Lifespan Development: Key Concepts in Developmental Psychology

Lifespan Development

Developmental Psychology

Developmental psychology studies the physical, cognitive, social, and behavioral changes that occur throughout the human lifespan. It seeks to understand how we become who we are and why individuals develop differently even in similar environments.

• Methods:

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

  • Cohort effects: Differences due to generational or historical context.

  • Longitudinal design: Follows the same individuals over time to observe changes.

Prenatal Development

Prenatal development involves the growth and maturation of the fetus from conception to birth. The age of viability is typically around 22 weeks.

Weeks	Major Developments
1-8	Formation of CNS, heart, limbs, eyes, ears
8-20	Further development of organs, limbs, and senses
20-36	Growth and maturation of CNS, lungs, and other systems

Prenatal Development: Research Example

Research shows that babies can learn and recognize speech sounds before birth.

• Independent Variable (IV): Mothers read Cat in the Hat aloud daily during the last 6 weeks of pregnancy vs. mothers who did not read aloud.

• Procedure: Babies tested 2 days after birth; infants heard speech sounds while sucking on a pacifier.

• Dependent Variable (DV): Changes in sucking rate (indicator of preference).

• Results: Babies whose mothers read aloud changed their sucking pattern, indicating recognition/preference; control group showed no change.

Teratogens

Teratogens are substances or environmental factors that can harm a developing fetus, causing birth defects, growth problems, or miscarriage. Effects depend on timing of exposure.

• Alcohol: Fetal Alcohol Spectrum Disorder (FASD)

• Tobacco: Low birth weight

• Viruses: Zika

• Bacteria/Parasites: Toxoplasmosis

• Radiation

• Pollution: Lead, mercury, pesticides

• Drugs: Prescription/illegal (e.g., Accutane, Thalidomide)

Maternal Fluoride Exposure & IQ Scores

Research (Green et al., 2019) found that higher maternal exposure to fluoridated water was associated with slightly lower IQ scores in children aged 3-4 years.

• Study of 601 mother-child pairs

• 41% lived in communities with fluoridated water

• Only a few IQ points difference

Thalidomide

Thalidomide was a drug prescribed for morning sickness, pulled in 1962 due to its highly teratogenic effects (limb malformations, birth defects). Safety protocols were introduced in Canada as a result.

Teflon & C-8 (Forever Chemicals)

Exposure to certain chemicals (e.g., Teflon, C-8) can have long-term health effects, including developmental risks.

Infancy & Childhood

Motor Development

Children achieve motor milestones at varying ages, driven by biological maturation and environmental exploration.

• Examples: Rolling over (3.2 months), sitting without support (5.5 months), walking (12.3 months)

• Cultural differences and activity levels influence timing

Visual Perception

Newborns have sophisticated visual perception, preferring patterns with contours and edges, and can imitate adult expressions. This forms the basis for social interaction skills.

Kindchenschema (Baby Schema)

Humans are predisposed to protect and nurture infants due to physical features that trigger caregiving and affection (large eyes, round cheeks, soft movements). This is evolutionary and activates reward-related brain regions.

Attachment

Attachment is the emotional bond between child and caregiver, providing evolutionary advantages. Early studies by Konrad Lorenz (imprinting in goslings) and Harlow (monkey studies) highlight the importance of comfort and contact.

• Bowlby: Attachment is innate, evolved for survival; infants are programmed to form attachments to caregivers who provide safety and protection.

• Ainsworth's Strange Situation: Assesses attachment styles in children.

Attachment Styles

Style	Description
Secure	Uses mom as base, distressed when she leaves, comforted on return
Avoidant	Does not cry when mom leaves, avoids her on return
Ambivalent	Distressed when mom leaves, ambivalent on return
Disorganized-disoriented	Inconsistent, contradictory behavior

Consequences of Attachment

• Securely attached children are more socially and emotionally competent, have fewer psychological difficulties, and more successful relationships later in life.

Criticisms of Attachment Theory

• Cultural variations in parenting

• Does not account for temperament

• Genetic factors may influence attachment

Parenting

Parenting Styles & Social Development

Style	Parent Behaviour	Child Outcome
Authoritarian	Rigid, punitive, strict standards	Withdrawn, unfriendly, unsociable
Permissive	Lax, inconsistent, undemanding	Immature, moody, dependent, low self-control
Uninvolved	Detached emotionally, provides only basic needs	Indifferent, rejecting
Authoritative	Firm, sets limits, encourages independence	Good social skills, independent, self-reliant

How Parenting Shapes Morality & Motivation

• Attachment system: "Am I safe and secure?"

• Caregiving system: "How can I respond to your needs?"

• When people feel insecure, caregiving shuts down; when attachment needs are met, caregiving activates.

• Inductive discipline (explaining how actions affect others) works best, activating empathy and supporting internal moral values.

Cognitive Development in Infancy & Childhood

Jean Piaget's Theory of Cognitive Development

• Assimilation: Fitting new experiences into existing schemas

• Accommodation: Changing schemas when new experiences don't fit

Stages of Cognitive Development

1. Sensorimotor Stage (Birth-2 years): Understanding through touching, manipulating; develops object permanence.

2. Preoperational Stage (2-7 years): Language and symbolic thinking; egocentric thought; difficulty understanding others' perspectives.

3. Concrete Operational Stage (7-12 years): Logical thinking, principle of conservation, reversibility; bound to concrete reality.

4. Formal Operational Stage (12+ years): Abstract and logical thinking develops.

Self-Awareness & Theory of Mind

• Self-awareness emerges around 18-24 months (mirror/video recognition)

• Egocentrism is common in early childhood (cognitive limitation, not selfishness)

• Theory of mind emerges around 4-5 years (understanding others have different perspectives)

Early Social Understanding

• Infants and toddlers can recognize when someone needs help, prefer helpers, and show fairness

• "Helper stage" occurs from ~14 months to 7 years

Adolescence

Adolescent Emotion Regulation

• Emotions are intense; flexibility in regulation strategies is key

• Cognitive reframing helps delay gratification and focus on long-term goals

Risky Decisions

• Adolescents are prone to impulsive, risky decisions due to peer pressure and developing brain systems

• Major public health concerns: unprotected sex, substance use

Peer Influence & Risk-Taking

• Teens take more risks when with peers; adults are less affected

Cognitive Development in Adolescence

• Adolescent egocentrism: Heightened self-focus

• Imaginary audience: Belief that others are constantly observing/judging

• Personal fables: Belief in uniqueness and invulnerability

• Emotion often overrides logic; impulse control is immature

Social Development: Identity & Relationships

• Identity formation: Figuring out one's role, exploring careers, beliefs, values

• Peer groups: Friendships are a top priority; cliques are dynamic

• Romantic relationships: Teens explore emotional and physical intimacy; risk of psychological and sexual aggression

Adulthood

Transitions of Life

• Emerging adulthood (18-24): Still determining identity, career path; peak health

• Middle adulthood (20s-40s): Physical declines minor, body less efficient, more susceptible to disease

Marriage

• Relationships provide health benefits, financial security, and satisfaction

• 40% of Canadian marriages end in divorce

Four Horsemen of the Apocalypse (Relationship Conflict)

Horseman	Description
Criticism	Picking out flaws, expressing disappointment
Defensiveness	Responding to perceived attacks with counterattacks
Contempt	Eye rolling, sarcasm, cutting tones
Stonewalling	Shutting down verbally and emotionally

Parenthood & Marital Satisfaction

• Marital satisfaction highest before birth of first child, declines until children leave home

• High SES parents more negatively affected; younger parents report lower satisfaction

• "Sandwich generation": caring for children and aging parents

Protective Factors for Marital Satisfaction After Children

• Fair division of labor

• Good communication and conflict management

• Protect couple time

• Social support

• Realistic expectations

• Strong pre-baby relationship

• Mental health and stress regulation

• Structural support (paid leave, flexible work, affordable childcare)

Late Adulthood: Happiness & Relationships

Socioemotional Selectivity Theory

• Older adults focus on positive, meaningful experiences

• Prefer activities that emphasize joy and connection

• Better attention to positive emotions, optimism, and adversity handling

• Wisdom and experience guide choices toward rewarding experiences