Developmental Psychology: From Infancy to Childhood

Introduction

An infant can't distinguish itself from the world; by age three, they're a tiny philosopher asking "why?" about everything. Developmental psychology asks how children progress from helpless infants to thinking, feeling, social beings. Understanding these processes reveals what's hardwired versus what emerges through experience, and how early experiences shape lifelong patterns.

Key Concepts

• Piaget's Cognitive Development: Four stages of increasingly complex thinking, each with a characteristic way of understanding the world
  • Sensorimotor (0–2): Learning through senses and motor actions; object permanence emerges late
  • Preoperational (2–7): Symbolic thinking, language, but logic is limited (egocentrism, conservation failures)
  • Concrete Operational (7–11): Logical thinking about concrete objects but not abstract concepts
  • Formal Operational (11+): Abstract reasoning and hypothetical thinking
• Object Permanence: Understanding that objects continue to exist when out of sight; emerges ~8 months
• Theory of Mind: Understanding that others have beliefs, desires, and perspectives different from your own; emerges ~4–5 years
• Attachment: Deep emotional bond between infant and caregiver; primary attachment is usually the mother or primary caregiver
• Secure vs. Insecure Attachment: Secure (caregiver is responsive) vs. insecure (anxious, avoidant, disorganized); affects social development and stress regulation
• Temperament: Innate behavioral patterns (activity level, emotional reactivity, adaptability); relatively stable across development
• Critical/Sensitive Periods: Windows of heightened readiness to learn certain skills (language, motor milestones); missing them creates lasting deficits
• Nature vs. Nurture in Development: Both genes and environment interact; nature sets constraints and predispositions, nurture shapes expression
• Scaffolding: Adults provide temporary support that children gradually internalize, enabling more complex functioning

Examples & Classic Experiments

Piaget's Conservation Task (1954)

A child sees two identical glasses with equal water. You pour one into a taller, thinner glass. Before age ~7, children insist the tall glass has more water—they're fooled by height. After age 7, they understand volume is conserved.

Implication: Children don't gradually acquire logic; they have fundamentally different ways of reasoning about the world.

Ainsworth's Strange Situation (1969)

Researchers observed 1-year-old infants' reactions to:

1. Parent present
2. Stranger arrives
3. Parent leaves
4. Parent returns

Results: Secure infants (60%) distressed by separation, comforted by reunion. Insecure infants showed avoidant or resistant patterns.

Long-term finding: Attachment patterns predicted social competence years later, suggesting early relationships shape later functioning.

Traction of Object Permanence

Infants 0–6 months don't search for hidden objects out of sight is literally gone. By 8 months, they search. By 18 months, they search even after invisible displacements (adult hides object in hand, hand goes into box, object stays in box but infant doesn't see it).

Implication: Cognitive abilities emerge gradually through sensorimotor exploration.

Theory of Mind: The False Belief Task (Baron-Cohen et al., 1985)

A child watches character A put a marble in a basket. A leaves. Character B moves the marble to a box. Child is asked: "Where will A look for the marble?"

Before age ~4: Most say the box (where the marble is).
After age 4–5: Most say the basket (where A believes it is).

Critical finding: Understanding that others hold false beliefs is a developmental milestone; autistic children often show delays in this task.

Language Development Milestones

• 6 months: Babbling with language-specific sounds
• 12 months: First words
• 18 months: Vocabulary explosion (~200+ words)
• 24 months: Two-word combinations ("more milk")
• 3 years: Complex sentences, grammatical mistakes ("I goed")
• 4–5 years: Near-adult grammatical competence

Pattern: Development follows predictable sequences despite variation in timing; environmental language exposure affects vocabulary but not sequence.

Key Takeaways

1. Development is stage-like in some domains, continuous in others cognitive reasoning shows discrete stage transitions, but motor development and language are more gradual

2. Early attachment shapes social and emotional development secure early relationships support later competence; insecure attachment increases vulnerability to stress and social difficulties

3. Cognitive abilities emerge from action and experience children learn by exploring, manipulating, and testing the world; abstract reasoning develops later from concrete foundations

4. Critical/sensitive periods exist but are not hard deadlines missing early language exposure creates lasting deficits, but recovery is possible; windows are critical but not irreversible

5. Individual variation is normal children develop at different rates and with different temperaments; variation reflects normal differences, not necessarily deficits

Final Note

Early childhood isn't just preparation for later life, it's foundational. Experiences, relationships, and environments during infancy and childhood shape how brains organize themselves, affecting learning capacity, emotional regulation, and social competence for years to come.