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

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

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

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

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

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

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

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

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

linked lives 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.

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

living will A document that indicates what medical intervention an individual prefers if he or she is not conscious when a decision is to be expressed. For example, some do not want to be given mechanical breathing.

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

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

low birthweight (LBW) A body weight at birth of less than 5½ pounds (2,500 grams).