Definition: in psychology, the attitudes, feelings, and behaviors that a given culture associates with a person's biological sex.

Definition: demonstrated by infants who display a clinging, anxious attachment; an avoidant attachment that resists closeness; or a disorganized attachment with no consistent behavior when separated from or reunited with caregivers.

Definition: our personal sense of being male, female, neither, or some combination of male and female, regardless of whether this matches our sex assigned at birth, and the social affiliation that may result from this.

Definition: the time of natural cessation of menstruation; also refers to the biological changes a woman experiences as her ability to reproduce declines.

Definition: the fear of unknown people that infants commonly display, beginning by about 8 months of age.

Definition: in Piaget's theory, the stage of cognitive development (normally beginning about age 12) at which people begin to think logically about abstract concepts.

Definition: research that follows and retests the same people over time.

Definition: in a language, the smallest unit that carries meaning; may be a word or a part of a word (such as a prefix).

Definition: the stage in speech development, beginning around 4 months, during which an infant spontaneously utters various sounds that are not all related to the household language.

Definition: a person's characteristic emotional reactivity and intensity.

Definition: any physical or verbal behavior intended to harm someone physically or emotionally.

Definition: a procedure for studying child-caregiver attachment; a child is placed in an unfamiliar environment while their caregiver leaves and then returns, and the child's reactions are observed.

Definition: a theory of the social environment's influence on human development, using five nested systems (microsystem, mesosystem, exosystem, macrosystem, chronosystem) ranging from direct to indirect influences.

Definition: all our thoughts and feelings about ourselves, in answer to the question, "who am I?"

Definition: in Piaget's theory, the stage of cognitive development (from about 7 to 11 years of age) at which children can perform the mental operations that enable them to think logically about concrete (actual, physical) events.

Definition: a brain area, usually in the left temporal lobe, involved in language comprehension and expression.

Definition: the theory that we learn social behavior by observing and imitating and by being rewarded or punished.

Definition: physical and cognitive function deficits in children caused by their birth mother's heavy drinking during pregnancy. In severe cases, symptoms include a small, out-of-proportion head and distinct facial features.

Definition: in Erikson's theory, the ability to form close, loving relationships; a primary developmental task in young adulthood.

Definition: the most important male sex hormone. Males and females have it, but the additional __________ in males stimulates the growth of the male sex organs during the fetal period, and the development of male sex characteristics during puberty.

Definition: the transition period from childhood to adulthood, extending from puberty to independence.

Definition: an emotional tie with others; shown in young children by their seeking closeness to caregivers and showing distress on separation.

Definition: decreasing responsiveness with repeated stimulation.

Definition: a frontal lobe brain area, usually in the left hemisphere, that helps control language expression by directing the muscle movements involved in speech.

Definition: the culturally preferred timing of social events such as marriage, parenthood, and retirement.

Definition: sex hormones that contribute to female sex characteristics and are secreted in greater amounts by females than by males.

Definition: biological growth processes that enable orderly changes in behavior, relatively uninfluenced by experience.

Definition: an optimal period early in the life of an organism when exposure to certain stimuli or experiences produces normal development.

Definition: in Piaget's theory, the preoperational child's difficulty taking another's point of view.

Definition: impairment of language, usually caused by left hemisphere damage either to Broca's area (impairing speaking) or to Wernicke's area (impairing understanding).

Definition: the first menstrual period.

Definition: the period of sexual maturation, during which a person usually becomes capable of reproducing.

Definition: agents, such as chemicals and viruses, that can reach the embryo or fetus during prenatal development and cause harm.

Definition: in psychology, the biologically influenced characteristics by which people define male, female, and intersex.

Definition: according to Erik Erikson, a sense that the world is predictable; said to be formed during infancy by appropriate experiences with responsive caregivers.

Definition: a period from about age 18 to the mid-twenties, when many persons in prosperous western cultures are no longer adolescents but have not yet achieved full independence as adults.

Definition: humans' innate predisposition to understand the principles and rules that govern grammar in all languages.

Definition: the body structures (ovaries, testes, and external genitalia) that make sexual reproduction possible.

Definition: the first ejaculation.

Definition: research that compares people of different ages at the same point in time.

Definition: the early speech stage in which a child speaks like a telegram —"go car"— using mostly nouns and verbs.

Definition: a person's sexual and emotional attraction to another person and the behavior and/or social affiliation that may result from this attraction.

Definition: a set of expectations (norms) about a social position, defining how those in the position ought to behave.

Definition: nonreproductive sexual traits, such as female breasts and hips, male voice quality, and body hair.

Definition: our agreed-upon systems of spoken, written, or signed words, and the ways we combine them to communicate meaning.

Definition: a set of expected behaviors, attitudes, and traits for men and for women.

Definition: the awareness that things continue to exist even when not perceived.

Definition: in developmental psychology, adapting our current schemas (understandings) to incorporate new information.

Definition: our sense of self; according to Erikson, the adolescent's task is to solidify a sense of self by testing and integrating various roles.

Definition: interpreting our new experiences in terms of our existing schemas.

Definition: in Vygotsky's theory, a framework that offers children temporary support as they develop higher levels of thinking.

Definition: demonstrated by infants who comfortably explore environments in the presence of their caregiver, show only temporary distress when the caregiver leaves, and find comfort in the caregiver's return.

Definition: a branch of psychology that studies physical, cognitive, and social-emotional development throughout the lifespan.

Definition: an act of aggression (physical or verbal) intended to harm a person's relationship or social standing.

Definition: in Piaget's theory, the stage (from birth to nearly 2 years of age) at which infants know the world mostly in terms of their sensory impressions and motor activities.

Definition: possessing male and female biological sexual characteristics at birth.

Definition: in a language, the smallest distinctive sound unit.

Definition: the process by which certain animals form strong attachments during early life.

Definition: an umbrella term describing people whose gender identity or expression differs from that associated with their birth-assigned sex.

Definition: in Piaget's theory, the stage (from about 2 to 6 or 7 years of age) at which a child learns to use language but does not yet comprehend the mental operations of concrete logic.

Definition: the principle (which Piaget believed to be a part of concrete operational reasoning) that properties such as mass, volume, and number remain the same despite changes in the forms of objects.

Definition: in a language, a system of rules that enables us to communicate with and understand others. semantics is the language's set of rules for deriving meaning from sounds, and syntax is its set of rules for combining words into grammatically sensible sentences.

Definition: people's ideas about their own and others' mental states — about their feelings, perceptions, and thoughts, and the behaviors these might predict.

Definition: the stage in speech development, beginning about age 2, during which a child speaks mostly in two-word sentences.

Definition: the stage in speech development, from about age 1 to 2, during which a child speaks mostly in single words.