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accommodation  Modifying an existing schema to fit a new experience.
achievement motivation  A person's tendency to strive for successful performance, to evaluate her performance against standards of excellence, and to feel pleasure at having performed successfully.
acquired immune deficiency syndrome (AIDS)  A viral disease that attacks the body's immune systems; transmitted to a fetus or newborn in the form of the human immunodeficiency virus (HIV), this disorder weakens the child's immune system and may ultimately cause its death.
active genetic-environmental interaction  A kind of interaction in which people's genes encourage them to seek out experiences compatible with their inherited tendencies.
adaptation  Adjusting one's thinking to fit with environmental demands.
age cohort  People born within the same generation.
age of viability  The age of 22 to 26 weeks from conception, at which point the fetus's physical systems are advanced enough that it has a chance to survive if born prematurely.
aggression  Behavior that intentionally harms other people by inflicting pain or injury on them.
aggressive rejected children  Rejected children who have low self-control, are highly aggressive, and exhibit behavior problems.
allele  An alternate form of a gene; typically, a gene has two alleles, one inherited from the individual's mother, and one from the father.
alpha-fetoprotein (AFP) assay  A maternal blood test performed prenatally to detect such problems as Down syndrome, the presence of multiple embryos, and defects of the central nervous system.
altruism  An unselfish concern for the welfare of others.
altruistic behavior  Intrinsically motivated behavior that is intended to help others without expectation of acknowledgment or concrete reward.
amniocentesis  A technique for sampling and assessing fetal cells for indications of abnormalities in the developing fetus; performed by inserting a needle through the abdominal wall and into the amniotic sac and withdrawing a small amount of the amniotic fluid.
amniotic sac  A membrane that contains the developing organism and the amniotic fluid around it; sac and fluid protect the organism from physical shocks and temperature changes.
androgynous  Possessing both feminine and masculine psychological characteristics.
animistic thinking  The attribution of life to inanimate objects.
anorexia nervosa  An eating disorder in which people, usually young women, are preoccupied with avoiding obesity and often diet to the point of starvation.
approach/avoidance behavior  A pattern of interaction in which the infant or child shows an inconsistent pattern of approaching and retreating from a person or an object.
assimilation  Applying an existing schema to a new experience.
associative learning  According to Jen sen, lower level learning tapped in tests of such things as short-term memorization and recall, attention, rote learning, and simple associative skills. Also called level I learning.
attachment  A strong emotional bond that forms between infant and caregiver in the second half of the child's first year.
Attachment Q Sort (AQS)  An assessment method in which a caregiver or observer judges the quality of a child's attachment based on the child's behavior in naturalistic situations, often including brief separations from parents.
attention  The identification and selection of particular sensory input for more detailed processing.
attention deficit/hyperactivity disorder (ADHD)  A childhood disorder characterized by a persistent pattern of inattention and hyperactivity or impulsivity that far exceeds such behaviors observed in children at comparable levels of development.
authoritarian parenting  Parenting that is harsh, unresponsive, and rigid and in which parents tend to use power-assertive methods of control.
authoritative parenting  Parenting that is warm, responsive, and involved yet unintrusive and in which parents set reasonable limits and expect appropriately mature behavior from their children.
autistic disorder  A disorder in which children's ability to communicate and interact socially is seriously impaired; children with autism have specific language deficiencies, demonstrate a need for sameness in their environment, and often engage in repetitive and stereotyped kinds of behaviors.
autobiographical memory  A collection of memories of things that have happened to a person at a specific time or place.
automatization  The process of transforming conscious, controlled behaviors into unconscious and automatic ones.
autosomes  The 22 paired non-sex chromosomes.
autostimulation theory  The theory that during REM sleep the infant's brain stimulates itself and that this, in turn, stimulates early development of the central nervous system.
average children  Children who have some friends but who are not as well liked as popular children
babbling  An infant's production of strings of consonant-vowel combinations.
basic reflex activity  An infant's exercise of, and growing proficiency in, the use of innate reflexes.
Bayley Scales of Infant Development  A set of nonverbal tests that measure specific developmental milestones and are generally used with children thought to be at risk for abnormal development.
behavior therapy  A psychological form of treatment, often used in treating conduct disorders, that is based on such learning principles as reinforcement and social learning.
behaviorism  A learning perspective that holds that theories of psychology must be based on observations of behavior rather than on speculations about motives or unobservable factors.
bilingualism  The acquisition of two languages.
brain hemispheres  The two halves of the brain's cerebrum, left and right.
Brazelton Neonatal Assessment Scale  A scale containing a battery of tests used to measure an infant's sensory and perceptual capabilities, motor development, range of states, and ability to regulate these states, as well as whether the brain and central nervous system are properly regulating involuntary responses.
bulimia nervosa  An eating disorder in which people, usually young women, alternate periods of binge eating with vomiting and other means of compensating for the weight gained.
canalization  The genetic restriction of a phenotype to a small number of developmental outcomes, permitting environmental influences to play only a small role in these outcomes.
case study method  A form of research in which investigators study an individual person or group very intensely.
catch-up growth  The tendency for human beings to regain a normal course of physical growth after injury or deprivation.
categorical speech perception  The tendency to perceive as the same a range of sounds belonging to the same phonemic group.
catharsis  Presumably, discharging aggressive impulses by engaging in actual or symbolic aggressive acts that do not impinge on another person.
center care  A child-care context in which children are cared for in a "school-like" environment by professional caregivers.
centration  Focusing one's attention on only one dimension or characteristic of an object or situation.
cephalocaudal  The pattern of human physical growth in which development begins in the area of the brain and proceeds downward to the trunk and legs.
cerebral cortex  The covering layer of the cerebrum that contains the cells that control specific functions such as seeing, hearing, moving, and thinking.
cerebrum  The two connected hemispheres of the brain.
cesarean delivery  The surgical delivery of a baby; the baby is removed from the mother's uterus through an incision made in her abdomen and uterus in a procedure also known as cesarean section.
child development  A field of study that seeks to account for the gradual evolution of the child's cognitive, social, and other capacities first by describing changes in the child's observed behaviors and then by uncovering the processes and strategies that underlie these changes.
chlamydia  Probably the most widespread bacterial sexually transmitted disease; can cause pneumonia or a form of conjunctivitis in a pregnant woman's baby.
chorionic villi sampling  A technique for sampling and assessing cells withdrawn from the chorionic villi, projections from the chorion that surrounds the amniotic sac; cells are withdrawn either through a tube inserted into the uterus through the vagina or through a needle inserted through the abdominal wall.
chromosomes  Threadlike structures, located in the nucleus of a cell, that carry genetic information to help direct development.
chronosystem  The time-based dimension that can alter the operation of all other systems in Bronfen-brenner's model, from microsystem through macrosystem.
classical conditioning  A type of learning in which two stimuli are repeatedly presented together until individuals learn to respond to the unfamiliar stimulus in the same way they respond to the familiar stimulus.
clique  A voluntary group formed on the basis of friendship.
codominance  A genetic pattern in which heterozygous alleles express the variants of the trait for which they code simultaneously and with equal force.
cognition  The mental activity through which human beings acquire and process knowledge.
cognitive behavior therapy  A group therapy technique particularly useful in treating depression in adolescents. Therapeutic goals include reducing self-consciousness and feelings of being different and teaching strategies for dealing with depressive moods and for acquiring a more positive outlook and improving social interactions.
cognitive developmental theory of gender typing  Kohlberg's theory that children use physical and behavioral clues to differentiate gender roles and to gender-type themselves very early in life.
cognitive developmental view of attachment  The view that to form attachments infants must differentiate between mother and stranger and understand that people exist independent of the infant's interaction with them.
cognitive learning  According to Jensen, higher level learning tapped in tests of such things as abstract thinking, symbolic processing, and the use of language in problem solving. Also called level II learning.
cognitive map  A mental representation of the spatial layout of a physical or geographic place.
cognitive processes  Ways that the human mental system operates on information.
cognitive social learning theory  A learning theory that stresses the importance of observation and imitation in the acquisition of new behaviors, with learning mediated by cognitive processes.
colic  A prolonged period of unexplained crying by an infant.
communicative competence  The ability to convey thoughts, feelings, and intentions in a meaningful and culturally patterned way.
community of learners  An approach to classroom learning in which adults and children work together in shared activities, peers learn from each other, and the teacher serves as a guide.
comorbidity  The co-occurrence of two or more problem behaviors.
concrete operations stage  Stage in which the child is able to reason logically about materials that are physically present.
conduct disorder  A disorder characterized by a repetitive and persistent pattern of behavior in which a young person violates the basic rights of others or major age-appropriate societal norms or rules.
congenital  Characteristic acquired during development in the uterus or during the birth process and not through heredity.
connectionist models  Information processing approaches that describe mental processes in terms of the interconnections of the neural network.
conscience  The child's internalized values and standards of behavior.
conservation  The understanding that altering an object's or a substance's appearance does not change its basic attributes or properties.
constructivist view  The idea that children actively create their understanding of the world as they encounter new information and have new experiences.
control group  In an experiment, the group that is not exposed to the treatment, or the independent variable.
control phase  According to Kopp, the first phase in learning self-regulation, when children are highly dependent on caregivers to remind them about acceptable behaviors.
controversial children  Children who are liked by many peers but also disliked by many.
conventional level  Kohlberg's second level of moral development, in which the child's behavior is designed to solicit others' approval and maintain good relations with them. The child accepts societal regulations unquestioningly and judges behavior as good if it conforms to these rules.
cooing  A very young infant's production of vowel like sounds.
coordination of secondary circular reactions  An infant's combination of different schemas to achieve a specific goal.
co-parenting  Parenting in which spouses work together as a team, coordinating their child-rearing practices with each other; co parenting can be cooperative, hostile, or characterized by different levels of investment in the parenting task.
core knowledge systems  Ways of reasoning about ecologically important objects and events, such as the solidity and continuity of objects.
corpus callosum  The band of nerve fibers that connects the two hemispheres of the brain.
correlational method  A research design that permits investigators to establish relations among variables as well as assess the strength of those relations.
creativity  The ability to solve problems, create products, or pose questions in a way that is novel or unique.
creole language  A language spoken by children of pidgin-language speakers that, in contrast with pidgin, is highly developed and rule governed.
criminal offense  Behavior that is illegal.
critical period  A specific period in children's development when they are sensitive to a particular environmental stimulus that does not have the same effect on them when encountered before or after this period.
crossing over  The process by which equivalent sections of homologous chromosomes switch places randomly, shuffling the genetic information each carries.
cross-sectional method  A research method in which researchers compare groups of individuals of different age levels at approximately the same point in time.
crowd  A collection of people whom others have stereotyped on the basis of their perceived shared attitudes or activities—for example, populars or nerds.
culture-fair test  A test that attempts to minimize cultural biases in content that might influence the test taker's responses.
cumulative risk  The notion that risk factors in children's life circumstances have cumulative negative effects on their intellectual performance.
deductive reasoning  Logical thinking that involves reaching a necessary and valid conclusion based on a set of premises.
deferred imitation  Mimicry of an action some time after having observed it; requires that the child have some sort of mental representation of the action.
delay gratification  To put off until another time possessing or doing something that gives one pleasure.
delinquency  Juvenile behavior in violation of the law.
deoxyribonucleic acid (DNA)  A ladder like molecule that stores genetic information in cells and transmits it during reproduction.
dependent variable  The variable, or factor, that researchers expect to change as a function of change in the independent variable.
depression in childhood  Like adult depression, a mood disorder often manifested in a depressed mood and loss of interest in familiar activities but also likely to be expressed as irritability and crankiness. Difficulty concentrating or focusing on tasks and concomitant drops in school grades are not uncommon, and children with depression often complain of physical problems such as headache.
developmental psychopathology  The investigation of the origins, course, changes, and continuities in disordered or maladaptive behavior over a person's life span.
deviation IQ  An IQ score that indicates the extent to which a person's performance on a test deviates from age-mates' average performance.
diagnosis  The identification of a physical or mental disorder on the basis of symptoms and of knowledge of the cause or causes of the disorder and its common course. A diagnosis may also include information about effective forms of treatment.
diagnostic reliability  A measure of how often two or more clinicians arrive independently at the same diagnosis of a particular disorder.
diethylstilbestrol (DES)  A synthetic hormone once prescribed for pregnant women to prevent miscarriage but discontinued when cancer and precancerous conditions were detected in their children.
direct observation  A method of observation in which researchers go into settings in the natural world or bring participants into the laboratory to observe behaviors of interest.
discourse  Socially based conversation.
dizygotic  Characterizing fraternal twins, who have developed from two separate fertilized eggs.
dominance hierarchy  An ordering of individuals in a group from most to least dominant; a "pecking order."
dominant  The more powerful of two alleles in a heterozygous combination.
Down syndrome  A form of chromosome abnormality in which the person suffers disabling physical and mental development and is highly susceptible to such illnesses as leukemia, heart disorders, and respiratory infections.
dynamic systems theory  A theory that proposes that individuals develop and function within systems and that studies the relationships among individuals and systems and the properties by which these relationships operate.
dyslexia  A term for the difficulties some people experience in reading or in learning to read.
ecological theory  A theory of development that stresses the importance of understanding not only the relationships between organisms and various environmental systems but also the relations among such systems themselves.
ecological validity  The degree to which a research study accurately represents events or processes that occur in the natural world.
ego  In Freudian theory, the rational, controlling component of the personality, which tries to satisfy needs through appropriate, socially acceptable behaviors.
egocentric speech  According to Vygotsky, a form of self-directed dialogue by which the child instructs herself in solving problems and formulating plans; as the child matures, this becomes internalized as inner speech.
egocentrism  The tendency to view the world from one's own perspective and to have difficulty seeing things from another's viewpoint.
elaboration  A memory strategy in which one adds to information to make it more meaningful and thus easier to remember.
elementary mental functions  Psychological functions with which the child is endowed by nature, including attention, perception, and involuntary memory, that emerge spontaneously during children's interaction with the world.
embryo  The developing organism between the second and eighth week of gestation; the embryonic period comprises the differentiation of the major physiological structures and systems.
emotional display rules  Rules that dictate which emotions one may appropriately display in particular situations.
emotional script  A complex scheme that enables a child to identify the emotional reaction likely to accompany a particular sort of event.
emotions  Subjective reactions to the environment that are usually experienced cognitively as either pleasant or unpleasant, generally accompanied by physiological arousal, and often expressed in some visible form of behavior.
empathic  Able to experience the same emotion that someone else is experiencing.
empathy  The capacity to experience the same emotion that someone else is experiencing.
encoding  The transformation of information from the environment into a mental representation.
ends over means focus  Consideration of only the end state of a problem in evaluating an event; failure to consider the means by which that end state was obtained.
episodic memory  Memory for specific events, often autobiographical in nature.
estrogens  Hormones that, in the female, are responsible for sexual maturation.
ethological theory  A theory that holds that behavior must be viewed and understood as occurring in a particular context and as having adaptive or survival value.
ethological theory of attachment  Bowlby's theory that attachment derives from the biological preparation of both infant and parents to respond to each other's behaviors in such a way that parents provide the infant with care and protection.
etiology  In medicine and psychiatry, the cause or causes of a specific disorder.
evocative genetic-environmental inter action  The expression of the genes' influence on the environment through an individual's inherited tendencies to evoke certain environmental responses; for example, a child's smiling may elicit smiles from others.
evolutionary psychology  An approach that holds that critical components of psychological functioning reflect evolutionary changes and are critical to the survival of the species.
executive control process  A cognitive process that serves to control, guide, and monitor the success of a problem-solving approach a child uses.
executive control structure  According to Case, a mental blueprint or plan for solving a class of problems.
exosystem  The collection of settings, such as a parent's daily work, that impinge on a child's development but in which the child does not play a direct role.
expansion  A technique adults use in speaking to young children in which they imitate and expand or add to a child's statement.
experience-dependent processes  Brain processes that are unique to the individual and responsive to particular cultural, community, and family experiences.
experience-expectant processes  Brain processes that are universal, experienced by all human beings across evolution
experimental group  In an experiment, the group that is exposed to the treatment, or the independent variable.
expressive characteristics  Presumably typical of females, these characteristics include nurturance and concern with feelings.
extended family  A family that includes relatives such as grandparents, aunts, uncles, nieces, and nephews within the basic family unit of parents and children.
factor analysis  A statistical procedure used to determine which of a number of factors, or scores, are both closely related to each other and relatively independent of other groups of factors, or scores.
Fagan Test of Infant Intelligence  A test of how infants process information, including encoding attributes of objects and seeing similarities and differences across objects.
family child care  A child-care arrangement in which an individual cares for three or four children in her home.
fetal alcohol syndrome  A disorder exhibited by infants of alcoholic mothers and characterized by stunted growth, a number of physical and physiological abnormalities, and often, mental retardation.
fetus  The developing organism from the third month of gestation through delivery; during the fetal period, bodily structures and systems develop to completion.
field experiment  An experiment in which researchers deliberately create a change in a real-world setting and then measure the outcome of their manipulation.
Flynn effect  Increase in the average IQ score in the populations of the United States and other developed countries since the early 1900s, a phenomenon identified by J. R. Flynn.
formal operations stage  Stage in which the child becomes capable of abstract thinking, complex reasoning, and hypothesis testing.
fragile X syndrome  A form of chromosomal abnormality, more common in males than in females, in which an area near the tip of the X chromosome is narrowed and made fragile due to a failure to condense during cell division. Symptoms include physical, cognitive, and social problems.
friendship  A reciprocal commitment between two people who see themselves more or less as equals.
gender constancy  The awareness that superficial alterations in appearance or activity do not alter gender.
gender identity  The perception of oneself as either masculine or feminine.
gender role preference  The desire to possess certain gender-typed characteristics.
gender roles  Composites of the behaviors actually exhibited by a typical male or female in a given culture; the reflection of a gender stereotype in everyday life.
gender stability  The notion that gender does not change; males remain male and females remain female.
gender stereotypes  Beliefs that members of a culture hold about how females and males should behave; that is, what behaviors are acceptable and appropriate for each sex.
gender typing  The process by which children acquire the values, motives, and behaviors considered appropriate for their gender in their particular culture.
gender-based beliefs  Ideas and expectations about what is appropriate behavior for males and females.
gender-schema theory  The notion that children develop schemas, or naive theories, that help them organize and structure their experience related to gender differences and gender roles.
gene  A portion of DNA located at a particular site on a chromosome and that codes for the production of certain kinds of proteins.
general factor (g)  General mental ability involved in all cognitive tasks.
generalization  The application of a strategy learned while solving a problem in one situation to a similar problem in a new situation.
genital herpes  A common viral infection spread primarily through sexual contact; if contracted by an infant during birth, it can cause blindness, motor abnormalities, mental retardation, and a wide range of neurological disorders.
genotype  The particular set of genes a person inherits from his or her parents.
gestation  The carrying of an embryo or fetus during pregnancy, usually for 9 months in humans.
glial cell  A nerve cell that supports and protects neurons and serves to encase them in myelin sheaths.
gonorrhea  A sexually transmitted bacterial infection that, in a pregnant woman, can cause blindness in her infant; normally treatable with antibiotics.
goodness of fit  A measure of the degree to which a child's temperament is matched by her environment; the more effectively parents and other agents of socialization accept and adapt to the child's unique temperament, the better this "fit."
grammar  The structure of a language; consists of morphology and syntax.
guided participation  Learning that occurs as children participate in activities of their community and are guided in their participation by the actions of more experienced partners in the setting.
habituation  A process of learning by which an individual reacts with less and less intensity to a repeatedly presented stimulus, eventually responding only faintly or not at all.
Head Start  A federally funded program that provides disadvantaged young children with preschool experience, social services, and medical and nutritional assistance.
hedonistic reasoning  Making a decision to perform a prosocial act on the basis of expected material reward.
hemispheric specialization  Differential functioning of the two cerebral hemispheres; the left controlling the right side of the body, the right controlling the left side.
hemophilia  A disorder, caused by an X-linked recessive gene, in which the blood fails to clot; found more often in males than in females.
heritability factor  A statistical estimate of the contribution heredity makes to a particular trait or ability.
heterozygous  The state of an individual whose alleles for a particular trait from each parent are different.
hierarchical categorization  The organization of concepts into levels of abstraction that range from the specific to the general.
higher mental functions  Psychological functions, such as voluntary attention, complex memory processes, and problem solving, that entail the coordination of several cognitive processes and the use of mediators.
holophrase  A single word that appears to represent a complete thought.
homozygous  The state of an individual whose alleles for a particular trait from each parent are the same.
horizontal décalage  The term Piaget used to describe unevenness in children's thinking within a particular stage; for example, in developing an understanding of conservation, children conserve different objects or substances at different ages.
hormones  Powerful and highly specialized chemical substances that are produced by the cells of certain body organs and that have a regulatory effect on the activity of certain other organs.
hostile aggression  Directing aggressive behavior at a particular person or group, criticizing, ridiculing, tattling on, or calling names.
human behavior genetics  The study of the relative influences of heredity and environment on the evolution of individual differences in traits and abilities.
Huntington disease  A genetically caused, fatal disorder of the nervous system that begins in mid adulthood and is manifested chiefly in uncontrollable spasmodic movements of the body and limbs and eventual mental deterioration.
id  In Freudian theory, the person's instinctual drives; the first component of the personality to evolve, the id operates on the basis of the pleasure principle.
identification  The Freudian notion that children acquire gender identity by identifying with and imitating their same-sex parents.
immanent justice  The notion that any deviation from rules will inevitably result in punishment or retribution.
imprinting  The process by which birds and other infrahuman animals develop a preference for the person or object to which they are first exposed during a brief, critical period after birth.
inclusion  A policy by which children of all ability levels, whether learning disabled, physically handicapped, or mentally retarded, are included in the same classroom.
independent variable  The variable, or factor, that researchers deliberately manipulate in an experiment.
infant state  A recurring pattern of arousal in the newborn, ranging from alert, vigorous, wakeful activity to quiet, regular sleep.
infant-directed, or child-directed, speech  A simplified style of speech parents use with young children, in which sentences are short, simple, and often repetitive and the speaker enunciates especially clearly, slowly, and in a higher pitched voice, often ending with a rising intonation. Also called motherese.
information-processing approaches  Theories of development that focus on the flow of information through the child's cognitive system and particularly on the specific operations the child performs between input and output phases.
Information-processing approaches  Theories of development that focus on the flow of information through the child's cognitive system and particularly on the specific operations the child performs between input and output phases.
informed consent  Agreement, based on a clear and full understanding of the purposes and procedures of a research study, to participate in that study.
inner speech  Internalized egocentric speech that guides intellectual functioning.
insecure-avoidant attachment  A type of attachment shown by babies who seem not to be bothered by their mothers' brief absences but specifically avoid them on their return, sometimes becoming visibly upset.
insecure-disorganized attachment  A type of attachment shown by babies who seem disorganized and disoriented when reunited with their mothers after a brief separation.
insecure-resistant attachment  A kind of attachment shown by babies who tend to become very upset at the departure of their mothers and who exhibit inconsistent behavior on their return, sometimes seeking contact, sometimes pushing their mothers away.
instrumental aggression  Quarreling and fighting with others over toys and possessions.
instrumental characteristics  Presumably typical of males, these characteristics include task and occupation orientation.
intellectual giftedness  A characteristic defined by an IQ score of 130 or over; gifted children learn faster than others and may show early exceptional talents in certain areas.
intelligence quotient (IQ)  An index of the way a person performs on a standardized intelligence test relative to the way others her age perform.
intent community participation  Children's participation in the authentic activities of their community with the purpose of learning about the activity.
intermodal perception  The use of sensory information from more than one modality to identify a stimulus and make sense of it; also, the identification of a stimulus already identified by means of one modality by the use of another modality.
internal working model  According to Bowlby, a person's mental representation of himself as a child, his parents, and the nature of his interaction with his parents, as he reconstructs and interprets that interaction; also referred to as an attachment representation.
intuitive substage  The second substage of the preoperational stage during which the child begins to solve problems by using mental operations but cannot explain how she arrives at the solutions.
inventing new means by mental combination  Children begin to combine schemas mentally and rely less on physical trial and error.
iron-deficiency anemia  A disorder in which inadequate amounts of iron in the diet cause listlessness and may retard a child's physical and intellectual development.
joint legal custody  A form of child custody in which both parents retain and share responsibility for decisions regarding the child's life, although the child usually resides with one parent.
joint physical custody  As in joint legal custody, parents make decisions together regarding their child's life, but they also share physical custody so that the child lives with each parent for a portion of the year.
Kaufman Assessment Battery for Children (K-ABC)  An intelligence test designed to measure several types of information processing skills as well as achievement in some academic subjects.
Klinefelter's syndrome  A form of chromosome abnormality in which a male inherits an extra X sex chromosome, resulting in the XXY pattern; many feminine physical characteristics, language deficits, and, sometimes, mental retardation are present.
laboratory experiment  A research design that allows investigators to determine cause and effect by controlling variables and treatments and assigning participants randomly to treatments.
language  A communication system in which words and their written symbols combine in rule-governed ways and enable speakers to produce an infinite number of messages.
language acquisition device (LAD)  Chomsky's proposed mental structure in the human nervous system that incorporates an innate concept of language.
language acquisition support system (LASS)  According to Bruner, a collection of strategies and tactics that environmental influences—initially, a child's parents or primary care givers—provide the language-learning child.
lanugo  A fine, soft hair that covers the fetus's body from about the fifth month of gestation on; may be shed before birth or after.
latchkey children  Children who must let themselves into their homes after school because one parent or both parents are working outside the home.
lateralization  The process by which each half of the brain becomes specialized for certain functions—for example, the control of speech and language by the left hemisphere and of visual-spatial processing by the right.
learned helplessness  A kind of behavior that results from the belief that one is helpless to control the events in one's world.
learning disabilities  Deficits in one or more cognitive processes important for learning.
learning theory of attachment  The theory that infants become attached to their mothers because a mother provides food, or primary reinforcement, and thus becomes a secondary reinforcer.
life-span perspective  A view of development as a process that continues throughout the life cycle, from infancy through adulthood and old age.
longitudinal method  A method in which investigators study the same people repeatedly at various times in the participants' lives.
long-term memory  The mental processing unit in which information may be stored permanently and from which it may later be retrieved.
macrosystem  The system that surrounds the microsystem, mesosystem, and exosystem; represents the values, ideologies, and laws of the society or culture.
maturation  A genetic or biologically determined process of growth that unfolds over a period of time.
mediational deficiency  Inability to use strategies to store information in long-term memory.
mediators  Psychological tools and signs—such as language, counting, mnemonic devices, algebraic symbols, art, and writing—that facilitate and direct thinking processes.
meiosis  The process by which a germ cell divides to produce new germ cells with only half the normal complement of chromosomes; thus male and female germ cells (sperm and ovum) each contain only 23 chromosomes so that when they unite, the new organism they form will have 46 chromosomes, half from each parent.
memory span  The amount of information one can hold in short-term memory.
menarche  In females, the beginning of the menstrual cycle.
mental age  An index of a child's actual performance on an intelligence test compared with his true age.
mental representation  Information stored mentally in some form (e.g., verbal, pictorial, procedural).
mental retardation  A characteristic defined by an IQ score below 70 together with difficulty in coping with age-appropriate activities of everyday life.
mesosystem  The interrelations among the components of the microsystem.
metacognition  The individual's knowledge about knowing and his control of cognitive activities.
metalinguistic awareness  The understanding that language is a rule bound system of communicating.
microgenetic analysis  A very detailed examination of how a child solves a problem.
microgenetic change  Changes associated with learning that occur over the time of a specific learning experience or episode.
microsystem  In Bronfenbrenner's ecological theory, the context in which children live and interact with the people and institutions closest to them, such as parents, peers, and school.
miscarriage  The natural or spontaneous end of a pregnancy before the infant is capable of survival outside the womb and generally defined in humans as prior to 20 weeks gestation.
mitosis  The process in which a body cell divides in two, first duplicating its chromosomes so that the new daughter cells produced each contain the usual 46 chromosomes.
modifier genes  Genes that exert their influence indirectly, by affecting the expression of still other genes.
monozygotic  Characterizing identical twins, who have developed from a single fertilized egg.
moral realism  Piaget's second stage of moral development, in which the child shows great respect for rules but applies them quite inflexibly.
morality of reciprocity  Piaget's third stage of moral development, in which the child recognizes that rules may be questioned and altered, considers the feelings and views of others, and believes in equal justice for all.
morpheme  A language's smallest unit of meaning, such as a prefix, a suffix, or a root word.
morphology  The study of morphemes, language's smallest units of meaning.
multischematic  Possessing both multiple cultural schemas for responding to the environment and the necessary criteria for deciding what schema to use in a particular situation.
multistore model  A model of information processing in which information moves through a series of organized processing units—sensory register, short-term memory, and long-term memory.
mutual antipathy  A relationship of mutual dislike between two people.
myelination  The process by which glial cells encase neurons in sheaths of the fatty substance myelin.
naming explosion  The rapid increase in vocabulary that the child typically shows at about the age of 1.5 years.
narrative form  A temporally sequenced account that conveys meaning about an event.
national survey  A method of sampling in which a very large, nationally representative group of people are selected for a particular study.
natural experiment  An experiment in which researchers measure the results of events that occur naturally in the real world.
needs-oriented reasoning  Reasoning in which children express concern for others' needs even though their own needs may conflict with those needs.
negative gossip  Sharing some negative information about another child with a peer.
neglected children  Children who are often socially isolated and, although they are not necessarily disliked by others, have few friends.
neonate  A newborn baby.
neo-Piagetian theories  Theories of cognitive development that reinterpret Piaget's concepts from an information-processing perspective.
neural migration  The movement of neurons within the brain that ensures that all brain areas have a sufficient number of neural connections.
neuron  A cell in the body's nervous system, consisting of a cell body, a long projection called an axon, and several shorter projections called dendrites; neurons send and receive neural impulses, or messages, throughout the brain and nervous system.
neuron proliferation  The rapid formation of neurons in the developing organism's brain.
neuronal death  The death of some neurons that surround newly formed synaptic connections among other neurons; also called programmed cell death.
niche picking  Seeking out or creating environments compatible with one's genetically based predispositions.
nonaggressive rejected children  Rejected children who tend to be anxious, withdrawn, and socially unskilled.
nonshared environment  A set of conditions or activities experienced by one child in a family but not shared with another child in the same family.
nucleotide  A compound containing a nitrogen base, a simple sugar, and a phosphate group.
obesity  A condition in which a person's weight is 30% or more in excess of the average weight for his or her height and frame.
object permanence  The notion that entities external to the child, such as objects and people, continue to exist independent of the child's seeing or interacting with them.
observer bias  The tendency of observers to be influenced in their judgments by their knowledge of the hypotheses guiding the research.
obsessive self-stimulatory behavior  Behavior common in children with autism in which they engage in repetitive actions that seemingly have no purpose.
operant behavior therapy  A form of behavior therapy in which behavior is carefully monitored and consistently rewarded with such things as food.
operant conditioning  A type of learning that depends on the consequences of behavior; rewards increase the likelihood that a behavior will recur, whereas punishment decreases that likelihood.
operations  Schemas based on internal mental activities.
organization  Combining simple mental structures into more complex systems, a term used by Piaget or also refers to a memory strategy that involves putting together in some organized form the information to be remembered; usually entails categorization and hierarchical relations.
organization  Combining simple mental structures into more complex systems, a term used by Piaget or also refers to a memory strategy that involves putting together in some organized form the information to be remembered; usually entails categorization and hierarchical relations.
overcontrolled disorders  A group of psychological disturbances in which a child appears overly controlled, withdrawing from others, lacking spontaneity, and generally appearing to be not a happy child.
overextension  The use, by a young child, of a single word to cover many different things.
overregularization  The application of a principle of regular change to a word that changes irregularly.
ovum  The female germ cell, or egg.
passive genetic-environmental interaction  The interactive environment created by parents with particular genetic predispositions who encourage the expression of these tendencies in their children.
patterned speech  A form of pseudospeech in which the child utters strings of phonemes that sound very much like real speech but are not.
peer victimization  Ill treatment of one child by another (or by others) that can range from teasing to bullying to serious physical harm; typically, victimizing is a continuing behavior that persists over time.
peer-group network  The cluster of peer acquaintances who are familiar with and interact with one another at different times for common play or task-oriented purposes.
perception  The interpretation of sensations to make them meaningful.
permissive parenting  Parenting that is lax and in which parents exercise inconsistent discipline and encourage children to express their impulses freely.
pervasive developmental disorders  Childhood disorders characterized by gross deficits in many areas of cognitive, emotional, and social development that are linked with severe and pervasive impairment of social interaction and communication skills.
phenotype  The visible expression of the person's particular physical and behavioral characteristics; created by the interaction of a person's genotype, or genetic makeup, with the environment.
phenylketonuria (PKU)  A disease caused by a recessive allele that fails to produce an enzyme necessary to metabolize the protein phenylalanine; if untreated immediately at birth, damages the nervous system and causes mental retardation.
phoneme  The basic unit of a language's phonetic system; phonemes are the smallest sound units that affect meaning.
phonological awareness  The understanding of the sounds of a language and of the properties, such as the number of sounds in a word, related to these sounds.
phonology  The system of sounds that a language uses.
Piagetian theory  A theory of cognitive development that sees the child as actively seeking new information and uses two basic principles of biology and biological change: organization and adaptation.
pituitary gland  A so-called master gland, located at the base of the brain, that triggers the secretion of hormones by all other hormone-secreting, or endocrine, glands.
placenta  A fleshy, disk like structure formed by cells from the lining of the uterus and from the zygote that, together with the umbilical cord, serves to protect and sustain the life of the growing organism.
planning  The deliberate organization of a sequence of actions oriented toward achieving a goal.
plasticity  The capacity of the brain, particularly in its developmental stages, to respond and adapt to input from the external environment.
popular children  Children who are liked by many peers and disliked by very few.
postconventional level  Kohlberg's third level of moral development, in which the child's judgments are rational and his conduct is controlled by an internalized ethical code that is relatively independent of the approval or disapproval of others.
pragmatics  A set of rules that specify appropriate language for particular social contexts.
preconceptual substage  The first substage of Piaget's preoperational period, during which the child's thought is characterized by the emergence of symbolic function, the rapid development of language, animistic thinking, and egocentricity.
preconventional level  Kohlberg's first level of moral development, in which he sees the child's behavior as based on the desire to avoid punishment and gain rewards.
premoral stage  Piaget's first stage of moral development, in which the child shows little concern for rules.
preoperational stage  In this stage, the ability to use symbols facilitates the learning of language; this stage is also marked by semilogical reasoning, egocentricity—in which the child sees the world from her own point of view—and intuitive behavior, in which the child can solve problems using mental operations but cannot explain how she did so.
preterm  A term describing a premature baby who is born before its due date and whose weight, although less than that of a full-term infant, may be appropriate to its gestational age.
primary circular reactions  Behaviors focused on the infant's own body that the infant repeats and modifies because they are pleasurable and satisfying.
proactive aggression  The use of force to dominate another person or to bully or threaten others.
problem solving  The identification of a goal and of steps to reach that goal.
production deficiency  Inability to generate and use a known memory strategies spontaneously.
productive language  The production of speech.
progesterone  A hormone that, in females, helps regulate the menstrual cycle and prepares the uterus to receive and nurture a fertilized egg.
propositional reasoning  Logical thinking that involves evaluating a statement or series of statements based on the information in the statement alone.
prosocial behavior  Behavior designed to help or benefit other people.
prosocial reasoning  Thinking and making judgments about prosocial issues.
protodeclarative  A gesture that an infant uses to make some sort of statement about an object.
protoimperative  A gesture that either an infant or a young child may use to get someone to do something she or he wants.
proximal-distal  The pattern of human physical growth wherein development starts in central areas, such as the internal organs, and proceeds to more distant areas, such as arms and legs.
psychoanalytic theory of attachment  Freud's theory that babies become attached first to the mother's breast and then to the mother herself as a source of oral gratification.
psychodynamic theory  In this view of development, which is derived from Freudian theory, development occurs in discrete stages and is determined largely by biologically based drives shaped by encounters with the environment and through the interaction of the personality's three components—the id, ego, and superego.
psychometrician  A psychologist who specializes in the construction and use of tests designed to measure various psychological constructs such as intelligence and various personality characteristics.
psychosocial theory  Erikson's theory of development that sees children developing through a series of stages largely through accomplishing tasks that involve them in interaction with their social environment.
psychostimulant medications  Drugs, such as amphetamines and caffeine, that increase alertness and attention as well as psychomotor activity.
puberty  The onset of sexual maturity.
random assignment  The technique by which researchers assign individuals randomly to either an experimental or control group.
range of reaction  The notion that the human being's genetic makeup establishes a range of possible developmental outcomes, within which environmental forces largely determine how the person actually develops.
reactive aggression  Aggressive behavior as a response to attack, threat, or frustration.
recast  A technique adults use in speaking to young children in which they render a child's incomplete sentence in a more complex grammatical form.
receptive language  Under standing the speech of others.
recessive  The weaker of two alleles in a heterozygous combination.
reciprocal instruction  A tutoring approach based on the ideas of the zone of proximal development and scaffolding.
recovery  The ability to recognize a new stimulus as novel and to direct attention to it in preference to a familiar stimulus.
reflex  A human's involuntary response to external stimulation.
reflex smile  A smile seen in the newborn that is usually spontaneous and appears to depend on some internal stimulus rather than on something external such as another person's behavior.
rehearsal  A memory strategy in which one repeats a number of times the information one wants to remember, either mentally or orally.
rejected children  Children who are disliked by many peers and liked by very few.
relational aggression  Damaging or destroying interpersonal relationships by such means as excluding another or gossiping about or soiling another's reputation.
relational victimization  The attempt by a peer to damage or control another child's relationships with others.
relationship  A continuing succession of interactions between two people that are affected by their shared past interactions and that also affect their future interactions.
reliability  The degree to which a test yields consistent results over time or successive administrations.
REM sleep  REM, or rapid eye movement, sleep is characterized by rapid, jerky movements of the eyes and, in adults, is often associated with dreaming.
representativeness  The degree to which a sample actually possesses the characteristics of the larger population it represents.
reputational bias  Children's tendency to interpret peers' behavior on the basis of past encounters with and feelings about them.
respiratory distress syndrome  A condition of the newborn marked by labored breathing and a bluish discoloration of the skin or mucous membranes; can result in infant death.
reversibility  The understanding that the steps of a procedure or operation can be reversed and that the original state of the object or event can be obtained.
Rh factor incompatibility  A condition in which an infant's Rh negative blood opposes its mother's Rh-positive blood and threatens fetuses in later births, when the mother's body has had time to produce antibodies that will attack fetal blood cells.
sample  A group of individuals who are representative of a larger population.
scaffolding  An instructional process in which the more knowledgeable partner adjusts the amount and type of support he offers to the child to fit with the child's learning needs over the course of the interaction.
schema (plural, schemas)  An organized unit of knowledge that the child uses to try to understand a situation; a schema forms the basis for organizing actions to respond to the environment.
scientific method  The use of measurable and replicable techniques in framing hypotheses and collecting and analyzing data to test a theory's usefulness.
script  A mental representation of an event or situation of daily life, including the order in which things are expected to happen and how one should behave in that event or situation.
secondary circular reactions  Behaviors focused on objects outside the infant's own body that the infant repeatedly engages in be cause they are pleasurable and satisfying.
secondary reinforcer  A person or other stimulus that acquires reinforcing properties by virtue of repeated association with a primary reinforcer.
secular trend  A shift in the normative pattern of a characteristic, such as height, that occurs over a historical time period, such as a decade or century.
secure attachment  A kind of attachment displayed by babies who are secure enough to explore novel environments, who are minimally disturbed by brief separations from their mothers, and who are quickly comforted by their mothers when they return.
secure base  According to Ainsworth, a caregiver to whom an infant has formed an attachment and whom the child uses as a base from which to explore and as a safe haven in times of stress.
selective attention  A strategy in which one focuses on some features of the environment and ignores others.
self-control phase  According to Kopp, the second phase in learning self-regulation, when the child becomes able to comply with caregiver expectations in the absence of the caregiver.
self-disclosure  The honest sharing of information of a very personal nature, often with a focus on problem solving; a central means by which adolescents develop friendships.
self-regulation  The child's ability to control behavior on her own without reminders from others.
self-regulation phase  According to Kopp, the third phase in learning self-regulation, when children become able to use strategies and plans to direct their own behavior and to delay gratification.
self-report  Information that people provide about themselves, either in a direct interview or in some written form, such as a questionnaire.
self-socialization  The child's spontaneous adoption of gender-appropriate behavior.
semantic memory  All the world knowledge and facts a person possesses.
semantics  The study of word meanings and word combinations, as in phrases, clauses, and sentences.
sensation  The detection of stimuli by the sensory receptors.
sensitive care  Consistent and responsive caregiving that begins by allowing an infant to play a role in determining when feeding will begin and end and at what pace it will proceed.
sensorimotor stage  Piaget's first stage of cognitive development, during which children change from basic reflexive behavior to the beginnings of symbolic thought and goal-directed behaviors.
sensory register  The mental processing unit that takes information from the environment and stores it in original form for brief periods of time.
separation protest  An infant's distress reaction to being separated from his or her mother, which typically peaks at about 15 months of age.
sequential method  A research method that combines features of both the cross-sectional and the longitudinal methods.
sex chromosomes  In both males and females, the 23rdpair of chromosomes, which determine the individual's sex and are responsible for sex-related characteristics; in females, this pair normally comprises two X chromosomes, in males an X and a Y chromosome.
sexual abuse  Inappropriate sexual activity between an adult and a child for the perpetrator's pleasure or benefit; the abuse may be direct (sexual contact of any type) or indirect (exposing a child to pornography or to the live exhibition of body parts or sexual acts).
sexual preferences  The preference for same or opposite gender sexual partners.
shape constancy  The ability to perceive an object's shape as constant despite changes in its orientation and the angle from which one views it.
shared environment  A set of conditions or experiences shared by children raised in the same family; a parameter commonly examined in studies of individual differences.
short-term, or working, memory  The mental processing unit in which information is stored temporarily; the "work space" of the mind, where a decision is made to discard information, work on it, or transfer it to permanent storage in longterm memory.
sickle-cell anemia  A disorder, caused by a recessive gene, in which the red blood cells become distorted when low in oxygen, causing fatigue, shortness of breath, and severe pain and posing a threat to life from blockage of crucial blood vessels.
size constancy  The tendency to perceive an object as constant in size regardless of changes in its distance from the viewer and in the image it casts on the retinas of the eyes.
small for date  A term describing a premature baby who may be born close to its due date but who weighs significantly less than would be appropriate to its gestational age.
social comparison  The process by which we evaluate our own abilities, values, and other qualities by comparing ourselves with others, usually our peers.
social referencing  The process of "reading" emotional cues in others to help determine how to act in an uncertain situation.
social-convention rules  Socially based rules about everyday conduct.
socialization  The process by which parents and others ensure that a child's standards of behavior, attitudes, skills, and motives conform closely to those deemed appropriate to her role in society.
socially unskilled  Being unskilled at solving interpersonal problems.
sociocultural theory  A theory of development, proposed by Lev Vygotsky, that sees development as emerging from children's interactions with more skilled people and the institutions and tools provided by their culture.
sociometric technique  A procedure for determining children's status within their peer group; each child in the group either nominates others whom she likes best and least or rates each child in the group for desirability as a companion.
specific factors (s)  Factors unique to particular cognitive tasks.
speech acts  One- or two-word utterances that clearly refer to situations or to sequences of events.
sperm  The male germ cell.
spermarche  In males, the first ejaculation of semen-containing ejaculate.
stages of development  Comprehensive, qualitative changes over time in the way a child thinks.
standardization  The process by which test constructors ensure that testing procedures, instructions, and scoring are identical, or as nearly so as possible, on every testing occasion.
Stanford-Binet Test  The modern version of the first major intelligence test; emphasizes verbal and mathematical skills.
status offense  Illegal behavior in an underage offender.
stereoscopic vision  The sense of a third spatial dimension, that of depth, produced by the brain's fusion of the separate images contributed by each eye, each of which reflects the stimulus from a slightly different angle.
stereotype threat  Being at risk of confirming a negative stereotype about the group to which one belongs.
Strange Situation  A testing scenario in which mother and child are separated and reunited several times; enables investigators to assess the nature and quality of a mother-infant attachment relationship.
stranger distress  A fear of strangers that typically emerges in infants around the age of 9 months.
strategies  Conscious cognitive or behavioral activities used to enhance mental performance.
structural-organismic perspectives  Theoretical approaches that describe psychological structures and processes that undergo qualitative or stage like changes over the course of development.
structured observation  A form of observation in which researchers structure a situation so that behaviors they wish to study are more likely to occur.
substance abuse  The excessive use of legal or illegal drugs in such a way as to interfere seriously with one or more important areas of functioning in life: work, intimacy with another, or general interpersonal and social relationships.
successful intelligence  Ability to fit into, change, and choose environments that best fulfill one's own needs and desires as well as the demands of one's society and culture. Includes analytical, creative, and practical abilities.
sudden infant death syndrome (SIDS)  The sudden, unexplained death of an infant while sleeping; also called crib death.
superego  In Freudian theory, the personality component that is the repository of the child's internalization of parental or societal values, morals, and roles.
symbolic function  The ability to use symbols, such as images, words, and gestures, to represent objects and events in the world.
symbolic thought  The use of mental images and concepts to represent people, objects, and events.
synapse  A specialized site of intercellular communication where information is exchanged between nerve cells, usually by means of a chemical neurotransmitter.
synaptic pruning  The brain's disposal of the axons and dendrites of a neuron that is not often stimulated.
synaptogenesis  The forming of synapses.
syntax  The part of grammar that prescribes how words may combine into phrases, clauses, and sentences.
syphilis  A sexually transmitted bacterial disease that can usually be treated with antibiotics, but if untreated in the pregnant woman, can cause miscarriage or blindness, mental retardation, or other physical abnormalities in her baby.
tacit knowledge  Implicit knowledge that is shared by many people and that guides behavior.
telegraphic speech  Two-word utterances that include only the words essential to convey the speaker's intent.
temperament  The individual's typical mode of response to the environment, including such things as activity level, emotional intensity, and attention span; used particularly to describe infants' and children's behavior.
teratogen  An environmental agent, such as a drug, medication, dietary imbalance, or polluting substance, that may cause developmental deviations in a growing human organism; most threatening in the embryonic stage but capable of causing abnormalities in the fetal stage as well.
tertiary circular reactions  Behaviors in which infants experiment with the properties of external objects and try to learn how objects respond to various actions.
test norms  Values, or sets of values, that describe the typical test performance of a specific group of people.
testosterone  A hormone that, in males, is responsible for the development of primary and secondary sex characteristics and is essential for the production of sperm.
thalidomide  A drug once prescribed to relieve morning sickness in pregnant women but discontinued when found to cause serious fetal malformations. Current controversy surrounds its possible use in treating symptoms of such diseases as AIDS, cancer, and Hansen's disease (leprosy).
theory of mind  Understanding of the mind and how it works.
theory of multiple intelligences  Gardner's multifactorial theory that proposes eight distinct types of intelligence.
time-out  Removing children from a situation or context in which they are acting inappropriately until they are able and ready to act appropriately.
toxoplasmosis  A parasitic disease acquired by eating undercooked meat or by contact with feces, as in handling cat litter.
traditional nuclear family  The traditional family form, composed of two parents and one or more children, in which the father is the breadwinner and the mother the homemaker.
transitive inference  The mental arrangement of things along a quantitative dimension.
triarchic theory of intelligence  A theory that proposes three major components of intelligence: information-processing skills, experience with a task, and ability to adapt to the demands of a context.
Turner syndrome  A form of chromosome abnormality found in females in which secondary sex characteristics develop only if female hormones are administered, and abnormal formation of internal reproductive organs causes permanent sterility.
two-generation program  A program of early cognitive intervention that extends help to parents as well as to their children.
ultrasound  A technique that uses sound waves to visualize deep body structures; commonly used to reveal the size and structure of a developing fetus. Also called ultrasonography.
umbilical cord  A tube that contains blood vessels connecting the growing organism and its mother by way of the placenta; it carries oxygen and nutrients to the growing infant and removes carbon dioxide and waste products.
undercontrolled disorders  A group of psychological disturbances in which a child appears to lack self-control and to act-out in a variety of ways, through such behaviors as noncompliance, disobedience, and aggression.
underextension  The use, by a young child, of a single word in a restricted and individualistic way.
uninvolved parenting  Parenting that is indifferent and neglectful and in which parents focus on their own needs rather than their children's needs.
utilization deficiency  Inability to use a known memory strategy or to benefit from the use of such a memory strategy.
validity  The extent to which a test actually measures what it claims to measure.
visual acuity  Sharpness of vision; the clarity with which fine details can be detected.
visual cliff  An apparatus that tests an infant's depth perception by using patterned materials and an elevated, clear glass platform to make it appear that one side of the platform is several feet lower than the other.
visual preference method  A method of studying infants' abilities to distinguish one stimulus from another in which researchers measure and compare the amounts of time babies spend attending to different stimuli.
Wechsler Intelligence Scales  Three intelligence tests for preschool children, school-age children, and adults that yield separate scores for verbal and performance IQ as well as a combined IQ score.
world knowledge  What a child has learned from experience and knows about the world in general.
X-linked genes  Genes that are carried on the X chromosome and that, in males, may have no analogous genes on the Y chromosome.
zone of proximal development (ZPD)  The region of sensitivity for learning characterized by the difference between the developmental level of which a child is capable when working alone and the level she is capable of reaching with the aid of a more skilled partner.
zygote  The developing organism from the time sperm and egg unite to about the second week of gestation; the period of the zygote comprises the implantation of the fertilized egg in the wall of the uterus.





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