AP Psychology · Lesson 1

Development across the lifespan

Know Know it

Physical development starts before birth. In the prenatal period, teratogens such as alcohol, nicotine and some viruses can harm the growing baby. Newborns arrive with reflexes, such as rooting (turning toward a touch on the cheek) and grasping. Skills like sitting and walking unfold through maturation, in roughly the same order for most children, though the timing varies.

Some skills depend on a critical period, an early window when the right experience must happen. In adolescence, puberty brings sexual maturity, and the brain's emotional and reward areas mature before the prefrontal cortex, which keeps developing into the mid-20s. In late adulthood, reactions slow and some senses weaken.

Cognitive development, in Piaget's theory, moves through four stages. Children build mental frameworks called schemas. They assimilate new experiences into existing schemas and accommodate by changing schemas that do not fit. Vygotsky stressed social learning: a more skilled helper offers scaffolding within the child's zone of proximal development.

Language grows from babbling (around 4 to 6 months) to single words (around 1 year) to two-word telegraphic speech (around 2 years). Young children often overgeneralize grammar rules, as in saying goed for went. With age, fluid intelligence (fast reasoning on new problems) tends to decline, while crystallized intelligence (stored knowledge and vocabulary) holds steady or grows.

Social-emotional development begins with attachment. Harlow's research with infant monkeys showed that comfort from contact, not just food, builds attachment. In Ainsworth's strange situation, securely attached children explore with the caregiver near and are easily comforted on return. Babies also differ in temperament from birth. Baumrind described parenting styles: authoritative (warm with clear rules), authoritarian (strict with little warmth), permissive (warm with few rules); later researchers added a fourth, neglectful (little warmth and few rules). Erikson described eight stages, each with a social challenge, such as identity versus role confusion in the teen years.

Piaget's four stages of cognitive development
StageTypical agesWhat the child can do or still lacks
SensorimotorBirth to about 2Learns through senses and actions; develops object permanence
PreoperationalAbout 2 to 7Uses words and pretend play; shows egocentrism; lacks conservation
Concrete operationalAbout 7 to 11Masters conservation; reasons logically about concrete events
Formal operationalAbout 12 and upReasons about abstract ideas and hypothetical situations

Trap Egocentrism is not selfishness

In Piaget's sense, egocentrism means a young child has trouble taking another person's point of view. A 4-year-old who holds up a picture facing herself while showing it to you is not being rude. She assumes you see what she sees.

Worked example Easy

A 6-month-old reaches for a rattle. When her father covers it with a towel, she looks away and stops reaching. According to Piaget, which ability has she not yet developed?

  1. Abstract reasoning
  2. Object permanenceAnswer
  3. Telegraphic speech
  4. Stranger anxiety

How to solve it

  1. The toy is still there, just hidden.
  2. She behaves as though it is gone.
  3. Knowing that hidden things still exist is object permanence, which develops in the sensorimotor stage.

Why each choice is right or wrong

  • A. Incorrect. Abstract reasoning belongs to the formal operational stage, and nobody expects it in a baby.
  • B. Correct. She acts as if the rattle stopped existing once it was hidden, which shows object permanence has not yet developed.
  • C. Incorrect. Telegraphic speech is a two-word language stage around age 2, unrelated to searching for a hidden toy.
  • D. Incorrect. Stranger anxiety is fear of unfamiliar people, and the scenario is about a hidden object, not a stranger.

Explain Explain it

Task verbs: identify, explain

To explain a developmental idea, name the stage or concept, then point to the exact behavior in the scenario that shows it. Ages are rough guides, so lean on the behavior, not just the age.

Worked example Medium

In a playroom study, 14-month-old Nia plays with toys while her mother sits nearby, often glancing back at her. When her mother leaves, Nia cries and stops playing. When her mother returns, Nia reaches for her, calms within a minute and goes back to the toys.

Which attachment pattern does Nia show?

  1. Avoidant attachment
  2. Anxious-ambivalent attachment
  3. Disorganized attachment
  4. Secure attachmentAnswer

How to solve it

  1. Note how Nia explores: freely, checking back with her mother.
  2. Note the return: she seeks comfort and calms quickly.
  3. Exploring from a safe base plus quick comfort marks secure attachment.

Why each choice is right or wrong

  • A. Incorrect. An avoidant child shows little distress when the caregiver leaves and ignores her on return, but Nia seeks her mother.
  • B. Incorrect. An anxious-ambivalent child is hard to comfort and may cling and resist at once, while Nia calms within a minute.
  • C. Incorrect. Disorganized attachment shows confused or contradictory behavior, and Nia's behavior is clear and consistent.
  • D. Correct. Nia explores with her mother as a safe base, is upset when she leaves, and is quickly comforted on return.

Explain Your turn

A 5-year-old watches juice poured from a short, wide glass into a tall, thin glass and says the tall glass now has more juice. Explain this answer using Piaget's theory.

Write it, then compare. Nothing you type here is saved or graded.

Compare with a model answer

A full answer does this

  • Says the child lacks conservation or is in the preoperational stage
  • Explains that the child judges by height and misses that the amount did not change

Model answer

The child is in Piaget's preoperational stage and has not yet mastered conservation. He focuses on one feature, the higher level of juice in the tall glass, and misses that nothing was added or taken away, so the amount of juice is the same.

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