Dictionary of Terms


B Lymphocytes Cells that develop in bone marrow and release immunoglobulins to defend the body against antigens.

Backward Masking The ability of a stimulus to interfere with the perception of a stimulus presented just before it.

Balint’s Syndrome A syndrome caused by bilateral damage to the parieto-occipital region of the brain; includes difficulty in perceiving the location of objects and reaching for them under visual guidance.

Barbiturate A drug that causes sedation; one of several derivatives of barbituric acid.

Base-Rate Fallacy The failure to consider the likelihood that a person, place, or thing is a member of a particular category.

Basic Orientations Horney’s sets of personality characteristics that correspond to the strategies of moving toward others, moving against others, and moving away from others.

Basic Rest-Activity Cycle (BRAC) A 90-minute cycle (in humans) of waxing and waning alertness controlled by a biological clock in the pons; during sleep, it controls cycles of REM sleep and slow-wave sleep.

Basic-Level Concept A concept that makes important distinctions between different categories.

Basilar Membrane A membrane that divides the cochlea of the inner ear into two compartments. The receptive organ for audition resides here.

Behavior Analysis A branch of psychology that studies the effect of the environment on behavior; primarily, the effects of the consequences of behaviors on the behaviors themselves.

Behavior Genetics The branch of psychology that studies the role of genetics in behavior.

Behavior Modification Behavior therapy based on the principles of operant conditioning.

Behavioral Pharmacology The study of how drugs influence behavior; combines the principles of operant conditioning with the principles of drug action.

Behaviorism A movement in psychology that asserts that the only proper subject matter for scientific study in psychology is observable behavior.

Belief In a Just World The belief that people get what they deserve in life; a fundamental attribution error.

Benzodiazepine A class of drugs having anxiolytic ("tranquilizing") effects; examples are Librium and Valium.

Beta Activity The irregular, high-frequency activity of the electroencephalogram, usually indicating a state of alertness or arousal.

Binet-Simon Scale An intelligence test developed by Binet and Simon in 1905; the precursor of the Stanford-Binet Scale.

Biological Evolution Changes in the genetic or physical characteristics of a population or group of organisms over time.

Bipedalism The ability to move about the environment on two feet.

Bipolar Cell A neuron in the retina that receives information from photoreceptors and passes it on to the ganglion cells, from which axons proceed through the optic nerves to the brain.

Bipolar Disorder Alternating states of depression and mania separated by periods of relatively normal affect.

Bottom-Up Processing A perception based on successive analyses of the details of the stimuli that are present.

Brain Lesion Damage to a particular region of the brain.

Brain Stem The "stem" of the brain, including the medulla, pons, and midbrain.

Brightness A perceptual dimension of color, most closely related to the intensity or degree of radiant energy emitted by a visual stimulus.

Brightness Constancy The tendency to perceive objects as having constant brightness even when they are observed under varying levels of illumination.

Broca’s Aphasia Severe difficulty in articulating words, especially function words, caused by damage that includes Broca’s area, a region of the frontal cortex on the left (speech-dominant) side of the brain.

Bulimia Nervosa A loss of control over food intake characterized by gorging binges followed by self-induced vomiting or use of laxatives; also accompanied by feelings of guilt and depression.

Bystander Intervention The intervention of a person in a situation that appears to require his or her aid.

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