hi this is Bart pulson and this is a video for psychology 1100 lifespan development this is for chapter three of our book on infancy and this is part two about physical development in infancy the first thing you here is uh the sequence of physical development going from two months uh still a fetus up to 16 years old and there are a few different patterns number one of course you can see here it's the proportions change dramatically that the head account for half the size uh two months um want to talk about three different sequences uh patterns of Dev the first one is seilo sealoc codal that means from head to tail and sealoc codal development means that the head grows first um and then that the other parts of the body that are below it grow later and this is logical especially since the brain regulates uh functions like heartbeat that are essential for the growth of the rest of the body the second one is proximodistal and this means things take take place from the trunk the the Torso outward and so for instance you see that arms are much shorter relative to body size way over on the left as opposed to on the right and this again makes sense because nerves have to develop from the spinal cord and spread out before infants can control their arms or their legs and also life functions um like uh breathing the heart those things are all right there in the central axis and so it makes sense to get those developed first uh the third uh pattern is differentiation and this as children become more mature their physical reactions again the example we had was touching a hot stove for a very young child it's a Global Response the whole body thrashes on the other hand as they get older it becomes a more specific response just the part of the um a body that actually touched the stove uh they may they still cry but that's the part that takes place uh where the movement takes place also want to look at changes in weight um infants usually double their birth weight in about 5 months and they they triple it by their first birthday also their height increases by about 50% in the first year so a child whose length of birth was 20 in is likely to be about 30 in tall at 12 months and then among newborns the arms and legs are about equal in length you can see that here on our newborn the third one from the left and each is only about one and a half times the length of the head now by the first birthday the the neck has begun to lengthen ascept the arms and legs and the arms grow more rapidly than the legs at first and by the second birthday the arms are actually longer than the legs um you see the proportions change over time the next thing is about the failure to thrive uh abbreviated ftt and failure to thrives a serious disorder it impairs growth in infancy and in early childhood and its causes can be either biological or non-biological they call it organic or non-organic and but usually feeding problems are at the core of the whole thing and failure to thrive is linked not only to slow physical growth but to cognitive behavioral and emotional problems as we talked about in class though especially for organic failure to thrive where it's a biological cause um if those causes are addressed then the child is actually able to often catch up uh in their development okay the next thing here is about nutrition and we want to talk a little bit about uh breastfeeding versus uh bottles now there's a lot of advantages to breast milk and there are some disadvantages the advantages are that breast milk is less likely to upset an infant stomach it has antibodies that can uh help word off some problems it actually protects against lymphoma serious thing it also fewer digestive problems fewer allergic responses and interestingly a decreased chance for obesity later in life I think that's interesting because breast milk is incredibly high in fat but that has more to do with neurological development than anything um on the other hand uh there are disadvantages to breastfeeding these are things that people need to keep in mind one of course is that if the mother is drinking or taking some kind of either prescription medication or uh recreational drugs those can be passed along through the milk and then if the mother has a disease like HIV that can be passed along through the breast milk um and so you got to be very careful and properly talk with the doctor before uh you see breastfeed to see what sorts of things could be transmitted um also the mothers have to have adequate nourishment for the milk to be uh good um there you know sort of what goes in has to be sufficient also um simply producing milk for the body produced milk it's physically demanding as well as uh there are other things we talked about for instance like the advantages of a bottle is that other people can feed the baby or uh it the baby does not have to be fed through the breast immediately at the time time hungry so for instance if you're at work or on the bus or something you can put off till later um on the other hand you know there's a lot of uh very strong feelings about breastfeeding versus bottle feeding it's just something that uh if you get to the point where you have children of your own that you need to explore the two possibilities pretty thoroughly next I want to talk about development of the brain and the nervous system now what we have here the basic unit of the nervous system is a neuron and a neuron um they receive and transmit messages from other neurons or other parts of the body to one another and babies are born with about a 100 billion neurons most of which are in the brain and that's pretty much the quantity that you're going to have for the rest of your life now each neuron has a cell body that's the big part here at the top they have dendrites which are the little branchy things in fact dendrite is Greek for branch um that just reach out to the other neurons and um they have an axon that's the long skinny part and then axon terminals are like dendrites at the other end that connect with the dendrites of other neurons and um some axons like this one right here are encased by a myin sheath and then through myelination which by the way is made of fat which is one of the reasons that Fat's so important in a baby's diet uh through myelination communication become between neurons can become more efficient also it provides uh insulation these These are electrochemical impulses and this provides a form of insulation that protects uh neurons uh from cross-firing which is uh one of the symptoms by the way of multiple sclerosis um also myelination in the prefrontal cortex continues into the second decade of life um and it's connected with a lot of advances in working memory and language ability in fact let's look at growth here uh we have the the patterns of growth and what you see in this one is that the brain of a newborn will triple in weight by one year I mean their their heads are really big when they're born but there's so much more going on and what happens here is not so much that they're they're not getting more neurons what they are is they're getting a tremendous amount of growth in both the milin and in the dendri and the connections uh it's that density of interconnections that's really critical and so uh the neurons they form they proliferate um but the grow spur you see here is the dendrites and the axon terminals also myelination continues um it results in the continued development of intentional physical activity as the newborns better able to control their movement so it's very unorganized and Global and nonspecific and the myelination makes it uh so they can control it better they become increasingly capable of complex and integrated sensory motor activities as well besides brain development uh reflects both nature such as just through biological maturation and nurture such as through stimulation nutrition and so on um in fact let's look at the rest of physical growth we don't talk about motor development motor means moving here and infants make massive strides in motor abilities within the first year of Life they go from being very helpless to being very mobile making very purposeful movements all within a few years and although most neonates or newborns can't support even their own neck that's resolved within a few months uh they can track objects with their eyes but it takes about six months to be successful at grasping objects and that's when they begin rolling over and shortly after they can begin sitting up crawling for most children begins around 8 or n months and most can stand at 10 months old uh and then somewhere around 12 to 15 months most are walking by themselves which gets them the name of toddler now there's an interesting exception to this whole uh progression here and this is from a study done in 1940 by Wayne and marcena Dennis um they studied Native American Hy children who spent their entire first year strapped to a cradle board and consequently didn't engage in any form of motor activity or locomotion they found that despite uh having really this uh this major setback um not having physical experiences per se that these children when they got out of the Cradle board they they quickly caught up with others in terms of walking and there were really no noticeable differences one way or the other okay sensory and perceptual development this is last slide for this particular section um Vision let's say dramatic gra uh excuse me dramatic gain in visual Acuity uh between birth and 6 months of age remember they're very near side they can't see well uh also peripheral vision it's very poor at Birth but by six months of age it's the same as an adult um also infants generally respond to cues for depth by the time they're able to crawl six to eight months old and so what you have here for instance is the visual Cliff you see we got this piece of glass or plastic that goes across and the pattern shows that it dips down now a very very young child would not be able to really see that we have this dip down here but it's wonderful that by the time children are old enough to crawl they're also able to respond well to depth cues and so they're basically not going to go across um also we have things about um size and shape constancy that means that even though the image on the eyeballs can be very different um people can tell that something stays the same size and it has the same shape even if you're going closer or farther away or walking around it and that gets and that actually is a very sophisticated cognitive procedure also a hearing at Birth uh newborns can Orient their heads in the direction of a sound um as long as they're lying down because it's hard for them they can't hold up their head and then by 18 months their sound localizing abilities are basically the same as adults their range of pitch of sounds gradually expands uh as does their ability to detect differences in pitch and loudness and that's where we're going to stop this section