5. What Is It Like to Be a Baby: The Development of Thought

What this lecture covers

This lecture turns to cognitive development, starting with Jean Piaget's influential stage theory of how children come to understand the physical world, then presenting modern research suggesting infants know more, earlier, than Piaget's methods could detect. It closes with the question of whether development is a single general process or made up of separate specialized systems, using autism as a key piece of evidence.

After watching, you should be able to describe Piaget's four stages and his core findings (object permanence, conservation, egocentrism), explain how habituation and looking-time methods let researchers study what infants understand, and explain why autism and the false-belief task support the idea that social understanding is a distinct cognitive system from physical reasoning.

Key ideas

• Piaget's stage theory: children move through the sensorimotor, preoperational, concrete operations, and formal operations stages, each marked by different capacities and limitations, driven by assimilation (expanding what you respond to) and accommodation (changing how you respond).
• Object permanence: Piaget's claim that young infants do not understand that objects continue to exist when out of sight, illustrated by the A-not-B error, where infants keep reaching for an object at its old hiding place after watching it move.
• Egocentrism and conservation: preoperational children struggle to see the world from another's viewpoint (the three-mountains task) and fail to understand that quantity is preserved despite a change in appearance (the checkers or liquid conservation tasks).
• Limits of Piaget's method: his reliance on verbal question-and-answer likely underestimated what young children and infants actually know.
• Modern infant-cognition methods: looking-time studies use preference and habituation-and-surprise designs, since infants cannot talk; longer looking at an "impossible" event signals surprise and suggests underlying knowledge.
• Evidence for early physical knowledge: studies (for example by Elizabeth Spelke, Rene Baillargeon, and Karen Wynn) show infants as young as a few months old expect solid objects to persist, follow expected trajectories, and behave consistently with simple addition and subtraction, though some physical knowledge (like gravity's effect on unsupported objects) still develops later.
• Two explanations for early failures: children may lack knowledge outright, or may have the knowledge but struggle with inhibitory control (an immature frontal lobe), as shown by studies where infants look toward the correct location while still reaching toward the wrong one.
• Modularity versus general development: an alternative to Piaget's view of one unified developmental process is that the mind has separate, partly pre-wired systems (for physical objects, for people, possibly for artifacts or biology), a view associated with Noam Chomsky and Jerry Fodor.
• Autism as evidence for a social module: autism involves a marked social/theory-of-mind impairment (failing false-belief tasks like the Maxie/ball task) alongside largely intact reasoning about the physical world, suggesting social cognition is a distinct system rather than part of general intelligence.

Walkthrough

Jean Piaget, stage theory, and its limits (0:00)

Bloom introduces Piaget's view of children as active "little scientists" building theories of the world through assimilation and accommodation, and presents his four-stage theory. He details the sensorimotor stage's lack of object permanence (the A-not-B error), the preoperational stage's egocentrism (the three-mountains task) and failure of conservation (the checkers demonstration), and briefly the concrete and formal operations stages. He then evaluates Piaget's legacy, crediting his falsifiable, well-supported findings while noting theoretical, methodological, and factual limitations — especially that reliance on verbal answers may have underestimated young children's actual knowledge.

The modern science of infant cognition (12:50)

He introduces looking-time methods (preference and habituation-and-surprise) as tools for studying preverbal infants, then walks through studies revisiting Piagetian questions: infants expecting a rod to be a single connected object behind an occluder, expecting a block to stop a rising screen, and (Karen Wynn's research) showing surprise at impossible outcomes of simple addition and subtraction. He notes that some physical understanding, like objects needing support against gravity, is not present at six months but appears by twelve months, and discusses neural maturation, synaptic growth, and myelination as partial explanations for cognitive change, alongside the alternative explanation that failures like the A-not-B error may reflect poor inhibitory control rather than lack of knowledge.

Babies in the social world (25:12)

Bloom turns to social cognition, describing newborns' preference for face-like patterns, early imitation (Andrew Meltzoff's tongue-protrusion studies), and his own research with Valerie Kuhlmeier and Karen Wynn showing that infants around nine to twelve months expect a character to approach a helper rather than a hinderer, and tend to prefer helpful characters when given a choice.

Question and answer on learning and development (31:26)

Students ask about the age at which children pass false-belief and deception tasks, whether operant conditioning has been used to study infant concepts, and interpretation of specific experimental choices, with Bloom noting that looking-time measures are generally more informative than conditioning methods for infants.

Review of studies presented in class and autism (33:53)

Bloom revisits studies where young children fail deception and false-belief tasks, weighing whether this reflects genuine lack of understanding of others' minds or an inhibitory-control problem, since even adults are slower on tasks involving deception. He introduces modularity as an alternative to Piaget's general-development view and presents autism as key evidence: autistic individuals show a distinctive pattern of "mind blindness" (difficulty inferring others' gaze-based desires, failing the false-belief task) alongside intact reasoning about the physical world, supporting the idea that social cognition is a separable system.

Question and answer on autism (40:38)

Further questions cover Simon Baron-Cohen's "extreme male brain" theory of autism, whether autism maps onto normal developmental stages, prospects for people with autism, and autistic savants (illustrated by the film "Rain Man"), which Bloom notes are a small minority of autistic individuals. He closes by briefly raising other candidate cognitive modules (artifacts, social groups, intuitive biology) and the distinct question of how language itself may reshape cognition, ending with a Stephen Jay Gould example showing why developmental evidence can answer questions about adult biology that adult observation alone cannot.

Before you watch

• This lecture builds on the discussion of learning in the previous lecture on Skinner and behaviorism, particularly the concept of habituation.
• No prior background in developmental psychology is assumed.

Check your understanding

1. What is the difference between assimilation and accommodation in Piaget's theory?
2. How do habituation and surprise-based looking-time studies let researchers test what preverbal infants understand?
3. Why might the A-not-B error reflect a problem with inhibitory control rather than a lack of knowledge about objects?
4. What does the false-belief task test, and why do autistic individuals typically struggle with it despite often reasoning normally about the physical world?
5. How does modularity, as a theory of development, differ from Piaget's view of a single general developmental process?