Lecture: Infancy and Toddlerhood: Cognitive and Language Development
Lecture script · about 15–20 minutes spoken · Week 6
Opening
Picture three people in three different places. A teacher in a childcare center's infant room is hiding a toy under a blanket during play. An assistant at a pediatric clinic is answering a family's question about first words. And a grandparent at home is chatting with a baby in one language while the baby's parent uses another. Each of them is watching a small mind at work, and each of them is wondering what the baby actually knows.
That's what this lecture is about. In Week 2 you met Piaget's name and his four stages, and I promised we'd teach his theory starting in Week 6. Here we are. In Week 3 you learned to keep what a child did apart from what it might mean. And in Week 5 you followed the body through the first two years, from the newborn reflexes to walking alone.
In this lecture we stay with those same infants and turn to their thinking and their first words. I'll take you through eight ideas in order, from Piaget's building blocks to first words and milestone checklists. By the end, I want you to be able to watch a baby search for a toy, or listen to a toddler's first words, and say what you saw in one plain sentence.
1. Schemes, and two ways to handle something new
Let's start with a picture book. A toddler sits on a parent's lap, looking at farm animals. The toddler knows the family dog very well. On the first page there's a cow, and the toddler points and says, "Doggie!" The parent says, "That's a cow. Cows say moo." A couple of pages later the toddler points at another cow and says, "Moo."
Piaget had words for every part of that little scene. A scheme is an organized pattern of action or thought that a child uses to make sense of the world, such as grabbing and shaking a rattle. The toddler's scheme here is "four legs means doggie."
When the cow shows up, the toddler fits it into the scheme that's already there. That's assimilation: fitting a new experience into a scheme the child already has. Then the parent says "cow," and the old scheme doesn't fit anymore. So the toddler changes it. That's accommodation: changing a scheme, or building a new one, so that it fits a new experience.
And there's a third word. Equilibration is the push toward balance between assimilation and accommodation that moves a child's thinking forward. When the toddler names the next cow without help, the new scheme and the world are back in balance, at least for now.
Here's the trick for keeping the first two apart. Ask what changed. If the experience got squeezed into the old scheme, that's assimilation. If the scheme itself changed, that's accommodation.
Pause and try this. In the farm book, which moment is accommodation: calling the cow "doggie," or starting a new name for animals that moo?
Think about what changed before you go on.
Here's the answer. Starting a new name for animals that moo is accommodation, because the toddler's scheme itself changed to fit the cow.
2. The sensorimotor stage, step by step
Now let's zoom out. Think about a baby in the first weeks of life, sucking when something touches the mouth. Then think about the same child near age 2, hunting for a lost shoe in another room. Piaget saw the whole change between those two pictures as one stage.
The sensorimotor stage is Piaget's first stage of cognitive development, from about birth to 2, in which infants learn through their senses and actions. He described it in six steps, the sensorimotor substages, from reflexes to the beginnings of mental representation.
Let me walk you through them in words. The first is reflexes, the built-in responses you met in Week 5. The second is repeating simple actions centered on the baby's own body, like bringing a thumb back to the mouth. The third is repeating actions that make something interesting happen in the world, like kicking to shake a crib toy, again and again. The fourth is coordinating actions toward a goal, at about 8 to 12 months, like pushing one thing aside to reach another. The fifth is experimenting with new actions to see what happens, at about 12 to 18 months. Think of a toddler dropping a spoon, then a cup, then a cracker from a high chair. And the sixth is the beginnings of mental representation: holding an object or an action in mind without seeing it.
One warning here. Those ages are approximate. The order is what the model fixes. Real babies move through the steps at their own pace, so a stage list is never a timetable.
Pause and try this. A toddler drops a spoon, then a cup, then a cracker, watching how each one falls. Which substage does that behavior fit?
Picture the high chair for a second.
Here's the answer. It fits the fifth substage, experimenting with new actions to see what happens, because the toddler is varying the action to watch what changes.
3. The hidden toy and the A-not-B error
Think about peekaboo. When a face disappears behind a napkin, a very young baby may look somewhere else, as if the face were gone. A few months later, the same baby grabs at the napkin. Something has changed in what that baby knows.
The term is object permanence: knowing that a thing still exists when you can no longer see it. And here's the key idea. It doesn't switch on all at once. It grows in steps. In Piaget's cloth task, a baby in the early substages stops searching once a toy is covered, and a baby in the later substages lifts the cloth to find it.
Then there's a famous mistake in the middle. The A-not-B error is what happens when an infant who has found a toy under one cloth, call it A, keeps searching there after watching the toy hidden under a second cloth, B.
Let's read the running case. Record R2 is illustrative, written at 9 months, in the family home, with a parent present. The infant finds a toy twice under the left cloth. Then the infant watches it hidden under the right cloth, and searches under the left cloth again. So the left cloth is A, and the right cloth is B. That's 3 hidings, and the infant searched the left cloth all 3 times, so 2 of the 3 searches found the toy.
Here's what I want you to notice. Finding the toy twice means this infant already knows a covered toy still exists. That's real object permanence. The error shows that the idea of where the toy is still leans on the infant's own past actions: I found it there before.
Pause and try this. Using Piaget's account, which substage fits R2's search under the left cloth, and at about what ages?
Give yourself a moment to place it.
Here's the answer. It fits the fourth sensorimotor substage, at about 8 to 12 months, because searching under A after watching the toy go to B is that substage's typical response. In the fifth substage, at about 12 to 18 months, the typical response is to search under B.
4. Copying an action later
Here's a scene from a family kitchen. A grandparent stirs a pot of soup at the stove while a toddler watches from a booster seat. The next day, with the grandparent out of the room, the toddler picks up a wooden spoon and an empty bowl and stirs, round and round, with the same serious face.
That's deferred imitation: copying an action seen earlier, after a delay, when the person who modeled it is no longer there.
Why does this matter so much? To copy something a day later, the toddler has to hold a memory of the action in mind. Nobody is there to copy in the moment. That kind of holding in mind is what Piaget placed at the end of the sensorimotor stage, the beginnings of mental representation. So deferred imitation is a window on memory in the first two years.
And it connects to a theory you already know. In Week 2 you met social learning theory, the idea that children learn by watching others. Deferred imitation shows that watching can pay off later, not only in the moment.
There's a bigger lesson here, too. Babies are not passive. The farm book, the hidden toy, and the soup all show infants exploring, testing, and remembering. They're busy learners from the start.
Pause and try this. A friend says babies only learn when an adult teaches them directly. Which scene from this lecture would you use to answer, and why?
Pick one scene before I go on.
Here's the answer. The soup scene works well, because the toddler copied the stirring a day later with nobody teaching, which shows active learning and memory.
5. What newer research adds to Piaget
Let me raise a puzzle. Piaget's tasks ask the baby to do something: reach, lift, search. But what if a baby knows where a toy is and can't yet plan the reach?
Later researchers tried a different approach. Instead of asking for a reach, they measured how long babies look. Babies tend to look longer at something surprising. So researchers showed babies possible events and impossible ones, like a toy that seems to pass through a solid wall.
The term is looking-time research: infant research that measures how long babies look at possible and impossible events. It suggests infants understand some properties of objects earlier than reaching tasks show.
Here's the careful way to say it. A search task asks for a reach; a looking task asks only for a look. The newer work is a refinement of Piaget's account, not a refutation. Piaget's order of steps still organizes much of what researchers see. The newer methods suggest the first steps may begin sooner than a reach can reveal. And each method has a limitation. A reach needs planning and movement, while a long look can be hard to interpret.
Memory grows in these same years. Infants come to recognize familiar people, places, and routines, and toddlers can recall an action they saw earlier, the way the soup scene shows. In plain words, early memory holds more and lasts longer as the first two years go on.
Pause and try this. Someone says, "The looking-time studies proved Piaget wrong." How would you correct that sentence?
Try your own version first.
Here's the answer. I'd say the looking-time studies refine Piaget's account, because they suggest some knowledge starts earlier while his order of steps still holds.
6. Understanding words, and saying them
Picture a childcare center at morning drop-off. A caregiver says, "Want to go up?" and a toddler lifts both arms. The toddler has never said "up" to this caregiver, yet understood it.
Language runs on two tracks. Receptive language is understanding words and sentences that others say. Expressive language is producing words and sentences to communicate, by speaking or signing. Receptive language usually runs ahead. A toddler typically understands more words than the toddler says.
There's also a typical order, with wide timing. First comes cooing, soft, drawn-out vowel sounds like "ooo." Then babbling, repeated consonant-vowel strings like "ba-ba-ba." Then first words. Then two-word combinations, a toddler's first short phrases made of two words, like "more ball." The order holds, but the ages vary a lot, and this course pins no single age for any step.
Back to the running case. In R2, at 9 months, the infant babbles "ba-ba-ba." In R3, at 14 months, at the childcare center's morning drop-off, the toddler says "ball," "up," and "more." That's 3 single words, and no two-word combination yet.
Pause and try this. Are R3's 3 words receptive language or expressive language?
Say it to yourself before I go on.
Here's the answer. They're expressive language, because the toddler is producing the words, and receptive language usually runs ahead of them.
One more thing. Babbling isn't meaningless noise. It practices the sounds of the language a child hears, and it's the bridge to first words.
7. How adults help, in one language or two
Listen to almost anyone talking to a baby. The voice goes up. The words slow down. "Look at the big dog! Is that a dog?" Most adults do this without anyone teaching them.
That's infant-directed speech: the higher-pitched, slower, exaggerated speech adults use with babies. It holds infants' attention and highlights the sounds and structure of language. The stretched vowels and the clear pauses make it easier for a baby to hear where one word ends and the next begins. It's nature and nurture together again. Babies arrive ready to pay attention to voices, and adults give them something rich to pay attention to.
Now picture a household where a parent speaks one language with the baby and a grandparent who lives with them speaks another. A neighbor worries that two languages will confuse the baby and slow down talking. The worry is common, because a bilingual toddler may know fewer words in each single language.
But here's what researchers find. Children exposed to two languages from infancy typically reach early language milestones on a typical timeline when both languages are counted together. The key is counting both. No language, and no family, is the norm the others fall short of.
Pause and try this. Why does it matter whether you count a bilingual toddler's words in one language or in both?
Think about what each count would miss.
Here's the answer. Counting one language misses the words in the other, so counting both gives the fair picture that matches a typical timeline.
8. Reading a milestone checklist fairly
Picture a parent at a pediatric checkup, filling out a short checklist about a toddler. Does the child point to show you something? Does the child say a few words? The parent stops at one item the toddler doesn't do yet, and starts to worry.
The CDC publishes checklists like this in its "Learn the Signs. Act Early." program. A milestone checklist is a list of what most children, 75 percent or more, do by a given age. The checklists were revised in 2022 so that each one lists what most children, 75 percent or more, do by that age, and checklists were added for 15 and 30 months.
Let's work out what that rule means. 75 percent or more means at least 75 of every 100 children, which is 3 of every 4. Take 75 away from 100 and you get 25. So as many as 1 in 4 children may not yet do a listed item at that age. That's why a missed item is a reason for a family to talk with a health professional, never a diagnosis. And it's why this course never judges whether a real child is behind.
Now let's put the week together with R2 and R3. Searching under the left cloth after watching the toy move to the right cloth is the A-not-B error, which Piaget placed in the fourth sensorimotor substage, at about 8 to 12 months. R2's babbling and R3's 3 first words follow the typical language sequence, with wide timing. And the looking-time research adds that infants may know more about hidden objects than a reach can show.
Pause and try this. A parent says, "My toddler missed one item on the checklist, so something must be wrong." What does the checklist rule tell you about that sentence?
Take a breath and frame your reply kindly.
Here's the answer. The rule says up to 1 in 4 children may not yet do an item, so a missed item is a reason to talk with a health professional, not proof of a problem.
Closing
Let's recap in the order we went. Infants build schemes, assimilate new experiences into them, and accommodate when the world doesn't fit. The sensorimotor stage runs from about birth to 2 in six substages, and the ages are approximate. Object permanence grows in steps, and the A-not-B error sits in the fourth substage, at about 8 to 12 months.
Deferred imitation shows a toddler holding an action in memory. Looking-time research refines Piaget; it doesn't refute him. Receptive language usually runs ahead of expressive language, and sounds move from cooing to babbling to first words to two-word combinations, with wide timing. Infant-directed speech helps babies hear language, and children learning two languages stay on a typical timeline when both are counted. And a milestone checklist lists what most children, 75 percent or more, do by an age: a reason to talk, never a diagnosis.
Next in this module, you'll find the slide deck, the Readings and Resources page, the lecture tutorial, the practice set, and the quiz. And in Week 7, we stay with these same infants and toddlers and turn to their feelings and first relationships, through temperament and attachment.
Built with The Course Maker · samples.thecoursemaker.com