race A group of people who are regarded by themselves or by others as distinct from other groups on the basis of physical appearance, typically skin color. Social scientists think race is a misleading concept, as biological differences are not signified by outward appearance.

reaction time The time it takes to respond to a stimulus, either physically (with a reflexive movement such as an eyeblink) or cognitively (with a thought).

reactive aggression An impulsive retaliation for another person’s intentional or accidental action, verbal or physical.

reflex An unlearned, involuntary action or movement in response to a stimulus. A reflex occurs without conscious thought.

Reggio Emilia A program of early-childhood education that originated in the town of Reggio Emilia, Italy, and that encourages each child’s creativity in a carefully designed setting.

reinforcement The process by which a behavior is followed by something desired, such as food for a hungry animal or a welcoming smile for a lonely person.

relational aggression Nonphysical acts, such as insults or social rejection, aimed at harming the social connection between the victim and other people.

religious coping The process of turning to faith as a method of coping with stress.

REM (rapid eye movement) sleep A stage of sleep characterized by flickering eyes behind closed lids, dreaming, and rapid brain waves.

reminder session A perceptual experience that helps a person recollect an idea, a thing, or an experience.

replication The repetition of a study, using different participants.

reported maltreatment Harm or endangerment about which someone has notified the authorities.

resilience The capacity to adapt well to significant adversity and to overcome serious stress.

response to intervention (RTI) An educational strategy intended to help children who demonstrate below-average achievement in early grades, using special intervention.

role confusion A situation in which an adolescent does not seem to know or care what his or her identity is. (Sometimes called identity or role diffusion.)

rough-and-tumble play Play that mimics aggression through wrestling, chasing, or hitting, but in which there is no intent to harm.

rumination Repeatedly thinking and talking about past experiences; can contribute to depression.