In this video I introduce some terms for understanding infant development, particularly for motor and perceptual skills. Infants are born with a number of reflexes (such as the rooting reflex and sucking reflex) which are gradually replaced with voluntary control as motor skills improve. Developmental milestones for motor skills generally follow the cephalocaudal rule (head-to-tail) and the proximodistal rule (near-to-far). Techniques for investigating the perceptual development include preferential looking and habituation, which allow us to make inferences about infants’ perceptual skills.

Don’t forget to subscribe to the channel to see future videos! Have questions or topics you’d like to see covered in a future video? Let me know by commenting or sending me an email!

Check out my full psychology guide: Master Introductory Psychology: http://amzn.to/2eTqm5s

Video Transcript

Hi I’m Michael Corayer and this is Psych Exam Review. In this video we look at infant development. We’re going to focus on motor development and perceptual development. Now we’ll start with motor development and when infants are first born they have very little voluntary control over their movements but they do have a bunch of reflexes. So a reflex is a pattern of motor responses that’s triggered by sensory stimulation. Now infants have a number of reflexes but we’re just going to focus on two in this video; the rooting reflex and the sucking reflex. Now the rooting reflex refers to the idea that if you touch an infant’s cheek the infant will turn his or her mouth in that direction. Touch this cheek they’ll turn this way. And this is combined with a sucking reflex and the sucking reflex just refers to the idea that an infant will automatically suck an object placed in the mouth.

Now these two reflexes together make it much easier to feed an infant. The infant will automatically turn in the appropriate direction and suck on an object placed in the mouth and this means even though the infant doesn’t have much voluntary control over their movements these reflexes ensure that the infant can be fed. Now over time the infant will gain greater control over their movement and this means that the reflexes will fade and eventually just become voluntary behaviors. So eventually an infant won’t automatically suck an object placed in the mouth and won’t automatically turn his or her head in a particular direction.

Now when we talk about motor development we often discuss developmental milestones these are a progression of things that happens for all infants in terms of the motor skills that they develop. Parents often worry about these because they start thinking in terms of precise timing so they say “oh you know many children are walking by 11 months, so if my kid isn’t walking by 11 months I’m a bad parent and it’s the end of the world” and something like that. But it’s important to remember those numbers are generally averages and so that means that half of kids will walk a little bit earlier than that and half will walk a little bit later than that. And so the timing isn’t particularly precise, but what is consistent is the progression through these milestones. So in other words, kids will all crawl before they stand with support, and then after standing with support they can stand independently, and then they can begin to walk and so we see the same progression of skills even though the timing is not precise and not identical for all children.

Now in these progressions we can see two rules at play the cephalocaudal rule and the proximodistal rule. So the cephalocaudal rule, this is Latin for “head-to-tail” and it refers to a idea that the way the infants gain control over their body is generally starting with head movements, they gain greater control over moving their head, followed by movement of their arms and then lastly movement of the legs. And then this is combined with the proximodistal rule this is the idea proximo-distal is Latin for “near to far” that we sort of start with the center and move outward. So they gain control over their trunk, followed by their elbows and knees, and then lastly followed by their hands and feet.

Now when we think about perceptual development in infants you might wonder how can we know anything. I mean infants can’t report to us what they’re perceiving, so how can we study this? So one of the techniques that we can use to study perceptual development was developed by Robert Fantz and it’s called preferential looking, or it’s also called visual preference. And it’s actually a very simple idea. If you give an infant two stimuli, they will look at the one that they find more interesting. So by seeing which stimulus an infant is looking at, we can make some inferences about their perception. So for instance, we might want to investigate visual acuity of infants.

So we might show two very similar stimuli; one which is a solid color and the other which has thin stripes on it and if the infant looks at the striped one, that tells us they recognize these stripes. They’re able to perceive that there’s something different about this one; there’s something more interesting than just a solid color. And that allows us to make some estimates about the infant’s visual acuity based on how thin those stripes are, or how far away the stimulus is, how close together the stripes are, etc. And if you’re wondering, in very young infants their clear vision is initially limited to only about a foot. But this makes sense if we think about the distance from the mothers face to the infant’s face during breastfeeding. It’s about a foot away.

And we also see a preference in infants to look at human faces. So if we take the parts of a face and we arrange them as a face infants will prefer to look at that rather than those same shapes arranged in a slightly different order where they don’t make up the face. And this makes sense if we think that we have a natural inclination to be interested in faces because faces are so important to us. We need to learn how to recognize faces eventually. We need to be able to recognize emotional expressions and things like this. So it makes sense that we would prefer to look at faces rather than other patterns.

Now another technique that can help us to investigate perception in infants is habituation. So the idea of habituation is that infants will respond more strongly to a new stimulus. So if something is novel the infants will have a stronger response to it than if it’s repeated, they’ve already seen it before. What habituation refers to is we show a stimulus and if we keep showing that same stimulus to the child over and over again they will lose interest. And the way that we often measure this habituation, although this is not the only way, is through what’s called looking time. So we just see, how long does the infant stare at the stimulus? Now you show an infant something new they will stare at it very intently, they’ll scrutinize it, and they’ll look at it for a long time. But if you keep showing them the same thing then their looking time will gradually decrease. So eventually, the tenth time you’ve shown them this stimulus, they look at it, they see it’s the same thing and they very quickly look away.

Now we can use this to make some inferences about perception because we can see if children can detect a slight change. So if I show the same stimulus over and over until this habituation occurs. So now the infant is not very interested in this stimulus; I show it they immediately look away. Then I switch to a slightly different stimulus, so let’s say I’m showing two colors; I show one color and I want to know, can the child perceive this slightly different color as being different? And now when I switch to the new color I want to see, does the infant stare at this new color longer than the old color? And if the response strength, in this case, the looking time, has increased this suggests that the infant is able to recognize that a change has occurred in the stimulus. And that can tell us something about their perception.

Alright, in the next video we’ll take a look at brain development in infants. I hope you found this helpful, if so, please like the video and subscribe to the channel for more. Thanks for watching!