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Psychology, 6/e

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Absolute threshold The minimum amount of stimulus energy that can be detected 50 percent of the time.

Accessory structures Structures, such as the lens of the eye, that modify a stimulus.

Accommodation (in cognitive development) The process of modifying schemas as an infant tries out familiar schemas on objects that do not fit them.

Accommodation (in eye structure) The ability of the lens to change its shape and bend light rays so that objects are in focus.

Acetylcholine A neurotransmitter used by neurons in the peripheral and central nervous systems in the control of functions ranging from muscle contraction and heart rate to digestion and memory.

Achievement tests Measures of what a person has accomplished or learned in a particular area.

Acoustic encoding The mental representation of information as a sequence of sounds

Action potential An abrupt wave of electrochemical changes traveling down an axon when a neuron becomes depolarized.

Actor-observer bias The tendency to attribute other people's behavior to internal causes while attributing one's own behavior (especially errors and failures) to external causes.

Actualizing tendency According to Rogers, an innate inclination toward growth that motivates all people to seek the full realization of their highest potential.

Acuity Visual clarity, which is greatest in the fovea because of its large concentration of cones.

Adaptation The process through which responsiveness to an unchanging stimulus decreases over time.

Addiction Development of a physical need for a psychoactive drug.

Aggression An act that is intended to cause harm or damage to another person.

Agonists Drugs that mimic the effects of the neurotransmitter that normally binds to a neural receptor.

Agoraphobia A strong fear of being alone or away from the security of home.

Alcoholism A pattern of drinking that may lead to addiction and almost always causes severe social, physical, and other problems.

Algorithms Systematic procedures that cannot fail to produce a solution to a problem.

Altered state of consciousness A condition in which changes in mental processes are extensive enough that a person or others notice significant differences in psychological and behavioral functioning.

Altruism An unselfish concern for another's welfare.

Amplitude The difference between the peak and the baseline of a waveform.

Amygdala A structure in the forebrain that, among other things, associates features of stimuli from two sensory modalities, such as linking the shape and feel of objects in memory.

Anal stage The second of Freud's psychosexual stages, usually occurring during the second year of life, in which the focus of pleasure and conflict shifts from the mouth to the anus.

Analgesia The absence of the sensation of pain in the presence of a normally painful stimulus.

Anchoring heuristic A mental shortcut that involves basing judgments on existing information.

Androgens Masculine hormones that circulate in the bloodstream and regulate sexual motivation in both sexes; relatively more androgens circulate in men than in women.

Anorexia nervosa An eating disorder characterized by self-starvation and dramatic weight loss.

Antagonists Drugs that bind to a receptor and prevent the normal neurotransmitter from binding.

Anterograde amnesia A loss of memory for any event that occurs after a brain injury.

Antidepressants Drugs that relieve depression.

Antisocial personality disorder A disorder involving impulsive, selfish, unscrupulous, even criminal behavior.

Anxiety disorder A condition in which intense feelings of apprehension are long-standing or disruptive.

Anxiolytics Drugs that reduce feelings of anxiety.

Aptitude tests Tests designed to measure a person's capacity to learn certain things or perform certain tasks.

Arousal A general level of activation that is reflected in several physiological systems and can be measured by electrical activity in the brain, heart action, muscle tension, and the state of many other organ systems.

Arousal theories Theories of motivation stating that people are motivated to behave in ways that maintain what is, for them, an optimal level of arousal.

Arousal: cost-reward theory A theory attributing people's helping behavior to their efforts to reduce the unpleasant arousal they feel in the face of someone's need or suffering.

Artificial intelligence (AI) The field that studies how to program computers to imitate the products of human perception, understanding, and thought.

Assertiveness and social skills training Methods for teaching clients how to interact with others more comfortably and effectively.

Assimilation The process of trying out existing schemas on objects that fit those schemas.

Association cortex Those parts of the cerebral cortex that receive information from more than one sense or combine sensory and motor information to perform such complex cognitive tasks.

Attachment A deep and enduring relationship with the person with whom a baby has shared many experiences.

Attention The process of directing and focusing certain psychological resources to enhance information processing, performance, and mental experience.

Attitude A predisposition toward a particular cognitive, emotional, or behavioral reaction to objects.

Attribution The process of explaining the causes of people's behavior, including one's own.

Auditory nerve The bundle of axons that carries stimuli from the hair cells of the cochlea to the brain.

Auditory scene analysis The perceptual process through which sounds are mentally represented and interpreted.

Authoritarian parents Firm, punitive, and unsympathetic parents who value obedience from the child and authority for themselves.

Authoritative parents Parents who reason with the child, encourage give and take, are firm but understanding.

Autoimmune disorders Physical problems caused when cells of the body's immune system attack normal body cells as if they were foreign invaders.

Autonomic nervous system (ANS) A subsystem of the peripheral nervous system that carries messages between the central nervous system and the heart, lungs, and other organs and glands.

Availability heuristic A mental shortcut through which judgments are based on information that is most easily brought to mind.

Aversive conditioning A method that uses classical conditioning to create a negative response to some stimulus.

Avoidance conditioning A type of learning in which an organism responds to a signal in a way that avoids exposure to an aversive stimulus.

Axons Fibers that carry signals from the cell body of a neuron out to where communication occurs with other neurons.






Babblings The first sounds infants make that resemble speech.

Basilar membrane The floor of the fluid-filled duct that runs through the cochlea.

Behavior modification Treatments that use operant conditioning methods to change behavior.

Behavior therapy Treatments that use classical conditioning principles to change behavior.

Behavioral approach An approach to psychology emphasizing that human behavior is determined mainly by what a person has learned, especially from rewards and punishments the person has experienced in interacting with other people. Also called behavioral model.

Behavioral approach system (BAS) Brain regions that affect people's sensitivity to rewards.

Behavioral genetics The study of the effect of genes on behavior.

Behavioral inhibition system (BIS) Brain regions that affect people's sensitivity to punishment

Biased sample A group of research participants selected from a population each of whose members did not have an equal chance of being chosen.

Big-five model Five trait dimensions found in many factor-analytic studies of personality: neuroticism, extraversion, openness to experience, agreeableness, and conscientiousness.

Binocular disparity A depth cue based on the difference between two retinal images of the world.

Biological approach An approach to psychology in which behavior and behavior disorders are seen as the result of physical processes, especially those relating to the brain and to hormones and other chemicals. Also called biological model.

Biological psychologists Psychologists who analyze the biological factors influencing behavior and mental processes. Also called physiological psychologists.

Biological psychology The psychological specialty that researches the physical and chemical changes that cause and occur in response to behavior and mental processes.

Biopsychosocial model A view of mental disorders as caused by a combination of interacting biological, psychological, and sociocultural factors.

Bipolar I disorder A condition in which a person alternates between deep depression and mania.

Bisexual People who engage in sexual activities with partners of both sexes

Blind spot The light insensitive point at which axons from all of the ganglion cells converge and exit the eyeball.

Blood-brain barrier A feature of blood vessels supplying the brain that allows only certain substances to leave the blood and interact with brain tissue.

Bottom-up processing Aspects of recognition that depend first on the information about the stimulus that comes up to the brain from the sensory receptors.

Brightness The overall intensity of all of the wavelengths that make up light.

Brown-Peterson procedure A method for determining how long unrehearsed information remains in short-term memory.

Bulimia nervosa An eating disorder that involves eating massive quantities of food and then eliminating the food by self-induced vomiting or the use of strong laxatives.

Burnout A gradually intensifying pattern of physical, psychological, and behavioral dysfunctions in response to a continuous flow of stressors.






Case study A research method involving the intensive examination of some phenomenon in a particular individual, group, or situation. It is especially useful for studying complex or relatively rare phenomena.

Central nervous system (CNS) The part of the nervous system encased in bone, including the brain and the spinal cord.

Cerebellum The part of the hindbrain whose function is to control finely coordinated movements and to store learned associations that involve movement.

Cerebral cortex The outer surface of the brain.

Cerebral hemispheres The left and right halves of the rounded, outermost part of the brain.

Chromosomes Long, thin structures in every biological cell that contain genetic information.

Chunks Stimuli that are perceived as one unit or a meaningful grouping of information.

Circadian rhythm A cycle, such as waking and sleeping, that repeats about once a day.

Classical conditioning A procedure in which a neutral stimulus is paired with a stimulus that elicits a reflex or other response until the neutral stimulus alone comes to elicit a similar response.

Client-centered therapy (person-centered therapy) A therapy that allows the client to decide what to talk about, without direction, judgment, or interpretation from the therapist.

Clinical psychologists Psychologists who seek to assess, understand, and correct abnormal behavior.

Cochlea A fluid-filled spiral structure in the ear in which auditory transduction occurs.

Coding Translating the physical properties of a stimulus into a pattern of neural activity that specifically identifies those properties.

Cognitive ability The capacity to reason, remember, understand, solve problems, and make decisions.

Cognitive approach A way of looking at human behavior that emphasizes research on how the brain takes in information, creates perceptions, forms and retrieves memories, processes information, and generates integrated patterns of action.

Cognitive dissonance theory A theory asserting that attitude change is driven by efforts to reduce tension caused by inconsistencies between attitudes and behaviors.

Cognitive map A mental representation of familiar parts of the environment.

Cognitive psychologists Psychologists who study the mental processes underlying judgment, decision making, problem solving, imagining, and other aspects of human thought or cognition.

Cognitive psychology The study of the mental processes by which information from the environment is modified, made meaningful, stored, retrieved, used, and communicated to others.

Cognitive therapy A treatment in which the therapist helps clients to notice and change negative thoughts associated with anxiety and depression.

Cognitive-behavior therapy Treatment methods that help clients change the way they think as well as the way they behave.

Community psychologists Psychologists who work to obtain psychological services for people in need of help and to prevent psychological disorders by changing social systems.

Community psychology A movement to minimize or prevent psychological disorders through changes in social systems and through community mental health programs.

Competition Behavior in which individuals try to attain a goal for themselves while denying that goal to others.

Compliance Adjusting one's behavior because of an explicit or implicit request.

Computational approach An approach to perception that focuses on how computations by the nervous system translate raw sensory stimulation into an experience of reality.

Concepts Categories of objects, events, or ideas that have common properties.

Concrete operations According to Piaget, the third stage of cognitive development, during which children's thinking is no longer dominated by visual appearances

Conditioned response (CR) In classical conditioning, the response that the conditioned stimulus elicits.

Conditioned stimulus (CS) In classical conditioning, the originally neutral stimulus that, through pairing with the unconditioned stimulus, comes to elicit a conditioned response.

Conditions of worth According to Rogers, the feelings an individual experiences when the person, instead of behavior, is evaluated.

Cones Photoreceptors in the retina whose color-sensitive photopigment helps us to distinguish colors.

Confirmation bias The tendency to pay more attention to evidence in support of one's hypothesis than to evidence that refutes that hypothesis.

Conflict The result of a person or group believing that another person or group stands in the way of achieving a valued goal.

Conformity Changing one's behavior or beliefs to match those of other group members, generally as a result of real or imagined, though unspoken, group pressure.

Confounding variable In an experiment, any factor that affects the dependent variable along with or instead of the independent variable. Confounding variables include random variables, the placebo effect, and experimenter bias.

Congruence A consistency between the way therapists feel and the way they act toward clients.

Conscious level The level at which mental activities that people are normally aware of occur.

Consciousness Awareness of external stimuli and one's own mental activity.

Conservation The ability to recognize that the important properties of a substance remain constant despite changes in shape, length, or position.

Constructivist approach A view of perception taken by those who argue that the perceptual system uses fragments of sensory information to construct an image of reality.

Contact hypothesis The idea that stereotypes and prejudice toward a group will diminish as contact with the group increases.

Context-dependent Referring to memories that can be helped or hindered by similarities or differences between the context in which they are learned and that in which they are recalled.

Continuous reinforcement schedule In operant conditioning, a pattern in which a reinforcer is delivered every time a particular response occurs.

Control group In an experiment, the group that receives no treatment or provides some other base line against which to compare the performance or response of the experimental group.

Conventional moral reasoning Reasoning that reflects the belief that morality consists of following rules and conventions.

Convergence A depth cue involving the rotation of the eyes to project the image of an object on each retina.

Convergent thinking The ability to apply the rules of logic and knowledge to narrow down the number of possible solutions to a problem or perform some other complex cognitive task.

Conversion disorder A somatoform disorder in which a person displays blindness, deafness, or other symptoms of sensory or motor failure without a physical cause.

Cooperation Any type of behavior in which several people work together to attain a goal.

Cornea The curved, transparent, protective layer through which light rays enter the eye.

Corpus callosum A massive bundle of fibers that connects the right and left cerebral hemispheres and allows them to communicate with each other.

Correlation In research, the degree to which one variable is related to another; the strength and direction of the relationship is measured by a correlation coefficient.

Correlation coefficient A statistic, r, that summarizes the strength and direction of a relationship between two variables.

Counseling psychologists See clinical psychologists.

Couples therapy A form of therapy focusing on improving communication between partners.

Creativity The capacity to produce new, high quality ideas or products.

Critical period An interval during which certain kinds of growth must occur if development is to proceed normally.

Critical thinking The process of assessing claims and making judgments on the basis of well-supported evidence.

Crystallized intelligence The specific knowledge gained as a result of applying fluid intelligence.

Culture The accumulation of values, rules of behavior, forms of expression, religious beliefs, occupational choices, and the like, for a group of people who share a common language and environment.

Cyclothymic disorder A form of bipolar disorder characterized by comparatively mild mood swings.






Dark adaptation The increasing ability to see in the dark as time in the dark increases.

Data Numbers that represent research findings and provide the basis for research conclusions.

Decay The gradual disappearance of the mental representation of a stimulus.

Deep structure An abstract representation of the underlying meanings of a given sentence.

Defense mechanisms According to Freud, psychological responses that help protect a person from anxiety and guilt.

Deficiency orientation According to Maslow, a preoccupation with perceived needs for things a person does not have.

Deindividuation A psychological state occurring in group members that results in loss of individuality and a tendency to do things not normally done when alone.

Delusions False beliefs, such as those experienced by people suffering from schizophrenia or extreme depression.

Dendrites Neuron fibers that receive signals from the axons of other neurons and carry that signal to the cell body.

Deoxyribonucleic acid (DNA) The molecular structure of a gene that provides the genetic code.

Dependent variable In an experiment, the factor affected by the independent variable.

Depressants Psychoactive drugs that inhibit the functioning of the central nervous system.

Depth perception Perception of distance, one of the most important factors underlying size and shape constancy.

Descriptive statistics Numbers that summarize a set of research data.

Developmental psychologists Psychologists who seek to understand, describe, and explore how behavior and mental processes change over the course of a lifetime.

Developmental psychology The psychological specialty that documents the course of people's social, emotional, moral, and intellectual development over the life span and explores how development in different domains fits together, is affected by experience, and relates to other areas of psychology.

Diathesis-stress approach Viewing psychological disorders as arising when a predisposition for disorder combines with sufficient amounts of stress to trigger symptoms.

Difference threshold See just-noticeable difference.

Discrimination Differential treatment of various groups; the behavioral component of prejudice.

Discriminative stimuli Stimuli that signal whether reinforcement is available if a certain response is made.

Diseases of adaptation Illnesses that are caused or promoted by stressors.

Dissociation theory A theory defining hypnosis as a socially agreed-upon opportunity to display one's ability to let mental functions become dissociated.

Dissociative amnesia A disorder marked by a sudden loss of memory.

Dissociative disorders Rare conditions that involve sudden and usually temporary disruptions in a person's memory, consciousness, or identity.

Dissociative fugue A sudden loss of memory and the assumption of a new identity in a new locale.

Dissociative identity disorder A dissociative disorder in which a person reports having more than one identity.

Divergent thinking The ability to think along many alternative paths to generate many different solutions to a problem.

Dopamine A neurotransmitter used in the parts of the brain involved in regulating movement and experiencing pleasure.

Double-blind design A research design in which neither the experimenter nor the participants know who is in the experimental group and who is in the control group.

Dreams Story-like sequences of images, sensations, and perception occurring mainly during REM sleep.

Drive In drive reduction theory, a psychological state of arousal, created by an imbalance in homeostasis that prompts an organism to take action to restore the balance and, in the process, reduce the drive. (See also need, primary drives, and secondary drives.)

Drive reduction theory A theory of motivation stating that much motivation arises from constant imbalances in homeostasis. (See also drive and homeostasis.)

Dysthymic disorder A pattern of comparatively mild depression that lasts for at least two years.






Ecological approach An approach to perception maintaining that humans and other species are so well adapted to their natural environment that many aspects of the world are perceived automatically, without requiring higher-level analysis and inferences.

Educational psychologists Psychologists who study methods by which instructors teach and students learn, and who apply their results to improving such methods.

Ego According to Freud, the part of the personality that mediates conflicts between and among the demands of the id, the superego, and the real world.

Elaboration likelihood model A model suggesting that attitude change can be driven by evaluation of the content of a persuasive message (central route) or by irrelevant persuasion cues (peripheral route).

Elaborative rehearsal A memorization method that involves thinking about how new information relates to information already stored in long-term memory.

Electra complex A pattern described by Freud in which a young girl develops an attachment to her father and competes with her mother for his attention.

Electroconvulsive therapy (ECT) Brief electric shock administered to the brain, usually to reduce depression that does not respond to drug treatments.

Embryo The developing individual from the fourteenth day after fertilization until the end of the second month after conception.

Emotion A transitory positive or negative experience that is felt as happening to the self, is generated, in part, by the cognitive appraisal of a situation, and is accompanied by both learned and reflexive physical responses.

Empathy The therapistís effort or ability, emphasized in client-centered therapy, to appreciate another personís point of view and feelings.

Empathy-altruism theory A theory suggesting that people help others because of empathy with their needs.

Empirically supported therapies Treatments whose effects have been validated by controlled experimental research.

Encoding The process of putting information into a form that the memory system can accept and use.

Encoding specificity principle A principle stating that the ability of a cue to aid retrieval depends on the degree to which it taps into information that was encoded at the time of the original learning.

Endocrine system Cells that form organs called glands and communicate with one another by secreting chemicals called hormones.

Endorphin One of a class of neurotransmitters that bind to opiate receptors and moderate pain.

Engineering psychology A field in which psychologists study human factors in the use of equipment, and help designers create better versions of that equipment.

Environmental psychologists Psychologists who study the effects of the physical environment on behavior and mental processes.

Environmental psychology The study of the relationship between behavior and the physical environment.

Episodic memory Memory of an event that happened while one was present.

Escape conditioning A type of learning in which an organism learns to make a particular response in order to terminate an aversive stimulus.

Estrogens Feminine hormones that circulate in the bloodstream of both men and women; relatively more estrogens circulate in women. (See also progestins.)

Ethnic identity The part of a person's identity associated with the racial, religious, or cultural group to which the person belongs.

Evoked brain potential A small, temporary change in EEG voltage that is evoked by some stimulus.

Evolutionary approach An approach to psychology that emphasizes the inherited, adaptive aspects of behavior and mental processes.

Excitatory postsynaptic potential (EPSP) A postsynaptic potential that depolarizes the neuronal membrane, bringing the cell closer to threshold for firing an action potential.

Expected value The total benefit to be expected if a decision were to be repeated several times.

Experimental group In an experiment, the group that receives the experimental treatment; its performance or response is compared with that of one or more control groups.

Experimental psychologists Psychologists who conduct experiments aimed at understanding learning, memory, perception, and other basic behavioral and mental processes.

Experimenter bias A confounding variable that occurs when an experimenter unintentionally encourages participants to respond in a way that supports the hypothesis.

Experiments Situations in which the researcher manipulates one variable and then observes the effect of that manipulation on another variable, while holding all other variables constant.

Explicit memory The process in which people intentionally try to remember something.

Extinction The gradual disappearance of a conditioned response or operant behavior due to elimination either of the association between conditioned and unconditioned stimuli or of rewards for certain behaviors.






Family therapy Treatment of two or more individuals from the same family.

Feature detectors Cells in the cortex that respond to a specific feature of an object.

Fetal alcohol syndrome A pattern of physical and mental defects found in babies born to women who abused alcohol during pregnancy.

Fetus The developing individual from the third month after conception until birth.

Fiber tracts Axons that travel together in bundles. Also called pathways.

Fight-or-flight syndrome Physical reactions initiated by the sympathetic nervous system that prepare the body to fight or to run from a threatening situation.

Fixed-interval (FI) schedule In operant conditioning, a type of partial reinforcement schedule that provides reinforcement for the first response that occurs after some fixed time has passed since the last reward.

Fixed-ratio (FR) schedule In operant conditioning, a type of partial reinforcement schedule that provides reinforcement following a fixed number of responses.

Flooding A procedure for reducing anxiety that involves keeping a person in a feared, but harmless, situation.

Fluid intelligence The basic power of reasoning and problem solving.

Forebrain The most highly developed part of the brain; it is responsible for the most complex aspects of behavior and mental life.

Forensic psychologists Psychologists who create criminal profiles, assist in jury selection, evaluate defendants' mental competence to stand trial, and deal with other issues involving psychology and the law.

Formal concepts Concepts that can be clearly defined by a set of rules or properties.

Formal operational period According to Piaget, the fourth stage in cognitive development, usually beginning around age eleven.

Formal reasoning The process of following a set of rigorous procedures for reaching valid conclusions.

Fovea A region in the center of the retina where cones are highly concentrated.

Frequency The number of complete waveforms, or cycles, that pass by a given point in space every second.

Frequency matching The view that some sounds are coded in terms of the frequency of neural firing. Also called volley theory.

Frustration-aggression hypothesis A proposition that frustration always leads to some form of aggressive behavior.

Functional analysis Analyzing behavior by studying what responses occur under what conditions of operant reward and punishment.

Functional fixedness A tendency to think about familiar objects in familiar ways that may prevent using them in other ways.

Fundamental attribution error A bias toward overattributing the behavior of others to internal causes.






g A general intelligence factor that Charles Spearman postulated as accounting for positive correlations between people's scores on all sorts of mental ability tests.

GABA A neurotransmitter that inhibits the firing of neurons.

Ganglion cells Cells in the retina that generate action potentials.

Gate control theory A theory suggesting that a functional gate in the spinal cord can either let pain impulses travel upward to the brain or block their progress.

Gender roles Patterns of work, appearance, and behavior that a society associates with being male or female.

Gender schemas The generalizations children develop about what toys, activities, and occupations are "appropriate" for males versus females.

General adaptation syndrome (GAS) A three-stage pattern of responses triggered by the effort to adapt to any stressor.

Generalized anxiety disorder A condition that involves relatively mild but long-lasting anxiety that is not focused on any particular object or situation.

Generativity Adult concerns about producing or generating something.

Genes The biological instructions, inherited from both parents and located on the chromosomes, that provide the blueprint for physical development.

Genetics The biology of inheritance.

Genital stage The last of Freud's psychosexual stages, which begins during adolescence when sexual impulses appear at the conscious level.

Genotype The full set of genes, inherited from both parents, contained in twenty-three pairs of chromosomes.

Gestalt therapy An active treatment designed to help client's get in touch with genuine feelings and to disown foreign ones.

Glands Organs that secrete hormones into the bloodstream.

Glial cells Cells in the nervous system that hold neurons together and help them communicate with one another.

Glutamate An excitatory neurotransmitter that helps strengthen synaptic connections between neurons.

Grammar A set of rules for combining the words used in a given language.

Group therapy Psychotherapy involving several unrelated clients.

Groupthink A pattern of thinking in which group members fail to evaluate realistically the wisdom of various options and decisions.

Growth orientation According to Maslow, drawing satisfaction from what is available in life, rather than focusing on what is missing.

Gustation The sense that detects chemicals in solutions that come into contact with receptors inside the mouth; the sense of taste.






Habituation The process of adapting to stimuli that do not change.

Hallucinations A symptom of disorder in which people perceive voices or other stimuli when there are no stimuli present.

Hallucinogens Psychoactive drugs that alter consciousness by producing a temporary loss of contact with reality and changes in emotion, perception, and thought.

Health promotion The process of (a) altering or eliminating behaviors that pose risks to health and (b) encouraging healthy behavior patterns.

Health psychologists Psychologists who study the effects of behavior and mental processes on health and illness, and vice versa.

Health psychology A field in which psychologists conduct and apply research aimed at promoting human health and preventing illness.

Height in the visual field A depth cue whereby more distant objects are higher in the visual field than those nearby.

Helping behavior Any act that is intended to benefit another person.

Heterosexual Sexual motivation that is focused on members of the opposite sex.

Heuristics Time-saving mental shortcuts used in reasoning.

Hindbrain An extension of the spinal cord contained inside the skull where nuclei control blood pressure, heart rate, breathing, and other vital functions.

Hippocampus A structure in the forebrain associated with the formation of new memories.

Homeostasis The tendency for organisms to keep their physiological systems at a stable, steady level by constantly adjusting themselves in response to change.

Homosexual Sexual motivation that is focused on members of one's own sex.

Hormones Chemicals secreted by glands into the bloodstream, which carries them throughout the body.

Hue The essential color determined by the dominant wavelength of light.

Humanistic approach An approach to psychology that views behavior as controlled by the decisions that people make about their lives based on their perceptions of the world; a view in which personality is seen as developing through an actualizing tendency which unfolds in accordance with each person's unique perceptions of the world.

Hunger The general state of wanting to eat.

Hypnosis A phenomenon brought on by special induction techniques and characterized by varying degrees of responsiveness to suggestions for changes in experience and behavior.

Hypochondriasis A strong, unjustified fear of physical illness.

Hypothalamus A structure in the forebrain that regulates hunger, thirst, and sex drives.

Hypothesis In scientific research, a prediction stated as a specific, testable proposition about a phenomenon.






Id In Freud's psychodynamic theory, the unconscious portion of personality containing basic impulses and urges.

Identity crisis A phase during which an adolescent attempts to develop an integrated self image.

Images Mental representations of visual information.

Immediate memory span The maximum number of items a person can recall perfectly after one presentation of the items.

Immune system The body's system of defense against invading substances and microorganisms.

Impaired functioning Difficulty in fulfilling appropriate and expected family, social and work-related roles.

Implicit memory The unintentional influence of prior experiences.

Incentive theory A theory of motivation stating that behavior is directed toward attaining desirable stimuli and avoiding unwanted stimuli.

Independent variable The variable manipulated by the researcher in an experiment.

Industrial/organizational psychologists Psychologists who study ways to improve efficiency, productivity, and satisfaction among workers and the organizations that employ them.

Inferential statistics A set of procedures that provides a measure of how likely it is that research results came about by chance.

Informal reasoning The process of evaluating a conclusion, theory, or course of action on the basis of the believability of evidence.

Information-processing approach An approach to the study of intelligence that focuses on mental operations, such as attention and memory, that underlie intelligent behavior.

Information-processing model A model of memory in which information is seen as passing through sensory memory, short-term/working memory, and long-term memory.

Information-processing system Mechanisms for receiving, mentally representing, and manipulating information.

Inhibitory postsynaptic potential (IPSP) A postsynaptic potential that hyperpolarizes the neuronal membrane, making a cell less likely to fire an action potential.

Insight In problem solving, a sudden understanding about what is required to produce a desired effect.

Insomnia A sleep disorder in which a person feels tired during the day because of trouble falling asleep or staying asleep at night.

Instinct theory A view that explains human behavior as motivated by automatic, involuntary, and unlearned responses.

Instincts Innate, automatic dispositions toward responding in a particular way when confronted with a specific stimulus; instincts produce behavior over which an organism has no control.

Instrumental conditioning A process through which responses are learned that help produce some rewarding or desired effect.

Intelligence Those attributes that center around reasoning skills, knowledge of one's culture, and the ability to arrive at innovative solutions to problems.

Intelligence quotient An index of intelligence that reflects the degree to which a person's score on an intelligence test deviates from the average score of others in the same age group.

Interference The process through which either the storage or the retrieval of information is impaired by the presence of other information.

Interposition A depth cue whereby closer objects block one's view of things farther away.

IQ score See intelligence quotient.

IQ test A test designed to measure intelligence on an objective, standardized scale.

Iris The colorful part of the eye that constricts or relaxes to adjust the amount of light entering it.






Jet lag A syndrome of fatigue, irritability, inattention, and sleeping problems caused by air travel across several time zones.

JND See just-noticeable difference.

Just-noticeable difference (JND) The smallest detectable difference in stimulus energy.






Kinesthesia The sense that tells you where the parts of your body are with respect to one another.






Language Symbols and a set of rules for combining them that provides a vehicle for communication.

latency period The fourth of Freud's psychosexual stages, in which sexual impulses lie dormant.

Latent learning Learning that is not demonstrated at the time it occurs.

Lateral geniculate nucleus (LGN) A region of the thalamus in which axons from most of the ganglion cells in the retina end and form synapses.

Lateralized Referring to the tendency for one cerebral hemisphere to excel at a particular function or skill compared to the other hemisphere.

Law of effect A law stating that if a response made in the presence of a particular stimulus is followed by a reward, that same response is more likely to be made the next time the stimulus is encountered. Responses that are not rewarded are less likely to be performed again.

Learned helplessness A failure to try to exert control over the environment when an organism has, or believes that it has, no such control.

Learning The modification through experience of pre-existing behavior and understanding.

Lens The part of the eye behind the pupil that bends light rays, focusing them on the retina.

Levels-of-processing model A view stating that how well something is remembered depends on the degree to which incoming information is mentally processed.

Libido According to Freud, the psychic energy contained in the id.

Light intensity A physical dimension of light waves that refers to how much energy the light contains; it determines the brightness of light.

Light wavelength The distance between peaks in light waves; at a given intensity, different wavelengths produce sensations of different colors.

Limbic system A set of brain structures that play important roles in regulating emotion and memory.

Linear perspective A depth cue whereby objects closer to the point where two lines appear to converge are perceived as being at a greater distance.

Locus coeruleus A small nucleus in the reticular formation that contains about half of the cell bodies of neurons in the brain that use norepinephrine.

Long-term memory (LTM) A relatively long-lasting stage of memory whose capacity to store new information is believed to be unlimited.

Looming A motion cue involving a rapid expansion in the size of an image so that it fills the available space on the retina.

Loudness A psychological dimension of sound determined by the amplitude of a sound wave.

Lucid dreaming Awareness that a dream is a dream while it is happening.






Maintenance rehearsal Repeating information over and over to keep it active in short-term memory.

Major depressive disorder A condition in which a person feels sad and hopeless for weeks or months.

Mania An elated, very active emotional state.

Matching hypothesis The notion that people are most likely to form relationships with those who are similar to themselves in physical attractiveness.

Maturation Natural growth or change that unfolds in a fixed sequence relatively independent of the environment.

Mean A measure of central tendency that is the arithmetic average of the scores in a set of data; the sum of the values of all the scores divided by the total number of scores.

Median A measure of central tendency that is the halfway point in a set of data: Half the scores fall above the median, half fall below it.

Medulla An area in the hindbrain that controls blood pressure, heart rate, breathing, and other vital functions.

Menopause The process whereby a woman's reproductive capacity ceases.

Mental model A cluster of propositions representing our understanding of objects and processes that guides our interaction with those objects and processes.

Mental set The tendency for old patterns of problem solving to persist, even when they might not always be the most efficient alternative.

Metacognition The knowledge of what strategies to apply, when to apply them, and how to deploy them in new situations so that new specific knowledge can be gained and different problems mastered.

Method of savings Measuring forgetting by computing the difference between the number of repetitions needed to learn, and after a delay, relearn, the same material.

Midbrain A small structure, between the hindbrain and forebrain, that relays information from the eyes, ears, and skin, and controls certain types of automatic behaviors in response to information received through those senses.

Midlife transition A point at around age forty when adults take stock of their lives.

Minority influence A phenomenon whereby members of a numerical minority in a group alters the view of the majority.

Mnemonics Strategies for placing information in an organized context in order to remember it.

Mode A measure of central tendency that is the value or score that occurs most frequently in a data set.

Modeling Demonstrating desirable behaviors as a way of teaching them to clients.

Mood disorder Conditions in which a person experiences extreme moods, such as depression or mania.

Morpheme The smallest unit of language that has meaning.

Motion parallax A depth cue whereby a difference in the apparent rate of movement of different objects provides information on the relative distance of those objects.

Motivation The influences that account for the initiation, direction, intensity, and persistence of behavior.

Motive A reason or purpose for behavior.

Motor cortex The part of the cerebral cortex whose neurons control voluntary movements in specific parts of the body.

Motor systems The parts of the nervous system that influence muscles and other organs to respond to the environment in some way.

Multiple intelligences Howard Gardner's theory that people are possessed of eight semi-independent kinds of intelligence, only three of which are measured by standard IQ tests.

Myelin A fatty substance that wraps around some axons and increases the speed of action potentials






Narcolepsy A daytime sleep disorder in which a person switches abruptly from an active, often emotional waking state into several minutes of REM sleep.

Natural concepts Concepts that have no fixed set of defining features but instead share a set of characteristic features

Naturalistic observation The process of watching without interfering as a phenomenon occurs in the natural environment.

Need In drive reduction theory, a biological requirement for well-being that is created by an imbalance in homeostasis. (See also drive, primary drives, and secondary drives.)

Need achievement A motive influenced by the degree to which a person establishes specific goals, cares about meeting those goals, and experiences feelings of satisfaction by doing so.

Negative feedback system An arrangement in which the output of a system is monitored and maintained at some particular level.

Negative reinforcers The removal of unpleasant stimuli such as pain.

Negative symptoms Schizophrenic symptoms such as absence of pleasure, lack of speech, and flat affect.

Nervous system A complex combination of cells whose primary function is to allow an organism to gain information about what is going on inside and outside the body and to respond appropriately.

Neural networks Neurons that operate together to perform complex functions.

Neurobiological model A modern name for the medical model, in which psychological disorders are seen as reflecting disturbances in the anatomy and chemistry of the brain and other biological processes.

Neuroleptics(antipsychotics) Drugs that alleviate the symptoms of severe disorders such as schizophrenia.

Neurons Fundamental units of the nervous system; nerve cells.

Neurotransmitter system A group of neurons that communicates by using the same neurotransmitter.

Neurotransmitters Chemicals that transfer signals from one neuron to another.

Night terrors Rapid awakening from stage 4 sleep accompanied by a horrific dream that causes the dreamer to experience intense fear for up to thirty minutes.

Nightmares Frightening, sometimes recurring dreams that take place during REM sleep.

Nonconscious level A level of mental activity that is inaccessible to conscious awareness.

Norepinephrine A neurotransmitter involved in arousal, as well as in learning and mood regulation. Also called noradrenaline.

Norm A description of the frequency at which a particular score occurs, which allows scores to be compared statistically.

Norms Socially based rules that prescribe what people should or should not do in various situations.

Nuclei Collections of nerve cell bodies in the central nervous system.






Obedience A form of compliance in which people comply with a demand, rather than with a request.

Obesity A condition in which a person is severely overweight, as measured by a body mass index above 30.

Object permanence The knowledge that objects exist even when they are not in view.

Objective tests Personality tests containing direct, unambiguous items relating to the individual being assessed.

Observational learning Learning how to perform new behaviors by watching the behavior of others.

Obsessive-compulsive disorder An anxiety disorder involving repetitive thoughts and urges to perform certain rituals.

Oedipus complex A pattern described by Freud in which a boy has sexual desire for his mother and wants to eliminate his father's competition for her attention.

Olfaction The sense that detects chemicals that are airborne, or volatile; the sense of smell.

Olfactory bulb The brain structure that receives messages regarding olfaction.

One-word stage A stage of language development during which children tend to use one word at a time.

Operant A response that has some effect on the world.

Operant conditioning A process through which an organism learns to respond to the environment in a way that produces positive consequences.

Operational definitions Statements that define variables describing the exact operations or methods used in research.

Opiates Psychoactive drugs, such as opium, morphine, or heroin, that produce both sleep-inducing and pain-relieving effects.

Opponent-process theory A theory of color vision stating that color sensitive visual elements are grouped into red-green, blue-yellow, and black-white elements

Optic chiasm Part of the bottom surface of the brain where half of each optic nerve's fibers cross over to the opposite side of the brain.

Optic nerve A bundle of fibers composed of axons from ganglion cells that carries visual information to the brain.

Oral stage The first of Freud's psychosexual stages, in which the mouth is the center of pleasure.






Pain disorder A somatoform disorder marked by complaints of severe pain with no physical cause.

Panic disorder An anxiety disorder involving sudden panic attacks.

Papillae Structures on the tongue containing groups of taste receptors, or taste buds.

Parallel distributed processing (PDP) models An approach to understanding object recognition in which various elements of the object are thought to be simultaneously analyzed by a number of widely distributed but connected neural units in the brain; memory models in which new experiences change one's overall knowledge base.

Parasympathetic system The subsystem of the autonomic nervous system that typically influences activity related to the protection, nourishment, and growth of the body.

Partial reinforcement extinction effect A phenomenon in which behaviors learned under a partial reinforcement schedule are more difficult to extinguish than those learned on a continuous reinforcement schedule.

Partial reinforcement schedule A pattern of reinforcement in which a reinforcer is administered only some of the time after a particular response occurs.

Perceived self-efficacy According to Bandura, learned expectations about the probability of success in given situations.

Perception The process through which people take raw sensations from the environment and interpret them, using knowledge, experience, and understanding of the world, so that the sensations become meaningful experiences.

Perceptual constancy The perception of objects as constant in size, shape, color, and other properties despite changes in their retinal image.

Perceptual organization The task of determining what edges and other stimuli go together to form an object.

Peripheral nervous system (PNS) The parts of the nervous system not housed in bone.

Permissive parents Those who give their child great freedom and lax discipline.

Personality The pattern of psychological and behavioral characteristics by which each person can be compared and contrasted with others.

Personality disorders Long-standing, inflexible ways of behaving that create a variety of problems.

Personality psychologists Psychologists who study the characteristics that make individuals similar to, and different from, one another.

Person-oriented leaders Leaders who provide loose supervision, ask for group members' ideas, are concerned with subordinates' feelings, and are usually well liked by those they lead.

Phallic stage The third of Freud's psychosexual stages, in which the focus of pleasure shifts to the genital area.

Phenotype How an individual looks and acts, which depends on how inherited characteristics interact with the environment.

Pheromones Chemicals released by one animal and detected by another that shape the second animal's behavior or physiology.

Phobia Strong, irrational fear of an object or situation that does not objectively justify such a reaction.

Phoneme The smallest unit of sound that affects the meaning of speech.

Photopigments Chemicals in photoreceptors that respond to light and assist in converting light into neural activity.

Photoreceptors Nerve cells in the retina that code light energy into neural activity.

Physical dependence Development of a physical need for a psychoactive drug.

Pitch How high or low a tone sounds.

Place theory A theory that hair cells at a particular place on the basilar membrane respond most to a particular frequency of sound.

Placebo A physical or psychological treatment that contains no active ingredient but produces an effect because the person receiving it believes it will. In an experiment, the placebo effect (a confounding variable) occurs when the participant responds to the belief that the independent variable will have an effect, rather than to the actual effect of the independent variable.

Pleasure principle In Freud's psychodynamic theory, the id's operating principle which guides people toward whatever feels good.

Polygenic Describing characteristics that are determined by more than one gene.

Positive reinforcement A therapy method using rewards to strengthen desirable behaviors.

Positive reinforcers Stimuli that strengthen a response if they follow that response.

Positive symptoms Schizophrenic symptoms such as disorganized thoughts, hallucinations, and delusions.

Postconventional moral reasoning Reasoning that reflects moral judgments based on personal standards or universal principles of justice, equality, and respect for human life.

Postsynaptic potential The change in the membrane potential of a neuron that has received stimulation from another neuron.

Posttraumatic stress disorder (PTSD) A pattern of adverse and disruptive reactions following a traumatic event.

Preconscious level A level of mental activity that is not currently conscious, but of which we can easily become conscious.

Preconventional moral reasoning Reasoning that is not yet based on the conventions or rules that guide social interactions in society.

Prejudice A positive or negative attitude toward an entire group of people.

Preoperational period According to Piaget, the second stage of cognitive development, during which children begin to use symbols to represent things that are not present.

Primacy effect A characteristic of memory in which recall of the first two or three items in a list is particularly good.

Primary auditory cortex The area in the brain's temporal lobe that is first to receive information about sounds.

Primary drives Drives that arise from basic biological needs.

Primary reinforcers Reinforcers that meet an organism's most basic needs, such as food, water, air, and moderate temperatures.

Primary visual cortex An area at the back of the brain, to which neurons in the lateral geniculate nucleus relay visual input.

Prisoner's dilemma A social dilemma in which mutual cooperation guarantees the best mutual outcome

Proactive interference A cause of forgetting in which information already in long-term memory interferes with the ability to remember new information.

Procedural memory A type of memory containing information about how to do things.

Progestins Feminine hormones that circulate in the bloodstream of both men and women; relatively more progestins circulate in women.

Progressive relaxation training A procedure for learning to relax that involves tensing then releasing muscles.

Projective tests Personality tests made up of unstructured stimuli which can be perceived and responded to in many ways.

Propositions Mental representations of the relationship between concepts.

Proprioceptive The sensory systems that allow us to know about where we are and what each part of our body is doing.

Prototype A member of a natural concept that possesses all or most of its characteristic features.

Psychiatrists Medical doctors who have completed special training in the treatment of mental disorders.

Psychoactive drugs Substances that act on the brain to create some psychological effect.

Psychoanalysis A method of psychotherapy that seeks to help clients gain insight by recognizing and understanding unconscious thoughts and emotions.

Psychodynamic approach A view developed by Freud that emphasizes the interplay of unconscious mental processes in determining human thought, feelings, behavior, and personality. Also called psychodynamic model.

Psychological dependence A condition in which a person uses a drug despite adverse effects, needs the drug for a sense of well-being, and becomes preoccupied with obtaining it.

Psychological model A view in which mental disorder is seen as arising from inner turmoil or other psychological processes.

Psychologists Among therapists, those whose education includes completion of a master's or doctoral degree in clinical or counseling psychology, often followed by additional specialty training.

Psychology The science of behavior and mental processes.

Psychometric approach A way of studying intelligence that emphasizes analysis of the products of intelligence, especially scores on intelligence tests.

Psychoneuroimmunology The field that examines the interaction of psychological and physiological processes that affect the ability of the body to defend itself against disease.

Psychopathology Patterns of thinking and behaving that are maladaptive, disruptive, or uncomfortable for the person affected or for those with whom he or she comes in contact.

Psychopharmacology The study of psychoactive drugs and their effects.

Psychophysics An area of research focusing on the relationship between the physical characteristics of environmental stimuli and the psychological experience those stimuli produce.

Psychosexual stages In Freud's psychodynamic theory, periods of personality development in which conflicts focus on particular issues.

Psychosurgery Surgical procedures that destroy tissue in small regions of the brain in an effort to treat psychological disorders.

Psychotherapy The treatment of psychological disorders through talking and other psychological methods.

Puberty The condition of being able for the first time to reproduce.

Punishment The presentation of an aversive stimulus or the removal of a pleasant stimulus; punishment decreases the frequency of the immediately preceding response; in therapy, weakening undesirable behavior by following it with an unpleasant stimulus.

Pupil An opening in the eye, just behind the cornea, through which light passes.






Random assignment The procedure by which random variables are evenly distributed in an experiment by putting participants into various groups by means of a coin flip or other random process.

Random sample A group of research participants selected from a population in which all members had an equal chance of being chosen for study.

Random variables In an experiment, confounding variables in which uncontrolled or uncontrollable factors affect the dependent variable along with or instead of the independent variable.

Range A measure of variability that is the difference between the highest and the lowest value in a data set.

Rapid eye movement (REM) sleep A stage of sleep in which EEG and other functions resemble the waking state, but is accompanied by rapid eye movements and virtual muscle paralysis.

Rational-emotive therapy (REBT) A treatment designed to identify and change self-defeating thoughts that lead to anxiety and other symptoms of disorder.

Reaction time The time between the presentation of a stimulus and an overt response to it.

Reality principle According to Freud, the operating principle of the ego that creates compromises between the id's demands and those of the real world.

Reasoning The process by which people evaluate and generate arguments and reach conclusions.

Recency effect A characteristic of memory in which recall is particularly good for the last few items on a list.

Receptive field The portion of the world that affects a given sensory neuron.

Receptors Sites on the surface of cells that allow only one type of neurotransmitter to fit into them, triggering a chemical response that may lead to an action potential.

Reconditioning The relearning of a conditioned response following extinction.

Reference groups Categories of people to which people compare themselves.

Reflection An active listening method in which a therapist conveys empathy by paraphrasing clients' statements and noting accompanying feelings.

Reflexes Involuntary, unlearned reactions in the form of swift, automatic, and finely coordinated movements in response to external stimuli.

Refractory period A short rest period between action potentials.

Reinforcer A stimulus event that increases the probability that the response that immediately preceded it will occur again.

Relative deprivation The belief that one is not doing as well as others in one's reference group.

Relative size A depth cue whereby larger objects are perceived as closer than smaller ones.

Reliability The degree to which a test can be repeated with the same results.

REM behavior disorder A sleep disorder in which a person does not lose muscle tone during REM sleep, allowing the person to act out dreams.

Representativeness heuristic A mental shortcut that involves judging whether something belongs in a given class on the basis of its similarity to other members of that class.

Resilience A quality allowing children to develop normally in spite of severe environmental risk factors.

Resource dilemma A situation in which people must share a common resource, creating conflicts between the short-term interests of individuals and the long-term interests of the group.

Response criterion The internal rule a person uses to decide whether or not to report a stimulus.

Reticular formation A network of cells and fibers threaded throughout the hindbrain and midbrain that alters the activity of the rest of the brain.

Retina The surface at the back of the eye onto which the lens focuses light rays.

Retrieval The process of recalling information stored in memory.

Retrieval cues Stimuli that allow people to recall or recognize information stored in memory.

Retroactive interference A cause of forgetting in which new information placed in memory interferes with the ability to recall information already in memory.

Retrograde amnesia A loss of memory for events prior to a brain injury.

Rods Highly light-sensitive, but color insensitive photoreceptors in the retina that allow vision even in dim light.

Role theory A theory that hypnotized people act in accordance with a special social role that provides a socially acceptable reason to follow the hypnotist's suggestions.

Rules of logic Sets of statements that provide a formula for drawing valid conclusions.






s A group of special abilities that Charles Spearman saw as accompanying general intelligence (g).

Sampling The process of selecting participants who are members of the population that the researcher wishes to study.

Satiety The condition of no longer wanting to eat.

Saturation The purity of a color.

Schemas Mental representations of what we know and have come to expect about objects, events, and people; generalizations based on experience that form the basic units of knowledge.

Schizophrenia A severe and disabling pattern of disturbed thinking, emotion, perception, and behavior.

School psychologists Psychologists who test IQs, diagnose students' academic problems, and set up programs to improve students' achievement.

Scripts Mental representations of familiar sequences of activity.

Secondary drives Stimuli that acquire the motivational properties of primary drives through classical conditioning or other learning mechanisms.

Secondary reinforcer A reward that people or animals learn to like.

Second-order conditioning A phenomenon in learning when a conditioned stimulus acts like a UCS, creating conditioned stimuli out of events associated with it.

Selective attention The focusing of mental resources on only part of the stimulus field.

Self-concept The way one thinks of oneself.

Self-esteem The evaluations people make about how worthy they are as human beings.

Self-fulfilling prophecy A process through which an initial impression of someone leads that person to behave in accordance with that impression.

Self-perception theory A theory suggesting that attitudes can change as people consider their behavior in certain situations, then infer what their attitude must be.

Self-regulation The ability to control one's emotions and behavior.

Self-schemas Mental representations that people form of themselves.

Self-serving bias The tendency to attribute one's successes to internal characteristics while blaming one's failures on external causes.

Semantic encoding The mental representation of an experience by its general meaning.

Semantic memory A type of memory containing generalized knowledge of the world.

Semantics Rules governing the meaning of words and sentences.

Semicircular canals Tubes in the inner ear whose fluid, when shifted by head movements, stimulates nerve cells that tell the brain about those movements.

Sensations Messages from the senses which comprise the raw information that affects many kinds of behavior and mental processes.

Sense A system that translates information from outside the nervous system into neural activity.

Sensitivity The ability to detect a stimulus.

Sensorimotor period The first of Piaget's stages of cognitive development, when the infant's mental activity is confined to sensory perception and motor skills.

Sensory cortex The parts of the cerebral cortex located in the parietal, occipital, and temporal lobes that receives stimulus information from the skin, eyes, and ears, respectively.

Sensory memory A type of memory that holds large amounts of incoming information very briefly, but long enough to connect one impression to the next.

Sensory receptors Specialized cells that detect certain forms of energy.

Sensory registers Memory systems that hold incoming information long enough for it to be processed further.

Sensory systems The parts of the nervous system that provide information about the environment.

Serotonin A neurotransmitter used by cells in parts of the brain involved in the regulation of sleep, mood, and eating.

Sex hormones Chemicals in the blood of males and females that have both organizational and motivational effects on sexual behavior.

Sexual dysfunctions Problems with sexual motivation, arousal, or orgasmic response.

Sexual response cycle The pattern of arousal during and after sexual activity.

Shaping A procedure that involves reinforcing responses that come successively closer to the desired response.

Short-term memory (STM) The maintenance component of working memory which holds unrehearsed information for about eighteen seconds.

Signal-detection theory A mathematical model of what determines a person's report that a near-threshold stimulus has or has not occurred.

Sleep apnea A sleep disorder in which people briefly but repeatedly stop breathing during the night.

Sleepwalking A phenomenon primarily occurring in non-REM sleep in which people walk while asleep.

Slow-wave sleep Sleep stages 1 through 4, which are accompanied by slow, deep breathing; a calm, regular heartbeat; and reduced blood pressure.

Social cognition Mental processes associated with people's perceptions of and reactions to other people.

Social comparison Using other people as a basis of comparison for evaluating oneself.

Social dilemmas Situations in which actions that produce rewards for one individual will produce negative consequences if adopted by everyone.

Social facilitation A phenomenon in which the presence of others improves a person's performance.

Social identity The beliefs we hold about the groups to which we belong.

Social impairment A reduction in performance due to the presence of other people.

Social loafing Exerting less effort when performing a group task than when performing the same task alone.

Social perception The processes through which people interpret information about others, draw inferences about them, and develop mental representations of them.

Social phobias Strong, irrational fears relating to social situations.

Social psychologists Psychologists who study how people influence one another's behavior and attitudes, individually and in groups.

Social psychology The study of how people's thoughts, feelings, and behavior influence, and are influenced by, the behavior of others.

Social referencing A phenomenon in which other people's facial expressions, tone of voice, and bodily gestures serve as guidelines for how to proceed in uncertain situations.

Social support network The friends and social contacts on whom one can depend for help and support.

Social-cognitive approach An approach in which personality is seen as the patterns of thinking and behavior that a person learns.

Sociocultural model A way of looking at mental disorders in relation to gender, age, ethnicity and other social and cultural factors.

Somatic nervous system The subsystem of the peripheral nervous system that transmits information from the senses to the central nervous system and carries signals from the CNS to the muscles that move the skeleton.

Somatic senses Senses, including touch, temperature, pain, and kinesthesia. Also called somatosensory systems.

Somatization disorder Somatoform disorders in which there are numerous physical complaints without verifiable physical illness.

Somatoform disorders Psychological problems in which there are symptoms of a physical disorder without a physical cause.

Sound A repetitive fluctuation in the pressure of a medium such as air.

Spatial codes Coding attributes of a stimulus in terms of the location of firing neurons relative to their neighbors.

Specific nerve energies A doctrine stating that stimulation of a particular sensory nerve provides codes for that sense, no matter how the stimulation takes place.

Specific phobias Phobias that involve fear and avoidance of heights, animals, and other specific stimuli and situations.

Spinal cord The part of the central nervous system within the spinal column that receives signals from peripheral senses and relays them to the brain. It also conveys messages from the brain to the rest of the body.

Spontaneous recovery The reappearance of the conditioned response after extinction and without further pairings of the conditioned and unconditioned stimuli.

Sport psychologists Psychologists who explore the relationships between athletic performance and such psychological variables as motivation and emotion.

Spreading activation A principle that explains how information is retrieved in semantic network theories of memory.

Standard deviation (SD) A measure of variability that is the average difference between each score and the mean of the data set.

Stanford-Binet A test for determining a person's intelligence quotient, or IQ.

State of consciousness The characteristics of consciousness at any particular moment.

State theory A theory that hypnosis is an altered state of consciousness.

State-dependent Referring to memories that are aided or impeded by a person's internal state.

Statistically significant In statistical analysis, a term used to describe the results of an experiment when the outcome of a statistical test indicates that the probability of those results occurring by chance is small (usually less than 5 percent).

Stereotypes False assumptions that all members of some group share the same characteristics.

Stimulants Psychoactive drugs that have the ability to increase behavioral and mental activity

Stimulus discrimination A process through which individuals learn to differentiate among similar stimuli and respond appropriately to each one.

Stimulus generalization A phenomenon in which a conditioned response is elicited by stimuli that are similar but not identical to the conditioned stimulus.

Storage The process of maintaining information in memory over time.

Stress The process of adjusting to circumstances that disrupt, or threaten to disrupt, a person's equilibrium.

Stressors Events or situations to which people must adjust.

Striatum A structure within the forebrain that is involved in the smooth initiation of movement.

Stroboscopic motion An illusion in which lights or images flashed in rapid succession are perceived as moving.

Subjective well-being A combination of a cognitive judgment of satisfaction with life, the frequent experiencing of positive moods and emotions, and the relatively infrequent experiencing of unpleasant moods and emotions.

Subliminal stimuli Stimuli that are too weak or brief to be consciously perceived.

Substance abuse The self-administration of psychoactive drugs in ways that deviate from a culture's social norms.

Substance-related disorders Problems that involve use of psychoactive drugs for months or years in ways that harm the user or others.

Substantia nigra An area of the midbrain involved in the smooth initiation of movement.

Sudden infant death syndrome (SIDS) A disorder in which a sleeping baby stops breathing and suffocates.

Superego According to Freud's psychodynamic theory, the component of personality that tells people what they should and should not do.

Suprachiasmatic nuclei Nuclei in the hypothalamus that generate biological rhythms.

Supraliminal stimuli Stimuli that fall above the absolute threshold and thus are consistently perceived.

Surface structures The order in which words are arranged in sentences.

Survey A research method that involves giving people questionnaires or special interviews designed to obtain descriptions of their attitudes, beliefs, opinions, and intentions.

Syllogisms Arguments made up of two propositions, called premises, and a conclusion based on those premises.

Sympathetic system The subsystem of the autonomic nervous system that usually prepares the organism for vigorous activity.

Synapse The tiny gap between neurons across which the neurons communicate.

Synaptic plasticity The ability to create synapses and to change the strength of synapses.

Synesthesia A blending of sensory experience that causes some people to "see" sounds or "taste" colors, for example.

Syntax The set of rules that govern the formation of phrases and sentences in a language.

Systematic desensitization A behavioral treatment for anxiety in which clients visualize a graduated series of anxiety-provoking stimuli while remaining relaxed.






Task-oriented leaders Leaders who provide close supervision, lead by directives, and generally discourage group discussion.

Temperament An individual's basic disposition, evident from infancy.

Temporal codes Coding attributes of a stimulus in terms of changes in the timing of neural firing.

Teratogens Harmful substances that can cause birth defects.

Terminal drop A sharp decline in mental functioning that tends to occur in late adulthood, a few years or months before death.

Test A systematic procedure for observing behavior in a standard situation and describing it with the help of a numerical scale or a category system.

Texture gradient A graduated change in the texture, or grain, of the visual field, whereby changes in texture across the retinal image are perceived as changes in distance; objects with finer, less detailed textures are perceived as more distant.

Thalamus A forebrain structure that relays signals from most sense organs to higher levels in the brain and plays an important role in processing and making sense out of this information.

Theory An integrated set of propositions that can be used to account for, predict, and suggest ways of controlling certain phenomena.

Thinking The manipulation of mental representations.

Timbre The mixture of frequencies and amplitudes that make up the quality of sound.

Token economy A system for improving the behavior of institutionalized clients in which desirable behaviors are rewarded with tokens that can be exchanged for desired items or activities.

Tolerance A condition in which increasingly larger drug doses are needed to produce a given effect.

Top-down processing Those aspects of recognition that are guided by higher-level cognitive processes and psychological factors such as expectations.

Trait approach A perspective in which personality is seen as a combination of characteristics that people display over time and across situations.

Transduction The process of converting incoming energy into neural activity through receptors.

Transfer-appropriate processing model A model of memory that suggests that a critical determinant of memory is how well the retrieval process matches the original encoding process.

Transferred excitation The process of carrying over arousal from one experience to an independent situation.

Triarchic theory of intelligence Sternberg's theory that describes intelligence as having analytical, creative, and practical dimensions.

Trichromatic theory A theory of color vision identifying three types of visual elements, each of which is most sensitive to different wavelengths of light.

Tympanic membrane A membrane in the middle ear that generates vibrations that match the sound waves striking it.






Unconditional positive regard A therapist attitude that conveys a caring for and acceptance of the client as a valued person.

Unconditioned response (UCR) The automatic or unlearned reaction to a stimulus.

Unconditioned stimulus (UCS) A stimulus that elicits a response without conditioning.

Unconscious level A level of mental activity that influences consciousness, but is not conscious.

Utility A subjective measure of value.






Validity The degree to which a test measures what it is supposed to measure, and leads to correct inferences about people.

Variable-interval (VI) schedule A type of partial reinforcement schedule that provides reinforcement for the first response after some varying period of time.

Variable-ratio (VR) schedule A type of partial reinforcement schedule that provides reinforcement after a varying number of responses.

Vestibular sacs Organs in the inner ear that connect the semicircular canals and the cochlea, and contribute to the body's sense of balance.

Vestibular sense The proprioceptive sense that provides information about the position of the body in space and about its movements.

Vicarious conditioning Learning the relationship between a response and its consequences (either reinforcement or punishment) or the association between a conditioned stimulus and a conditioned response by watching others.

Visible light Electromagnetic radiation that has a wavelength from about 400 nanometers to about 750 nanometers.

Visual encoding The mental representation of stimuli as images.

Vomeronasal organ A portion of the mammalian olfactory system that is sensitive to pheromones.






Wavelength The distance from one peak to the next in a waveform.

Weber's law A law stating that the smallest detectable difference in stimulus energy is a constant fraction of the intensity of the stimulus.

Withdrawal syndrome Symptoms associated with discontinuing the use of a habit-forming substance.

Words Units of language composed of one or more morphemes.

Working memory The part of the memory system that allows us to mentally work with, or manipulate, information being held in short-term memory.





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