clarity so if you remember the slide that we covered the overarching estimate statistically of the degree of similarity whether somebody was an identical twin raised together raised apart a fraternal twin raised together raised apart general siblings raised together raised apart or people from the general population all of the statistical work from the field of behavioral genetics would have to be completely revised if the base rate of Kaymer ism was actually reasonably high because the estimates of genetic similarity in the field of behavioral genetics all come from the assumption that every individual is created from one sperm and one egg and if the base rate of Kaymer ism naturally occurs at a high rate in the general population then that estimate from the field of behavioral genetics was incorrect and everything since 1980 has to actually be redone statistically in fact it would throw chaos into that general field and so this issue of Kaymer ISM which nobody was really aware of until it started to appear accidentally as a result of the use of genetic tests and paternity and other types of medical events simply threw a monkey wrench into the whole story so you have to be aware of this as a psychology student going forward especially if you plan on going to graduate school because if this issue of the base rate of Kaymer ism ever turns out to be a fairly high estimate then the entire field of behavioral genetics has to essentially be re-evaluated starting from the story of conception there are going to be three prenatal stages of development that are relevant for us in psychology now keep in mind of all the details that might exist developmental biology course we could spend years discussing all the underlying biological events that occur in the development of a fetus but we're focused very specifically on the aspects of development that will eventually play out in some useful aspect for us in the field of psychology so we are selectively cherry-picking events in early development to focus upon that are relevant for later aspects of psychology in this case these three prenatal stages of development give us different components of relevance with respect to the developing fetus the three stages of prenatal development are called the germinal period the embryonic period and the fetal period the germinal period runs about two weeks the embryonic period will run from about week three to week eight and the fetal period will run from about week nine to week 38 those stages are actually very important to remember and there is kind of an underlying rough estimate of the length of those time periods that you should be aware of note that the germinal period runs for two weeks if you multiply the length of that period by four you would be at the eighth week and that is of course the end of the embryonic period and if you multiplied the eighth week by four again you would be at 32 weeks now that's six weeks shy of the 38 period end of the fetal period however 32 weeks is actually the estimate for the earliest period in which you could have a normal birth so not a premature infant one thing to be aware of as terms of a rough estimate mnemonic to be to remember these stages is that the first stage is two weeks long multiplied by four to get to eight multiplied by four again to get 32 and that would be good enough for our purposes now in the germinal period most of your chimeric opportunities are going to a car as you might imagine you as an adult now have zero chimeric opportunities right you can't grab somebody's wrist on the street and then simply morph into a single individual all right there's no biological process for that type of absorption between people to occur after the time that they're born and certainly not in adulthood you have to go to a very early stage of development to see any of these chimeric opportunities and for the most part they typically exist within the first two weeks of life most of them certainly the ones in which there is going to be a full absorption between two separate fertilized eggs are going to have to occur within the first two weeks now when you get to the embryonic period starting at week three you begin to see a new process a separate process that's relevant for us and that is called the process of organogenesis if you look at that name organogenesis it's the organ genesis or the beginning the genesis of the development of the organs that's what the time period of organogenesis is the beginning of the development of the internal organs so and this is occurring of course only three weeks after conception so you start to see the very beginning of kidney and liver and gastrointestinal tract and so forth developing at this time now the reason why the development of these internal organs is relevant for us it's not because typically the kidney and the liver of really relevant for us in psychology but rather it is part of a broader context in understanding birth defects which we will focus on more so in terms of the central nervous system for a psychology course rather than just general aspects of birth defects but the basic rule in understanding birth defects is that you would maximize birth defects if you take an outside substance and make it present at the very beginning of the period of development for any particular organ so if you know that the kidney is just starting to develop today today is your best opportunity to maximize a kidney development disorder if you start throwing in some outside substance like cocaine or nicotine or caffeine or any other substance that the mother might actually be taking and that's true across the board so it sets a context for understanding what birth defects are relevant for psychology which are typically ones that are most closely related to brain development and that is what we're going to see in a fetal period in the fetal period that runs from about week nine to week 38 there is one specific component of development that occurs here that is relevant for us in a psychology class and that is brain development more than anything else your brain is developing during the fetal period now certainly it does exist back in the embryonic period but the rate of development of the brain during the fetal period actually reaches its maximum and so that rate of development is new cells being developed and taking their place in the structure of the brain and more cells being developed and more cells being developed and so on and so on and so on as a result that maximum rate of development of brain is giving itself the greatest opportunity for disruption if outside substances are thrown in like nicotine caffeine illicit drugs too much carbon monoxide from being in a polluted environment any number of different things if the mother ingests it it will very likely reach the fetus and as a result it could wind up affecting brain development as a result the types of birth defects that occur that are most closely related to psychology such things as fetal alcohol syndrome are much more likely to occur as a result of the mother's exposure to alcohol which the child is going to absorb during the fetal period rather than alcohol being consumed in the germinal or the embryonic period and that essentially that general rule is essentially true for any other substance like a nicotine or caffeine or cocaine or amphetamines or other types of neuro sensitive drugs that would be ingested throughout the entire period of pregnancy it is that exposure in the fetal period that will most likely increase the chance of damage to the developing brain completely aside from any influence that might have on other internal organs now in terms of the physical development of the brain early on there are some interesting facts that developed back in the late 70s early 80s and that is the recognition that the brain of a child is born with in excess of synaptic connections now back in chapter 2 when we talked about the brain as a physical object and how neural pathways are created in the processes of neurotransmission one of the things that we saw was that the use of a particular neural pathway would always increase the number of connections between the cells in that pathway it is not necessarily increasing the number of cells in the brain but rather increasing the number of connections between the cells in that particular pathway and so you would typically expect that an individual that has lots of experiences with their environment the way you might by doing lots of different types of physical activity and having a wide range of intellectual input you would wind up with additional synaptic connections in certain areas of your brain depending upon what you're doing but infants have this broad-based increase in synaptic connections which is actually going to start to reduce now why does this occur the theoretical reason why this appears to occur is that it makes infants more adaptable at the earliest stages of life your brain controls a lot of your behavior and it also is involved in a lot of basic medical functioning as well like temperature control for example and so if you have a child born above the Arctic Circle where it's cold and dry or in a place where it's mountainous and there's a rain forest where it's warm and wet in a desert in a mountain in a city in a country the child doesn't know where they're going to be born but they will be more likely adaptable to any physical environment if they have these additional synaptic connections on the day of their birth and then having interacted with that climate and the interactions with the parents and so forth the connections that are needed are primed to be used and the ones that are not used simply start to fade away so this increase in synaptic connections at birth seems to be related to an adaptability issue for infants but it also influences your ability to develop language if there is an excess of synaptic connections in the areas that comprise your language center which remember for 90% of the Yuma population is in the left hemisphere and as a series of circuits that travels from the back end of the frontal cortex over to the temporal lobe what you have is an opportunity to learn any possible human language because the synaptic connections are there and primed to be used for any language English French Spanish Mandarin it doesn't matter what it is you are primed to learn any human language and as you grow up in a culture where you use that one particular language the pathways that would allow you to control your lips and tongue and throat and your your breathing to make particular sounds are strengthened for the language that you practice and for the languages that you do not practice for the sounds that your language does not make simply disappear so now you as an adult are in high school or college and now you have to learn a second language you have greater difficulty learning that language in part because there is a reduction in synaptic connections in your language center to support the development of new language learning so consequently you can see in a very general sense that infants actually are biologically primed to develop language skills slightly better than adults are of course adults would have mnemonic techniques and other types of processes from experience that they could use the make up for this process but there is still a difference in the brain of an infant or a a very small child who's learning language as opposed to an adult where you have fewer synaptic connections except for the ones that have been practiced since the early time of your life now a broader aspect of this story of physical development of the brain as seen in terms of brain plasticity and this is now the third chapter in a row where we have been talking about brain plasticity I first brought it up in the neuroscience and behavior when we talked about the brain as a physical object and whether or not your body would repair nerves in your central nervous system as opposed to your peripheral nervous system and of course as a reminder your peripheral nervous system will do a reasonably good job of repairing damaged nerves but your central nervous system does a tremendously horrible job of repairing damaged nerves now this broader aspect of neuroplasticity the ability of the brain to rewire itself as well as repair damaged cells is a very important part of development from birth up to adulthood and the reason is neuroplasticity always exists in greater amounts the further back you go in your biological history so when you consider at about three weeks of age when your brain first starts to development there will be much more opportunities for any part of your nervous system to repair itself if there's any type of damage that occurs this is also true all throughout the process of development from the embryonic into the fetal periods so if there's early exposure to alcohol in the fetal period it does corrupt some of the development of the brain it is still possible that the brain may correct for some of that on its own if the mother stops drinking alcohol it's a possibility now once you're born you have much more neuroplasticity available at that time than you will by the time you're approximately age 12 and you know an ear near the time of puberty in fact you have after the time that you're born the greatest amount of neural plasticity so that a an infant or a one-year-old or two year old can recover fully from brain damage in their central nervous system in a way in which an adult never could because the amount of neuroplasticity that exists is always reducing itself over the course of your lifespan up until around age 12 or so at which point you reach a low level that largely rides itself out for the rest of your life so in this chapter we will talk about how some things must be learned early in life such as language development or some aspects of socialization because when the brain is more readily able to rewire itself you have to produce these rather complex circuits when that greater neuroplasticity is there but if you miss the opportunity to teach language at a young age once the individual reaches adulthood you are simply not going to get a fully functioning language out of the individual because the brain does not have sufficient neural plasticity to form the circuits that it needs to be able to generate the language and you do see this in a general idea in the field of psychology that early developed mental processes are important and this is part of the reason why this occurs now you can apply this early developmental business in every single scenario but it does occur with some things like language and some aspects of socialization so when you see very severe neglect in some children at an early stage that runs from possibly the first ten years of their life there is a much higher chance that there will be a change in personality intellectual skills and language that will be somewhat degraded relative to the rest of society as a result of that lengthy process of neglect now let's take a look at this question which of the following stages is most likely important with respect to psychological processes and the answer there is C the fetal stage and that answer fetal stage is correct because the fetal stage is the one prenatal stage where there's primarily brain development going on the germinal period is a the first two weeks of life and there's no brain at that time your brain will don't start to develop until about the third week of life and then you'll be in the embryonic stage but not a whole lot of brain development will occur during that time period most of it will occur during the fetal stage now this leads us to some basic questions regarding physical development of infants now physical developments come in terms of reflexes over time all infants are born with a wide set of reflexes that help them survive they need these reflexes at an early stage simply because they can't communicate with adults or other individuals to ask for food tell somebody that they're cold about their only capacity they have is to lay on their back and cry you know when something is uncomfortable for them and it's up to the adults to figure out what's actually going on of the things that help keep an infant alive they fall into two categories of reflexes the survival reflexes and the primitive reflexes as you might imagine from the name the survival reflexes are all reflexes that help the child survive within the first month or so of life and then there will even be some carryover beyond that the primitive reflexes are reflexes that exist that don't appear to have any relevant value at the current time theoretically they are holdovers from earlier periods in human evolutionary history so that they are parts of behavior that where at one time relevant but are no longer relevant and so they are simply just a vestige remain of our genetic history and we'll take a look at all of these reflexes in a video in a short while but let's run through the list of survival reflexes first to get an idea of what is helping keeping the child alive first the breathing reflex the breathing reflex essentially is not the fact that you just breathe naturally that's part of brain control actually the breathing that's occurring the breathing reflex is actually a reflex that occurs when you're suffocating so that one of the last things that you can do if you were for example holding your breath to try to see whether or not you can make yourself pass out there's only so long that you can hold your breath before you will uncontrollably breathe in and that's the breathing reflex so it's a reflex that force is breathing to occur after an extensive period of loss of oxygen now you're actually probably a little familiar with the breathing reflex as a result of typical plotlines and police shows so for example in you know typical CSI police show common plotline is that a corpse is pulled out of a lake and then the doctor who performs the autopsy tells the police this person was murdered somewhere else and then thrown into the lake and the police always ask well how do you know that and they'll say well because his lungs are not filled with fluid and then you sit there watching TV and think how are you how are his lungs not filled with fluid if he's a corpse in a lake but the reason is the breathing reflex if you are drowning in a lake one of the last things you're going to do as you can't breathe is to breathe in you simply won't be able to stop yourself you'll get to a point that you'll have so little oxygen that your lungs will simply breathe in which will pull the liquid the lake water into your lungs which will essentially be one of the last things that happens that kills you that will establish that you were drowned in the lake but if the body was in the lake and its lungs were not filled with fluid then you can establish that the body was where the person was murdered somewhere else and then placed in the lake afterward the eye blink reflex is a very basic one anything that gets in your eye like an eyelash or a bug or anything to poke your eye makes your eye blink and of course your eyes blink naturally to lubricate the outside of your eye which is all of a relevant aspect to maintain your vision throughout your life now I blink reflex and the breathing reflex will be with you for your entire life as will the pupillary reflex pupillary reflex very easy one this is probably something you've done in a biology class back in middle school is to shine a little bit of light into another person's eye to watch how their pupil constricts and then when you take the light away their pupil will dilate to let in more light that's going to be with you for the rest of your life as well now a couple reflexes that are going to disappear after about two to four weeks of after birth are going to be the rooting reflex and the sucking reflex those reflexes are part of feeding the rooting reflex is a process that you're about to see in a video in which if an infant's cheek is stroked very gently they tend to make a sucking motion with their mouths and turn her head in the direction of the stimulation so in the normal way that a human mother would hold an infant is to cradle the child in her arms that generally places the mother's breast right next to the child's head and that stimulation will cause a child to make the sucking motions and turn his head toward the breast and that is called the rooting reflex after about two weeks of the use of the rooting reflex the processes of learning will actually start to take place and override the rooting reflex and then the rooting reflex will disappear and feeding will then be in control by the process of learning same is also true with the sucking reflex which is again the only way for which infants are going to feed at that earlier time and then of course the swallowing reflex which you still have now as an adult which simply causes you to produce swallowing motions when food is in your mouth or something else is stuck in your throat the primitive reflexes I think it would be much easier to understand those by watching the video that we're going to see next the primitive reflexes are again are just a classification of reflexes that have no particular survival value at the current time and they are theorized to be a vestige remain genetically from an earlier time period in human evolutionary history reflexes like the palmar grasp stepping more oh and Babinski are an inverse toolkit to help an infant adapt to the world many reflexes breathing swallowing and sucking for example have survival value other more primitive reflexes like the Moro and grasping are considered leftovers from our evolutionary heritage survival reflexes usually become voluntary at some point during the first year while the primitive reflexes disappear some reflexes are predominantly related to the nourishment of the infant here in response to stroking at the corner of Aiden's mouth we see the rooting reflex one week old Aiden turns his head and opens his mouth he roots in the direction of the stroking this helps the infant find the breast or bottle and begin feeding sucking is another reflex that helps the infant find food Aidan will instinctively suck on any object that is placed in his mouth including the doctors finger some reflexes are predominantly related to the protection of the infant stroking the palm of Mackenzie's hand will cause her to close her hands and fingers in a grasp the grasping reflex may be so strong that the baby can support her own weight the Moro or startle reflex is seen when support for the head and neck is suddenly lost or in response to a loud noise or sudden movement here one week old Aiden throws his arms out and back in response to the doctors sudden drop of his hands the Moro reflex which should be fully present at birth begins to disappear at around five months of age Jess apena who is just two months old has already begun to lose the Moro reflex absence of the Moro reflex at birth or reappearance after the normal age of disappearance approximately five months may suggest damage to the central nervous system so she doesn't have a startle any more mature then she's overriding that some reflexes such as the stepping reflex are related to postural control when held upright with her feet just touching a flat surface two and a half week old Olivia appears to take steps and walk this reflex which typically disappears at around two to three months of age will not be seen again until Olivia learns to walk on her own and there like that starts taking some steps and you can get it too if you sort of touch the top of her foot pick up a little bit there like that reflexes are also used to identify normal brain activity absence persistence beyond the normal time for disappearance or the reappearance of a reflex later in life is suggestive of significant neurological problems for example of the Babinski reflex exhibited here by Olivia when the bottom of her foot is stroked causes the big toe to flex towards the top of the foot and the other toes to fan out the Babinski is normal in children under two years of age after two years of age the presence of the Babinski indicates damage to the nerve path connecting the spinal cord and the brain so in those final comments by the narrator in the video one of the things that you see is that the primitive reflexes because they have a set process for turning on and turning off over the first two years of life have been used in a creative manner by medical professionals to determine early stages of neurological impairment so these primitive reflexes are oftentimes what medical researchers focus upon to determine whether or not there is early stages of intellectual disability or autism or even possibly some type of intellectual impairment of other sorts that might show up many years down the line but as just being indicated at an early stage as a result of the rearrangement in which the primitive reflexes are appearing and disappearing take a look back at the set of reflexes on the previous slide which said do you think is more likely evaluated by physicians if you are 18 years old and the correct answer is a survival reflexes and that's because in the list of survival reflexes that you've already seen you're going to see the breathing reflex the pupillary reflex and the eye blink reflex now a doctor will check the eye blink reflex and the pupillary reflex very commonly typically they won't try to choke you out and see if you breathe as you as you're passing out but you know know if you have really good health insurance may be able to do that for you now we're off of the beginnings of physical development and we're moving on to cognitive development and in fact just to give you that overarching context again the definition of development psychology was all the physical cognitive and social changes that occur over the lifespan we have covered the physical now we're going to spend most of our time on the cognitive which are of course most relevant to psychology and then we'll talk about the social which tends to be a bit more complicated and so we will hold most of our discussions about social psychology until the last chapter of the semester in terms of cognitive development infants have many reflexes now they don't have knowledge from life experience because they've just been born they can only process things through the reflexes that they're born with and so any intellectual development that occurs has to initially come from the application of these reflexes to the limited lifestyle that they have at that time one of those things is the rooting reflex like I mentioned in the previous slide the rooting reflex helps the child feed and then disappears after about two weeks or so at which point learn behavior takes the role for feeding so that the child learns how that eat and that learning is more adaptive than a very rigid reflexive action that process allows the child to become more flexible with respect to how they're going to eat either from a mother's breast or from a nipple from a bottle and then eventually on to soft foods like applesauce and so on as you build up eventually to eating much harder things that adults would eat like broccoli or steak in terms of cognitive development there are going to be some basic preferences that will be shown reflexively in the infants and these reflexive preferences will start to expand and out into other aspects of intellectual development one of the things that infants tend to have a preference for is anything shaped like a human face and this is because there is an area in your temporal lobe called the fusiform face area which is specific to human beings and helps establish the understanding of an emotional expression from a human face so this is a circuit that is wired into your brain even before you've ever seen a human face so on the day that you're born when light goes in your eyes that set of cells will become active and it will cause a bias toward objects that have a human structure to them so if you take a look at the bottom of the screen there's a picture of a woman a generic happy face and an upside-down boxy face if you were to show these images to an infant recognizing that they don't have very good vision when they're born but the not blind they could still see they just are kind of seeing blurry images you will show that the infant will spend more time looking at the actual image of a human being a little bit less time looking at the generic happy face the least amount of time looking at the upside down box face and that would be expected anything that has the characteristic of two eyes nose and a mouth is actually what will draw the child's interest in and keep in mind this fusiform face area is an circuit that is existing in your brain currently as well and when you see abstract shapes when you're tired for example and you're staring at the rug just because you're zoning out and you kind of have an imaginary glimpse of a face in the rug that's actually the fusiform face area operating oh and you can even take this frequently into a much broader story of understanding why often times people see faces when they think they saw a ghost right whenever somebody sees a ghost they always say a ghost face they don't see the ghost foot they don't see its left elbow they don't typically see its hand they you typically see its face and that simply seems to be because at a time when you might think you're seeing ghosts you actually are priming yourself to see anything related to a face because of the way that your brain is structured now there are other things that infants will have a preference for for paying attention to one is their mother's voice now think about when a child first hears his or her mother's voice when a child is developing prenatally there's going to be some point where they do not have ears and then a later point in time where they do as the ears come online and start receiving information and that information starts to get processed by the brain the earliest sounds that the child should hear are going to be the sounds from inside the mother those sounds are going to be the mother's breathing and the mother's heartbeat but it will also be her voice as she speaks her voice will actually travel through her body and the child will hear it now one thing we haven't talked about yet is the process of habituation which we're going to be talking about and habituation is a process where you simply get used to something and that process actually causes preferences to occur for things that you are exposed to that caused no harm that are then offered to you in a choice between a thing you've seen many times before that has never caused you any harm and something is completely novel typically a choice for the previously experienced stimulus will actually be taken and that's part of a natural process of the way your nervous system operates that takes place here with a mother's voice having heard the mother's voice for at least four months prenatally if you play a variety of voices you will get more reaction in the child in the direction of the mother's voice as opposed to any of the other voices and I will talk about specifically how you would go through this in an experimental sense in the coming slides because it's actually very important for you to understand how what appears to be such an obtuse type of measurement can actually be taken in a very careful scientific fashion infants will also show preferences for their mother's smell the process that produces this type of preference is not very well understood although it certainly is seen from the standpoint of the behavior of the child and also taste in fact you frequently see instances of this when women are pregnant they sometimes have taste preferences and also some foods becoming very unpalatable to them and oftentimes those characteristics will carry over to the infant that they're carrying so if the mom loses a taste for mayonnaise for example while she's pregnant there's a reasonable chance that the child will actually not like mayonnaise either part of the cognitive development of infants is going to be related to language and languages of course a very important role with respect to cognitive development because as a human most of the processing of social function and your ability to get by in society is actually going to be processed by your language system now thankfully the language system develops in a fairly easy way that we can rough estimate the process in a simple mnemonic one-year-olds are generally estimated to say about one word at a time two-year-olds have generally estimated to say about two words at a time and three-year-olds are generally estimated to say three or more words at a time it's important to remember the or more because by the time you reach three you have many children that will say much longer than three word sentences and in fact it's a characteristic of rapid language development that we're going to be talking about soon now given this easy mean estimate of language development from one two and three years one thing that's very important to make note of is that there's a lot of variability across children when you estimate a mean the mean is just the average of all the children but it is important to recognize how much spread around that mean statistically occurs to recognize some degree of normalcy for language development it is generally estimated to be about plus or minus six months for each of those mean estimates so that means for a child to first start saying one word at a time which is an as a general social estimate going to be at about one year of age the child might start speaking all the way back to six months or might not start speaking until one and a half years but everything from six months up to one and a half years would be considered completely normal that is the rough estimate of language development at that time now if you asked a set of parents they were at a playground with their children playing this type of question I think most people would not be aware of the degree of variability because you oftentimes hear people say things like oh my child's a genius because he started say mama at six months of age and the kid down the block he seems kind of delayed because he doesn't say mama until a year and a half but that's because the most people are of course not aware of the degree of variability which is actually fairly broad in this case the difference especially at one year of age being half the length of the mean itself is a really broad estimate so when your child goes to daycare as they probably will there are nail all set up by the state to evaluate a child's language development to see whether or not they fall within normal range and in this estimate of language development typically a child will not be flagged as having a possible language disorder unless they are a full year out of step with the estimate that you see on the screen so for example if a child is only saying two words at a time at age three then they are entire year out of step or if a child was only saying one word at a time at two years of age then there would be a full year out of step typically if your child goes to daycare the first thing they're going to recommend is that your child have their hearing checked because in most cases when children have language delays it is typically related to their ability to hear if they cannot hear well then they don't develop language because they don't hear people speaking to them so they don't learn to respond now I mentioned earlier that the process of habituation has a role in choosing preferences for things that you have been exposed to that are not harmful relative to things that are completely novel that you're not familiar with that process of habituation was recognized well back in the 1800s by early biologists and some of that were carried over even into the early work of Ivan Pavlov who we will talk about in the learning chapter in his early development of understanding the role of learning in human psychology for now the role of habituation is going to be used to try to understand how a small child can understand different aspects of stimuli in their environment how well they can retain it how well they can mix different characteristics of memories together and probably more importantly how you as a scientist can actually draw that information out of the infant when they don't have any language to explain what they're looking at or what they're thinking about that process is going to be called a habituation test which it will be used to evaluate the cognitive structure of small children that don't have good language or any language at all so what are the things you see with a situation is that all novel stimuli initially increase attention toward the new cue that is for anything that is completely new to a human being and you could do this in a laboratory with a lab rat as well because it's the same basic underlying function because remember in chapter 2 I talked about how the structure of the nervous system is essentially the same across all creatures on planet earth that have a nervous system it should not be a surprise that some very basic low-level skill sets actually exist across the entire animal kingdom including human beings and habituation is one of them for any creature that is exposed to a completely novel stimulus they will generally increase their attention toward that cue now as you repeatedly expose that subject to that cue they will simply reduce the amount of attention they spend on it and as a result what you can do is take a novel cue and present it to the subject to see differences in the degree to which the subject responds to the stimuli we will be able to determine what the subject detects how well it relates to other stimuli in the environment how much they can distinguish you from other stimuli and how well they can remember it when you set up a habituation test one of the first things you want to do is repeatedly expose the subject to a stimulus and measure the degree of a situation so initially a brand new stimulus will cause a lot of interest in it and as you show it to the subject over and over and over again it will die out over time then you could come along and present an entirely new stimulus now what you're going to do with this new stimulus is evaluate how well the child can distinguish between the new stimulus and the old stimulus so this might be an estimate to determine whether or not a one-month-old has sufficient visual acuity to distinguish the difference between a circle and an octagon and if you want to evaluate that in a one-month-old you could simply take the circle show it to the child over and over and over again in the experimental method because the child's never seen the circle before in this experimental setup they'll pay a lot of attention to it and then they will stop paying attention to it over time and then you could present the Octagon if the child does not detect the difference between the two cues then both stimuli will produce habituated levels of responding if the child does detect the difference between the two Q's then the novel stimulus will produce enhance responding it may be easier to understand this in these particular figures if you look at these hypothetical data that I drew we take a red circle and we show it to a child we turned it on for 10 seconds for example and then we turn it off for 30 seconds and we turn it back on for 10 seconds and we turn it back off for 30 seconds we do this over and over and over again and over multiple trials the child will initially look at the red circle quite a bit and then slowly stop doing this now I have to interject a little aspect in here that you might be curious about how do you know that a child is looking at a red circle if you show it to them off a computer screen well there's actually devices that allow you to evaluate where a person is looking if you take a child and place them in a car seat in front of a computer screen you can use cameras that are embedded in the computer screen or placed on the sides that are focused upon the child's face that have software that will detect the child's pupils with a little bit of trigonometry you can estimate wherever the child's pupils are what its field of view will be and if you know what the child's field of view is you can then estimate whether or not the child's looking at the circle so you can make this circle larger or smaller you can move it around on the screen and you can evaluate where the child is looking moment by moment and so in instances where you have a brand new red circle on the screen that the child's never seen before you can prove that the child is looking at it because the child keeps that red circle in its centre field of view and as the red circle has shown to the child over and over and over again the child will slowly look at other things more random looking across the screen and around the room now if the child has a bit she waited to the circle as is drawn here in these hypothetical data you can then start interleaving presentations of circle with the presentations of the Octagon so a trial with the circle than a trial with the octagon then it's trial with a circle on the trial with the octagon and so on and so forth and then take the average amount of time the child looks at the circle versus the octagon and present them as two numbers on this particular figure in this case because the circle has already been habituated you would expect the child to show very little responding to the circle which is what's shown here however in the way that these data are drawn these hypothetical data we make it so that this one month old infant can tell the difference between a circle and an octagon and the proof of that is that the amount of time the child spends looking at the octagon specifically relative to the circle is actually much higher in this case you have proof that the child must be able to distinguish the difference between the octagon and the circle if the child could not then the child could not treat the octagon specifically different from the circle because in its poor blurry vision it couldn't tell the difference between the two but it would in scenarios like this be estimated that child has sufficient visual acuity to tell that the octagon is different than the circle and in fact sufficiently different to really draw the child's attention to the octagon relative to the circle itself as you might imagine if you do a scenario like this you could do it with anything that the child can see and that would be in terms of vision aspects of color or shape or even simulated three-dimensional objects for example there's any aspect of vision that you can work with you can do with the infant to determine whether or not they can tell differences between slight variations in the stimuli in fact one of the types of work that actually started to occur back in the 1990s was after Photoshop as a piece of software was developed researchers would take the image of the child's parent let's say it's mother and Photoshop it differently like move her eyes apart rotate her nose change her mouth do different things to the face to see to what degree the child was actually sensitive to these changes so the child would recognize these differences in the face of the parent and in fact it's actually research similar to that that led to the recognition that you have this fusiform face area in your temporal lobe that allows infants to detect the differences between eyes nose and mouth on a human face so having had that behavioral data later work in terms of brain scanning activity led to the recognition of specifically where that circuitry actually exists in the brain now we focused on aspects of vision here but I mentioned earlier on a previous slide that you could determine whether or not an infant could tell its mother's voice or had a preference for its mother's voice as opposed to another voice how could you do that well you don't have the equipment evaluating where the child's looking but you can evaluate where the child Orient's its head and so in a slight variation of this process you can have sounds come from 360 degrees around the child's head and try to estimate where the child's looking depending upon where the sound is coming from and that would be a variation on doing this with sound now how about memory early memory development would actually be really interesting to take a look at because we're finding out here that by using this basic obituaries you can determine what a child sees and how good its vision is at a point in its life well before it actually has language and can actually tell you what it's looking at the same is also true with hearing now just sticking with vision and sound how could we evaluate memory for vision or sound so that is if we played a novel sound to a one month old today how long would that child remember that sound if it never hears that sound again well evaluations like this can be done also with the habituation process but in a slight variation of the technique when you habituate a child to a particular cue the child remains habituated to that cue for as long as it remembers the cue now if the child forgot about the cue completely and then sole it again that cue would be treated like a brand new cue itself and so the child would respond to it maximally so in this case what you see is a brand-new never seen cue before we draw a lot of attention to it after repeated exposure creating this that establishing habituation the child would stop responding to it if the child does not respond to it that indicates that the child remembers it if you don't show that q2 the child for a very long period of time and they completely forget what it is they will then respond to it again because that's how they treat novel stimuli so the rate at which the child begins to respond to a cue is actually the rate of memory decay or memory loss that had occurred over time you know and this seems you know a little odd because it's backwards for the way that you would assess your own memory if I told you something today and I asked you about it you could respond to it and when you forget it you would say I don't know and then you don't respond and that seems right that seems normal to you but the way in which you do it with an infant seems backwards where if you do know it you don't respond to it and then when you forget it you actually do respond to it but that's exactly how it works because you're using a [ __ ] ooh a sh anind this case not a verbal response to recognize what had happened but whether or not habituation is actually being used as an assessment and that's a very important point to keep in mind so let's take a look at this basic process how long an infant's memory retains information can be assessed by looking for a reaction to the cue so low amounts of responding to a habituated stimulus indicates that it's remembered and increased responding over time indicates that this Themis functions more like a novel stimulus which indicates that the child has forgotten the cue over time now let's look at a question that's related to this information which of the following cannot be studied in infants through the habituation methodology and the answer there is e all of the above things can be studied with a habituation methodology facial recognition as I've already mentioned we kind of actually walk through those examples as well and in fact even if you took a face that a child would recognize like the child's mother's face and then you could play with it in Photoshop to change the face so the face started to look like the dad or look like a stranger or you've rotated things in odd ways like made the eyes you know vertical those kinds of aspects would be responded to by the infant and in an appropriate way as the face had changed shape perception as a very simple way to recognize the child's visual acuity you know can a child tell the difference between a circle and a line okay well maybe they can so well how about a circle and a triangle could they recognize that well maybe if they could okay how about then a circle and a cube or a circle and a five-sided image or six and seven eight nine you can do a very basic thing can a one-month-old tell the difference between a circle and a 12 sided object 13 sided object 14 sided object and so on that would give you a very clear estimate of how well the child's vision actually operates and in fact if you take this information into the next chapter on sensation and perception you'll actually have a mathematical basis for establishing how good a child's vision is so they won't just be rough estimates of whether they can do it or not but you'll actually be able to turn the entire system into a sequence of equations which will give you a very specific information regarding the child's visual acuity at an early age and at that point you really start to see a very nicely defined theoretical structure underpinned with mathematics that gives you a great deal of understanding of how visual systems operate in developing children [Music]