Week 6 · Chapter

Chapter 6 — Infancy and Toddlerhood: Cognitive and Language Development

Child Development Free sample edition

The module's primary reading · ~40–50 minutes · Objective 4 (analyze physical, cognitive, and language development in infancy and toddlerhood: brain development, reflexes, motor milestones as windows of achievement, safe sleep, the sensorimotor stage, object permanence, and early language) · Read it first this week; the lecture, the slides, the tutorial, the quiz, and the workshop all build on it.

In plain language

This chapter is about how babies come to think and talk in the first two years. Jean Piaget described infants as active explorers who build schemes (organized patterns of action or thought) and keep adjusting them as the world surprises them. One big step is object permanence (knowing that a thing still exists when you can no longer see it), which grows in steps rather than all at once. At the same time, sounds turn into words: babies coo, then babble, then say first words, then put two words together. You will also learn to read a milestone checklist (a list of what most children do by a given age) the way its issuing body means it: as a reason to talk with a health professional, never as a diagnosis.

Why you already care about this

Picture a family dinner. An aunt lifts a napkin in front of her face, and the baby in the high chair goes still. The napkin drops, the face is back, and the baby squeals with delight. The aunt does it again. The baby leans forward this time, watching the napkin, waiting. Two cousins at the table start counting how many times the game can go before the baby gets bored.

You have probably played peekaboo, and you may have wondered what the baby is thinking. When the face disappears, does the baby know the aunt is still there? Later in the same evening, the baby's babbling sounds almost like a word, and a grandparent at the table insists it was "ba" for "bottle". Is it a word yet? These are the two questions of this week: how infants come to know that hidden things still exist, and how their sounds grow into words.

By the end of this chapter you will be able to:

explain Piaget's schemes, assimilation, accommodation, and equilibration, and tell assimilation apart from accommodation in an example;
put the six sensorimotor substages in order and describe each in words, with ages read as approximate;
read an infant's search for a hidden toy against Dataset D, including the A-not-B error;
explain deferred imitation and what later looking-time research adds to Piaget's account;
tell receptive from expressive language, and describe the sequence from cooing to two-word combinations;
read the CDC's 2022 milestone checklists as a reason to talk with a health professional, never as a diagnosis.

Carry this line with you: an infant who searches is thinking, not waiting.

Where we are

Already covered: Week 1 gave you the three domains and nature and nurture as interaction. Week 2 named the theories, including Piaget's cognitive-developmental theory, and promised to teach it from this week. Week 3 taught you to keep what a child did apart from what it might mean. Week 4 followed development to birth. Week 5 covered the physical domain in the first two years, from reflexes to walking alone.
This week: the cognitive domain in the first two years — Piaget's core ideas and his sensorimotor stage, object permanence and the A-not-B error, deferred imitation, later research that refines Piaget, and early language, read with the CDC's 2022 checklists.
How they connect: Week 5 ended with the newborn reflexes; Piaget's first sensorimotor substage begins with those same reflexes, so this week picks up where last week stopped.
Where we're going next: Week 7 stays with the same infants and toddlers and turns to the social-emotional domain, where temperament and attachment take center stage.

Three earlier ideas carry this week. From Week 2, a developmental theory organizes observations into an explanation that makes testable predictions, and no theory is the one right answer. From Week 3, an observation record keeps the behavior in one column and the interpretation in another. From Week 5, every age is a range, never a deadline. You will use all three on the running case, the illustrative, unnamed child whose records follow them from birth to 15.

1. Build schemes: assimilation, accommodation, and equilibration

Watch a toddler on a parent's lap with a picture book of farm animals (an illustrative scene). The toddler knows the family dog well. On the first page there is a cow. The toddler points and says, "Doggie!" The parent smiles and says, "That's a cow. Cows say moo." Two pages later the toddler points at another cow and says, "Moo."

Piaget had words for each part of that scene. Here are the course's terms, set off so you can find them:

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.
Assimilation is fitting a new experience into a scheme the child already has.
Accommodation is changing a scheme, or building a new one, so that it fits a new experience.
Equilibration is the push toward balance between assimilation and accommodation that moves a child's thinking forward.

Worked example — the farm book. Walk the scene in order.

The toddler's scheme: four-legged animals are "doggie".
The cow arrives. Calling it "doggie" fits the cow into the scheme the toddler already has. That is assimilation.
The parent says "cow" and "moo". The toddler's old scheme does not fit anymore, so it changes: big animals that moo are cows. That is accommodation.
The next cow is named "moo" without help. For now, the new scheme and the world are back in balance. That is equilibration at work.

In words: calling the cow "doggie" is assimilation, and starting a new name for animals that moo is accommodation.

Misconception check — two words for one move. Students often think assimilation and accommodation are the same thing, because both happen when something new shows up. The cure: ask what changes. In assimilation, the experience is fitted to the child's scheme, and the scheme stays the same. In accommodation, the scheme itself changes to fit the experience.

Pause and think. Choose one option and answer it in two or three sentences:

(a) Think of a time you first met a new kind of phone, game, or tool. When did you treat it like the old one, and when did you have to change how you used it?
(b) Why might an infant need both assimilation and accommodation, rather than one alone? Use the farm book in your reply.

2. Walk the sensorimotor stage: six substages in order

Picture a baby in the first weeks of life. The baby sucks when something touches the mouth, and grips a finger pressed into the palm. By the end of the second year, the same child can look for a lost shoe in another room. Piaget described the 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.

Piaget described the stage in six sensorimotor substages, the ordered steps from reflexes to the beginnings of mental representation. In words, in order:

Reflexes. The infant uses the built-in responses you met in Week 5, such as sucking and grasping.
Repeating simple actions centered on the infant's own body. A baby who once found their thumb by chance keeps bringing it back to the mouth.
Repeating actions that make something interesting happen in the world. A kick that shakes a crib toy gets repeated, again and again.
Coordinating actions toward a goal, at about 8 to 12 months. The infant pushes one thing aside to reach another.
Experimenting with new actions to see what happens, at about 12 to 18 months. A toddler drops a spoon, then a cup, then a cracker, watching how each one falls.
The beginnings of mental representation. The child can hold an object or action in mind without seeing it, which opens the door to pretend play and words.

The sensorimotor stage runs from about birth to 2, about 0 to 24 months, across 6 substages. Only the fourth and fifth carry ages in this course's Dataset D, and even those are approximate.

Misconception check — the timetable. Students often read a stage model as a timetable, as if every baby enters the fourth substage on the day they turn 8 months. It is tempting, because a list of steps with ages looks like a schedule. The cure: Piaget's ages are approximate. The stage names and their order are what the model fixes; the ages describe typical ranges, and real infants move through the steps at their own pace.

There is a limitation worth naming here too. Piaget built much of his account from careful observation of a small number of infants, so later researchers tested his ideas with new methods. You will meet one of those methods in Section 5.

3. Find the hidden toy: object permanence and the A-not-B error

Go back to the peekaboo game. When the aunt's face disappears behind the napkin, a very young baby may look elsewhere, as if the face were gone. A few months later, the same baby pulls at the napkin. Something has changed in what the baby knows.

Object permanence is knowing that a thing still exists when you can no longer see it.

Object permanence does not switch on all at once. It grows in steps, and Piaget's tasks show the steps. Here are the two tasks the course uses this week, from Dataset D, the standard Piaget tasks.

Dataset D (the standard Piaget tasks): the object permanence and A-not-B tasks, with the typical earlier and later responses
Task	What the child is asked	Typical response earlier	Typical response later
Object permanence (cloth)	Find a toy hidden under a cloth while the child watches	early sensorimotor: stops searching once the toy is covered	later sensorimotor: lifts the cloth to find it
A-not-B	Find a toy moved from cloth A to cloth B while the child watches	fourth sensorimotor substage (about 8 to 12 months): searches under A	fifth sensorimotor substage (about 12 to 18 months): searches under B

The second task names a famous mistake.

The A-not-B error is what happens when an infant who has found a toy under one cloth (A) keeps searching there after watching it hidden under a second cloth (B).

Worked example — reading record R2. The running case (Dataset A) is illustrative, constructed for this course, and describes no real child. Record R2 was written at 9 months, in the family home, with a parent present.

Record R2 of the running case (illustrative), with behavior and interpretation in separate columns
What the infant did (behavior only)	What it might show (interpretation)
Finds a toy twice under the left cloth	object permanence for a toy hidden in one place
Watches the toy hidden under the right cloth, then searches under the left cloth again	the A-not-B error
Babbles "ba-ba-ba"	babbling (Section 6)

Now work it step by step.

Name the cloths. The left cloth, where the toy was found first, is A. The right cloth, where the toy was moved, is B.
Count the hidings: 2 hidings under the left cloth + 1 hiding under the right cloth = 3 hidings.
Count the searches. The infant searched under the left cloth all 3 times, so 2 of the 3 searches found the toy.
Place R2 on Dataset D. 9 months falls inside the fourth sensorimotor substage, at about 8 to 12 months, whose typical response is to search under A. The window is 12 − 8 = 4 months wide.
Look ahead. In the fifth sensorimotor substage, at about 12 to 18 months, the typical response is to search under B. That window is 18 − 12 = 6 months wide.

In words: 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.

Notice what the infant in R2 already knows. Finding the toy twice under the left cloth means the infant knows a covered toy still exists. That is a real step. The error shows that the infant's idea of where the toy is still leans on the infant's own past actions: "I found it there before."

Misconception check — all at once. Students often think object permanence appears all at once, as if a baby either has it or does not. It is tempting, because the term sounds like a single switch. The cure: R2 shows a middle step. The infant searches for a covered toy, which is real object permanence, yet still makes the A-not-B error. Object permanence grows in steps across the sensorimotor stage.

4. Copy it later: deferred imitation

Picture a grandparent stirring a pot of soup at the stove while a toddler watches from a booster seat (an illustrative scene). The next day, with the grandparent out of the room, the toddler takes a wooden spoon and an empty bowl and stirs, round and round, with the same serious face.

Deferred imitation is copying an action seen earlier, after a delay, when the person who modeled it is no longer there.

Why does this matter? To copy something a day later, the toddler has to hold a memory of the action in mind. That is the kind of mental representation Piaget placed at the end of the sensorimotor stage. Deferred imitation is one window on memory in the first two years.

Worked example — reading the soup scene. Walk the course's order.

What the child did: stirs an empty bowl with a wooden spoon, round and round, the day after watching a grandparent stir soup.
What it might show: deferred imitation, because the model is not present and the action is copied after a delay.
Which theory explains it: Piaget's account reads it as a sign of mental representation.
What a second theory adds: Week 2's social learning theory reminds you that children learn by watching others.

In words: stirring an empty bowl the day after watching the grandparent is deferred imitation, which shows the toddler held the action in memory.

Misconception check — the passive baby. Students often picture infants as passive, waiting for adults to teach them. It is tempting, because babies cannot yet tell you what they know. The cure: the soup scene, the farm book, and the peekaboo game all show infants actively exploring, testing, and remembering. Infants are busy learners from the start.

5. Refine Piaget: what infants seem to know earlier

Piaget's tasks ask the infant to do something: reach, lift, search. Later researchers asked a different question. What if an infant knows where a toy is but cannot yet plan the reach?

Instead of asking for a reach, these researchers measured how long infants look at events. Infants tend to look longer at something surprising. So researchers showed infants possible events and impossible ones, such as a toy that seems to pass through a solid wall.

Looking-time research is 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 is the course's careful reading of that work. Researchers who measure how long infants look at possible and impossible events report that infants understand some properties of objects earlier than Piaget's search tasks showed. The search task asks for a reach; a looking task asks only for a look. This is a refinement of Piaget's account, not a refutation. Piaget's order of steps still organizes much of what researchers see, while the newer methods suggest the first steps may begin sooner than a reaching task can reveal.

Memory grows in the same years. Infants come to recognize familiar people, places, and routines, and toddlers can recall an action seen earlier, as deferred imitation shows. Early memory, in plain words, holds more and lasts longer as the first two years go on.

Misconception check — Piaget was wrong. Students often hear about the newer research and conclude that Piaget was wrong. It is tempting, because "infants know more, earlier" sounds like a correction. The cure: the newer research refines the ages and methods; it does not erase the steps. Each method shows something, and each has a limitation. A reach needs planning and movement, while a long look can be hard to interpret.

Pause and think. Choose one option and answer it in two or three sentences:

(a) Why might a baby "know" something before the baby can show it with a reach? Compare it with something you understood before you could explain it.
(b) A looking task and a search task disagree about when an infant knows a hidden toy exists. Which one would you trust more, and why? Name one limitation of each.

6. Hear the first words: receptive and expressive language

Listen to a childcare center's morning drop-off (the running case's setting this week). A caregiver says, "Want to go up?" and a toddler lifts both arms. The toddler has never said "up" to this caregiver, yet the toddler understood it. Language runs on two tracks at once.

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 of expressive language. A toddler typically understands more words than the toddler says.

Early language also follows a typical sequence, with wide timing:

Cooing — soft, drawn-out vowel sounds, such as "ooo" and "aah".
Babbling — repeated consonant-vowel strings, such as "ba-ba-ba".
First words — single words used with meaning.
Two-word combinations — a toddler's first short phrases made of two words, such as "more ball".

The steps come in that order, but the ages at which children reach each one vary widely. This course pins no single age for any of them.

Worked example — reading R2 and R3 for language. Two records of the running case (illustrative) carry the sequence.

Record R2, at 9 months in the family home: the infant babbles "ba-ba-ba". That is babbling, the step before first words.
Record R3, at 14 months at the childcare center's morning drop-off: the toddler says "ball", "up", and "more". That is 3 single words and no two-word combination yet.
Reading the tracks: R3's 3 words are expressive language. Receptive language usually runs ahead, so a toddler typically understands more words than the toddler says.
What the record cannot tell you: R3 carries no hiding task, so the record cannot tell you how this toddler searches. A record shows what was observed, and nothing more.

In words: R2's "ba-ba-ba" is babbling, and R3's 3 first words are expressive language that follows the typical sequence, with wide timing.

Misconception check — meaningless noise. Students often hear babbling as meaningless noise, because "ba-ba-ba" is not a word. It is tempting, since babbling has no dictionary meaning. The cure: babbling practices the sounds of the language a child hears. It is the bridge between cooing and first words, not random noise.

7. Talk to babies: infant-directed speech and two languages

Listen to almost any adult talking to a baby. The voice rises. The words slow down. "Look at the big dog! Is that a dog?" Many adults do this without being taught.

Infant-directed speech is the higher-pitched, slower, exaggerated speech adults use with babies.

Why does it help? Infant-directed speech holds infants' attention and highlights the sounds and structure of language. The stretched vowels and clear pauses make it easier for a baby to hear where one word ends and the next begins. Here nature and nurture work together again: infants arrive ready to attend to voices, and adults' speech gives them something rich to attend to.

Now picture a bilingual household (an illustrative scene). One parent speaks one language with the baby, and a grandparent who lives with the family speaks another. A neighbor worries out loud that two languages will confuse the baby.

Worked example — counting words in two languages. Suppose an illustrative toddler in that household says 4 words in one language and 3 different words in the other. Counted one language at a time, the toddler seems to have only 4 or 3 words. Counted together, the toddler has 4 + 3 = 7 words. That is why researchers count both languages.

Children exposed to two languages from infancy typically reach early language milestones on a typical timeline when both languages are counted together.

Misconception check — two languages, slower talking. Students often think bilingual exposure delays language, because a bilingual toddler may know fewer words in each single language. The cure: count both languages. Children exposed to two languages from infancy typically reach early language milestones on a typical timeline when both languages are counted together. No language and no family is the norm the others fall short of.

8. Read a milestone checklist: a reason to talk, not a diagnosis

Picture a pediatric checkup (an illustrative scene). A parent fills out a short checklist about a toddler: Does the child point to show you something? Does the child say a few words? The parent pauses at one item that the toddler does not do yet, and worries.

The Centers for Disease Control and Prevention publishes milestone checklists 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 CDC's "Learn the Signs. Act Early." checklists were revised in 2022 so that each lists what most children (75 percent or more) do by that age, and checklists were added for 15 and 30 months. A missed item is a reason for a family to talk with a health professional, never a diagnosis.

Worked example — reading the 75 percent rule. Work out what the rule means.

75 percent or more means at least 75 of every 100 children, which is 3 of every 4.
100 − 75 = 25, so as many as 1 in 4 children may not yet do a listed item at that age.

In words: a checklist item is something most children do by that age, and up to a quarter may not yet, which is why a missed item starts a conversation rather than ending one.

Misconception check — the test. Students often read a milestone checklist as a diagnostic test, as if a missed item proves something is wrong. It is tempting, because a checklist looks like a test form. The cure: the CDC's 2022 checklists list what most children (75 percent or more) do by that age. A missed item is a reason for a family to talk with a health professional, never a diagnosis, and this course never judges whether a real child is "behind".

Worked example — putting the week together. Read R2 and R3 once more in the developmental order, with two lenses.

What the child did: at 9 months (R2), finds a toy twice under the left cloth, watches it hidden under the right cloth, then searches under the left cloth again, and babbles "ba-ba-ba"; at 14 months (R3), says "ball", "up", and "more".
What it shows: the A-not-B error and babbling in R2; 3 first words, expressive language, in R3.
Theory one, Piaget's cognitive-developmental theory: R2's search under A shows an object concept still tied to the infant's own past actions, which Piaget placed in the fourth substage.
Theory two, the later looking-time research: it adds that infants may know more about hidden objects than a reaching task shows, a refinement of Piaget's account, not a refutation.

The reading in one plain sentence: 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, and R2's babbling and R3's 3 first words follow the typical language sequence, with wide timing.

That sentence is the habit this course grades. You name the behavior, the concept, and the evidence, in words a family could follow, and you leave the judging out.

Key terms

Scheme — In Piaget's theory, an organized pattern of action or thought, such as grabbing and shaking a rattle, that a child uses to make sense of the world. (first used: 1. Build schemes: assimilation, accommodation, and equilibration)
Assimilation — Fitting a new experience into a scheme the child already has, as when a toddler calls a cow "doggie" because it has four legs. (first used: 1. Build schemes: assimilation, accommodation, and equilibration)
Accommodation — Changing a scheme, or building a new one, so that it fits a new experience, as when a toddler learns that big animals that moo are cows. (first used: 1. Build schemes: assimilation, accommodation, and equilibration)
Equilibration — In Piaget's theory, the push toward balance between assimilation and accommodation that moves a child's thinking forward. (first used: 1. Build schemes: assimilation, accommodation, and equilibration)
Sensorimotor stage — Piaget's first stage of cognitive development, from about birth to 2, in which infants learn through their senses and actions; Piaget described it in six substages. (first used: 2. Walk the sensorimotor stage: six substages in order)
Sensorimotor substages — The six ordered steps of the sensorimotor stage, from reflexes, through repeated and then goal-directed actions and experiments with new actions, to the beginnings of mental representation; their ages are approximate. (first used: 2. Walk the sensorimotor stage: six substages in order)
Object permanence — Knowing that a thing still exists when you can no longer see it; it grows in steps across the sensorimotor stage. (first used: 3. Find the hidden toy: object permanence and the A-not-B error)
A-not-B error — An infant who has found a toy under one cover (A) keeps searching there after watching the toy hidden under a second cover (B); Piaget placed it in the fourth sensorimotor substage, at about 8 to 12 months. (first used: 3. Find the hidden toy: object permanence and the A-not-B error)
Deferred imitation — Copying an action seen earlier, after a delay, when the person who modeled it is no longer there; it shows that a child holds a memory of the action in mind. (first used: 4. Copy it later: deferred imitation)
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. (first used: 5. Refine Piaget: what infants seem to know earlier)
Receptive language — Understanding words and sentences that others say; in early childhood it usually runs ahead of expressive language. (first used: 6. Hear the first words: receptive and expressive language)
Expressive language — Producing words and sentences to communicate, by speaking or signing. (first used: 6. Hear the first words: receptive and expressive language)
Cooing — An infant's soft, drawn-out vowel sounds, such as "ooo" and "aah", which usually come before babbling. (first used: 6. Hear the first words: receptive and expressive language)
Babbling — An infant's repeated consonant-vowel strings, such as "ba-ba-ba", which practice the sounds of the language the infant hears. (first used: 6. Hear the first words: receptive and expressive language)
Two-word combinations — A toddler's first short phrases made of two words, such as "more ball", which usually follow a period of single words. (first used: 6. Hear the first words: receptive and expressive language)
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. (first used: 7. Talk to babies: infant-directed speech and two languages)
Milestone checklist — A list of what most children (75 percent or more) do by a given age, as in the CDC's 2022 "Learn the Signs. Act Early." checklists; a missed item is a reason to talk with a health professional, never a diagnosis. (first used: 8. Read a milestone checklist: a reason to talk, not a diagnosis)

Summary

Piaget's infants build schemes, assimilate new experiences into them, and accommodate them when the world does not fit.
The sensorimotor stage runs from about birth to 2, in six substages, from reflexes to the beginnings of mental representation; the ages are approximate.
Object permanence grows in steps; the A-not-B error belongs to the fourth substage, at about 8 to 12 months.
Deferred imitation shows a toddler holding an action in memory.
Looking-time research refines Piaget's account; it does not refute it.
Receptive language usually runs ahead of expressive language; cooing, babbling, first words, and two-word combinations come in order, with wide timing.
Infant-directed speech helps infants hear language; children learning two languages reach early milestones on a typical timeline when both are counted.
The CDC's 2022 checklists list what most children (75 percent or more) do by an age; a missed item is a reason to talk with a health professional, never a diagnosis.

Check your understanding

Work these before looking at the answers — they are ungraded, and the answers (with reasoning) are at the bottom of the page.

At an illustrative park, a toddler who rolls every round thing sees an orange on a picnic blanket and rolls it across the grass. An older cousin peels the orange, and the toddler tastes a piece; after that, the toddler tries to peel the next orange instead of rolling it. Name the move in each half of the scene.
Put these four illustrative infant behaviors in sensorimotor-substage order, and name the substage of each: (1) drops a cracker, then a block, then a sock from a high chair, watching each fall; (2) sucks when a nipple touches the mouth; (3) kicks again and again to make a hanging toy jingle; (4) pushes a pillow aside to reach a hidden rattle.
At an illustrative library story time, a caregiver notes four things a toddler does: (1) brings a book over when asked, "Can you get the duck book?"; (2) says "uh-oh" when a block falls; (3) points to the cat on the page when asked, "Where is the cat?"; (4) says "more book". Sort each into receptive or expressive language, and count each kind.
A neighbor says, "Talking to that baby in two languages will confuse her, so she'll talk late." Name the misconception and write a fairer sentence.

Answers (worked reasoning — read after attempting)

Rolling the orange fits the new object into the toddler's existing "round things roll" scheme, so the first half is assimilation. Trying to peel the next orange shows the scheme has changed to fit the new experience, so the second half is accommodation. The test is what changed: in the first half the orange was fitted to the scheme, and in the second half the scheme itself changed.
The order is (2), (3), (4), (1). Sucking at a touch is a reflex, the first substage. Kicking again and again to make a toy jingle repeats an action that makes something interesting happen in the world, the third substage. Pushing a pillow aside to reach a rattle coordinates actions toward a goal, the fourth substage. Dropping different things to watch each fall is experimenting with new actions, the fifth substage. The order is fixed; the ages at which any one child does each are not.
Items (1) and (3) show understanding of what someone else said, so they are receptive language. Items (2) and (4) are the toddler producing words, so they are expressive language; "more book" is a two-word combination. That makes 2 receptive and 2 expressive, and 2 + 2 = 4 notes in all.
The sentence reads bilingual exposure as delaying language. Children exposed to two languages from infancy typically reach early language milestones on a typical timeline when both languages are counted together. A fairer sentence: "She is learning two languages at once, so we should count her words in both languages together."

Next up in this module: the Readings & Resources page, the lecture tutorial, the practice set, the quiz, and the discussion — and next week, attachment theory and the Strange Situation take these same toddlers into their first relationships.

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