Lifespan Development: Key Concepts and Research Methods

Introduction to Lifespan Development

Overview of Lifespan Development

Lifespan development is the scientific study of how people change and remain the same throughout their lives. This field examines physical, cognitive, and psychosocial growth from conception to old age.

• Normative age-graded influences: Biological and environmental influences that are similar for individuals in a particular age group (e.g., puberty, retirement).

• Normative history-graded influences: Influences common to people of a particular generation due to historical circumstances (e.g., wars, pandemics).

• Nonnormative life events: Unusual occurrences that have a major impact on an individual's life (e.g., winning the lottery, losing a parent young).

• Continuity vs. discontinuity: Debate over whether development is a gradual, continuous process or a sequence of distinct stages.

• Dimensional vs. Categorical approach to diagnosis: Dimensional approaches view symptoms on a continuum, while categorical approaches classify disorders as distinct entities.

• Spectrum disorders: Disorders that exist on a continuum, such as autism spectrum disorder.

• DSM-5-TR: The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision, used for diagnosing mental disorders.

• Quantitative vs. qualitative changes: Quantitative changes involve measurable growth (e.g., height), while qualitative changes involve changes in type or kind (e.g., cognitive development).

Additional info: The "Big Names" in lifespan development refer to influential theorists such as Erik Erikson, Jean Piaget, and Sigmund Freud, whose theories are foundational but not detailed here.

Research Methods

Approaches to Studying Development

Research in lifespan development uses a variety of methods to investigate how and why people change over time. Understanding these methods is crucial for interpreting scientific findings.

• Research problems: Clearly defined questions or hypotheses that guide the study.

• Null and alternative hypotheses: The null hypothesis states there is no effect or difference; the alternative suggests there is.

• Independent, dependent, and control variables: The independent variable is manipulated, the dependent variable is measured, and control variables are held constant.

• Operationalizing variables: Defining variables in practical, measurable terms.

• Random assignment and matching: Techniques to ensure groups are comparable at the start of an experiment.

• Methods of collecting data: Includes lab settings, naturalistic observation, surveys, interviews, and standardized tests.

• Different types of research: Descriptive (observing and describing behavior), correlational (examining relationships), and experimental (manipulating variables to determine cause and effect).

• Cross-sectional, longitudinal, and sequential approaches:

  • Cross-sectional: Compares individuals of different ages at one point in time.

  • Longitudinal: Follows the same individuals over time.

  • Sequential: Combines cross-sectional and longitudinal methods.

• T-test: A statistical test used to compare the means of two groups. $t = \frac{\bar{X}_1 - \bar{X}_2}{\sqrt{\frac{s_1^2}{n_1} + \frac{s_2^2}{n_2}}}$

• Between groups vs. within groups design: Between groups compares different groups; within groups compares the same group at different times.

• Matching vs. randomization: Matching pairs participants on certain variables; randomization assigns them by chance.

• Ethical issues: Informed consent, debriefing, deception, and protection from harm.

• Milgram's study and Zimbardo's study: Classic studies highlighting ethical considerations in research.

• Ethnic gloss: Overgeneralization about an ethnic group that obscures cultural differences.

• Probability: The likelihood that a result occurred by chance.

• Statistical vs. clinical significance: Statistical significance means results are unlikely due to chance; clinical significance means results have practical importance.

• Institutional Review Board (IRB) and Human Subjects Committee (HSC): Committees that review research proposals to ensure ethical standards are met.

Nature-Nurture & Teratogens

Genetic and Environmental Influences on Development

The nature-nurture debate explores the relative contributions of genetics (nature) and environment (nurture) to human development. Teratogens are environmental agents that can cause harm during prenatal development.

• Genetic influences: Inherited characteristics that affect development.

• Environmental influences: External factors such as family, culture, and experiences.

• Teratogens: Substances or conditions that can cause birth defects (e.g., drugs, alcohol, infections).

• Diathesis-stress model: Suggests that psychological disorders result from a combination of genetic vulnerability and environmental stressors.

• Liability threshold model: Proposes that disorders develop when genetic and environmental risk factors exceed a certain threshold.

• Twin research: Studies of identical and fraternal twins to estimate genetic and environmental contributions to traits.

• Critical and sensitive periods: Times during development when certain experiences have a profound effect.

• Epigenetics: Study of how environmental factors affect gene expression without changing DNA sequence.

• Prenatal diagnostic tests: Medical tests to detect developmental problems before birth.

• Low birth weight: Associated with increased risk for health and developmental problems.

• Mother's age and father's age: Parental age can influence risk factors for the child.

• Mother's emotional state: Maternal stress can impact fetal development.

• Drug effects: Different drugs have varying effects on fetal development.

• Assessing the infant at birth: Methods such as the Apgar score are used to evaluate newborn health.

Brain Physiology, Aging, and Life Expectancy

Biological and Psychological Aspects of Aging

This section explores how the brain and body change with age, factors influencing life expectancy, and theories of aging.

• Patterns of growth: Cephalocaudal (head-to-tail), proximodistal (center-outward), and hierarchical integration (simple to complex skills).

• Principle of independence of systems: Different body systems develop at different rates.

• Physical changes throughout the lifespan: Includes changes in brain structure, muscle mass, and sensory abilities.

• Longevity/life expectancy: The average number of years an individual can expect to live.

• Sex differences in longevity: Women typically outlive men; theories include biological and social factors.

• Geographical differences: Life expectancy varies by country due to healthcare, lifestyle, and genetics.

• Psychological longevity: The impact of mental health and psychological factors on lifespan.

• Predictions of reaching 100: Factors that increase the likelihood of living to 100 include genetics, lifestyle, and social support.

• Major studies:

  • New England Centenarian Study

  • Results of the Seattle Longitudinal Study

  • Duke Longitudinal Study

  • Secondary versus primary aging: Primary aging is inevitable biological aging; secondary aging results from disease and lifestyle.

• Health disparities: Differences in health outcomes among different racial and ethnic groups.

• Theories of aging:

  • Cellular clock theory: Cells can divide only a limited number of times.

  • Free-radical theory: Aging is caused by damage from free radicals.

  • Mitochondrial theory: Aging is due to the decay of mitochondria.

  • Hormonal stress theory: Aging is related to the body's stress response system.

Additional info: Students are encouraged to review specific video lectures and readings as referenced in the original notes for further detail on these topics.