Human Development: Foundations of Developmental Psychology

Human Development

Studying Development

Developmental psychology is the scientific study of age-related changes in physical characteristics, behavior, and mental processes from conception to death. It seeks to understand how and why people change over time.

• Developmental Psychology examines both physical and mental changes across the lifespan.

• The nature position argues that human development is governed by genetically programmed processes known as maturation.

• Developmental scientists identify critical periods—optimal times when organisms are especially sensitive to environmental experiences, shaping future development.

Continuity or Stages of Development?

One of the central debates in developmental psychology is whether development occurs in discrete stages or as a continuous process.

• Stage theorists argue for discrete developmental steps, with some periods showing little change and others rapid transformation.

• Continuity theorists suggest development is a gradual, cumulative process, with skills and abilities added at a steady pace.

• The continuity model posits that adults have more of certain skills (e.g., math, verbal skills) than children, differing quantitatively rather than qualitatively.

Stability or Change?

Another key issue is whether traits and abilities remain stable or change throughout life.

• Physical and motor skills are primarily continuous in nature.

• Cognitive skills often develop in discrete stages.

• Some characteristics (e.g., temperament) are stable, while others (e.g., interests, attitudes) may vary greatly across the lifespan.

Research Approaches in Developmental Psychology

Researchers use different methods to study development across the lifespan:

• Cross-sectional studies compare individuals from different age groups at one point in time, providing information about age differences.

• Longitudinal studies follow the same individuals or groups over an extended period, revealing changes with age.

Cohort Effects

Cohort effects refer to differences among age groups that are due to the unique historical and cultural experiences of each group, rather than true age-related changes.

• Cross-sectional studies may show declines in reasoning and intelligence after age 25, but longitudinal studies often show increases into the mid-50s, with declines only after age 60.

• Cohort effects can confound results, as findings may not generalize across different historical periods.

• Cross-sectional studies are also limited by expense and generalizability.

The Importance of Sociocultural Context

Culture and environment are powerful determinants of development.

• Children raised in individualistic, competitive societies (e.g., Western cultures) may develop different traits than those raised in collectivist cultures (e.g., Africa, Asia, Latin America).

Physical Development

Prenatal Development

Prenatal development occurs in three stages:

• Germinal period

• Embryonic period

• Fetal period

Prenatal growth follows a cephalocaudal pattern (head and upper body develop before lower body). The placenta nourishes the fetus and eliminates toxins, but some substances (e.g., x-rays, drugs, alcohol) can cross the placental barrier and cause harm.

Adverse Prenatal Influences

• Most harm occurs during the first three months (critical period).

• Nicotine and alcohol are teratogens—substances that cause birth defects.

• Over 5% of Canadian infants are exposed prenatally to 10 or more cigarettes per day.

Fetal Alcohol Syndrome (FAS)

• Smoking during pregnancy increases risk of premature birth, low birth weight, fetal death, behavioral abnormalities, and cognitive problems.

• FAS is a birth risk for 15% of Canadian infants whose mothers consume alcohol during pregnancy; 1 to 3 per 1000 infants are born with FAS.

• Fetal Alcohol Spectrum Disorder (FASD) refers to a broader range of effects from prenatal alcohol exposure.

• There is no known safe amount of alcohol during pregnancy; risk increases with amount consumed.

Brain Development

• The brain and nervous system grow faster than any other body part during prenatal development and the first two years of life.

• At birth, the brain is 1/4 adult size; by age six, it is 9/10 adult weight.

• Learning and brain development are correlated, with increased numbers of neurons, axons, dendrites, and their interconnections.

Motor Development

• Movement skills emerge in an orderly sequence as infants develop voluntary actions.

• Reflexes (e.g., turning head when cheek is touched) are replaced by voluntary movements (e.g., rolling over at 2.8 months, sitting alone at 5.5 months, standing at 11.5 months, walking up steps at 17.1 months).

Sensory & Perceptual Development

• Senses develop early; newborns can smell most odors, distinguish flavors, and are sensitive to touch and pain.

• Vision is poorly developed at birth; hearing is highly acute, and fetuses can hear sounds outside the womb.

Fetal Learning

• Infants recognize their mother's voice and prefer stories read to them in the womb.

• Robert Fantz's studies showed infants prefer complex over simple patterns and faces over simple shapes.

Adolescence and Puberty

Definition and Characteristics

• Adolescence is the period of psychological development between childhood and adulthood, marked by puberty and teenage years.

• The most dramatic sign is the growth spurt—increases in height, weight, and skeletal growth, as well as changes in reproductive structures and sexual characteristics.

Post-pubertal Physical Changes

• Physical changes after puberty are less dramatic, usually limited to small changes in height and muscle development.

• For women, menopause (cessation of menstruation) typically occurs between ages 45 and 55.

Myths Associated with Menopause

• Women in cultures that devalue aging are more likely to experience anxiety and depression with menopause.

• Research does not support the belief that menopause causes serious mood swings or depression; issues are more related to social attitudes toward aging.

The Male Climacteric

• Middle-aged men experience gradual declines in sperm and testosterone production, associated with weight gain, reduced sexual responsiveness, and loss of muscle strength and hair.

• These changes can lead to feelings of depression and self-doubt.

Aging and Internal Changes

• Major changes in middle age and beyond include decreased cardiac output, increased blood pressure, and declines in sensory abilities (vision, hearing, smell).

Cognitive Changes and Alzheimer's Disease

• Dementia is not a necessary part of aging; Alzheimer's is a degenerative disorder, not normal aging.

• Normal forgetfulness is influenced by factors like worry and distraction.

• Neuroplasticity: the brain can develop and adapt in response to learning and stimulation throughout life.

Speed of Processing

• Aging slows cognitive processing speed, making information retrieval slower, but general processing and memory efficiency remain largely unaffected.

Primary and Secondary Aging

• Secondary aging: changes due to disease, neglect, or lack of use.

• Primary aging: gradual, age-related changes that are largely inevitable.

• Two main theories: programmed theory (aging is genetically controlled) and damage theory (aging results from accumulated cellular damage).

Programmed Theory; Damage Theory

• Programmed theory: Leonard Hayflick found that human cells have a limited number of divisions (the "Hayflick limit").

• Damage theory: aging results from accumulated damage to cells and organs over time.

Cognitive Development

Jean Piaget's Theory

Jean Piaget emphasized qualitative differences in how children and adults think, proposing that intellectual growth occurs in distinct stages.

• Infants begin at a cognitively primitive level and progress through stages.

• Three major concepts: schemas, assimilation, and accommodation.

Cognitive Schemas

• Schemas are cognitive structures or patterns that organize concepts and ideas, helping us carry out actions and interactions.

• They are the basic building blocks of intellect, acting as mental frameworks or blueprints for understanding the world.

• Schemas develop and change throughout life.

Assimilation and Accommodation

• Assimilation: absorbing new information into existing schemas.

• Accommodation: creating new schemas or modifying old ones when new information doesn't fit existing schemas.