palliative care 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.

parasuicide Any potentially lethal action against the self that does not result in death. (Also called attempted suicide or failed suicide.)

parent–infant bond The strong, loving connection that forms as parents hold, examine, and feed their newborn.

parental alliance 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.

parental monitoring Parents’ ongoing awareness of what their children are doing, where, and with whom.

Parkinson’s disease 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.

passive euthanasia A situation in which a seriously ill person is allowed to die naturally, through the cessation of medical intervention.

peer pressure 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.

percentile 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.

perception The mental processing of sensory information when the brain interprets a sensation.

permanency planning 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.

permissive parenting An approach to child rearing that is characterized by high nurturance and communication but little discipline, guidance, or control. (Also called indulgent parenting.)

perseveration The tendency to persevere in, or stick to, one thought or action for a long time.

personal fable An aspect of adolescent egocentrism characterized by an adolescent’s belief that his or her thoughts, feelings, and experiences are unique, more wonderful than, or more awful than anyone else’s.

phallic stage Freud’s third stage of development, when the penis becomes the focus of concern and pleasure.

phenotype The observable characteristics of a person, including appearance, personality, intelligence, and all other traits.

physician-assisted suicide 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.

pituitary A gland in the brain that responds to a signal from the hypothalamus by producing many hormones, including those that regulate growth and that control other glands, among them the adrenal and sex glands.

plaques Clumps of a protein called beta-amyloid, found in brain tissues surrounding the neurons; a normal brain contains some tau, but in brains of people with Alzheimer disease these plaques proliferate, especially in the hippocampus, a brain structure crucial for memory.

plasticity genes Genes and alleles that make people more susceptible to environmental influences, for better or worse. This is part of differential susceptibility.

polygamous family A family consisting of one man, several wives, and their children.

polygenic Referring to a trait that is influenced by many genes.

polypharmacy Refers to a situation in which elderly people have been prescribed several medications. The various side effects and interactions of those medications can result in dementia symptoms.

positivity effect 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.

postformal thought 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).

postpartum depression A new mother’s feelings of inadequacy and sadness in the days and weeks after giving birth.

practical intelligence The intellectual skills used in everyday problem solving. (Sometimes called tacit intelligence.)

pragmatics 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.

prefrontal cortex The area of the cortex at the very front of the brain that specializes in anticipation, planning, and impulse control.

preoperational intelligence 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 at this stage.

presbycusis A significant loss of hearing associated with senescence. Presbycusis usually is not apparent until after age 60.

preterm 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.

primary aging 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.

primary prevention 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.

private school A school funded by tuition charges, endowments, and often religious or other non-profit sponsors.

problem-focused coping A strategy to deal with stress by tackling a stressful situation directly.

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.

prosocial behavior Actions that are helpful and kind but are of no obvious benefit to oneself.

protein-calorie malnutrition 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.

proximal parenting Caregiving practices that involve being physically close to the baby, with frequent holding and touching.

pruning When applied to brain development, the process by which unused connections in the brain atrophy and die.

psychoanalytic theory A grand theory of human development that holds that irrational, unconscious drives and motives, often originating in childhood, underlie human behavior.

psychological control 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.

psychopathology Literally, an illness of the mind, or psyche. Various cultures and groups within cultures have different concepts of a specific psychopathology. A recent compendium of symptoms and disorders in the United States is in the DSM-5. Many other nations use an international set of categories, the ICD-10.

puberty 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.