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

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

secular trend: Advances in growth and maturation that result from modern nutrition. For example, improved nutrition and medical care over the past 200 years has led to earlier puberty and taller average height.

anorexia nervosa: An eating disorder characterized by self-starvation and obsession with weight. Affected individuals become pathologically thin, depriving their vital organs of nutrition.

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.

estradiol: A sex hormone, considered to be the chief estrogen (female hormone). Females produce much more estradiol than males do.

formal operational thought: In Piaget’s theory, the fourth and final stage of cognitive development, characterized by systematic logical thinking and by understanding abstractions.

adrenal glands: Two glands, located above the kidneys, that produce hormones in response to signals from the pituitary.

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

body image: A person’s idea of how his or her body looks, especially related to size and shape.

pituitary: A gland in the brain that produces many hormones, including those that regulate growth and that signal the adrenal and sex glands to produce additional hormones.

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

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

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

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

puberty: The time at the end of childhood between the first onrush of growth hormones and full adult size. Puberty usually lasts three to five years. Many more years are required to achieve psychosocial maturity.

gonads: The sex glands (ovaries in females, testicles in males). The gonads produce hormones and gametes.

middle school: A school for children after elementary school and before high school, usually grades 6 through 8.

adolescent egocentrism: A characteristic of adolescent thinking that leads young people to believe in their own uniqueness, and to imagine that other people are also focused on them.

PISA (Programme for International Student Assessment): An international test taken by 15-year-olds in 50 nations to measure problem solving and cognition in daily life.

incremental theory of intelligence: The idea that intelligence can be increased by effort, with attention and practice, as in class participation and homework.

invincibility fable: The fantasy that a person cannot be harmed by anything that might defeat a normal mortal, such as unprotected sex, drug abuse, or high-speed driving.

intuitive thought: Thought that arises from an emotion or a hunch, a “gut feeling” influenced by past experiences and cultural assumptions.

imaginary audience: The other people who, in an adolescent’s egocentric belief, watch his or her appearance, ideas, and behavior.

personal fable: The belief that one’s own emotions, experiences, and destiny are unique, more wonderful or awful than anyone else’s.

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

cyberbullying: Bullying that occurs when one person attacks and harms another via technology (e.g., e-mails, text messages, or cell phones).

entity theory of intelligence: The idea that intellectual ability is innate, a fixed quantity present at birth. Those who hold this view underrate the role of effort on achievement.

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

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

secondary education: Education that follows primary education (elementary or grade school) and precedes tertiary education (college). It usually occurs from about age 11 to age 18, although there is some variation by school and by nation.

high-stakes test: An evaluation that determines something very important. For example, if a single test determines promotion or graduation, it is a high-stakes test.

dual-process model: The idea that two modes of thinking exist within the human brain, one for intuitive emotional responses and one for analytical reasoning.

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