Glossary

absent grief A situation in which mourners do not grieve, either because other people do not allow grief to be expressed or because the mourners do not allow themselves to feel sadness.

acculturation The process of cultural and psychological change that occurs when individuals come into contact with a new culture.

achievement test A measure of mastery or proficiency in reading, mathematics, writing, science, or some other subject.

active euthanasia A situation in which someone takes action to bring about another person’s death, with the intention of ending that person’s suffering.

activities of daily life (ADLs) Typically identified as five tasks of self-care that are important to independent living: eating, bathing, toileting, dressing, and transferring from a bed to a chair. The inability to perform any of these tasks is a sign of frailty.

activity theory The view that elderly people want and need to remain active in social spheres—with relatives, friends, and community groups—and become withdrawn only unwillingly, as a result of ageism.

additive gene A gene that adds something to some aspect of the phenotype. Its contribution depends on additions from the other genes, which may come from either the same or the other parent.

adolescence-limited offender A person whose criminal activity stops by age 21.

adolescent egocentrism A characteristic of adolescent thinking that leads young people (ages 10 to 13) to focus on themselves to the exclusion of others.

adrenal glands Two glands, located above the kidneys, that produce hormones (including the “stress hormones” epinephrine [adrenaline] and norepinephrine).

age in place Remaining in the same home and community in later life, adjusting but not leaving when health fades.

age of viability The age (about 22 weeks after conception) at which a fetus may survive outside the mother’s uterus if specialized medical care is available.

ageism A prejudice whereby people are categorized and judged solely on the basis of their chronological age.

aggressive-rejected Someone rejected by peers because of antagonistic, confrontational behaviour.

allele Any of the possible forms in which a gene for a particular trait can occur.

allocare Literally, “other-care”; the care of children by people other than the biological parents.

allostasis A dynamic body adjustment, related to homeostasis, that over time affects overall physiology. The main difference is that while homeostasis requires an immediate response, allostasis requires longer-term adjustment.

Alzheimer’s disease (AD) The most common cause of neurocognitive disorder, characterized by gradual deterioration of memory and personality and marked by the formation of plaques of beta-amyloid protein and tangles of tau in the brain. (Previously referred to as senile dementia of the Alzheimer’s type.)

amygdala A tiny brain structure that registers emotions, particularly fear and anxiety.

analytic intelligence A form of intelligence that involves such mental processes as abstract planning, strategy selection, focused attention, and information processing, as well as verbal and logical skills.

analytic thought Thought that results from analysis, such as a systematic ranking of pros and cons, risks and consequences, and possibilities and facts. Analytic thought depends on logic and rationality.

andropause A term coined to signify a drop in testosterone levels in older men, which normally results in reduced sexual desire, erections, and muscle mass. (Also called male menopause.)

animism The belief that natural objects and phenomena are alive.

anorexia nervosa An eating disorder characterized by severe calorie restriction and the fear of being fat. Affected individuals undereat, or overeat and then overexercise or purge, depriving their vital organs of nutrition. Anorexia can be fatal.

A-not-B error The tendency to reach for a hidden object where it was last found rather than in the new location where it was last hidden.

anoxia A lack of oxygen that, if prolonged, can cause brain damage or death.

antipathy Feelings of dislike or even hatred for another person.

antisocial behaviour Actions that are deliberately hurtful or destructive to another person.

Apgar scale A quick assessment of a newborn’s body functioning. The baby’s heart rate, respiratory effort, muscle tone, colour, and reflexes are given a score of 0, 1, or 2 twice—at one minute and five minutes after birth—and each time the total of all five scores is compared with the ideal score of 10 (which is rarely attained).

aptitude The potential to master a specific skill or to learn a certain body of knowledge.

assisted living A living arrangement for elderly people that combines privacy and independence with medical supervision.

asthma A chronic disease of the respiratory system in which inflammation narrows the airways from the nose and mouth to the lungs, causing difficulty in breathing. Signs and symptoms include wheezing, shortness of breath, chest tightness, and coughing.

astronaut family A family where members live in different countries; children in such families are known as satellite or parachute children.

attachment A bond that an infant forms with a caregiver; a tie that binds them together in space and endures over time.

attention deficit hyperactivity disorder (ADHD) A condition in which a person not only has great difficulty concentrating for more than a few moments but also is inattentive, impulsive, and overactive.

authoritarian parenting An approach to child-rearing that is characterized by high behavioural standards, strict punishment of misconduct, and little communication.

authoritative parenting An approach to child-rearing in which the parents set limits and enforce rules but are flexible and listen to their children.

autism spectrum disorder A developmental disorder marked by difficulty with social communication and interaction—including difficulty seeing things from another person’s point of view—and restricted, repetitive patterns of behaviour, interests, or activities.

automatic processing Thinking that occurs without deliberate, conscious thought. Experts process most tasks automatically, saving conscious thought for unfamiliar challenges.

autonomy versus shame and doubt Erikson’s second crisis of psychosocial development. Toddlers either succeed or fail in gaining a sense of self-rule over their actions and their bodies.

average life expectancy The number of years the average newborn in a particular population group is likely to live.

axon A fibre that extends from a neuron and transmits electrochemical impulses from that neuron to the dendrites of other neurons.

babbling The extended repetition of certain syllables, such as ba-ba-ba, that begins when babies are between 6 and 9 months old.

balanced bilingual A person who is fluent in two languages, not favouring one over the other.

behavioural teratogens Agents and conditions that can harm the prenatal brain, impairing the future child’s intellectual and emotional functioning.

behaviourism A learning theory based on the idea that behaviours can be trained and changed in response to stimuli in the environment.

bickering Petty, peevish arguing, usually repeated and ongoing.

Big Five The five basic clusters of personality traits that remain quite stable throughout adulthood: openness, conscientiousness, extroversion, agreeableness, and neuroticism.

bilingual schooling A strategy in which school subjects are taught in both the learner’s original language and the second language.

binocular vision The ability to focus the two eyes in a coordinated manner to see one image.

bipolar disorder A condition characterized by extreme mood swings, from euphoria to deep depression, not caused by outside experiences.

body image A person’s idea of how his or her body looks.

body mass index (BMI) A person’s weight in kilograms divided by the square of height in metres.

boomerang children Adult children who move out of their parents’ home at some point in time before moving back.

Brazelton Neonatal Behavioral Assessment Scale (NBAS) A test often administered to newborns that measures responsiveness and records 46 behaviours, including 20 reflexes.

bulimia nervosa An eating disorder characterized by binge eating and subsequent purging, usually by induced vomiting and/or use of laxatives.

bullying Repeated, systematic efforts to inflict harm through physical, verbal, or social attack on a weaker person.

bullying aggression Unprovoked, repeated physical or verbal attack, especially on victims who are unlikely to defend themselves.

bully-victim Someone who attacks others and who is attacked as well. (Also called a provocative victim because the child does things that elicit bullying.)

Caesarean section (C-section) A surgical birth, in which incisions through the mother’s abdomen and uterus allow the fetus to be removed quickly, instead of being delivered through the vagina.

calorie restriction The practice of limiting dietary energy intake (while consuming sufficient quantities of vitamins, minerals, and other important nutrients) for the purpose of improving health and slowing down the aging process.

CARP A Canadian organization that advocates for Canadians as they age. It was originally called the Canadian Association of Retired Persons, but now only the initials CARP are used, since members need not be retired.

carrier A person whose genotype includes a gene that is not expressed in the phenotype. Such an unexpressed gene occurs in half the carrier’s gametes and thus is passed on to half the carrier’s children, who will most likely be carriers, too. Generally, the characteristic appears in the phenotype only when such a gene is inherited from both parents.

case study An in-depth study of one person, usually requiring personal interviews to collect background information and various follow-up discussions, tests, questionnaires, and so on.

cellular aging The ways in which molecules and cells are affected by age. Many theories aim to explain how and why aging causes cells to deteriorate.

centration A characteristic of preoperational thought whereby a young child focuses (centres) on one idea, excluding all others.

centre daycare Child care that occurs in a place especially designed for the purpose, where several paid adults care for many children. Usually, the children are grouped by age, the daycare centre is licensed, and providers are trained and certified in child development.

cerebral palsy A disorder that results from damage to the brain’s motor centres. People with cerebral palsy have difficulty with muscle control, so their speech and/or body movements are impaired.

child abuse Deliberate action that is harmful to a child’s physical, emotional, or sexual well-being.

child culture The particular habits, styles, and values that reflect the set of rules and rituals that characterize children as distinct from adult society.

child maltreatment Intentional harm to or avoidable endangerment of anyone under 18 years of age.

child neglect Failure to meet a child’s basic physical, educational, or emotional needs.

child sexual abuse Any erotic activity that arouses an adult and excites, shames, or confuses a child, whether or not the victim protests and whether or not genital contact is involved.

child-directed speech The high-pitched, simplified, and repetitive way adults speak to infants. (Also called baby talk, motherese, or parentese.)

childhood obesity A child having a BMI above the 95th percentile.

childhood overweight A child having a BMI above the 85th percentile.

choice overload Having so many options that a thoughtful choice becomes difficult, and regret after making a choice is more likely.

chromosome One of the 46 molecules of DNA (in 23 pairs) that each cell of the human body contains and that, together, contain all the genes. Other species have more or fewer chromosomes.

circadian rhythm A day-night cycle of biological activity that occurs approximately every 24 hours (circadian means “about a day”).

classical conditioning A learning process in which a meaningful stimulus (such as the smell of food to a hungry animal) gradually comes to be connected with a neutral stimulus (such as a particular sound) that had no special meaning before the learning process began. (Also called respondent conditioning.)

classification The logical principle that things can be organized into groups (or categories or classes) according to some characteristic they have in common.

clinical depression Feelings of hopelessness, lethargy, and worthlessness that last two weeks or more.

clique A group of adolescents made up of close friends who are loyal to one another while excluding outsiders.

cluster suicides Several suicides committed by members of a group within a brief period.

cognitive theory A theory of human development that focuses on changes in how people think over time. According to this theory, our thoughts shape our attitudes, beliefs, and behaviours.

cohabitation An arrangement in which two people live together in a committed romantic relationship but are not formally married.

cohort A group defined by the shared age of its members, who, because they were born at about the same time, move through life together, experiencing the same historical events and cultural shifts.

comorbid The presence of two or more disease conditions at the same time in the same person.

complicated grief A type of grief that impedes a person’s future life, usually because the person clings to sorrow or is buffeted by contradictory emotions.

compression of morbidity A shortening of the time a person spends ill or infirm, accomplished by postponing illness.

compulsive hoarding The urge to accumulate and hold on to familiar objects and possessions, sometimes to the point of their becoming health and/or safety hazards. This impulse tends to increase with age.

concrete operational thought Piaget’s term for the ability to reason logically about direct experiences and perceptions.

conditioning According to behaviourism, the processes by which responses become linked to particular stimuli and learning takes place. The word “conditioning” is used to emphasize the importance of repeated practice, as when an athlete conditions his or her body to perform well by training for a long time.

consequential strangers People who are not in a person’s closest friendship circle but nonetheless have an impact.

conservation The principle that the amount of a substance remains the same (i.e., is conserved) even when its appearance changes.

control processes Mechanisms (including selective attention, metacognition, and emotional regulation) that combine memory, processing speed, and knowledge to regulate the analysis and flow of information within the information-processing system. (Also called executive processes.)

conventional moral reasoning Kohlberg’s second level of moral reasoning, emphasizing social rules.

corpus callosum A long, thick band of nerve fibres that connects the left and right hemispheres of the brain and allows communication between them.

correlation A number that indicates the degree of relationship between two variables, expressed in terms of the likelihood that one variable will (or will not) occur when the other variable does (or does not). A correlation indicates only that two variables are related, not that one variable causes the other to occur.

cortex The outer layers of the brain in humans and other mammals. Most thinking, feeling, and sensing involve the cortex.

cortisol The primary stress hormone; fluctuations in the body’s cortisol level affect human emotion.

co-sleeping A custom in which parents and their children (usually infants) sleep together in the same room.

couvade Symptoms of pregnancy and birth experienced by fathers.

creative intelligence A form of intelligence that involves the capacity to be intellectually flexible and innovative.

critical period A time when a particular type of developmental growth (in body or behaviour) must happen if it is ever going to happen.

cross-sectional research A research design that compares groups of people who differ in age but are similar in other important characteristics.

cross-sequential research A hybrid research design in which researchers first study several groups of people of different ages (a cross-sectional approach) and then follow those groups over the years (a longitudinal approach). (Also called cohort-sequential research or time-sequential research.)

crowd A larger group of adolescents who have something in common but who are not necessarily friends.

crystallized intelligence Those types of intellectual ability that reflect accumulated learning. Vocabulary and general information are examples. Some developmental psychologists think crystallized intelligence increases with age, while fluid intelligence declines.

culture A system of shared beliefs, norms, behaviours, and expectations that persist over time and prescribe social behaviour and assumptions.

cyberbullying Bullying that occurs when one person spreads insults or rumours about another by means of technology (e.g., emails, text messages, or cellphone videos).

deductive reasoning Reasoning from a general statement, premise, or principle, through logical steps, to figure out (deduce) specifics. (Also called top-down reasoning.)

deferred imitation A sequence in which an infant first perceives something done by someone else and then performs the same action hours or even days later.

demographic shift A shift in the proportions of the populations of various ages.

dendrite A fibre that extends from a neuron and receives electrochemical impulses transmitted from other neurons via their axons.

dependency ratio A calculation of the number of self-sufficient, productive adults compared with the number of dependents (children and the elderly) in a given population.

dependent variable In an experiment, the variable that may change as a result of whatever new condition or situation the experimenter adds. In other words, the dependent variable depends on the independent variable.

developmental theory A group of ideas, assumptions, and generalizations that interpret and illuminate the thousands of observations that have been made about human growth. A developmental theory provides a framework for explaining the patterns and problems of development.

deviancy training Destructive peer support in which one person shows another how to rebel against authority or social norm

difference-equals-deficit error The mistaken belief that a deviation from some norm is necessarily inferior to behaviour or characteristics that meet the standard.

differential sensitivity The idea that some people are more vulnerable than others are to certain experiences, usually because of genetic differences.

disenfranchised grief A situation in which certain people, although they are bereaved, are prevented from mourning publicly by cultural customs or social restrictions.

disengagement theory The view that aging makes a person’s social sphere increasingly narrow, resulting in role relinquishment, withdrawal, and passivity.

disorganized attachment A type of attachment that is marked by an infant’s inconsistent reactions to the caregiver’s departure and return.

disruptive mood dysregulation disorder (DMDD) A condition in which a child has chronic irritability and anger that culminates in frequent tantrums that are inappropriate to the circumstances and to the child’s age.

distal parenting Caregiving practices that involve remaining distant from the baby, providing toys, food, and face-to-face communication with minimal holding and touching.

dizygotic twins Twins who are formed when two separate ova are fertilized by two separate sperm at roughly the same time. (Also called fraternal twins.)

DNA (deoxyribonucleic acid) The molecule that contains the chemical instructions for cells to manufacture various proteins.

DNR (do not resuscitate) order A written order from a physician (sometimes initiated by a patient’s advance directive or by a health care proxy’s request) that no attempt should be made to revive a patient if he or she suffers cardiac or respiratory arrest.

dominant-recessive pattern The interaction of a pair of alleles in such a way that the phenotype reveals the influence of one allele (the dominant gene) more than that of the other (the recessive gene).

double effect A situation in which an action (such as administering opiates) has both a positive effect (relieving a terminally ill person’s pain) and a negative effect (hastening death by suppressing respiration).

doula A woman who helps with the birth process. Doulas are trained to offer support to new mothers, including massage and suggestions for breastfeeding positions.

Down syndrome A condition in which a person has 47 chromosomes instead of the usual 46, with three rather than two chromosomes at the 21st position. People with Down syndrome typically have distinctive characteristics, including atypical facial features (thick tongue, round face, slanted eyes), heart abnormalities, and language difficulties. (Also called trisomy-21.)

drug abuse The ingestion of a drug to the extent that it impairs the user’s biological or psychological well-being.

dual-process model The notion that two networks exist within the human brain, one for emotional and one for analytical processing of stimuli.

dynamic-systems approach A view of human development as an ongoing, ever-changing interaction between a person’s physical and emotional being and between the person and every aspect of his or her environment, including the family and society.

dyscalculia Unusual difficulty with math, probably originating from a distinct part of the brain.

dyslexia Unusual difficulty with reading; thought to be the result of some neurological underdevelopment.

ecological niche The particular lifestyle and social context that adults settle into because it is compatible with their individual personality needs and interests.

ecological validity The idea that cognition should be measured in settings that are as realistic as possible and that the abilities measured should be those needed in real life.

ecological-systems approach The view that in the study of human development, the person should be considered in all the contexts and interactions that constitute a life. (Later renamed bioecological theory.)

egocentrism Piaget’s term for young children’s tendency to think about the world entirely from their own personal perspective.

elderspeak A condescending way of speaking to older adults that resembles baby talk, with simple and short sentences, exaggerated emphasis, repetition, and a slower rate and a higher pitch than used in normal speech.

Electra complex The unconscious desire of girls to replace their mothers and win their fathers’ exclusive love.

embryo The name for a developing human organism from about the third through the eighth week after conception.

embryonic period The stage of prenatal development from approximately the third through the eighth week after conception, during which the basic forms of all body structures, including internal organs, develop.

emerging adulthood The period of life between the ages of 18 and 25. Emerging adulthood is now widely thought of as a separate developmental stage.

emotional regulation The ability to control when and how emotions are expressed.

emotion-focused coping A strategy to deal with stress by changing feelings about the stressor rather than changing the stressor itself.

empathy The ability to understand the emotions and concerns of another person, especially when they differ from one’s own.

empirical evidence Evidence based on data from scientific observation or experiments; not theoretical.

empty nest The time in the lives of parents when their children have left the family home to pursue their own lives.

entity approach to intelligence An approach to understanding intelligence that sees ability as innate, a fixed quantity present at birth; those who hold this view do not believe that effort enhances achievement.

epigenetic Referring to the effects of environmental forces on the expression of an individual’s, or a species’, genetic inheritance.

equifinality A basic principle of developmental psychopathology that holds that one symptom can have many causes.

ESL (English as a second language) An approach to teaching English in which all children who do not speak English are placed together in an intensive course to learn basic English so that they can be educated in the same classroom as native English speakers. (Also known as EAL, English as an alternative language, or ELL, English Language Learning.)

estradiol A sex hormone, considered the chief estrogen. Females produce much more estradiol than males do.

ethnic group People whose ancestors were born in the same region and who often share a language, culture, and religion.

ethnic identity The extent to which a person identifies with a particular ethnic group’s roles and behaviours. (Also known as ethnocultural identity or cultural identity.)

experiment A research method in which the researcher tries to determine the cause-and-effect relationship between two variables by manipulating one (the independent variable) and then observing and recording the ensuing changes in the other (the dependent variable).

expert One who is notably more accomplished, proficient, and/or knowledgeable in a particular skill, topic, or task than the average person.

expertise Accomplishment at a particular skill or in-depth knowledge of a particular subject that is greater than that of the average person.

extended family A family of three or more generations living in one household.

externalizing problems Difficulty with emotional regulation that involves expressing powerful feelings through uncontrolled physical or verbal outbursts, as by lashing out at other people or breaking things.

extreme sports Forms of recreation that include apparent risk of injury or death and are attractive and thrilling as a result.

extremely low birth weight (ELBW) A body weight at birth of less than 1000 grams.

extrinsic motivation A drive, or reason to pursue a goal, that arises from the need to have one’s achievements rewarded from outside, perhaps by receiving material possessions or another person’s esteem.

extrinsic rewards of work The tangible benefits, usually in the form of compensation (e.g., salary, health insurance, pension), that one receives for doing a job.

family daycare Child care that includes several children of various ages and usually occurs in the home of a woman who is paid to provide it.

family function The way a family works to meet the needs of its members. Children need families to provide basic material necessities, to encourage learning, to help them develop self-respect, to nurture friendships, and to foster harmony and stability.

family structure The legal and genetic relationships among relatives living in the same home; includes nuclear family, extended family, stepfamily, and so on.

family systems theory A theory of human behaviour that focuses on the family as a unit or functioning system, with each member having a role to play and rules to respect.

fast-mapping The speedy and sometimes imprecise way in which children learn new words by tentatively placing them in mental categories according to their perceived meaning.

fetal alcohol syndrome (FAS) A cluster of birth defects, including abnormal facial characteristics, slow physical growth, and intellectual disabilities, that may occur in the child of a woman who drinks alcohol while pregnant.

fetal period The stage of prenatal development from the ninth week after conception until birth, during which the fetus grows in size and matures in functioning.

fetus The name for a developing human organism from the start of the ninth week after conception until birth.

fictive kin Someone who becomes accepted as part of a family to which he or she has no blood relation.

filial responsibility The obligation of adult children to care for their aging parents.

fine motor skills Physical abilities involving small body movements, especially of the hands and fingers, such as drawing and picking up a coin. (The word fine here means “small.”)

flextime An arrangement in which work schedules are flexible so that employees can balance personal and occupational responsibilities.

fluid intelligence Those types of basic intelligence that make learning of all sorts quick and thorough. Abilities such as short-term memory, abstract thought, and speed of thinking are all usually considered part of fluid intelligence.

Flynn effect The rise in average IQ scores that has occurred over the decades in many nations.

focus on appearance A characteristic of preoperational thought whereby a young child ignores all attributes that are not apparent.

foreclosure Erikson’s term for premature identity formation, which occurs when an adolescent adopts his or her parents’ or society’s roles and values wholesale, without questioning or analysis.

formal operational thought In Piaget’s theory, the fourth and final stage of cognitive development, characterized by more systematic logical thinking and by the ability to understand and systematically manipulate abstract concepts.

frail elderly People older than 65, and often older than 85, who are physically infirm, very ill, or cognitively disabled.

frontal lobe disorder Deterioration of the amygdala and frontal lobes that may be the cause of 15 percent of all neurocognitive disorders. (Also called frontotemporal lobar degeneration.)

gamete A reproductive cell; that is, a sperm or an ovum that can produce a new individual if it combines with a gamete from the other sex to form a zygote.

gender constancy The ability of children to understand that gender cannot change, regardless of their outside appearance, such as cutting their hair or wearing a dress.

gender differences Differences in the roles and behaviours that are prescribed by a culture for males and females.

gender identity (adolescence) A person’s acceptance of the roles and behaviours that society associates with the biological categories of male and female.

gender identity (early childhood) The ability of children to make gender distinctions by accurately labelling themselves as a boy or girl.

gender schema A child’s cognitive concept or general belief about sex differences, which is based on his or her observations and experiences.

gender stability The ability of children to understand that their gender is stable over time and will not change.

gene A small section of a chromosome; the basic unit for the transmission of heredity. A gene consists of a string of chemicals that provide instructions for the cell to manufacture certain proteins.

general intelligence (g) The idea of g assumes that intelligence is one basic trait, underlying all cognitive abilities. According to this concept, people have varying levels of this general ability.

generational forgetting The idea that each new generation forgets what the previous generation learned. As used here, the term refers to knowledge about the harm drugs can do.

generativity versus stagnation The seventh of Erikson’s eight stages of development. Adults seek to be productive in a caring way, perhaps through art, caregiving, and employment.

genetic clock A purported mechanism in the DNA of cells that regulates the aging process by triggering hormonal changes and controlling cellular reproduction and repair.

genome The full set of genes that are the instructions to make an individual member of a certain species.

genotype An organism’s entire genetic inheritance, or genetic potential.

germinal period The first two weeks of prenatal development after conception, characterized by rapid cell division and the beginning of cell differentiation.

grammar All the methods—word order, verb forms, and so on—that languages use to communicate meaning, apart from the words themselves.

grief The deep sorrow that people feel at the death of another. Grief is personal and unpredictable.

gross motor skills Physical abilities involving large body movements, such as walking and jumping. (The word gross here means “big.”)

growth spurt The relatively sudden and rapid physical growth that occurs during puberty. Each body part increases in size on a schedule: Weight usually precedes height, and growth of the limbs precedes growth of the torso.

Hayflick limit The number of times a human cell is capable of dividing into two new cells. The limit for most human cells is approximately 50 divisions, an indication that the life span is limited by our genetic program.

Head Start The most widespread early-childhood education program in the United States, begun in 1965 and funded by the federal government.

head-sparing A biological mechanism that protects the brain when malnutrition disrupts body growth. The brain is the last part of the body to be damaged by malnutrition.

health care proxy A person chosen by an individual to make medical decisions if that individual becomes unable to do so.

heritability A statistic that indicates what percentage of the variation in a particular trait within a particular population, in a particular context and era, can be traced to genes.

hidden curriculum The unofficial, unstated, or implicit rules and priorities that influence the academic curriculum and every other aspect of learning in a school.

hippocampus A brain structure that is a central processor of memory, especially memory for locations.

holophrase A single word that is used to express a complete, meaningful thought.

homeostasis The adjustment of all the body’s systems to keep physiological functions in a state of equilibrium, moment by moment. As the body ages, it takes longer for these homeostatic adjustments to occur, so it becomes harder for older bodies to adapt to stress.

hormone An organic chemical substance that is produced by one body tissue and conveyed via the bloodstream to another to affect some physiological function.

hormone replacement therapy (HRT) Taking hormones (in pills, patches, or injections) to compensate for hormone reduction. HRT is most common in women at menopause or after removal of the ovaries, but it is also used by men to help restore their decreased testosterone level. HRT has some medical uses but also carries health risks.

hospice An institution or program in which terminally ill patients receive care to reduce suffering; family and friends of the dying are helped as well.

HPA (hypothalamus-pituitary-adrenal) axis A sequence of hormone production that originates in the hypothalamus, moves to the pituitary, and then ends in the adrenal glands.

HPG (hypothalamus-pituitary-gonad) axis A sequence of hormone production that originates in the hypothalamus, moves to the pituitary, and then ends in the gonads.

humanism A theory that stresses the potential of all human beings for good and the belief that all people have the same basic needs, regardless of culture, gender, or background.

hybrid theory A perspective that combines various aspects of different theories to explain how language, or any other developmental phenomenon, occurs.

hypothalamus A brain area that responds to the amygdala and the hippocampus to produce hormones that activate other parts of the brain and body.

hypothesis A specific prediction that can be tested.

hypothetical thought Reasoning that includes propositions and possibilities that may not reflect reality.

identification An attempt to defend one’s self concept by taking on the behaviours and attitudes of someone else.

identity achievement Erikson’s term for the attainment of identity, or the point at which a person understands who he or she is as a unique individual, in accord with past experiences and future plans.

identity versus role confusion Erikson’s term for the fifth stage of development, in which the person tries to figure out “Who am I?” but is confused as to which of many possible roles to adopt.

imaginary audience The other people who, in an adolescent’s egocentric belief, are watching and taking note of his or her appearance, ideas, and behaviour. This belief makes many teenagers very self-conscious.

immersion A strategy in which instruction in all school subjects occurs in a second language that a child is learning.

immunization A process that stimulates the body’s immune system to defend against attack by a particular contagious disease. Immunization may be accomplished either naturally (by having the disease) or through vaccination (often by having an injection). (Also called vaccination.)

implantation The process, beginning about 10 days after conception, in which the developing organism burrows into the tissue that lines the uterus, where it can be nourished and protected as it continues to develop.

in vitro fertilization (IVF) A technique in which ova (egg cells) are surgically removed from a woman and fertilized with sperm in a laboratory. After the original fertilized cells (the zygotes) have divided several times, they are inserted into the woman’s uterus.

incomplete grief A situation in which circumstances, such as a police investigation or an autopsy, interfere with the process of grieving.

incremental approach to intelligence An approach to understanding intelligence that holds that intelligence can be directly increased by effort; those who subscribe to this view believe they can master whatever they seek to learn if they pay attention, participate in class, study, complete their homework, and so on.

independent variable In an experiment, the variable that is introduced to see what effect it has on the dependent variable. (Also called experimental variable.)

individual education plan (IEP) A document that specifies educational goals and plans for a child with special needs.

inductive reasoning Reasoning from one or more specific experiences or facts to reach (induce) a general conclusion. (Also called bottom-up reasoning.)

industry versus inferiority The fourth of Erikson’s eight psychosocial crises, during which children attempt to master many skills, developing a sense of themselves as either industrious or inferior, competent or incompetent.

infant mortality rate The rate, per 1000 live births, at which babies of less than one year of age die.

infertility The inability to conceive a child after trying for at least a year.

information-processing theory A perspective that compares human thinking processes, by analogy, to computer analysis of data, including sensory input, connections, stored memories, and output.

initiative versus guilt Erikson’s third psychosocial crisis, in which children undertake new skills and activities and feel guilty when they do not succeed at them.

injury control (or harm reduction) Practices that are aimed at anticipating, controlling, and preventing dangerous activities; these practices reflect the beliefs that accidents are not random and that injuries can be made less harmful if proper controls are in place.

insecure-avoidant attachment A pattern of attachment in which an infant avoids connection with the caregiver, as when the infant seems not to care about the caregiver’s presence, departure, or return.

insecure-resistant/ambivalent attachment A pattern of attachment in which an infant’s anxiety and uncertainty are evident, as when the infant becomes very upset at separation from the caregiver and both resists and seeks contact on reunion.

instrumental activities of daily life (IADLs) Actions (e.g., budgeting and preparing food) that are important to independent living and that require some intellectual competence and forethought. The ability to perform these tasks may be even more critical to self-sufficiency than ADL ability.

instrumental aggression Hurtful behaviour that is intended to get something that another person has and to keep it.

integrity versus despair The final stage of Erik Erikson’s developmental sequence, in which older adults seek to integrate their unique experiences with their vision of community.

intelligence quotient (IQ) test A test designed to measure intellectual aptitude, or ability to learn in school. Originally, intelligence was defined as mental age divided by chronological age, multiplied by 100—hence the term intelligence quotient, or IQ.

internalizing problems Difficulty with emotional regulation that involves turning one’s emotional distress inward, by feeling excessively guilty, ashamed, or worthless.

intimacy versus isolation The sixth of Erikson’s eight stages of development. Adults seek someone with whom to share their lives in an enduring and self-sacrificing commitment. Without such commitment they risk profound loneliness and isolation.

intrinsic motivation A drive, or reason to pursue a goal, that comes from inside a person, such as the need to feel smart or competent.

intrinsic rewards of work The intangible gratifications (e.g., job satisfaction, self-esteem, pride) that come from within oneself as a result of doing a job.

intuitive thought Thought that arises from an emotion or a hunch, beyond rational explanation, and is influenced by past experiences and cultural assumptions.

invincibility fable An adolescent’s egocentric conviction that he or she cannot be overcome or even harmed by anything that might defeat a normal mortal, such as unprotected sex, drug abuse, or high-speed driving.

irreversibility A characteristic of preoperational thought whereby a young child thinks that nothing can be undone. A thing cannot be restored to the way it was before a change occurred.

just right The tendency of children to insist on having things done in a particular way. This can include clothes, food, bedtime routines, and so on.

kangaroo care A child-care technique in which a new mother holds the baby between her breasts, like a kangaroo that carries her immature newborn in a pouch on her abdomen.

kinkeeper A caregiver who takes responsibility for maintaining communication among family members.

kinship care A form of foster care in which a relative of a maltreated child, usually a grandparent, becomes the approved caregiver.

knowledge base A body of knowledge in a particular area that makes it easier to master new information in that area.

kwashiorkor A disease of chronic malnutrition during childhood, in which a protein deficiency makes the child more vulnerable to other diseases, such as measles, diarrhea, and influenza.

language acquisition device (LAD) Chomsky’s term for a hypothesized mental structure that enables humans to learn language, including the basic aspects of grammar, vocabulary, and intonation.

latency Freud’s term for middle childhood, during which children’s emotional drives and psychosexual needs are quiet (latent). Freud thought that sexual conflicts from earlier stages are only temporarily submerged, bursting forth again at puberty.

lateralization Literally, “sidedness,” referring to the specialization in certain functions by each side of the brain, with one side dominant for each activity. The left side of the brain controls the right side of the body, and vice versa.

learning theory A theory of human development that describes the laws and processes by which observable behaviour is learned.

least restrictive environment (LRE) A legal requirement that children with special needs be assigned to the most general educational context in which they can be expected to learn.

leptin A hormone that affects appetite and is believed to affect the onset of puberty. Leptin levels increase during childhood and peak at around age 12.

Lewy bodies Deposits of a particular kind of protein in the brain that interfere with communication between neurons; Lewy bodies cause neurocognitive disorder.

life review An examination of one’s own role in the history of human life, engaged in by many elderly people.

life-course-persistent offender A person whose criminal activity typically begins in early adolescence and continues throughout life; a career criminal.

life-span perspective An approach to the study of human development that takes into account all phases of life, not just childhood or adulthood.

limbic system The major brain region crucial to the development of emotional expression and regulation; its three main areas are the amygdala, the hippocampus, and the hypothalamus, although recent research has found that many other areas of the brain are involved with emotions.

linked lives Lives in which the success, health, and well-being of each family member are connected to those of other members, including members of another generation, as in the relationship between parents and children.

little scientist The stage-five toddler (age 12 to 18 months) who experiments without anticipating the results, using trial and error in active and creative exploration.

living will A document that indicates what medical intervention an individual prefers if he or she is not conscious when a decision must be made.

longitudinal research A research design in which the same individuals are followed over time and their development is repeatedly assessed.

long-term memory The component of the information-processing system in which virtually limitless amounts of information can be stored indefinitely.

low birth weight (LBW) A body weight at birth of less than 2500 grams.

marasmus A disease of severe protein-calorie malnutrition during early infancy, in which growth stops, body tissues waste away, and the infant eventually dies.

massification The idea that establishing higher learning institutions and encouraging college and university enrolment could benefit everyone (the masses), leading to marked increases in the number of emerging adults in post-secondary institutions.

maximum life span The oldest possible age that members of a species can live under ideal circumstances. For humans, that age is approximately 122 years.

menarche A girl’s first menstrual period, signalling that she has begun ovulation. Pregnancy is biologically possible, but ovulation and menstruation are often irregular for years after menarche.

menopause The time in middle age, usually around age 50, when a woman’s menstrual periods cease and the production of estrogen, progesterone, and testosterone drops. Strictly speaking, menopause is dated one year after a woman’s last menstrual period, although many months before and after that date are considered part of the period of menopause.

metacognition “Thinking about thinking,” or the ability to evaluate a cognitive task to determine how best to accomplish it, and then to monitor and adjust one’s performance on that task.

middle childhood The period between early childhood and early adolescence, approximately from ages 6 to 11.

middle school A school for children in the grades between elementary and high school. Middle school usually begins with Grade 6 and ends with Grade 8.

midlife crisis A supposed period of unusual anxiety, radical self-examination, and sudden transformation that was once widely associated with middle age, but that actually had more to do with developmental history than with chronological age.

mirror neurons Cells in an observer’s brain that respond to an action performed by someone else in the same way they would if the observer had actually performed that action.

monozygotic twins Twins who originate from one zygote that splits apart very early in development. (Also called identical twins.)

Montessori schools Schools that offer early childhood education based on the philosophy of Maria Montessori (an Italian educator more than a century ago). It is child-centred, emphasizing individual achievement and providing a variety of literacy-related tasks.

moratorium An adolescent’s choice of a socially acceptable way to postpone making identity-achievement decisions. Going to college or university is a common example.

motor skills The learned abilities to move some part of the body, in actions ranging from a large leap to a flicker of the eyelid. (The word motor here refers to movement of muscles.)

mourning The ceremonies and behaviours that a religion or culture prescribes for people to employ in expressing their bereavement after a death.

multifinality A basic principle of developmental psychopathology that holds that one cause can have many (multiple) final manifestations.

multiple intelligences The idea that human intelligence is comprised of a varied set of abilities rather than a single, all-encompassing one.

myelination The process by which axons become coated with myelin, a fatty substance that speeds the transmission of nerve impulses from neuron to neuron.

naming explosion A sudden increase in an infant’s vocabulary, especially in the number of nouns, that begins at about 18 months of age.

naturally occurring retirement community (NORC) A neighbourhood or apartment complex whose population is mostly retired people who moved to the location as younger adults and never left.

nature A general term for the traits, capacities, and limitations that each individual inherits genetically from his or her parents at the moment of conception.

neurocognitive disorder (NCD) Impairment of intellectual functioning caused by organic brain damage or disease. NCD may be diagnosed as major or mild, depending on the severity of symptoms. It becomes more common with age, but it is abnormal and pathological even in the very old

neuron One of billions of nerve cells in the central nervous system, especially in the brain.

neurotransmitter A brain chemical that carries information from the axon of a sending neuron to the dendrites of a receiving neuron.

norm An average, or standard, measurement, calculated from the measurements of many individuals within a specific group or population.

nuclear family A family that consists of a father, a mother, and their biological children under age 18.

nurture A general term for all the environmental influences that affect development after an individual is conceived.

object permanence The realization that objects (including people) still exist even if they can no longer be seen, touched, or heard.

Oedipus complex The unconscious desire of young boys to replace their fathers and win their mothers’ exclusive love.

oldest-old Elderly adults (generally, those older than 85) who are dependent on others for almost everything, requiring supportive services such as nursing homes and hospital stays.

old-old Older adults (generally, those older than 75) who suffer from physical, mental, or social deficits.

operant conditioning A learning process in which a particular action is followed either by something desired (which makes the person or animal more likely to repeat the action) or by something unwanted (which makes the action less likely to be repeated). (Also called instrumental conditioning.)

organ reserve The extra capacity built into each organ, such as the heart and lungs, that allows a person to cope with extraordinary demands or to withstand organ strain.

osteoporosis Fragile bones that result from primary aging, which makes bones more porous, especially if a person is at genetic risk.

overimitation The tendency of children to copy an action that is not a relevant part of the behaviour to be learned; common among 2- to 6-year-olds when they imitate adult actions that are irrelevant and inefficient.

overregularization The application of rules of grammar even when exceptions occur, making the language seem more “regular” than it actually is.

palliative care Care designed not to treat an illness but to provide physical and emotional comfort to the patient and support and guidance to his or her family.

parasuicide Any potentially lethal action against the self that does not result in death. (Also called attempted suicide or failed suicide.)

parental monitoring Parents’ ongoing awareness of what their children are doing, where, and with whom.

parent–infant bond The strong, loving connection that forms as parents hold, examine, and feed their newborn.

Parkinson’s disease A chronic, progressive disease that is characterized by muscle tremor and rigidity and sometimes cognitive impairment; caused by reduced dopamine production in the brain.

passive euthanasia A situation in which a seriously ill person is allowed to die naturally, through the cessation of medical intervention.

peer pressure Encouragement to conform to one’s friends or contemporaries in behaviour, dress, and attitude; usually considered a negative force, as when adolescent peers encourage one another to defy adult authority.

perception The mental processing of sensory information when the brain interprets a sensation.

permanency planning An effort by child welfare authorities to find a long-term living situation that will provide stability and support for a maltreated child. A goal is to avoid repeated changes of caregiver or school, which can be particularly harmful to the child.

permissive parenting An approach to child-rearing that is characterized by high nurturance and communication but little discipline, guidance, or control.

perseveration The tendency to persevere in, or stick to, one thought or action for a long time.

personal fable An aspect of adolescent egocentrism characterized by an adolescent’s belief that his or her thoughts, feelings, and experiences are unique, and more wonderful or awful than anyone else’s.

phallic stage Freud’s third stage of development, when the penis becomes the focus of concern and pleasure.

phenotype The observable characteristics of a person, including appearance, personality, intelligence, and all other traits.

physician-assisted suicide A form of active euthanasia in which a doctor provides the means for someone to end his or her own life.

pincer movement The use of the thumb and forefinger to pick up objects.

pituitary A gland in the brain that responds to a signal from the hypothalamus by producing many hormones, including those that regulate growth and that control other glands, among them the adrenal and sex glands.

plaques Clumps of a protein called beta-amyloid, found in brain tissues surrounding the neurons; a normal brain contains some beta-amyloid protein, but in brains of people with Alzheimer’s disease these plaques proliferate, especially in the hippocampus, a brain structure crucial for memory.

plasticity The ability to be modified or changed.

polypharmacy A situation in which elderly people are prescribed several medications. The various side effects and interactions of those medications can result in symptoms of neurocognitive disorder.

positivity effect The tendency for elderly people to perceive, prefer, and remember positive images and experiences more than negative ones.

postconventional moral reasoning Kohlberg’s third level of moral reasoning, emphasizing moral principles.

postformal thought A proposed adult stage of cognitive development, following Piaget’s four stages. Postformal thought goes beyond adolescent thinking by being more practical, more flexible, and more dialectical (i.e., more capable of combining contradictory elements into a comprehensive whole).

postpartum depression The sadness and inadequacy felt by some new mothers in the days and weeks after giving birth.

practical intelligence The intellectual skills used in everyday problem solving. (Sometimes called tacit intelligence.)

pragmatics The practical use of language that includes the ability to adjust language communication according to audience and context.

preconventional moral reasoning Kohlberg’s first level of moral reasoning, emphasizing rewards and punishments.

prefrontal cortex The area of the cortex at the very front of the brain that specializes in anticipation, planning, and impulse control.

preoperational intelligence Piaget’s term for cognitive development between the ages of about 2 and 6; it includes language and imagination (which involve symbolic thought), but logical, operational thinking is not yet possible.

preterm birth A birth that occurs three or more weeks before the full 38 weeks of the typical pregnancy have elapsed—that is, at 35 or fewer weeks after conception.

primary aging The universal and irreversible physical changes that occur in all living creatures as they grow older.

primary prevention Actions that change overall background conditions to prevent some unwanted event or circumstance, such as injury, disease, or abuse.

primary sex characteristics The parts of the body that are directly involved in reproduction, including the vagina, uterus, ovaries, testicles, and penis.

problem-focused coping A strategy to deal with stress by tackling a stressful situation directly.

Programme for International Student Assessment (PISA) An international assessment program that measures achievement in reading, math, and science for 15-year-olds.

Progress in International Reading Literacy Study (PIRLS) Inaugurated in 2001, a planned five-year cycle of international trend studies in the reading ability of Grade 4 students.

prosocial behaviour Actions that are helpful and kind but that are of no obvious benefit to the person doing them.

protein-calorie malnutrition A condition in which a person does not consume sufficient food of any kind. This deprivation can result in several illnesses, severe weight loss, and even death.

proximal parenting Caregiving practices that involve being physically close to the baby, with frequent holding and touching.

pruning When applied to brain development, the process by which unused connections in the brain atrophy and die.

psychoanalytic theory A theory of human development that holds that irrational, unconscious drives and motives, often originating in childhood, underlie human behaviour.

psychological control A disciplinary technique that involves threatening to withdraw love and support and that relies on a child’s feelings of guilt and gratitude to the parents.

psychopathology An illness or disorder of the mind.

puberty The time between the first onrush of hormones and full adult physical development. Puberty usually lasts three to five years. Many more years are required to achieve psychosocial maturity.

qualitative research Research that considers qualities instead of quantities. Descriptions of particular conditions and participants’ expressed ideas are often part of qualitative studies.

quantitative research Research that provides data that can be expressed with numbers, such as ranks or scales.

race A group of people regarded as distinct from other groups on the basis of appearance, typically skin colour. Social scientists think race is a misleading concept, as biological differences are not signified by outward appearance.

reaction time The time it takes to respond to a stimulus, either physically (with a reflexive movement such as an eyeblink) or cognitively (with a thought).

reactive aggression An impulsive retaliation for another person’s intentional or accidental action, verbal or physical.

reflex An unlearned, involuntary action or movement in response to a stimulus. A reflex occurs without conscious thought.

Reggio Emilia A famous program of early childhood education that originated in the town of Reggio Emilia, Italy; it encourages each child’s creativity in a carefully designed setting.

reinforcement A technique for conditioning a particular behaviour in which that behaviour is followed by something desired, such as food for a hungry animal or a welcoming smile for a lonely person.

rejecting-neglecting parenting An approach to child-rearing in which the parents are indifferent toward their children and unaware of what is going on in their children’s lives.

relational aggression Non-physical acts, such as insults or social rejection, aimed at harming the social connection between the victim and other people.

REM (rapid eye movement) sleep A stage of sleep characterized by flickering eyes behind closed lids, dreaming, and rapid brain waves.

reminder session A perceptual experience that is intended to help a person recollect an idea, a thing, or an experience, without testing whether the person remembers it at the moment.

replication The repetition of a study, using different participants.

reported maltreatment Harm or endangerment about which someone has notified the authorities.

resilience The capacity to adapt well to significant adversity and to overcome serious stress.

response to intervention (RTI) An educational strategy that uses early intervention to help children who demonstrate below-average achievement. Only children who are not helped are designated for more intense measures.

role confusion A situation in which an adolescent does not seem to know or care what his or her identity is. (Sometimes called identity or role diffusion.)

rough-and-tumble play Play that mimics aggression through wrestling, chasing, or hitting, but in which there is no intent to harm.

rumination Repeatedly thinking and talking about past experiences; can contribute to depression.

sandwich generation The generation of middle-aged people who are supposedly “squeezed” by the needs of the younger and older members of their families. In reality, some adults do feel pressured by these obligations, but most are not burdened by them, either because they enjoy fulfilling them or because they choose to take on only some of them or none of them.

scaffolding Temporary support that is tailored to a learner’s needs and abilities and aimed at helping the learner master the next task in a given learning process.

science of human development The science that seeks to understand how and why people of all ages and circumstances change or remain the same over time.

scientific method A way to answer questions that requires empirical research and data-based conclusions.

scientific observation A method of testing a hypothesis by unobtrusively watching and recording participants’ behaviour in a systematic and objective manner—in a natural setting, in a laboratory, or in searches of archival data.

Seattle Longitudinal Study The first cross-sequential study of adult intelligence. This study began in 1956; the most recent testing was completed in 2013.

secondary aging The specific physical illnesses or conditions that become more common with aging but are caused by health habits, genes, and other influences that vary from person to person.

secondary education Literally, the period after primary education (elementary or grade school) and before tertiary education (college or university). It usually occurs from about age 12 to 18, although there is some variation by school and by nation.

secondary prevention Actions that avert harm in a high-risk situation, such as stopping a car before it hits a pedestrian or installing traffic lights at dangerous intersections.

secondary sex characteristics Physical traits that are not directly involved in reproduction but that indicate sexual maturity, such as a man’s beard and a woman’s breasts.

secure attachment A relationship in which an infant obtains both comfort and confidence from the presence of his or her caregiver.

selective attention The ability to concentrate on some stimuli while ignoring others.

selective optimization with compensation The theory, developed by Paul and Margret Baltes, that people try to maintain a balance in their lives by looking for the best way to compensate for physical and cognitive losses and to become more proficient in activities they can already do well.

self theories Theories of late adulthood that emphasize the core self, or the search to maintain one’s integrity and identity.

self-actualization The final stage in Maslow’s hierarchy of needs, characterized by aesthetic, creative, philosophical, and spiritual understanding.

self-awareness A person’s realization that he or she is a distinct individual whose body, mind, and actions are separate from those of other people.

self-concept A person’s understanding of who he or she is, incorporating self-esteem, physical appearance, personality, and various personal traits, such as gender and size.

self-righting The inborn drive to remedy a developmental deficit; literally, to return to sitting or standing upright after being tipped over. People of all ages have self-righting impulses, for emotional as well as physical imbalance.

senescence A gradual physical decline related to aging. Senescence occurs in everyone and in every body part, but the rate of decline is highly variable within and between persons.

sensation The response of a sensory system (eyes, ears, skin, tongue, nose) when it detects a stimulus.

sensitive period A time when a certain type of development is most likely to happen or happens most easily, although it may still happen later with more difficulty. For example, early childhood is considered a sensitive period for language learning.

sensorimotor intelligence Piaget’s term for the way infants think—by using their senses and motor skills—during the first period of cognitive development.

sensory memory The component of the information-processing system in which incoming stimulus information is stored for a split second to allow it to be processed. (Also called the sensory register.)

separation anxiety An infant’s distress when a familiar caregiver leaves, most obvious between 9 and 14 months.

sex differences Biological differences between males and females, in organs, hormones, and body shape.

sex homophily A preference to interact with one’s own sex.

sexual orientation A term that refers to whether a person is sexually and romantically attracted to others of the same sex, the opposite sex, or both sexes.

sexually transmitted infection (STI) An infection spread by sexual contact; includes syphilis, gonorrhea, genital herpes, chlamydia, and HIV (Formerly called sexually transmitted disease or venereal disease.)

shaken baby syndrome (SBS) A life-threatening injury that occurs when an infant is forcefully shaken back and forth, a motion that ruptures blood vessels in the brain and breaks neural connections.

single-parent family A family that consists of only one parent and his or her biological children under age 18.

slippery slope The argument that a given action will start a chain of events that will culminate in an undesirable outcome.

small for gestational age (SGA) Having a body weight at birth that is significantly lower than expected, given the time since conception. For example, a 2265-gram newborn is considered SGA if born on time but not SGA if born two months early. (Also called small-for-dates.)

social comparison The tendency to assess one’s abilities, achievements, social status, and other attributes by measuring them against those of other people, especially one’s peers.

social construction An idea that is based on shared perceptions, not on objective reality. Many age-related terms, such as childhood, adolescence, yuppie, and senior citizen, are social constructions.

social convoy Collectively, the family members, friends, acquaintances, and even strangers who move through life with an individual.

social learning The acquisition of behaviour patterns by observing the behaviour of others.

social learning theory An extension of behaviourism that emphasizes that other people influence each person’s behaviour. The theory’s basic principle is that even without specific reinforcement, every individual learns many things through observation and imitation of other people.

social referencing Seeking information about how to react to an unfamiliar or ambiguous object or event by observing someone else’s expressions and reactions. That other person becomes a social reference.

social smile A smile evoked by a human face, normally first evident in infants about 6 weeks after birth.

sociodramatic play Pretend play in which children act out various roles and themes in stories that they create.

socioeconomic status (SES) A person’s position in society as determined by income, wealth, occupation, education, and place of residence. (Sometimes called social class.)

specific learning disorder A marked deficit in a particular area of learning that is not caused by an apparent physical disability, by another disorder, or by an unusually stressful home environment. (Commonly referred to as learning disability.)

spermarche A boy’s first ejaculation of sperm. Erections can occur as early as infancy, but ejaculation signals sperm production. Spermarche may occur during sleep (in a “wet dream”) or via direct stimulation.

static reasoning A characteristic of preoperational thought whereby a young child thinks that nothing changes. Whatever is now has always been and always will be.

stem cells Cells from which any other specialized type of cell can form.

stereotype threat The possibility that one’s appearance or behaviour will be misread to confirm another person’s oversimplified, prejudiced attitudes.

still-face technique An experimental practice in which an adult keeps his or her face unmoving and expressionless in face-to-face interaction with an infant.

Strange Situation A laboratory procedure for measuring attachment by evoking infants’ reactions to the stress of various adults’ comings and goings in an unfamiliar playroom.

stranger wariness An infant’s expression of concern—a quiet stare while clinging to a familiar person, or a look of fear—when a stranger appears.

stratification theories Theories that emphasize that social forces, particularly those related to a person’s social stratum or social category, limit individual choices and affect a person’s ability to function in late adulthood because past stratification continues to limit life in various ways.

stressor Any situation, event, experience, or other stimulus that causes a person to feel stressed. Many circumstances become stressors for some people but not for others.

stunting The failure of children to grow to a normal height for their age due to severe and chronic malnutrition.

substantiated maltreatment Harm or endangerment that has been reported, investigated, and verified.

sudden infant death syndrome (SIDS) The term used to describe an infant’s unexpected death; when a seemingly healthy baby, usually between 2 and 6 months old, suddenly stops breathing and dies unexpectedly while asleep.

suicidal ideation Thinking about suicide, usually with some serious emotional and intellectual or cognitive overtones.

superego In psychoanalytic theory, the judgmental part of the personality that internalizes the moral standards of the parents.

survey A research method in which information is collected from a large number of people by interviews, written questionnaires, or some other means.

symbolic thought The concept that an object or word can stand for something else, including something pretended or something not seen. Once symbolic thought is possible, language becomes much more useful.

synapse The intersection between the axon of one neuron and the dendrites of other neurons.

synchrony A coordinated, rapid, and smooth exchange of responses between a caregiver and an infant.

tangles Twisted masses of threads made of a protein called tau within the neurons of the brain; a normal brain contains some tau, but in brains of people with Alzheimer’s disease these tangles proliferate, especially in the hippocampus, a brain structure crucial for memory.

telecommuting Working at home and keeping in touch with the office via computer and telephone.

temperament Inborn differences between one person and another in emotions, activity, and self-regulation. It is measured by the person’s typical responses to the environment.

teratogen Any agent or condition, including viruses, drugs, and chemicals, that can impair prenatal development, resulting in birth defects or complications.

terror management theory (TMT) The idea that people adopt cultural values and moral principles in order to cope with their fear of death. This system of beliefs protects individuals from anxiety about their mortality and bolsters their self-esteem, so they react harshly when other people go against any of the moral principles involved.

tertiary prevention Actions, such as immediate and effective medical treatment, that are taken after an adverse event (such as illness, injury, or abuse) occurs and that are aimed at reducing the harm or preventing disability.

testosterone A sex hormone, the best known of the androgens (male hormones); secreted in far greater amounts by males than by females.

thanatology The study of death and dying, especially of the social and emotional aspects.

theory of mind A person’s theory of what other people might be thinking. In order to have a theory of mind, children must realize that other people are not necessarily thinking the same thoughts that they themselves are. That realization is seldom achieved before age 4.

theory-theory The idea that children attempt to explain everything they see and hear.

threshold effect A situation in which a certain teratogen is relatively harmless in small doses but becomes harmful once exposure reaches a certain level (the threshold).

time out A disciplinary technique in which a child is separated from other people and activities for a specified time.

transient exuberance The great but temporary increase in the number of dendrites that develop in an infant’s brain during the first two years of life.

Trends in Math and Science Study (TIMSS) An international assessment of the math and science skills of Grade 4 and Grade 8 students. Although the TIMSS is very useful, different countries’ scores are not always comparable because sample selection, test administration, and content validity are hard to keep uniform.

trust versus mistrust Erikson’s first crisis of psychosocial development. Infants learn basic trust, if the world is a secure place where their basic needs (for food, comfort, attention, and so on) are met.

ultrasound An image of a fetus (or an internal organ) produced by using high-frequency sound waves. (Also called sonogram.)

universal design Designing physical space and common tools that are suitable for people of all ages and all levels of ability.

vascular neurocognitive disorder A form of neurocognitive disorder characterized by sporadic and progressive loss of intellectual functioning caused by repeated infarcts, or temporary obstructions of blood vessels, which prevent sufficient blood from reaching the brain.

very low birth weight (VLBW) A body weight at birth of less than 1500 grams.

wasting The tendency for children to be severely underweight for their age as a result of malnutrition.

wear and tear A view of aging as a process by which the human body wears out because of the passage of time and exposure to environmental stressors.

withdrawn-rejected Someone rejected by peers because of timid, withdrawn, and anxious behaviour.

working memory The component of the information-processing system in which current conscious mental activity occurs. (Formerly called short-term memory.)

working model In cognitive theory, a set of assumptions that the individual uses to organize perceptions and experiences. For example, a person might assume that other people are trustworthy and be surprised by an incident that suggests this working model of human behaviour was erroneous.

X-linked A gene carried on the X chromosome. If a male inherits an X-linked recessive trait from his mother, he expresses that trait because the Y from his father has no counteracting gene. Females are more likely to be carriers of X-linked traits but are less likely to express them.

XX A 23rd chromosome pair that consists of two X-shaped chromosomes, one each from the mother and the father. XX zygotes become females.

XY A 23rd chromosome pair that consists of an X-shaped chromosome from the mother and a Y-shaped chromosome from the father. XY zygotes become males.

young-old Healthy, vigorous, financially secure older adults (generally, those aged 60 to 75) who are well integrated into the lives of their families and communities.

zone of proximal development (ZPD) Vygotsky’s term for the intellectual arena where new cognitive and physical skills can be mastered.

zygote The single cell that is formed from the fusing of two gametes, a sperm and an ovum.