Narcolepsy A sleep disorder characterized by an irresistible compulsion to sleep during the daytime.
Natural selection Darwin's theory that favorable adaptations to features of the environment allow some members of a species to reproduce more successfully than others.
Nature-nurture controversy The debate concerning the relative importance of heredity (nature) and learning or experience (nurture) in determining development and behavior.
Need for achievement (n Ach) An assumed basic human need to strive for achievement of goals that motivates a wide range of behavior and thinking.
Negative punishment A behavior is followed by the removal of an appetitive stimulus, decreasing the probability of that behavior.
Negative reinforcement A behavior is followed by the removal of an aversive stimulus, increasing the probability of that behavior.
Neuromodulator Any substance that modifies or modulates the activities of the postsynaptic neuron.
Neuron A cell in the nervous system specialized to receive, process, and/or transmit information to other cells.
Neuropathic pain Pain caused by abnormal functioning or overactivity of nerves; it results from injury or disease of nerves.
Neuroscience The scientific study of the brain and of the links between brain activity and behavior.
Neurotic disorders Mental disorders in which a person does not have signs of brain abnormalities and does not display grossly irrational thinking or violate basic norms but does experience subjective distress; a category dropped from DSM-III.
Neurotransmitters Chemical messengers released from neurons that cross the synapse from one neuron to another, stimulating the postsynaptic neuron.
Nociceptive pain Pain induced by a noxious external stimulus; specialized nerve endings in the skin send this pain message from the skin, through the spinal chord, into the brain.
Nonconscious Information not typically available to consciousness or memory.
Non-REM (NREM) sleep The period during which a sleeper does not show rapid eye movement; characterized by less dream activity than REM sleep.
Norm crystallization The convergence of the expectations of a group of individuals into a common perspective as they talk and carry out activities together.
Normal curve The symmetrical curve that represents the distribution of scores on many psychological attributes; allows researchers to make judgments of how unusual an observation or result is.
Normative influence Group effects that arise from individuals' desire to be liked, accepted, and approved of by others.
Normative investigations Research efforts designed to describe what is characteristic of a specific age or developmental stage.
Norms Standards based on measurements of a large group of people; used for comparing the scores of an individual with those of others within a well-defined group.