Development is the sequence of age-related changes that occur as a person progresses from conception to death. 

• Longitudinal studies: investigators observe one group of participants repeatedly over a period of time

• Cross-sectional studies: investigators compare groups of participants of differing age at a single point in time

• Cohort effects occur when differences between age groups growing up in different time periods.  

Fertilization creates a zygote, a one-celled organism formed by the union of a sperm and an egg. 

The prenatal period extends from fertilization to birth, usually encompassing nine months of pregnancy. Because there is no clear way to know when an egg has been fertilized, pregnancy is measured starting from the last known menstrual cycle.

The germinal stage is the first phase of prenatal development, encompassing the first two weeks after fertilization. 

Within 36 hours of fertilization, rapid cell division begins as the zygote makes its way from the fallopian tube to the uterine cavity. 

During the implantation process, the placenta (a structure that allows oxygen and nutrients to pass into the fetus from the mother’s bloodstream and bodily wastes to pass out to the mother) begins to form. 

The embryonic stage is the second stage of prenatal development, lasting from two weeks until the end of the second month. 

• Vital organs and bodily systems begin to form

• Embryo takes human shape

• Great vulnerability; time of most miscarriages

The fetal stage is the third stage of prenatal development, lasting from two months through birth. 

• Rapid body growth

• Muscles and bones form

• Organs complete formation and begin to function; Central nervous, respiratory & digestive systems, eyes, ears, genitals, and teeth

• Fat develops for insulation

• Brain cells multiply rapidly

• Around 23 – 26 weeks, the fetus reaches the threshold of viability, meaning they can survive premature birth.

While the fetus develops in the protective buffer of the womb, events that occur in the external environment can affect development.

• Teratogens are any external agents, such as drugs or viruses, that can harm an embryo or fetus. 

  • Fetal alcohol syndrome is a collection of congenital problems associated with excessive alcohol use during pregnancy. 

Other Factors:

• Recreational drug use

• Illnesses/Diseases

• Pollution/Toxins

• Nutrition

• Emotions/Stress

• Maturation is development that reflects the gradual unfolding of one’s genetic blueprint.

• Developmental norms indicate the typical age at which individuals display various behaviors and abilities. 

Culture can play a role in the rate of development. In African societies, children develop motor skills quicker because they are encouraged to move, while some tribes in the South American rainforests discourage motor skills to keep children from wandering from safety. 

Motor development refers to the progression of muscular coordination required for physical activities, including grasping, reaching, sitting, crawling, walking, and running. 

• • Cephalocaudal trend – the head-to-foot direction of motor development (rocking)

  • Proximodistal trend – center-outward direction of motor development (crawling, reaching)

Temperament refers to characteristic mood, activity level, and emotional reactivity. 

In a longitudinal study conducted by Alexander Thomas and Stella Chess, three types of temperament were identified:

• • Easy children

  • Slow-to-warm up children

  • Difficult children 

Another study done by Jerome Kagan found that 15% of children display inhibited temperament (shyness, wariness), while 25% display uninhibited temperament (less restrained, approachable), and the rest fall in the middle. 

Attachment refers to the close emotional bonds of affection that develop between infants and their caregivers. 

• • Infants do not immediately attach to their mothers, but by 2-3 months, they begin to show affection toward their mothers. 

  • By 6-8 months, infants begin to show pronounced preference for their mothers. 

    • Separation anxiety: emotional distress seen in many infants when they are separated from people with whom they have formed an attachment

The type of attachment that emerges between an infant and mother may depend on the nature of the infant’s temperament as well as the mother’s sensitivity.

Evidence suggests that the quality of the attachment relationship can have important consequences for children’s subsequent development. Internal working models – the dynamics of close relationships that influence their future interactions. 

• Critical periods: an optimal period shortly after birth when an organism’s exposure to certain stimuli or experiences produces proper development (Remember "Genie the Wild Child"? The belief was that she was incapable of learning language fully because she had passed the critical period for language development.)

  • Imprinting: the process by which certain animals form attachments early in life

• Diana Baumrind's Parenting Styles:

  • Authoritarian: overbearing and demanding; expect obedience 

  • Authoritative: demanding but responsive 🡪 yields best results

  • Permissive: relaxed; give in to every whim and rarely punish

While Sigmund Freud believed personality was cemented by age 5, Erik Erikson proposed that the development of personality occurred in stages throughout one’s life, shaped by experiences. 

Erikson’s Psychosocial Crisis (or Stage) Theory:

• • Stage 1: trust vs. mistrust (0-1 year) - Is my world safe?

  • Stage 2: autonomy vs. shame & doubt (2-3 years) - Can I do things for myself?

  • Stage 3: initiative vs. guilt (4-6 years) - Am I a good person? Do I have control over my destiny?

  • Stage 4: industry vs. inferiority (6 – puberty) - Am I as good as my peers?

  • Stage 5: identity vs. confusion (adolescence) - Who am I?

  • Stage 6: intimacy vs. isolation (early adulthood) - What kind of life will I have?

  • Stage 7: generativity  vs. self-absorption (middle adulthood) - Have I helped contribute to society?

  • Stage 8: integrity vs. despair (late adulthood) - Do I have regrets?

Cognition refers to all the mental activities associated with thinking, knowing, remembering, and communicating. Cognitive development refers to transitions in youngsters’ patterns of thinking, including reasoning, remembering, and problem solving. You are born with the most brain cells you will ever have, but neural networks form as you grow. 

Jean Piaget, an exceptionally gifted child, went on to study natural science before turning his focus to psychology. While administering intelligence tests to a variety of children, he noticed that certain ages commonly made the same mistakes. From there, he decided to study how children use and develop intelligence. Piaget proposed the stage theory of cognitive development, which divided our development of thought processes into four key periods: sensorimotor, preoperational, concrete operational, and formal operational. 

Critics of Piaget claim that:

• • He underestimated young children’s cognitive development

  • Children often display patterns of thinking that are characteristics of several stages

  • The time table of the stages depends on environmental factors

The mind makes moral judgments quickly and automatically. 

We feel disgust when humans engage in degrading actions, and feel warm and fuzzy when we witness acts of generosity. 

Joshua Greene’s research proved that moral judgment includes both reasoning and “gut-feeling”. Our morality can also be altered by our situation. 

Jonathan Hardt’s “social intuitionist” account of morality claimed that moral feelings precede moral reasoning.

Lawrence Kohlberg believed that children’s moral judgments build on their cognitive reasoning, so he sought to describe the development of moral reasoning. Kohlberg proposed a series of moral dilemmas to children, adolescents, and adults then analyzed their answers for evidence of stages of moral thinking. 

After his research was concluded, Kohlberg argued that we pass through as many as six stages of moral development, but clustered them into three levels:

• • Pre-conventional: (age 0-9) moral of self-interest; avoiding punishment or gaining a reward

  • Conventional: (9-adolesence) caring for others, upholding social laws and norms; can understand another’s perspective but still follows rules

  • Post-conventional: (after adolescence) abstract reasoning; affirms people’s agreed upon rights or follows basic ethical principles

In her book, A Different Voice, Carol Gilligan criticized Kohlberg for claiming women had a lower level of moral development than boys, especially as few girls were included in his study. 

Adolescence is a transitional period between childhood and adulthood.

• • Adolescent growth spurt – rapid growth in height and weight brought on by hormonal changes

Pubescence – the two-year span preceding puberty during which the changes leading to physical and sexual maturity take place

• • Secondary sex characteristics – physical features that distinguish one sex from the other but that are not essential for reproduction (ex. Facial hair, muscle growth, breast growth, widening on pelvis, etc.)

Puberty is the stage during which sexual functions reach maturity, which marks the beginning of adolescence. 

• • Primary sex characteristics: structures necessary for reproductions (testes, ovaries, etc.)

For females, the onset of puberty is signaled at 12 to 13 years old by menarche – the first occurrence of menstruation. Sexual maturation continues until the age of 16. 

For males, the onset of puberty is signaled at 13 or 14 by the experience of spermarche – the first occurrence of ejaculation. Sexual maturation continues until the age of 18. 

Generational changes have occurred in the last 150 years that have altered the timing of puberty. Generally, girls who mature early and boys who mature late seem to experience more subjective distress and emotional difficulty with the transition to adolescence. 

Neurons become better insulated with thicker myelin sheaths.

• • Enhanced conductivity and connectivity in the brain

  • Gray matter decreases in volume

Synaptic pruning: the elimination of less-active synapses, which plays a key role in the formation of neural networks

Most development occurs in the prefrontal cortex, the last area of the brain to fully mature (around age 25). Theorists suggest that this explains why teens engage in risky behavior. 

To refine their sense of identity, adolescents in Western cultures usually try out different selves in different situations  - trying out different social groups or being a different person at home than at work or school.

This role confusion usually gets resolved by forming a self-definition that unifies that various selves into a consistent and comfortable sense of who one is – an identity. Traditional cultures inform adolescents who they are rather than leaving it up to them to decide. 

According to James Marcia, the presence or absence of a sense of commitment and a sense of crisis can combine to form four different identity statuses:

• Identity diffusion: a state of apathy with no commitment to an ideology

• Identity foreclosure: a premature commitment to visions, values, and goals

• Identity moratorium involves delaying commitment for a while to experiment with alternative ideologies and careers

• Identity achievement: arriving at one’s sense of self and direction after thinking through alternatives

Adolescence is typically a time of diminishing parental influence and growing peer influence. Heredity determines much of our character and personality, but what remains is determined by our peers.

The adolescent identity stage is also characterized by the developing capacity for intimacy – the ability to form emotionally close relationships. Carol Gilligan, who challenged Kohlberg’s model of morality, also believed that females are less concerned with viewing themselves as individuals and being more concerned about making connections than males.

During adolescence, women become less assertive and more flirtatious, while men become more domineering and unexpressive. These differences remain until late adulthood. Both sexes downplay traits that interfere with their roles.

Sex usually refers to the biologically based categories of female and male. Gender usually refers to culturally constructed distinctions between femininity and masculinity.

Typically, you are born either male or female, but you become feminine or masculine through complex developmental processes that take years to unfold. 

Gender stereotypes are widely held beliefs about females’ and males’ abilities, personality traits, and social behavior. Men are expected to be aggressive, adventurous, dominant, independent, and confident, while women are expected to be emotional, nurturing, expressive, gentle, and creative. 

Gender differences are actual disparities between the sexes in typical behavior or average ability.

Cognitive Abilities

• Females demonstrate better verbal skills than males.

• Males demonstrate better mathematical skills than females.

• Males tend to score higher on tests involving visual-spacial ability

Personality & Social Behavior

• Females tend to be more agreeable, extraverted, conscientious, and neurotic.

• Males are more physically aggressive than females, who prefer to be verbally aggressive.

• Women are more sensitive to nonverbal communication and interpersonal sensitivity. 

• Males are more sexually active than females. 

Socialization is the acquisition of the norms and behaviors expected of people in a particular society.

Gender roles are expectations about what is appropriate behavior for each sex. Gender roles are reinforced through operant conditioning, observational learning, and self-socialization. Gender roles are also reinforced by one’s family, school, and the media.

Because of the variety of physical, emotional, and psychological changes that take place during adulthood, it is often divided into three stages:

• • Early adulthood (20s-30s)

  • Middle adulthood (40s-60s)

  • Late adulthood (65+)

“Social clock” – the cultural prescription of the “right time” to meet a certain milestone (marry, have kids, get a job, retire, etc.)