PSYC 201: Human Development Notes

Chapter 9: Human Development

What is Development?

• Development is a series of changes, encompassing both improvements (for the better) and declines (for the worse).
• These changes often involve trade-offs.

Domains of Development

This course examines human life-span development in the following key domains:

• Intelligence
• Memory
• Mental (specifically Piaget's theory of cognitive development)
• Psychosocial (specifically Erikson's psychosocial stages)

Terminology

• Chronological Age:
  • The number of months or years since an individual's birth.
  • $E.g.$, $3$ months old, $2$ years old.
• Developmental Age:
  • The chronological age at which most children typically achieve a particular level of physical or mental development.
  • $E.g.$: The developmental age for walking without assistance is $12$ months old.
  • A $10$-month-old child who can walk without assistance is considered to have a developmental age of $12$ months.
• Normative Investigations:
  • Research efforts aimed at describing characteristics typical of a specific age or developmental stage.

Research Design

• Longitudinal Design:
  • The same participants are observed repeatedly over an extended period, sometimes many years.
  • Advantages:
    • Researchers can identify individual differences in development (e.g., the developmental age for walking varies across individuals).
    • Allows examination of relationships between early and later events and behaviors.
    • Can help test the direction of causation.
  • Disadvantages:
    • Time-consuming and costly.
    • High drop-out rates can lead to data loss.
    • Data can be contaminated by:
      1. Practice effects: Participants' repeated exposure to tasks may improve performance, not due to development but familiarity.
      2. Cohort effects:
         • A cohort is a group of people who develop in the same time period and are influenced by shared cultural and historical conditions.
         • Results based on one cohort may not be generalizable to another cohort because different cohorts experience different historical and cultural environments.
         • Cohort effects refer to the impact of cultural-historical changes on research findings' accuracy.
• Cross-sectional Design:
  • Groups of participants of different chronological ages are observed and compared at a single point in time.
  • Advantages:
    • Takes less time to complete.
    • Less costly.
    • Not subject to practice effects.
  • Disadvantages:
    • Cannot determine if an early event impacts a later event.
    • Vulnerable to cohort effects, especially when comparing cohorts with significant age differences (e.g., differences in IQ between generations might be due to accessibility and quality of education rather than age-related decline).

Types of Intelligence

• Crystallized Intelligence:
  • Involves recalling facts, general knowledge, and information from a stored base of knowledge.
  • This data can then be applied to new situations.
  • $E.g.$: A chef who has memorized many recipes over decades and no longer needs cookbooks.
• Fluid Intelligence:
  • The ability to solve newly encountered problems based on logic and reason.
  • $E.g.$: People who enjoy solving murder-mystery dinners using logic and deduction.

Intelligence Development Across the Life Span

• Developmental Trajectories:
  • Fluid intelligence typically peaks in early adulthood (early $20s$) and then shows a decline with age.
  • Crystallized intelligence tends to increase from early adulthood, peaking in midlife and old age, and is generally preserved over age.
• Z-Scores and Performance:
  • Z-scores illustrate that performance on tasks requiring speed of processing, working memory, and long-term memory declines with increasing age (e.g., Digit Symbol, Letter Comparison, Pattern Comparison from $20s$ to $80s$).
  • Conversely, performance on tasks related to world knowledge (crystallized intelligence like Shipley Vocabulary, Antonym Vocabulary, Synonym Vocabulary) is generally preserved or even shows a slight increase across ages.
• Aging and Intelligence:
  • Fluid intelligence demonstrates a greater decline with age compared to crystallized intelligence.
  • The decrease in fluid intelligence is often attributed to a general slowing down of processing speed.
  • Older adults' performance on intellectual tasks that demand numerous mental processes in short timeframes is significantly impaired.
• Cross-sectional vs. Longitudinal Comparisons of Intellectual Change:
  • Cross-sectional assessments often suggest that intellectual ability begins to decline earlier in life.
  • Longitudinal assessments reveal that intellectual ability can increase from early adulthood and peak in middle adulthood, particularly for some aspects of intelligence.