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A U.S. organization of people aged 50 and older that advocates for the elderly. It was originally called the American Association of Retired Persons, but now only the initials AARP are used, since members need not be retired.
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.
A measure of mastery or proficiency in reading, mathematics, writing, science, or some other subject.
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.
The view that elderly people want and need to remain active in a variety of social spheres—with relatives, friends, and community groups—and become withdrawn only unwillingly, as a result of ageism.
A characteristic of adolescent thinking that leads young people (ages 10 to 13) to focus on themselves to the exclusion of others.
A legal proceeding in which an adult or couple unrelated to a child is granted the joys and obligations of being that child's parent(s).
Two glands, located above the kidneys, that produce hormones (including the "stress hormones" epinephrine [adrenaline] and norepinephrine).
An opportunity for perception and interaction that is offered by a person, place, or object in the environment.
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.
A prejudice whereby people are categorized and judged solely on the basis of their chronological age.
aging in place
Remaining in the same home and community in later life, adjusting but not leaving when health fades.
A variation that makes a gene different in some way from other genes for the same characteristics. Many genes never vary; others have several possible alleles.
The total, combined burden of physiological stresses (such as high blood pressure) that an individual lives with. A high allostatic load increases the risk of disease.
Alzheimer disease (AD)
The most common cause of dementia, 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. (Sometimes calledsenile dementia of the Alzheimer type.)
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.
Thought that results from analysis, such as a systematic ranking of pros and cons, risks and consequences, possibilities and facts. Analytic thought depends on logic and rationality.
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.)
An eating disorder characterized by self-starvation. Affected individuals voluntarily undereat and often overexercise, depriving their vital organs of nutrition. Anorexia can be fatal.
Chemical compounds that nullify the effects of oxygen free radicals by forming a bond with their unattached oxygen electron.
Feelings and actions that are deliberately hurtful or destructive to another person.
A proposition or statement of belief that opposes the thesis; the second stage of the process of dialectical thinking.
A quick assessment of a newborn's health. The baby's color, heart rate, reflexes, muscle tone, and respiratory effort 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 maximum score of 10 (rarely attained).
apprenticeship in thinking
Vygotsky's term for how cognition is stimulated and developed in people by older and more skilled members of society.
A living arrangement for elderly people that combines privacy and independence with medical supervision.
assisted reproductive technology (ART)
A general term for the techniques designed to help infertile couples conceive and then sustain a pregnancy.
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.
According to Ainsworth, an affectional tie 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.
An approach to child rearing that is characterized by high behavioral standards, strict punishment of misconduct, and little communication.
An approach to child rearing in which the parents set limits but listen to the child and are flexible.
A developmental disorder marked by an inability to relate to other people normally, extreme self-absorption, and an inability to acquire normal speech.
autistic spectrum disorder
Any of several disorders characterized by inadequate social skills, impaired communication, and unusual play.
Thinking that occurs without deliberate, conscious thought. Experts process most tasks automatically, saving conscious thought for unfamiliar challenges.
A process in which repetition of a sequence of thoughts and actions makes the sequence routine, so that it no longer requires conscious thought.
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 own actions and bodies.
average life expectancy
The number of years the average newborn in a particular population group is likely to live.
A fiber that extends from a neuron and transmits electrochemical impulses from that neuron to the dendrites of other neurons.
Immune cells manufactured in the bone marrow that create antibodies for isolating and destroying bacteria and viruses that invade the body.
The extended repetition of certain syllables, such as ba-ba-ba, that begins when babies are between 6 and 9 months old.
base rate neglect
A common fallacy in which a person ignores the overall frequency of some behavior or characteristic (called the base rate) in making a decision. For example, a person might bet on a "lucky" lottery number without considering the odds that that number will be selected.
Agents and conditions that can harm the prenatal brain, impairing the future child's intellectual and emotional functioning.
A grand theory of human development that studies observable behavior. Behaviorism is also called learning theory because it describes the laws and processes by which behavior is learned.
The five basic clusters of personality traits that remain quite stable throughout adulthood: openness, conscientiousness, extroversion, agreeableness, and neuroticism.
A strategy in which school subjects are taught in both the learner's original language and the second (majority) language.
The ability to focus the two eyes in a coordinated manner in order to see one image. This ability is absent at birth.
A condition characterized by extreme mood swings, from euphoria to deep depression, not caused by outside experiences.
The condition of data gatherers (and sometimes participants as well) who are deliberately kept ignorant of the purpose of the research so that they cannot unintentionally bias the results.
body mass index (BMI)
The ratio of a person's weight in kilograms divided by his or her height in meters squared.
Brazelton Neonatal Behavioral Assessment Scale (NBAS)
A test often administered to newborns that measures responsiveness and records 46 behaviors, including 20 reflexes.
An eating disorder characterized by binge eating and subsequent purging, usually by induced vomiting and/or use of laxatives.
Someone who attacks others and who is attacked as well. (Also calledprovocative victims because they do things that elicit bullying, such as stealing a bully's pencil.)
Repeated, systematic efforts to inflict harm through physical, verbal, or social attack on a weaker person.
Unprovoked, repeated physical or verbal attack, especially on victims who are unlikely to defend themselves.
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.
A person whose genotype includes a gene that is not expressed in the phenotype. Such an unexpressed gene occurs in half of the carrier's gametes and thus is passed on to half of the carrier's children, who will most likely be carriers, too. Generally, only when such a gene is inherited from both parents does the characteristic appear in the phenotype.
center day care
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 day-care center is licensed, and providers are trained and certified in child development.
A characteristic of preoperational thought in which a young child focuses (centers) on one idea, excluding all others.
A disorder that results from damage to the brain's motor centers. People with cerebral palsy have difficulty with muscle control, so their speech and/or body movements are impaired.
cesarean 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. (Also called simply section.)
A public school with its own set of standards that is funded and licensed by the state or local district in which it is located.
Deliberate action that is harmful to a child's physical, emotional, or sexual well-being.
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.
The high-pitched, simplified, and repetitive way adults speak to infants. (Also called baby talk or motherese.)
Having so many possibilities that a thoughtful choice becomes difficult. This is particularly apparent when social networking and other technology make many potential romantic partners available.
One of the 46 molecules of DNA (in 23 pairs) that virtually each cell of the human body contains and that, together, contain all the genes. Other species have more or fewer chromosomes.
The learning process in which a meaningful stimulus (such as the smell of food to a hungry animal) is connected with a neutral stimulus (such as the sound of a tone) that had no special meaning before conditioning. (Also calledrespondent conditioning.)
The logical principle that things can be organized into groups (or categories or classes) according to some characteristic they have in common.
Feelings of hopelessness, lethargy, and worthlessness that last two weeks or more.
A group of adolescents made up of close friends who are loyal to one another while excluding outsiders.
A custom in which parents and their children (usually infants) sleep together in the same room.
code of ethics
A set of moral principles that members of a profession or group are expected to follow.
In cognitive theory, a state of mental balance in which people are not confused because they can use their existing thought processes to understand current experiences and ideas.
A grand 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 behaviors.
An arrangement in which a couple live together in a committed romantic relationship but are not formally married.
A group defined by the shared age of its members. Each cohort was born at about the same time and moves through life together, experiencing the same historical events and cultural shifts.
Refers to the presence of two or more unrelated disease conditions at the same time in the same person.
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.
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.
According to behaviorism, 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.
People who are not in a person's closest friendship circle convoy but nonetheless have an impact.
The principle that the amount of a substance remains the same (i.e., is conserved) even when its appearance changes.
The part of the information-processing system that regulates the analysis and flow of information. Memory and retrieval strategies, selective attention, and rules or strategies for problem solving are all useful control processes. Also calledexecutive processes.)
A long, thick band of nerve fibers that connects the left and right hemispheres of the brain and allows communication between them.
A number between +1.0 and −1.0 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.
The outer layers of the brain in humans and other mammals. Most thinking, feeling, and sensing involve the cortex. (Sometimes called the neocortex.)
A form of intelligence that involves the capacity to be intellectually flexible and innovative.
A time when a particular type of developmental growth (in body or behavior) must happen if it is ever going to happen.
A research design that compares groups of people who differ in age but are similar in other important characteristics.
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.)
A larger group of adolescents who have something in common but who are not necessarily friends.
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 of children
The particular habits, styles, and values that reflect the set of rules and rituals that characterize children as distinct from adult society.
An addictive form of self-mutilation that is most prevalent among adolescent girls and that correlates with depression and drug abuse.
Bullying that occurs when one person spreads insults or rumors about another by means of e-mails, text messages, or cell phone videos.
DALYs (disability-adjusted life years)
A measure of the reduced quality of life caused by disability.
Reasoning from a general statement, premise, or principle, through logical steps, to figure out (deduce) specifics. (Also called top-down reasoning.)
A sequence in which an infant first perceives something that someone else does and then performs the same action a few hours or even days later.
Defining Issues Test (DIT)
A series of questions developed by James Rest and designed to assess respondents' level of moral development by having them rank possible solutions to moral dilemmas.
The tendency to undervalue, or downright ignore, future consequences and rewards in favor of more immediate gratification.
A temporary loss of memory, often accompanied by hallucinations, terror, grandiosity, and irrational behavior.
A situation in a romantic relationship wherein one partner wants to address an issue and the other refuses, resulting in opposite reactions—one insistent on talk while the other cuts short the conversation.
Irreversible loss of intellectual functioning caused by organic brain damage or disease. Dementia becomes more common with age, but it is abnormal and pathological even in the very old.
A fiber that extends from a neuron and receives electrochemical impulses transmitted from other neurons via their axons.
deoxyribonucleic acid (DNA)
The chemical composition of the molecules that contain the genes, which are the chemical instructions for cells to manufacture various proteins.
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.
The field that uses insights into typical development to understand and remediate developmental disorders, and vice versa.
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.
Destructive peer support in which one person shows another how to rebel against authority or social norms.
The most advanced cognitive process, characterized by the ability to consider a thesis and its antithesis simultaneously and thus to arrive at a synthesis. Dialectical thought makes possible an ongoing awareness of pros and cons, advantages and disadvantages, possibilities and limitations.
The view that psychological disorders, such as schizophrenia, are produced by the interaction of a genetic vulnerability (the diathesis) and stressful environmental factors and life events.
Difficulty in performing normal activities of daily life because of some physical, mental, or emotional condition.
A situation in which certain people, although they are bereaved, are prevented from mourning publicly by cultural customs or social restrictions.
The view that aging makes a person's social sphere increasingly narrow, resulting in role relinquishment, withdrawal, and passivity.
disorganized attachment (type D)
A type of attachment that is marked by an infant's inconsistent reactions to the caregiver's departure and return.
Caregiving practices that involve remaining distant from a baby, providing toys, food, and face-to-face communication with minimal holding and touching.
dizygotic (DZ) twins
Twins who are formed when two separate ova are fertilized by two separate sperm at roughly the same time. (Also called fraternal twins.)
DNR (do not resuscitate)
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.
The interaction of a heterozygous 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).
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).
A woman who helps with the birth process. Traditionally in Latin America, a doula was the only professional who attended childbirth. Now doulas are likely to arrive at the woman's home during early labor and later work alongside a hospital's staff.
A condition in which a person has 47 chromosomes instead of the usual 46, with 3 rather than 2 chromosomes at the 21st site. People with Down syndrome typically have distinctive characteristics, including unusual facial features, heart abnormalities, and language diffi culties. (Also called trisomy-21.)
The ingestion of a drug to the extent that it impairs the user's biological or psychological well-being.
A condition of drug dependence in which the absence of the given drug in the individual's system produces a drive—physiological, psychological, or both—to ingest more of the drug.
The notion that two networks exist within the human brain, one for emotional and one for analytical processing of stimuli.
A view of human development as an ongoing, ever-changing interaction between the physical and emotional being and between the person and every aspect of his or her environment, including the family and society.
Unusual difficulty with reading; thought to be the result of some neurological underdevelopment.
The approach taken by most developmentalists, in which they apply aspects of each of the various theories of development rather than adhering exclusively to one theory.
The particular lifestyle and social context that adults settle into because it is compatible with their individual personality needs and interests.
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.
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.)
Occupations or recreational activities that involve a degree of risk or danger. The prospect of "living on the edge" makes edgework compelling to some individuals.
A way to indicate, statistically, how much of an impact the independent variable had on the dependent variable.
The ability to regulate one's emotions and actions through effort, not simply through natural inclination.
Piaget's term for children's tendency to think about the world entirely from their own personal perspective.
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.
The unconscious desire of girls to replace their mother and win their father's romantic love.
The name for a developing human organism from about the third through the eighth week after conception.
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.
The period of life between the ages of 18 and 25. Emerging adulthood is now widely thought of as a separate developmental stage.
A strategy to deal with stress by changing feelings about the stressor rather than changing the stressor itself.
The ability to understand the emotions and concerns of another person, especially when they differ from one's own.
The time in the lives of parents when their children have left the family home to pursue their own lives.
Referring to environmental factors that affect genes and genetic expression; enhancing, halting, shaping, or altering the expression of genes, resulting in a phenotype that may differ markedly from the genotype.
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.
A sex hormone, considered the chief estrogen. Females produce much more estradiol than males do.
People whose ancestors were born in the same region and who often share a language, culture, and religion.
A theory that underlies the values and practices of a culture but is not usually apparent to the people within the culture.
experience-dependent brain functions
Brain functions that depend on particular, variable experiences and that therefore may or may not develop in a particular infant.
experience-expectant brain functions
Brain functions that require certain basic common experiences (which an infant can be expected to have) in order to develop normally.
A research method in which the researcher tries to determine the cause-and-effect relationship between two variables by manipulating one (called theindependent variable) and then observing and recording the ensuing changes in the other (called the dependent variable).
Memory that is easy to retrieve on demand (as in a specific test), usually with words. Most explicit memory involves consciously learned words, data and concepts.
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.
Forms of recreation that include apparent risk of injury or death and that are attractive and thrilling as a result. Motocross is one example.
extremely low birthweight (ELBW)
A body weight at birth of less than 2 pounds, 3 ounces (1,000 grams).
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.
The belief that family members should support one another, sacrificing individual freedom and success, if necessary, in order to preserve family unity.
family day care
Child care that occurs in the home of someone to whom the child is not related and who usually cares for several children of various ages.
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.
The legal and genetic relationships among relatives living in the same home; includes nuclear family, extended family, stepfamily, and so on.
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 retarded mental development, that may occur in the child of a woman who drinks alcohol while pregnant.
The stage of prenatal development from the ninth week after conception until birth, during which the fetus gains about 7 pounds (more than 3,000 grams) and organs become more mature, gradually able to function on their own.
The name for a developing human organism from the start of the ninth week after conception until birth.
Someone who becomes accepted as part of a family to which he or she has no blood relation.
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.")
An arrangement in which work schedules are flexible so that employees can balance personal and occupational responsibilities.
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.
Functional magnetic resonance imaging, a measuring technique in which the brain's electrical excitement indicates activation anywhere in the brain; fMRI helps researchers locate neurological responses to stimuli.
focus on appearance
A characteristic of preoperational thought in which a young child ignores all attributes that are not apparent.
Erikson's term for premature identity formation, which occurs when an adolescent adopts 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.
A legal, publicly supported system in which a maltreated child is removed from the parents' custody and entrusted to another adult or family, which is reimbursed for expenses incurred in meeting the child's needs.
fragile X syndrome
A genetic disorder in which part of the X chromosome seems to be attached to the rest of it by a very thin string of molecules. The cause is a single gene that has more than 200 repetitions of one triplet.
People over age 65, and often over age 85, who are physically infirm, very ill, or cognitively disabled.
frontal lobe dementia
Deterioration of the amygdala and frontal lobes that may be the cause of 15 percent of all dementias. (Also called frontotemporal lobar degeneration.)
A reproductive cell; that is, a sperm or ovum that can produce a new individual if it combines with a gamete from the other sex to make a zygote.
Differences in the roles and behavior of males and females that are prescribed by the culture.
A person's acceptance of the roles and behaviors that society associates with the biological categories of male and female.
A cognitive concept or general belief based on one's experiences—in this case, a child's understanding of sex differences.
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.
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.
A purported mechanism in the DNA of cells that regulates the aging process by triggering hormonal changes and controlling cellular reproduction and repair.
Consultation and testing by trained experts that enable individuals to learn about their genetic heritage, including harmful conditions that they might pass along to any children they may conceive.
The full set of genes that are the instructions to make an individual member of a certain species.
The first two weeks of prenatal development after conception, characterized by rapid cell division and the beginning of cell differentiation.
The paired sex glands (ovaries in females, testicles in males). The gonads produce hormones and gametes.
goodness of fit
A similarity of temperament and values that produces a smooth interaction between an individual and his or her social context, including family, school, and community.
All the methods—word order, verb forms, and so on—that languages use to communicate meaning, apart from the words themselves.
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.")
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.
The process by which people learn from others who guide their experiences and explorations.
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.
A biological mechanism that protects the brain when malnutrition affects body growth. The brain is the last part of the body to be damaged by malnutrition.
health care proxy
A person chosen by another person to make medical decisions if the second person becomes unable to do so.
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.
Defined by developmentalists as marriage between individuals who tend to be dissimilar with respect to such variables as attitudes, interests, goals, socioeconomic status, religion, ethnic background, and local origin.
Referring to two genes of one pair that differ in some way. Typically one allele has only a few base pairs that differ from the other member of the pair.
A Japanese word literally meaning "pull away," it is the name of an anxiety disorder common among young adults in Japan. Sufferers isolate themselves from the outside world by staying inside their homes for months or even years at a time.
The unofficial, unstated, or implicit rules and priorities that influence the academic curriculum and every other aspect of learning in a school.
An evaluation that is critical in determining success or failure. If a single test determines whether a student will graduate or be promoted, it is a high-stakes test.
A brain structure that is a central processor of memory, especially memory for locations.
The adjustment of all the body's systems to keep physiological functions in a state of equilibrium. As the body ages, it takes longer for these homeostatic adjustments to occur, so it becomes harder for older bodies to adapt to stress.
Defined by developmentalists as marriage between individuals who tend to be similar with respect to such variables as attitudes, interests, goals, socioeconomic status, religion, ethnic background, and local origin.
Referring to two genes of one pair that are exactly the same in every letter of their code. Most gene pairs are homozygous.
A sexual encounter between two people who are not in a romantic relationship. Neither intimacy nor commitment are expected.
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 as their testosterone decreases. HRT has some medical uses but also carries health risks.
An institution or program in which terminally ill patients receive palliative care to reduce suffering; family and friends of the dying are helped as well.
HPA (hypothalamus-pituitary-adrenal) axis
A sequence of hormone production originating in the hypothalamus and moving to the pituitary and then to the adrenal glands.
HPG (hypothalamus-pituitary-gonad) axis
A sequence of hormone production originating in the hypothalamus and moving to the pituitary and then to the gonads.
Human Genome Project
An international effort to map the complete human genetic code. This effort was essentially completed in 2001, though analysis is ongoing.
A theory that stresses the potential of all humans for good and the belief that all people have the same basic needs, regardless of culture, gender, or background.
A brain area that responds to the amygdala and the hippocampus to produce hormones that activate other parts of the brain and body.
Reasoning that includes propositions and possibilities that may not reflect reality.
An attempt to defend one's self-concept by taking on the behaviors and attitudes of someone else.
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.
The other people who, in an adolescent's egocentric belief, are watching and taking note of his or her appearance, ideas, and behavior. This belief makes many teenagers very self-conscious.
A strategy in which instruction in all school subjects occurs in the second (usually the majority) language that a child is learning.
The process, beginning about 10 days after conception, in which the developing organism burrows into the placenta that lines the uterus, where it can be nourished and protected as it continues to develop.
Unconscious or automatic memory that is usually stored via habits, emotional responses, routine procedures, and various sensations.
in vitro fertilization (IVF)
Fertilization that takes place outside a woman's body (as in a glass laboratory dish). The procedure involves mixing sperm with ova that have been surgically removed from the woman's ovary. If a zygote is produced, it is inserted into the woman's uterus, where it may implant and develop into a baby.
A situation in which circumstances, such as a police investigation or an autopsy, interfere with the process of grieving.
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.
Reasoning from one or more specific experiences or facts to reach (induce) a general conclusion. (Also calledbottom-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.
A perspec tive 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/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 (type A)
A pattern of attachment in which an infant avoids connection with the caregiver, as when the infant seems not to care about the care-giver's presence, departure, or return.
insecure-resistant/ambivalent attachment (type C)
A pattern of attachment in which anxiety and uncertainty are evident, as when an infant becomes very upset at separation from the caregiver and both resists and seeks contact on reunion.
Institutional Review Board (IRB)
A group that exists within most educational and medical institutions whose purpose is to ensure that research follows established guidelines and remains ethical.
instrumental activities of daily life (IADLs)
Actions (for example, paying bills and driving a car) 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.
Behavior that hurts someone else because the aggressor wants to get or keep a possession or a privilege.
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.
Difficulty with emotional regulation that involves turning one's emotional distress inward, as 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 aloneness and isolation.
A violent and demeaning form of abuse in a romantic relationship, where the victim (usually female) is frightened to fight back, seek help, or withdraw. In this case, the victim is in danger of physical as well as psychological harm.
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.
Thought that arises from an emotion or a hunch, beyond rational explanation, and is influenced by past experiences and cultural assumptions.
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.
A test designed to measure intellectual aptitude, or ability to learn in school. Originally, intelligence was defined as mental age divided by chronological age, times 100—hence the term intelligence quotient, or IQ.
A characteristic of preoperational thought in which a young child thinks that nothing can be undone. A thing cannot be restored to the way it was before a change occurred.
A form of newborn care in which mothers (and sometimes fathers) rest the baby between their breasts, like a kangaroo that carries her immature newborn in a pouch on her abdomen.
A form of foster care in which a relative of a maltreated child, usually a grandparent, becomes the approved caregiver.
A body of knowledge in a particular area that makes it easier to master new information in that area.
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.
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.
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.
A marked delay in a particular area of learning that is not caused by an apparent physical disability, by mental retardation, or by an unusually stressful home environment.
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.
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 body dementia
A form of dementia characterized by an increase in Lewy body cells in the brain. Symptoms include visual hallucinations, momentary loss of attention, falling, and fainting.
An examination of one's own role in the history of human life, engaged in by many elderly people.
A person whose criminal activity typically begins in early adolescence and continues throughout life; a career criminal.
An approach to the study of human development that takes into account all phases of life, not just childhood or adulthood.
Lives in which the success, health, and well-being of each family member are connected to those of other members, including those of another generation, as in the relationship between parents and children.
The stage-five toddler (age 12 to 18 months) who experiments without anticipating the results, using trial and error in active and creative exploration.
A document that indicates what medical intervention an individual prefers if he or she is not conscious when a decision is to be expressed. For example, some do not want mechanical breathing.
The component of the information-processing system in which virtually limitless amounts of information can be stored indefinitely.
A research design in which the same individuals are followed over time and their development is repeatedly assessed.
A disease of severe protein-calorie malnutrition during early infancy, in which growth stops, body tissues waste away, and the infant eventually dies.
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.
A girl's first menstrual period, signaling that she has begun ovulation. Pregnancy is biologically possible, but ovulation and menstruation are often irregular for years after menarche.
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 menopausal.
A technique of combining results of many studies to come to an overall conclusion. Meta-analysis is powerful, in that small samples can be added together to lead to significant conclusions, although variations from study to study sometimes make combining them impossible.
"Thinking about thinking," or the ability to evaluate a cognitive task in order to determine how best to accomplish it, and then to monitor and adjust one's performance on that task.
The period between early childhood and early adolescence, approximately from ages 6 to 11.
A school for children in the grades between elementary and high school. Middle school usually begins with grade 6 and ends with grade 8.
A supposed period of unusual anxiety, radical self-reexamination, 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.
mild cognitive impairment
Forgetfulness and loss of verbal fluency that often comes before the first stage of Alzheimer disease.
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.
The central process of social learning, by which a person observes the actions of others and then copies them. (Also called observational learning.)
monozygotic (MZ) twins
Twins who originate from one zygote that splits apart very early in development. (Also calledidentical twins.) Other monozygotic multiple births (such as triplets and quadruplets) can occur as well.
Schools that offer early-childhood education based on the philosophy of Maria Montessori, which emphasizes careful work and tasks that each young child can do.
morality of care
In Gilligan's view, moral principles that reflect the tendency of females to be reluctant to judge right and wrong in absolute terms because they are socialized to be nurturant, compassionate, and nonjudgmental.
morality of justice
In Gilligan's view, moral principles that reflect the tendency of males to emphasize justice over compassion, judging right and wrong in absolute terms.
An adolescent's choice of a socially acceptable way to postpone making identity-achievement decisions. Going to college is a common example.
Disease. As a measure of health, morbidity usually refers to the rate of diseases in a given population—physical and emotional, acute (sudden) and chronic (ongoing).
Death. As a measure of health, mortality usually refers to the number of deaths each year per 1,000 members of a given population.
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.)
The ceremonies and behaviors that a religion or culture prescribes for people to employ in expressing their bereavement after a death.
Referring to a trait that is affected by many factors, both genetic and environmental expression; enhancing, halting, shaping, or altering the expression of genes, resulting in a phenotype that may differ markedly from the genotype.
The idea that human intelligence is comprised of a varied set of abilities rather than a single, all-encompassing one.
The process by which axons become coated with myelin, a fatty substance that speeds the transmission of nerve impulses from neuron to neuron.
A sudden increase in an infant's vocabulary, especially in the number of nouns, that begins at about 18 months of age.
National Assessment of Educational Progress (NAEP)
An ongoing and nationally representative measure of U.S. children's achievement in reading, mathematics, and other subjects over time; nicknamed "the Nation's Report Card."
naturally occurring retirement community (NORC)
A neighborhood or apartment complex whose population is mostly retired people who moved to the location as younger adults and never left.
A general term for the traits, capacities, and limitations that each individual inherits genetically from his or her parents at the moment of conception.
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.
No Child Left Behind Act
A U.S. law enacted in 2001 that was intended to increase accountability in education by requiring states to qualify for federal educational funding by administering standardized tests to measure school achievement.
A family that consists of a father, a mother, and their biological children under age 18.
A general term for all the environmental influences that affect development after an individual is conceived.
In a child, having a BMI above the 95th percentile, according to the U.S. Centers for Disease Control's 1980 standards for children of a given age.
The realization that objects (including people) still exist when they can no longer be seen, touched, or heard.
Thinking that is not influenced by the thinker's personal qualities but instead involves facts and numbers that are universally considered true and valid.
The unconscious desire of young boys to replace their father and win their mother's romantic love.
Older adults (generally, those over age 75) who suffer from physical, mental, or social deficits.
Elderly adults (generally, those over age 85) who are dependent on others for almost everything, requiring supportive services such as nursing homes and hospital stays.
The learning process by which a particular action is followed 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.)
A description of the specific, observable behavior that will constitute the variable that is to be studied, so that any reader will know whether that behavior occurred or not. Operational definitions may be arbitrary (e.g., an IQ score at or above 130 is operationally defined as gifted), but they must be precise.
The capacity of organs to allow the body to cope with stress, via extra, unused functioning ability.
The application of rules of grammar even when exceptions occur, making the language seem more "regular" than it actually is.
In a child, having a BMI above the 85th percentile, according to the U.S. Centers for Disease Control's 1980 standards for children of a given age.
oxygen free radicals
Atoms of oxygen that, as a result of metabolic processes, have an unpaired electron. These atoms scramble DNA molecules or mitochondria, producing errors in cell maintenance and repair that, over time, may cause cancer, diabetes, and arteriosclerosis.
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.
The strong, loving connection that forms as parents hold, examine, and feed their newborn.
Cooperation between a mother and a father based on their mutual commitment to their children. In a parental alliance, the parents support each other in their shared parental roles.
Parents' ongoing awareness of what their children are doing, where, and with whom.
A chronic, progressive disease that is characterized by muscle tremor and rigidity, and sometimes dementia; caused by a reduction of dopamine production in the brain.
A situation in which a seriously ill person is allowed to die naturally, through the cessation of medical intervention.
Encouragement to conform to one's friends or contemporaries in behavior, dress, and attitude; usually considered a negative force, as when adolescent peers encourage one another to defy adult authority.
A universal principle of infant perception, consisting of an innate attraction to other humans, which is evident in visual, auditory, tactile, and other preferences.
A point on a ranking scale of 0 to 100. The 50th percentile is the midpoint; half the people in the population being studied rank higher and half rank lower.
The mental processing of sensory information when the brain interprets a sensation. Perception occurs in the cortex.
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.
An approach to child rearing that is characterized by high nurturance and communication but little discipline, guidance, or control.
An aspect of adolescent egocentrism characterized by an adolescent's belief that his or her thoughts, feelings, and experiences are unique, more wonderful or awful than anyone else's.
Freud's third stage of development, when the penis becomes the focus of concern and pleasure.
The observable characteristics of a person, including appearance, personality, intelligence, and all other traits.
A genetic disorder in which a child's body is unable to metabolize an amino acid called phenylalanine. Unless the infant immediately begins a special diet, the resulting buildup of phenylalanine in body fluids causes brain damage, progressive mental retardation, and other symptoms.
Teaching reading by first teaching the sounds of each letter and of various letter combinations.
A form of active euthanasia in which a doctor provides the means for someone to end his or her own life.
PISA (Programme for International Student Assessment)
An international test taken by 15-year-olds in 50 nations that is designed to measure problem solving and cognition in daily life.
A gland in the brain that responds to a signal from the hypothalamus by producing many hormones, including those that regulate growth and control other glands, among them the adrenal and sex glands.
A family consisting of one man, several wives, and the biological children of the man and his wives.
Refers to a situation in which elderly people are prescribed several medications. The various side effects and interactions of those medications can result in dementia symptoms.
The entire group of individuals who are of particular concern in a scientific study, such as all the children of the world or all newborns who weigh less than 3 pounds.
The tendency for elderly people to perceive, prefer, and remember positive images and experiences more than negative ones.
post-traumatic stress disorder (PTSD)
An anxiety disorder that develops as a delayed reaction to having experienced or witnessed a profoundly shocking or frightening event, such as rape, severe beating, war, or natural disaster. Its symptoms may include flashbacks to the event, hyperactivity and hypervigilance, displaced anger, sleeplessness, nightmares, sudden terror or anxiety, and confusion between fantasy and reality.
postconventional moral reasoning
Kohlberg's third level of moral reasoning, emphasizing moral principles.
A proposed adult stage of cognitive development, following Piaget's four stages, that goes beyond adolescent thinking by being more practical, more flexible, and more dialectical (that is, more capable of combining contradictory elements into a comprehensive whole).
A new mother's feelings of inadequacy and sadness in the days and weeks after giving birth.
The intellectual skills used in everyday problem solving. (Sometimes called tacit intelligence.)
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.
The area of cortex at the front of the brain that specializes in anticipation, planning, and impulse control.
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.
A significant loss of hearing associated with senescence. Presbycusis usually is not apparent until after age 60.
A birth that occurs 3 or more weeks before the full 38 weeks of the typical pregnancy—that is, at 35 or fewer weeks after conception.
The universal and irreversible physical changes that occur to all living creatures as they grow older.
primary circular reactions
The first of three types of feedback loops in sensorimotor intelligence, this one involving the infant's own body. The infant senses motion, sucking, noise, and other stimuli, and tries to understand them.
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.
Words or ideas presented in advance that make it easier to remember something. It is also possible for priming to impair cognition, as with stereotype threat.
The internal dialogue that occurs when people talk to themselves (either silently or out loud).
Progress in International Reading Literacy Study (PIRLS)
Inaugurated in 2001, a planned five-year cycle of international trend studies in the reading ability of fourth-graders.
Feelings and actions that are helpful and kind but are of no obvious benefit to oneself.
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.
Caregiving practices that involve being physically close to a baby, with frequent holding and touching.
A grand theory of human development that holds that irrational, unconscious drives and motives, often originating in childhood, underlie human behavior.
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.
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.
Measures that help prevent morbidity, mortality, and disability in the public at large, such as via immunization, monitoring the food and water supply, and increasing preventive health practices.
QALYs (quality-adjusted life years)
A way of comparing mere survival without vitality to survival with good health. A full year of health is a full QALY; people with less than full health have a fraction of QALY each year. Thus, their total QALY is less than the total years they live.
Research that considers qualities instead of quantities. Descriptions of particular conditions and participants' expressed ideas are often part of qualitative studies.
Research that provides data that can be expressed with numbers, such as ranks or scales.
A group of people who are regarded by themselves or by others as distinct from other groups on the basis of physical appearance. Social scientists think race is a misleading concept.
The time it takes to respond to a stimulus, either physically (with a reflexive movement such as an eyeblink) or cognitively (with a thought).
An impulsive retaliation for another person's intentional or accidental action, verbal or physical.
An unlearned, involuntary action or movement that responds to a stimulus. A reflex occurs without conscious thought.
A famous program of early-childhood education that originated in the town of Reggio Emilia, Italy, and that encourages each child's creativity in a carefully designed setting.
A technique for conditioning behavior in which that behavior is followed by something desired, such as food for a hungry animal or a welcoming smile for a lonely person.
Nonphysical acts, such as insults or social rejection, aimed at harming the social connection between the victim and other people.
Rapid eye movement sleep, a stage of sleep characterized by flickering eyes behind closed lids, dreaming, and rapid brain waves.
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.
A group of research participants who reflect the relevant characteristics of the larger population whose attributes are under study.
response to intervention
An educational strategy intended to help children in early grades who demonstrate below-average achievement by means of special intervention.
A situation in which an adolescent does not seem to know or care what his or her identity is. (Sometimes called identity diffusion.)
Play that mimics aggression through wrestling, chasing, or hitting, but in which there is no intent to harm.
A group of individuals drawn from a specified population. A sample might be the low-birthweight babies born in four particular hospitals that are representative of all hospitals.
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.
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.
A method of testing a hypothesis by unobtrusively watching and recording participants' behavior 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 conducted in 2005.
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 circular reactions
The second of three types of feedback loops in sensorimotor intelligence, this one involving people and objects. Infants respond to other people, to toys, and to any other object they can touch or move.
Literally, the period after primary education (elementary or grade school) and before tertiary education (college). It usually occurs from about age 12 to 18, although there is some variation by school and by nation.
Actions that avert harm in a high-risk situation, such as stopping a car before it hits a pedestrian.
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.
The long-term upward or downward direction of a certain set of statistical measurements, as opposed to a smaller, shorter cyclical variation. As an example, over the last two centuries, because of improved nutrition and medical care, children have tended to reach their adult height earlier and their adult height has increased.
secure attachment (type B)
A relationship in which an infant obtains both comfort and confidence from the presence of his or her caregiver.
The process by which living creatures (including people) adjust to their environment. Genes that enhance survival and reproductive ability are selected, over generations, to become more frequent.
Someone who is notably more skilled and knowledgeable than the average person about whichever activities are personally meaningful.
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.
Theories of late adulthood that emphasize the core self, or the search to maintain one's integrity and identity.
The final stage in Maslow's hierarchy of needs, characterized by aesthetic, creative, philosophical, and spiritual understanding.
One's realization that he or she is a distinct individual, whose body, mind, and actions are separate from those of other people.
A person's understanding of who he or she is, in relation to self-esteem, appearance, personality, and various traits.
In social learning theory, the belief of some people that they are able to change themselves and effectively alter the social context.
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.
The response of a sensory system (eyes, ears, skin, tongue, nose) when it detects a stimulus.
A time when a certain type of development is most likely, although it may still happen later. For example, early childhood is considered a sensitive period for language learning.
Piaget's term for the way infants think—by using their senses and motor skills—during the first period of cognitive development.
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.)
An infant's distress when a familiar caregiver leaves, most obvious between 9 and 14 months.
Biological differences between males and females, in organs, hormones, and body type.
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)
A disease spread by sexual contact, including syphilis, gonorrhea, genital herpes, chlamydia, and HIV.
shaken baby syndrome
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.
A family that consists of only one parent and his or her biological children under age 18.
situational couple violence
Fighting between romantic partners that is brought on more by the situation than by the deep personality problems of the individuals. Both partners are typically victims and abusers.
The argument that a given action will start a chain of events that will culminate in an undesirable outcome.
small for gestational age (SGA)
A term for a baby whose birthweight is significantly lower than expected, given the time since conception. For example, a 5-pound (2,265-gram) newborn is considered SGA if born on time but not SGA if born two months early. (Also called small-for-dates.)
The ability to understand social interactions, including the causes and consequences of human behavior.
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.
Collectively, the family members, friends, acquaintances, and even strangers who move through life with an individual.
Learning that is accomplished by observing others—both what they do and how other people react to that behavior.
social learning theory
An extension of behaviorism that emphasizes the influence that other people have over a person's behavior. Even without specific reinforcement, every individual learns many things through observation and imitation of other people.
Human interaction that expands and advances understanding, often through words that one person uses to explain something to another.
A Web site that allows users to publicly share details of their daily lives and connect with large numbers of friends, acquaintances, and potential romantic partners, among others.
social norms approach
A method of reducing risky behavior that uses emerging adults' desire to follow social norms by making them aware, through the use of surveys, of the prevalence of various behaviors within their peer group.
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.
An emergent theory that holds that development results from the dynamic interaction of each person with the surrounding social and cultural forces.
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.)
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.
A characteristic of preoperational thought in which a young child thinks that nothing changes. Whatever is now has always been and always will be.
The possibility that one's appearance or behavior will be misread to confirm another person's oversimplified, prejudiced attitudes.
An experimental practice in which an adult keeps his or her face umoving and expressionless in face-to-face interaction with an infant.
A laboratory procedure for measuring attachment by evoking infants' reactions to stress in eight episodes, lasting three minutes each.
An infant's expression of concern—a quiet stare, clinging to a familiar person, or sadness—when a stranger appears.
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.
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.
The failure of children to grow to a normal height for their age due to severe and chronic malnutrition.
Thinking that is strongly influenced by personal qualities of the individual thinker, such as past experiences, cultural assumptions, and goals for the future.
Thinking about suicide, usually with some serious emotional and intellectual or cognitive overtones.
sunk cost fallacy
The mistaken belief that if money, time, or effort that cannot be recovered (a "sunk cost," in economic terms) has already been invested in some endeavor, then more should be invested in an effort to reach the goal. Because of this fallacy, people spend money trying to fix a "lemon" of a car or send more troops to fight a losing battle.
In psychoanalytic theory, the judgmental part of the personality that internalizes the moral standards of the parents.
A research method in which information is collected from a large number of people by interviews, written questionnaires, or some other means.
A new idea that integrates the thesis and its antithesis, thus representing a new and more comprehensive level of truth; the third stage of the process of dialectical thinking.
Immune cells manufactured in the thymus gland that produce substances that attack infected cells in the body.
Working at home and keeping in touch with the office via computer, telephone, and fax.
An enzyme that increases the length of telomeres, which in turn may slow the advance of aging.
The ends of chromosomes in the cells; their length decreases with each cell duplication and seems to correlate with longevity.
Inborn differences between one person and another in emotions, activity, and self-regulation. Temperament originates in genes and prenatal development and is affected by early experiences.
Agents and conditions, including viruses, drugs, and chemicals, that can impair prenatal development and result in birth defects or even death.
An overall slowdown of cognitive abilities in the weeks and months before death. (Also called terminal drop.)
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 circular reactions
The third of three types of feedback loops in sensorimotor intelligence, this one involving active exploration and experimentation. Infants explore a range of new activities, varying their responses as a way of learning about the world.
Actions, such as immediate and effective medical treatment, that are taken after an adverse event (such as illness or injury) occurs and that are aimed at reducing the harm or preventing disability.
A sex hormone, the best known of the androgens (male hormones); secreted in far greater amounts by males than by females.
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 possible before age 4.
The idea that children attempt to explain everything they see and hear by constructing theories.
A proposition or statement of belief; the first stage of the process of dialectical thinking.
A situation in which a certain teratogen is relatively harmless in small doses but becomes harmful once exposure reaches a certain level (the threshold).
A disciplinary technique in which a child is separated from other people for a specified time.
The great but temporary increase in the number of dendrites that occurs 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 fourth- and eighth-graders. 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 psychosocial crisis. Infants learn basic trust if their basic needs (for food, comfort, attention, and so on) are met.
An image of a fetus (or an internal organ) produced by using high-frequency sound waves. (Also called sonogram.)
vascular dementia (VaD)
A form of dementia 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. (Also called multi-infarct dementia.)
An experimental apparatus that gives an illusion of a sudden drop-off between one horizontal surface and another.
A measure of health that refers to how healthy and energetic—physically, intellectually, and socially—an individual actually feels.
Permission for a parent to choose the school for the child, with some or all of the cost of that's child's education borne by the local government. Parents who have vouchers for their children often can choose a public or private school, although the specifics vary a great deal from one jurisdiction to another.
The tendency for children to be severely underweight for their age as a result of malnutrition.
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.
The gradual accumulation of stressors over a long period of time, wearing down the resilience and resistance of a person.
Teaching reading by encouraging early use of all language skills—talking and listening, reading and writing.
A term formerly used to denigrate domestic and caregiving tasks that were once thought to be the responsibility of females.
The component of the information-processing system in which current conscious mental activity occurs. (Formerly called short-term memory.)
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 evidence that this working model of human behavior is erroneous.
Referring to 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.
A 23rd chromosome pair that consists of two X-shaped chromosomes, one each from the mother and the father. XX zygotes become females.
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.
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)
In sociocultural theory, a metaphorical area, or "zone," surrounding a learner that includes all the skills, knowledge, and concepts that the person is close ("proximal") to acquiring but cannot yet master without help.
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