Human Development Across the Lifespan: Stages & Influences

Posted on Sep 26, 2025 in Psychology and Sociology

Understanding Developmental Psychology

Developmental psychology is the study of age-related changes in behavior and mental processes across the lifespan. Key periods of development include:

• Prenatal Stage: From conception to birth.
• Infancy: A child is highly dependent on adults.
• Early Childhood: Self-sufficiency and play emerge.
• Middle and Late Childhood: Academic skills develop.
• Adolescence: Marked by rapid physical and cognitive changes.

Biopsychosocial Model and Core Issues

The biopsychosocial model explains development through three interconnected factors:

• Biological Aspects: Physical changes.
• Cognitive Development: Thinking, intelligence, and language.
• Socioemotional Factors: Relationships, emotions, and personality.

Key developmental issues include:

• Nature vs. Nurture: Acknowledges epigenetic interactions.
• Continuity vs. Discontinuity: The gradual or stage-like progression of development.
• Early vs. Later Experiences: The lasting impact of different life stages.

Research Methods and Ethics

Research methods involve data collection through:

• Observations
• Surveys
• Tests
• Physiological measures

Research designs can be descriptive, correlational, or experimental. Ethical considerations are paramount, including informed consent and assent for older children.

Cultural and Societal Influences on Development

Culture significantly influences development, evident in differences between individualistic and collectivistic societies. Cultural biases are often present in research.

• Race: A socially constructed concept.
• Ethnicity: Reflects a shared cultural background.

Studies on WEIRD (Western, Educated, Industrialized, Rich, Democratic) samples highlight biases in psychological research. The immigrant paradox and familism emphasize how family values shape development.

Socioeconomic status (SES) impacts parenting styles, with poverty influencing developmental outcomes and intersecting with race. Technology also affects attention, learning, and social skills; the American Academy of Pediatrics recommends no screen time under age two, except for video calls.

Biological Foundations of Development

From an evolutionary perspective, natural selection and adaptive behavior influence development, including traits linked to attractiveness and survival.

Genetics and Heredity

Genetics shape development through chromosomes, DNA, genes, and the interaction of genotype and phenotype. Twin and adoption studies are crucial for examining the nature vs. nurture debate.

Prenatal Development Stages

Prenatal development occurs in three distinct stages:

• Germinal Stage: From conception to implantation.
• Embryonic Stage: Organs form.
• Fetal Stage: From eight weeks to birth.

Teratogens, such as drugs, environmental toxins, and maternal health conditions, can negatively impact prenatal development. Fetal Alcohol Syndrome is a well-documented example.

Birth and Postpartum Adjustments

Birth occurs in three stages:

• Contractions leading to full cervical dilation.
• The emergence of the baby.
• The expulsion of the placenta.

The Apgar scale assesses newborn health, with scores of 7-10 considered good and 0-3 indicating an emergency. Preterm and low birth weight infants face risks such as learning disabilities and respiratory issues.

Postpartum adjustments include postpartum depression, which affects 10-14% of mothers. Bonding and parental support are crucial for emotional well-being during this period.

Physical Development Across Childhood

Physical development follows predictable growth patterns. Newborns typically weigh between 5.5 and 10 pounds and measure 18-22 inches in length.

• Puberty: Generally begins between ages 8-16.
• Precocious Puberty: Occurs before age 8 in girls and age 9 in boys.

Brain development involves synaptic pruning and myelination, with early experiences shaping neural pathways. Newborns sleep about 16 hours per day, with 50% of that time spent in REM sleep.

Key nutritional and activity recommendations:

• Breastfeeding is considered ideal, but formula is a viable alternative.
• Solids are introduced between 4-6 months.
• Preschoolers require 2-3 hours of daily physical activity.
• School-age children need at least one hour per day.

Motor and Sensory Development

Motor, sensory, and perceptual development occur in stages. Newborn reflexes include:

• Rooting
• Sucking
• Grasping
• Moro (startle) reflex
• Babinski reflex

Gross motor skills, such as walking and running, develop before fine motor skills like grasping small objects and writing.

Sensory and perceptual development also follow a timeline:

• Vision improves from 20/240 at birth to 20/40 by six months, reaching 20/20 by two years.
• Newborns recognize parent voices and prefer high-pitched sounds.
• Their sense of smell and taste allows them to recognize their mother’s scent and react to flavors they were exposed to in the womb.

Detailed APGAR Score Assessment

The APGAR score is used to assess a newborn’s health at one and five minutes after birth, with each category scored from 0 to 2.

Heart Rate:

0 – Absent

1 – Slow (under 100 bpm)

2 – Fast (100-140 bpm)

Respiratory Effort:

0 – No breathing for over a minute

1 – Irregular and slow breathing

2 – Good breathing with normal crying

Muscle Tone:

0 – Limp and flaccid

1 – Weak with some flexion

2 – Strong and actively moving

Body Color:

0 – Blue or pale

1 – Pink body with blue extremities

2 – Entirely pink

Reflex Irritability:

0 – No response

1 – Grimace

2 – Response (coughing, sneezing, or crying)

Total Score Interpretation:

• 7-10: Considered normal.
• 4-6: Indicates moderate distress.
• 0-3: Signifies severe distress requiring immediate medical attention.

Individualistic vs. Collectivistic Cultures

Cultural perspectives profoundly shape individual and societal values, leading to distinct characteristics in individualistic and collectivistic societies.

Individualistic Cultures:

Prioritize the individual over the group.

Stable self-identity across different contexts.

Stronger focus on private self-awareness.

Emphasize achievement, competition, and personal freedom.

Tend to have many casual relationships.

Value saving one’s own face.

Collectivistic Cultures:

Prioritize the group over the individual.

Flexible self-identity based on in-group norms.

Greater emphasis on public self-awareness.

Value security, obedience, and social harmony.

Maintain fewer but closer relationships.

Emphasize saving both their own and others’ face.

Prenatal Testing Methods

Prenatal testing methods provide crucial insight into fetal health and development:

Ultrasound (Sonogram):

Uses sound waves to create fetal images.

Detects heartbeat, movement, placenta health, fetal dimensions, cervix size, and sex.

Noninvasive, no known risk.

MRI (Magnetic Resonance Imaging):

Uses a powerful magnet for detailed fetal images.

Used when ultrasound results are unclear.

Little to no known risk.

Chorionic Villus Sampling (CVS):

Invasive procedure requiring a placenta biopsy (cervix or abdomen).

Detects genetic or chromosomal defects.

Carries a small risk of miscarriage.

Amniocentesis:

Invasive procedure testing amniotic fluid (sample collected through abdomen).

Detects genetic or chromosomal defects.

Carries a small risk of miscarriage.

Maternal Blood Screening:

Noninvasive method testing maternal and fetal factors (genetics, diseases, nutrition, hormones).

Can detect fetal sex, spina bifida, and chromosomal disorders.

Noninvasive Prenatal Diagnosis (NIPD):

Uses fetal cells circulating in maternal blood to analyze DNA.

Offers a safer alternative to CVS and amniocentesis, which are now primarily used for follow-up testing when abnormalities are detected.