Study sheet: Human Development Across the Lifespan

📋 Course Outline

1. Studying Development Across Age
2. Nature Nurture and Genetics
3. Inheritance and Chromosomal Disorders
4. Prenatal Development and Teratogens
5. Newborn and Motor Development
6. Infant Senses Health and Environment
7. Cognitive Development Theories
8. Autism Spectrum Disorder
9. Psychosocial Development in Childhood
10. Classic Studies of Attachment and Perception
11. Harlow and Contact Comfort
12. Indian Adolescence and Social Context
13. Indian Ageing and Demographic Change
14. Psychosocial Challenges of Older Adults

📖 1. Studying Development Across Age

🔑 Key Concepts & Definitions

• Human development : the study of how a person changes from conception through death across physical, cognitive, emotional and social domains, shaped by genes, environment and personal experience

★ Must-know

📌 A longitudinal design repeatedly tests the same people over time, whereas a cross-sectional design compares different age groups at one point in time.

📌 A cohort effect is a difference between groups caused by growing up in different historical periods or conditions rather than by ageing itself.

• A cross-sequential design first compares different age groups and then retests those same groups later, helping separate age effects, cohort effects and time-of-measurement effects.

Further detail

📌 Longitudinal designs show individual change accurately but require substantial time and money, and participant dropout can bias the results.

💡 Memory Hook

Longitudinal follows the same people; cross-sectional compares different age groups.

📖 2. Nature Nurture and Genetics

🔑 Key Concepts & Definitions

• Behavioural genetics : the scientific study of how genes and environments contribute to differences in human traits
• Gene : a stretch of DNA that carries instructions for a particular protein or cell process
• DNA : a molecule made of two twisted strands whose chemical sequences provide instructions for building proteins and controlling cell function

📝 Essential Points

📌 Nature refers to inherited biological influences, whereas nurture refers to environmental influences such as caregiving, education, culture, nutrition and experience.

• Almost every human body cell contains 46 chromosomes arranged in 23 pairs, with one chromosome in each pair inherited from each parent.

💡 Memory Hook

Genes set potentials → environments shape how those potentials appear.

📖 3. Inheritance and Chromosomal Disorders

🔑 Key Concepts & Definitions

• Polygenic inheritance : occurs when many genes act together with the environment to influence one trait, such as height, intelligence or skin tone
• Carrier : has one copy of a recessive disease variant, usually shows no symptoms and can pass the variant to children
• Nondisjunction : an error during egg or sperm formation that produces a gamete with too many or too few chromosomes

★ Must-know

📌 A dominant allele is expressed when present, whereas a recessive allele usually appears only when paired with another identical recessive allele.

📌 In PKU, failure to break down phenylalanine can cause brain damage and severe intellectual disability unless newborn screening detects the condition and treatment begins early.

• Down syndrome is usually caused by an extra copy of chromosome 21, while Klinefelter syndrome involves XXY and Turner syndrome involves XO.

Further detail

• Recessive disorders named in the course include:
  • cystic fibrosis
  • sickle cell anaemia
  • Tay-Sachs disease
  • phenylketonuria, or PKU

💡 Memory Hook

A dominant allele appears when present; a recessive disorder usually requires two copies.

📖 4. Prenatal Development and Teratogens

🔑 Key Concepts & Definitions

• Zygote : the single cell formed when a sperm and egg join, carrying the complete set of 46 chromosomes
• Teratogen : a substance or infection that can harm a developing embryo or fetus, with effects depending on timing, dose, duration and genetic vulnerability

📝 Essential Points

📌 Monozygotic twins develop when one fertilised egg splits and are genetically alike and always the same sex, whereas dizygotic twins develop from two eggs fertilised by two sperm and may be different sexes.

• Prenatal development proceeds through: the germinal period from conception to about two weeks, the embryonic period from about week two to week eight, the fetal period from about eight weeks until birth

• During the fetal period, fetal programming links poor prenatal conditions such as poor nutrition or chronic stress to increased adult risks of high blood pressure, diabetes or heart disease.

💡 Memory Hook

Germinal → embryonic → fetal.

📖 5. Newborn and Motor Development

★ Must-know

• 🔄 After birth, the newborn begins:

  1. independent breathing
  2. independent circulation
  3. temperature regulation
  4. independent digestion

• Newborn reflexes include:

  • rooting
  • sucking
  • Moro or startle
  • grasping
  • stepping

📌 Motor development generally proceeds from head to foot and from the body centre outward toward the fingers.

• Synaptogenesis creates many new neural connections after birth, synaptic pruning removes unused connections, and myelination speeds nerve-signal transmission.

Further detail

• Walking normally emerges across a broad range from about nine to eighteen months.

💡 Memory Hook

Head control → rolling → sitting → crawling → walking.

📖 6. Infant Senses Health and Environment

★ Must-know

• Vision is the least developed sense at birth, whereas touch, smell, taste and hearing are already functional to important degrees.

📌 Placing a newborn on the back on a firm surface without loose bedding reduces the risk of sudden infant death syndrome.

📌 Severe early neglect can impair growth, emotional regulation, attachment and thinking, while enriched care or later adoption can reverse many, though not always all, effects.

Further detail

• Solid foods are introduced around six months, when nutrients such as iron and zinc become especially important.

💡 Memory Hook

Responsive enrichment supports development; severe deprivation disrupts it.

📖 7. Cognitive Development Theories

🔑 Key Concepts & Definitions

• Assimilation : Piaget's process of fitting a new experience into an existing mental scheme
• Accommodation : Piaget's process of changing an existing mental scheme to fit new information
• Zone of proximal development : the gap between what a child can do alone and what the child can do with guidance from a more capable person

★ Must-know

• Piaget proposed four stages:
  • sensorimotor from birth to about two years
  • preoperational from about two to seven years
  • concrete operational from about seven to eleven or twelve years
  • formal operational from about twelve years onward

Further detail

📌 Scaffolding is support provided by a teacher, parent or peer that is gradually removed as the child becomes more capable.

💡 Memory Hook

Piaget emphasizes independent discovery; Vygotsky emphasizes guided social learning.

📖 8. Autism Spectrum Disorder

🔑 Key Concepts & Definitions

• Autism Spectrum Disorder : a condition involving lasting difficulties in social communication and interaction together with restricted or repetitive behaviours or interests that affect daily functioning

★ Must-know

• Common ASD features include:
  • difficulty with reciprocal conversation
  • reduced eye contact or gestures
  • trouble forming friendships
  • repetitive movements
  • a strong need for sameness
  • unusual sensory responses

📌 High-quality research has found no causal link between vaccines and autism, and the original 1998 study suggesting such a link was fraudulent and retracted.

Further detail

📌 Paediatric ASD screening is recommended around eighteen and twenty-four months because signs often appear during the first two or three years of life.

📖 9. Psychosocial Development in Childhood

🔑 Key Concepts & Definitions

• Temperament : a baby's naturally occurring and fairly stable style of emotional reaction and self-regulation that forms a foundation for later personality
• Secure attachment : shown when a child uses a caregiver as a safe base, becomes upset by separation, calms quickly at reunion and returns to exploration

★ Must-know

• The three broad temperament styles are:

  • easy
  • difficult
  • slow to warm up

• Erikson's early psychosocial sequence is: trust versus mistrust in infancy, autonomy versus shame and doubt in toddlerhood, initiative versus guilt in preschool, industry versus inferiority in middle childhood

Further detail

• The Strange Situation assesses attachment through brief separations and reunions between a child and caregiver.

💡 Memory Hook

Trust → autonomy → initiative → industry.

📖 10. Classic Studies of Attachment and Perception

★ Must-know

• In Gibson and Walk's visual cliff study, about 81% of babies aged six to fourteen months refused to crawl across the deep-looking side. — Eleanor Gibson and Richard Walk

📌 Visual-cliff findings suggest that babies perceive depth early, but crawling experience and caregiver social referencing influence whether they act on that perception. — Gibson and Walk

• The monkeys spent much more time clinging to the soft cloth surrogate regardless of which surrogate provided milk, supporting contact comfort as a major basis of attachment. — Harry Harlow

Further detail

• In Harlow's experiment, infant rhesus monkeys were raised with a wire surrogate and a soft cloth surrogate, with milk provided by either surrogate in different conditions, and researchers measured clinging and responses to fear or separation. — Harry Harlow

• Kangaroo care applies the contact-comfort principle by holding a premature baby skin to skin against a parent's chest to support temperature stability, reduce stress and strengthen attachment.

💡 Memory Hook

The visual cliff tests depth perception; Harlow tests contact comfort.

📖 11. Harlow and Contact Comfort

★ Must-know

📌 Harlow's surrogate-mother experiment distinguished food provision from contact comfort by comparing a wire surrogate holding milk with a warmed, cloth-covered surrogate. — Harry Harlow

• Regardless of which surrogate provided milk, the baby monkeys spent much more time clinging to the soft cloth surrogate, used her as a safe base, and sought her when frightened. — Harry Harlow

📌 Harlow's findings support contact comfort as an important contributor to attachment, but later research shows that healthy attachment also requires sensitivity, consistent caregiving and normal social interaction. — Harry Harlow

Further detail

• Harlow raised baby rhesus monkeys with wire and cloth-covered surrogate mothers, varied which surrogate provided milk, measured time spent clinging and reactions to fear or separation, and compared their attachment behavior. — Harry Harlow

💡 Memory Hook

Soft cloth comfort, not milk alone, became the safe base.

📖 12. Indian Adolescence and Social Context

★ Must-know

• India's National Youth Policy of 2014 defines youth as ages fifteen to twenty-nine, whereas the United Nations defines adolescence as ages ten to nineteen.

• Adolescents make up close to twenty-one percent of India's population, including about fifty-three percent boys and forty-seven percent girls.

• Adolescent experiences in India vary by class, caste, region, religion and education, with wealthier urban adolescents generally having better schooling, coaching, career options and internet access than poorer or rural adolescents.

• Indian adolescents often develop a related-autonomous self that combines personal wishes and increasing independence with continuing family bonds, duties and respect for parents.

• Nurturant authority combines guidance, discipline and unconditional support in a respectful hierarchy, whereas adaptable authority uses a more friend-like balance of strictness, openness and discussion.

• Key policy priorities include:

  • education
  • health and nutrition
  • mental-health support
  • constructive family engagement

Further detail

• Traditional terms for this life phase included:

  • yuva
  • madhyavastha
  • kumaravastha
  • kishoravastha

• Common conflict areas include:

  • chores
  • academics
  • behaviour
  • academic streams
  • careers
  • friendships
  • social activities

• Around ten percent of young people in India are suggested to experience severe stress, depression or anxiety, linked to academic pressure, uncertain employment and rapid social change.

💡 Memory Hook

Teenage independence develops alongside family duty, not through cutting family ties.

📖 13. Indian Ageing and Demographic Change

🔑 Key Concepts & Definitions

• Ageing : a series of gradual, time-related physical and biological changes and can also refer positively to maturation or gaining desirable qualities over time

★ Must-know

📌 Primary ageing is natural, inherited age-related change, whereas secondary ageing results from external factors such as injury or disease and is not automatically inevitable.

• Many psychologists in developed countries use sixty-five years and above to define late adulthood, whereas the United Nations commonly uses sixty years and above.

• India's population aged sixty and above grew from around twenty million in 1951 to seventy-seven million in 2001 and one hundred and three million in 2011.

• Average life expectancy in India increased from roughly forty-one years in 1951 to sixty-nine years by 2008, contributing substantially to elderly population growth.

Further detail

• The proportion of Indians aged sixty and above rose from about seven and a half percent in 2006 to about eight and a half percent in 2011.

💡 Memory Hook

Better healthcare and longer life expectancy → a rapidly growing elderly population.

📖 14. Psychosocial Challenges of Older Adults

★ Must-know

• Urbanisation, industrialisation, globalisation, women's increased workforce participation and job migration are weakening India's traditional joint-family system and leaving more older parents alone or separated from familiar communities.

• About seventy-six percent of older women and forty-two percent of older men in India relied financially on family members, most often children or a spouse.

• Around forty-two percent of elderly people reported psychosocial problems connected to loneliness and neglect, while family breakdown, low socioeconomic status and social isolation were linked to higher psychiatric illness.

• Policy responses should include:

  • age-friendly infrastructure
  • psychosocial support
  • health services
  • community interaction
  • support for family caregivers

Further detail

📌 Older adults may struggle with rapidly changing technology because of poor eyesight, reduced dexterity, unfamiliarity or scepticism, whereas younger users are generally more accustomed to digital tools.

💡 Memory Hook

Migration, isolation and dependency → stress, vulnerability and psychiatric risk.

📊 Synthesis Tables

Developmental Research Designs

Design	Participants	Main strength or limitation
Cross-sectional	Different age groups tested once	Quick and inexpensive, but cohort effects may mimic ageing
Longitudinal	Same participants tested repeatedly	Shows individual change, but is costly and vulnerable to dropout
Cross-sequential	Different age groups retested later	Separates age, cohort and time-of-measurement effects

Primary and Secondary Ageing

Type	Cause	Inevitability
Primary ageing	Natural inherited timeline	Part of normal ageing
Secondary ageing	External factors such as injury or disease	Not automatically inevitable