Magnetic resonance imaging (MRI) A technique for brain imaging that scans the brain using magnetic fields and radio waves.
Major depressive disorder A mood disorder characterized by intense feelings of depression over an extended time, without the manic high phase of bipolar depression.
Manic episode A component of bipolar disorder characterized by periods of extreme elation, unbounded euphoria without sufficient reason, and grandiose thoughts or feelings about personal abilities.
Manifest content In Freudian dream analysis, the surface content of a dream, which is assumed to mask the dream's actual meaning.
Maturation The continuing influence of heredity throughout development; the age-related physical and behavioral changes characteristic of a species.
Mean The arithmetic average of a group of scores; the most commonly used measure of central tendency.
Measure of central tendency A statistic, such as a mean, median, or mode, that provides one score as representative of a set of observations.
Measures of variability A statistic, such as a range or standard deviation, that indicates how tightly the scores in a set of observations cluster together.
Median The score in a distribution above and below which lie 50 percent of the other scores; a measure of central tendency.
Meditation A form of consciousness alteration designed to enhance self-knowledge and well-being through reduced self-awareness.
Medulla The region of the brain stem that regulates breathing, waking, and heartbeat.
Memory The mental capacity to encode, store, and retrieve information.
Menarche The onset of menstruation.
Mental age In Binet's measure of intelligence, the age at which a child is performing intellectually, expressed in terms of the average "age at which normal children achieve a particular score.
Mental retardation Condition in which individuals have IQ scores 70 to 75 or below and also demonstrate limitations in the ability to bring adaptive skills to bear on life tasks.
Mental set The tendency to respond to a new problem in the manner used to respond to a previous problem.
Meta-analysis A statistical technique for evaluating hypotheses by providing a formal mechanism for detecting the general conclusions found in data from many different experiments.
Metamemory Implicit or explicit knowledge about memory abilities and effective memory strategies; cognition about memory.
Mnemonics Strategies or devices that use familiar information during the encoding of new information to enhance subsequent access to the information in memory.
Mode The score appearing most frequently in a set of observations; a measure of central tendency.
Mood disorder A mood disturbance such as severe depression or depression alternating with mania.
Morality A system of beliefs and values that ensures that individuals will keep their obligations to others in society and will behave in ways that do not interfere with the rights and interests of others.
Motivation The process of starting, directing, and maintaining physical and psychological activities; includes mechanisms involved in preferences for one activity over another and the vigor and persistence of responses.
Motor cortex The region of the cerebral cortex that controls the action of the body's voluntary muscles.
Motor neurons The neurons that carry messages away from the central nervous system toward the muscles and glands.