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Psychology Glossary

Psychology Glossary

Table of Contents

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A

Absolute refractory period -  The period during which a neuron lies dormant after an action potential has been completed.
Absolute threshold -  The minimum amount of stimulation needed for a person to detect the stimulus 50 percent of the time.
Accommodation -  The process by which the shape of an eye’s lens adjusts to focus light from objects nearby or far away. Also: the modification of a schema as new information is incorporated.
Acetylcholine -  A neurotransmitter involved in muscle movement, attention, arousal, memory, and emotion.
Achievement motive -  An impulse to master challenges and reach a high standard of excellence.
Achievement tests -  An assessment that measures skills and knowledge that people have already learned.
Acronym -  A word made out of the first letters of several words.
Acrostic -  A sentence or phrase in which each word begins with a letter that acts as a memory cue.
Action potential -  A short-lived change in electric charge inside a neuron.
Activation-synthesis theory -  A theory proposing that neurons in the brain activate randomly during REM sleep.
Active listening -  A feature of client-centered th erapy that involves empathetic listening, by which the therapist echoes, restates, and clarifies what the client says.
Adaptation -  An inherited characteristic that increases in a population because it provides a survival or reproductive advantage.
Adaptive behaviors -  Behaviors that increase reproductive success.
Additive strategy -  The process of listing the attributes of each element of a decision, weighing them according to importance, adding them up, and determining which one is more appealing based on the result.
Adoption studies -  Studies in which researchers examine trait similarities between adopted children and their biological and adoptive parents to figure out whether that trait might be inherited.
Adrenal cortex -  The outer part of the adrenal glands, which secretes corticosteroids.
Adrenal medulla -  The inner part of the adrenal glands, which secretes catecholamines.
Adrenocorticotropic hormone (ACTH) -  A hormone released by the pituitary gland that stimulates release of corticosteroids from the adrenal cortex.
Afferent nerves -  Bundles of axons that carry information from muscles and sense organs to the central nervous system.
Afterimage -  A color we perceive after another color is removed.
Age of viability -  The point at which a fetus has some chance of surviving outside the mother if born prematurely.
Agonists -  Chemicals that mimic the action of a particular neurotransmitter.
Agoraphobia -  A disorder involving anxiety about situations from which escape would be difficult or embarrassing or places where there might be no help if a panic attack occurred.
Algorithm -  A step-by-step procedure that is guaranteed to solve a problem.
All-or-none law -  States that neurons fire to generate an action potential only if stimulation reaches a minimum threshold.
Alpha waves -  Type of brain waves present when a person is very relaxed or meditating.
Alternate-forms reliability -  The ability of a test to produce the same results when two different versions of it are given to the same group of people.
Ambiguous language -  Language that can be understood in several ways.
Amplitude -  The height of a wave.
Amygdala -  A part of the limbic system of the brain that is involved in regulating aggression and emotions, particularly fear.
Animism -  The belief that inanimate objects are alive.
Anorexia nervosa -  A disorder characterized by refusal to maintain a body weight in the normal range, intense fear about gaining weight, and highly distorted body image.
Antagonists -  Chemicals that block the action of a particular neurotransmitter.
Anterograde amnesia -  An inability to remember events that occurred after a brain injury or traumatic event.
Antisocial personality disorder -  A disorder characterized by a lack of conscience and lack of respect for other people’s rights, feelings, and needs, beginning by age fifteen.
Appraisal -  The process of evaluating an environmental challenge to determine whether resources are available for dealing with it.
Approach-approach conflict -  A conflict between two desirable alternatives.
Approach-avoidance conflict -  A conflict that arises when a situation has both positive and negative features.
Aptitude tests -  An assessment that predicts people’s future ability to acquire skills or knowledge.
Archetypes -  Images or thoughts that have the same meaning for all human beings.
Assimilation -  The broadening of an existing schema to include new information.
Atherosclerosis -  Hardening of arteries because of cholesterol deposits.
Attachment -  The close bond between babies and their caregivers.
Attachment styles -  Types of attachment, which include secure attachment, anxious-ambivalent attachment, and avoidant attachment.
Attitudes -  Evaluations people make about objects, ideas, events, or other people.
Attributions -  Inferences people make about the causes of events and behavior.
Atypical antipsychotic drugs -  A new class of antipsychotic drugs that are effective for treating negative and positive symptoms of schizophrenia. They target the neurotransmitters serotonin and dopamine.
Auditory nerve -  A nerve that sends impulses from the ear to the brain.
Automatic thoughts -  Self-defeating judgments people make about themselves.
Autonomic nervous system -  The part of the peripheral nervous system connected to the heart, blood vessels, glands, and smooth muscles.
Availability heuristic -  A rule-of-thumb strategy in which people estimate probability based on how quickly they remember relevant instances of an event.
Avoidance-avoidance conflict -  A conflict that arises when a choice must be made between two undesirable alternatives.
Avoidant personality disorder -  A disorder involving social withdrawal, low self-esteem, and extreme sensitivity to being evaluated negatively.
Aversion therapy -  A therapy in which a stimulus that evokes an unpleasant response is paired with a stimulus that evokes a maladaptive behavior.
Axon -  A fiber that extends from a neuron and sends signals to other neurons.

B

Babbling -  A producton of sounds that resemble many different languages.
Basal metabolic rate -  The rate at which energy is used when a person is at complete rest.
Basilar membrane -  A membrane in the inner ear that runs along the length of the cochlea.
Behavior genetics -  The study of behavior and personality differences among people.
Behavior therapies -  Treatments involving complex conversations between therapists and clients that are aimed at directly influencing maladaptive behaviors through the use of learning principles.
Belief perseverance -  The process of rejecting evidence that refutes one’s beliefs.
Benzodiazepines -  A class of antianxiety drugs. They are also called tranquilizers.
Beta waves -  The type of brain waves present when a person is awake and alert.
Bias -  The distortion of results by a variable that is not part of the hypothesis.
Big Five -  Five basic personality traits from which other traits are derived. They include neuroticism, extraversion, openness to experience, agreeableness, and conscientiousness.
Binocular cues -  Depth perception cues that require both eyes.
Biological rhythms -  Periodic physiological changes.
Biomedical therapies -  Treatments that involve efforts to directly alter biological functioning through medication, electric shocks, or surgery.
Biopsychosocial model of illness -  The idea that physical illness is the result of a complicated interaction among biological, psychological, and sociocultural factors.
Bipolar disorders -  Disorders in which people alternate between periods of depression and mania.
Blood-brain barrier -  A membrane that lets some substances from the blood into the brain but keeps out others.
Borderline personality disorder -  A disorder characterized by impulsive behavior and unstable relationships, emotions, and self-image.
Brain -  The main organ in the nervous system.
Brain waves -  Tracings that show the electrical activity of the brain.
Broca’s area -  A part of the brain, in the left frontal lobe, that is involved in speech production.
Bulimia nervosa -  A disorder involving binge eating followed by compensatory behaviors such as vomiting, fasting, excessive exercise, or use of laxatives, diuretics, and other medications to control body weight.
Bystander effect -  The tendency of people to be less likely to offer help to someone who needs it if other people are also present.

C

Cannon-Bard theory -  The idea that the experience of emotion happens at the same time that physiological arousal happens.
Case study -  A research method in which an individual subject is studied in depth.
Castration anxiety -  The fear a male child has that his father will cut off his penis for desiring his mother.
Catatonic type -  A subtype of schizophrenia characterized by unnatural movement patterns such as rigid, unmoving posture or continual, purposeless movements, or by unnatural speech patterns such as absence of speech or parroting of other people’s speech.
Catecholamines -  Hormones released by the adrenal medulla in response to stress.
Catharsis -  The release of tension that results when repressed thoughts or memories move into a patient’s conscious mind.
Central nervous system -  The part of the nervous system that includes the brain and the spinal cord.
Centration -  The tendency to focus on one aspect of a problem and ignore other key aspects.
Cerebellum -  A part of the hindbrain that controls balance and coordination of movement.
Cerebrospinal fluid -  The fluid that cushions and nourishes the brain.
Cerebrum -  The largest part of the brain, involved in abstract thought and learning.
Chromosomes -  Thin strands of DNA that contain genes.
Chunking -  The process of combining small bits of information into bigger, familiar pieces.
Cilia -  Hair cells that are embedded in the basilar membrane of the ear.
Cingulotomy -  A surgical procedure that involves destruction of part of the frontal lobes. It is sometimes done to treat severe disorders that do not respond to other treatments.
Circadian rhythms -  Biological cycles that occur about every twenty-four hours.
Classical conditioning -  A type of learning in which a subject comes to respond to a neutral stimulus as he would to another stimulus by learning to associate the two stimuli. It can also be called respondent conditioning or Pavlovian conditioning.
Client-centered therapy -  A humanistic therapy, developed by Carl Rogers, that aims to help clients increase self-acceptance and personal growth by providing a supportive emotional environment.
Closure -  The tendency to interpret familiar, incomplete forms as complete by filling in gaps.
Cochlea -  A coiled tunnel in the inner ear that is filled with fluid.
Cognition -  Thinking. It involves mental activities such as understanding, problem solving, decision making, and creativity.
Cognitive appraisal -  The idea that people’s experience of emotion depends on the way they appraise or evaluate the events around them.
Cognitive development -  The development of thinking capacity.
Cognitive dissonance -  An unpleasant state of tension that arises when a person has related cognitions that conflict with one another.
Cognitive schema -  A mental model of some aspect of the world.
Cognitive therapies -  Therapies aimed at identifying and changing maladaptive thinking patterns that can result in negative emotions and dysfunctional behavior.
Collective unconscious -  The part of our minds, according to Carl Jung, that contains universal memories of our common human past.
Color blindness -  A hereditary condition that makes people unable to distinguish between colors.
Commitment -  The intent to continue a romantic relationship even in the face of difficulties.
Community mental health movement -  A movement that advocates treating people with psychological problems in their own communities, providing outpatient treatment, and preventing psychological disorders.
Compassionate love -  Warmth, trust, and tolerance of a person with whom one is romantically involved.
Compensation -  According to Alfred Adler, the process of striving to get rid of normal feelings of inferiority.
Complexity -  The range of wavelengths in light.
Componential intelligence -  The ability assessed by intelligence tests.
Compulsions -  Repetitive behaviors that help to prevent or relieve anxiety.
Computerized tomography (CT) -  A method for studying the brain that involves taking x-rays of the brain from different angles.
Concept -  A mental category that groups similar objects, events, qualities, or actions.
Concordance rate -  The percentage of both people in a pair having a certain trait or disorder.
Conditioned response -  In classical and operant conditioning, a response that resembles an unconditioned response, achieved by pairing a conditioned stimulus with an unconditioned stimulus.
Conditioned stimulus -  In classical conditioning, a neutral stimulus that comes to evoke a response similar to an unconditioned response through pairing with an unconditioned stimulus.
Cones -  Photoreceptor cells in the retina that allow people to see in color.
Confabulation -  A phenomenon in which a person thinks he or she remembers something that did not really happen.
Confirmation bias -  The tendency to look for and accept evidence that supports what one wants to believe and to ignore or reject evidence that refutes those beliefs.
Conflict -  The experience of having two or more incompatible desires or motives.
Conformity -  The process of giving in to real or imagined pressure from a group.
Congruence -  According to Carl Rogers, the accurate match between self-concept and reality.
Conscious -  The part of the mind that contains all the information that a person is paying attention to at a particular time.
Consciousness -  The awareness people have of themselves and the environment around them.
Conservation -  The ability to recognize that measurable physical characteristics of objects can be the same even when objects look different.
Consolidation -  Transfer of information into long-term memory.
Contact comfort -  Comfort derived from physical closeness with a caregiver.
Contact hypothesis -  A hyposthesis stating that prejudice declines when people in an ingroup become more familiar with the customs, norms, food, music, and attitudes of people in an outgroup.
Content validity -  A test’s ability to measure all the important aspects of the characteristic being measured.
Contextual intelligence -  The ability to function effectively in daily situations.
Continuity -  The tendency to perceive interrupted lines and patterns as being continuous by filling in gaps.
Continuous reinforcement -  A reinforcement schedule in which reinforcement happens every time a particular response occurs.
Control group -  A group of subjects in an experiment that receives the same treatment and is treated exactly like the experimental group, except with respect to the independent variable.
Convergence -  The turning inward of eyes when an object is viewed close up.
Convergent thinking -  A style of thinking in which a person narrows down a list of possibilities to arrive at a single right answer.
Conversion disorder -  A disorder characterized by medically unexplained symptoms that affect voluntary motor functioning or sensory functioning.
Coping -  Efforts to manage stress.
Cornea -  The transparent outer membrane of the eye.
Corpus callosum -  A band of fibers that divides the cerebrum into two halves.
Correlation coefficient -  A measurement that indicates the strength of the relationship between two variables. In a positive correlation, one variable increases as the other increases. In a negative correlation, one variable decreases as the other increases.
Correlational research method -  A research method that provides information about the relationship between variables. It is also called a descriptive research method.
Corticosteroids -  Hormones released by the adrenal cortex in response to stress.
Couples therapy -  A type of therapy in which a therapist helps couples identify and resolve conflicts.
Creativity -  The ability to generate novel, useful ideas.
Criterion validity -  A test’s ability to predict another criterion of the characteristic being measured.
Crystallized intelligence -  Intelligence based on the knowledge and skills accumulated over the life span.
Culture-bound disorders -  Psychological disorders that are limited to specific cultural contexts.

D

Dark adaptation -  The process by which receptor cells become more sensitive to light.
Decay theory -  A theory stating that memory traces fade with time.
Decentration -  The ability to focus simultaneously on several aspects of a problem.
Decision-making -  The process of weighing alternatives and choosing among them.
Declarative memory -  The remembering of factual information. Declarative memory is usually considered explicit.
Deductive reasoning -  The process by which a particular conclusion is drawn from a set of general premises or statements.
Defense mechanisms -  Behaviors that protect people from anxiety.
Deindividuation -  The tendency of people in a large, arousing, anonymous group to lose inhibitions, sense of responsibility, and self-consciousness.
Deinstitutionalization -  The trend toward providing treatment through community-based outpatient clinics rather than inpatient hospitals.
Delta waves -  The type of brain waves present when a person is deeply asleep.
Delusions -  False beliefs that are held strongly despite contradictory evidence.
Dementia -  A condition characterized by several significant psychological deficits.
Dendrite -  A fiber that extends from a neuron. It received signals from other neurons and sends them toward the cell body.
Dendritic trees -  Highly branched fibers extending from neurons.
Denial -  A defense mechanism that involves refusing to acknowledge something that is obvious to others.
Dependent variable -  The variable that is observed in an experiment and that may be affected by manipulations of the independent variable.
Descriptive statistics -  Numbers that researchers use to describe their data so it can be organized and summarized.
Development -  The series of age-related changes that occurs over the course of a person’s life span.
Developmental norms -  The median ages at which children develop specific behaviors and abilities.
Diabetes -  A condition caused by a deficiency of insulin.
Diagnosis -  The process of distinguishing among disorders.
Diagnostic and Statistical Manual of Mental Disorders (DSM)  -  A reference book used by psychologists and psychiatrists to diagnose psychological disorders.
Dialectical reasoning -  A process of going back and forth between opposing points of view in order to come up with a satisfactory solution to a problem.
Dichromat -  A person who is sensitive to only two of the three wavelengths of light.
Difference threshold -  The smallest difference in stimulation that is detectable 50 percent of the time. This threshold is also called the just noticeable difference, or jnd.
Diffusion of responsibility -  The tendency for an individual to feel less responsible in the presence of others because responsibility is distributed among all the people present.
Discriminative stimulus -  In operant conditioning, a cue that indicates the kind of consequence that’s likely to occur after a response.
Disease model of addiction -  The idea that addiction is a disease that has to be medically treated.
Disorganized type -  A subtype of schizophrenia characterized by disorganized behavior, disorganized speech, and emotional flatness or inappropriateness.
Displacement -  A defense mechanism that involves transferring feelings about a person or event to someone or something else.
Display rules -  Norms that tell people whether, which, how, and when emotions should be displayed.
Dissociative amnesia -  A disorder characterized by an inability to remember extensive, important personal information, usually about something traumatic or painful.
Dissociative disorders -  Disorders characterized by disturbances in consciousness, memory, identity, and perception.
Dissociative fugue -  A disorder in which a person suddenly and unexpectedly leaves home, fails to remember the past, and becomes confused about his or her identity.
Dissociative identity disorder -  A disorder in which a person fails to remember important personal information and has two or more identities or personality states that control behavior. It is also called multiple personality disorder.
Dissonance theory -  A theory that proposes that people change their attitudes when they have attitudes that are inconsistent with one another.
Distributed practice -  The practice of learning material in short sessions over a long period. It is also called the spacing effect.
Divergent thinking -  A style of thinking in which people’s thoughts go off in different directions as they try to generate many different solutions to a problem.
Dopamine -  A neurotransmitter involved in voluntary movement, learning, memory, and emotion.
Double-blind -  A procedure in which neither the subjects nor the experimenter knows which subjects belong to the experimental and control groups.
Drive reduction theories of motivation -  Ideas that suggest people act in order to reduce needs and maintain a constant physiological state.
Drug therapy -  Treatment that involves the use of medications. It is also called pharmacotherapy.
Dysthymic disorder -  A disorder involving depressed mood on a majority of days for at least two years.

E

Eating disorders -  Disorders characterized by problematic eating patterns, extreme concerns about body weight, and inappropriate behaviors aimed at controlling body weight.
Echoic memory -  Auditory sensory memory.
Efferent nerves -  Bundles of axons that carry information from the central nervous system to muscles and sense organs.
Ego -  The component of the personality that manages the conflict among the id, the superego, and the constraints of the real world.
Egocentrism -  The inability to take someone else’s point of view.
Elaboration -  A type of deep processing in which information being learned is associated with other meaningful material.
Elaboration likelihood model -  The idea that changes to attitudes tend to be longer lasting when people think about the content of persuasive messages they receive.
Electric stimulation of the brain -  An invasive method of studying the brain, in which an implanted electrode activates a particular brain structure.
Electrocardiograph (EKG) -  An instrument that records the activity of the heart.
Electroconvulsive therapy (ECT) -  A biomedical treatment that uses electrical shocks to treat severe depression.
Electroencephalograph (EEG) -  A device that records the overall electrical activity of the brain, via electrodes placed on the scalp.
Electromyograph (EMG) -  An instrument that records muscle activity.
Electrooculograph (EOG) -  An instrument that records eye movements.
Elimination by aspects -  The process of eliminating alternatives in a decision based on whether they do or do not possess aspects or attributes the decision maker has deemed necessary or desirable.
Embryo -  A ball of cells that develops during the embryonic stage.
Embryonic stage -  The period that begins two weeks after conception and ends two months after conception.
Emotion -  A complex, subjective experience that is accompanied by biological and behavioral changes.
Emotion work -  The process of acting out of an emotion that is not really felt.
Emotional intelligence -  An ability that helps people perceive, express, understand, and regulate emotions.
Empirically validated treatments -  Treatments that are shown by research to be more effective for a particular problem than a placebo or no treatment.
Empty nest -  The time in parents’ lives when their children have grown up and moved away from home.
Encoding -  The process of putting information into memory.
Endocrine system -  A network of tissues that allows the body to communicate via hormones.
Endogenous biological rhythms -  Biological cycles that originate from inside the body rather than depend on cues from the environment.
Endorphins -  A group of neurotransmitters involved in pain relief, pleasure, and modulating the action of other neurotransmitters.
Episodic memory -  The remembering of personal facts.
Ethics -  A system of moral values.
Etiology -  The cause or origin of a disorder.
Evolution -  A change in the frequency of genes in a population.
Excitatory postsynaptic potential -  A positive change in voltage that occurs when a neurotransmitter binds to an excitatory receptor site.
Existential therapies -  Therapies aimed at helping clients find meaning in their lives.
Expected value -  The process of adding the value of a win times the probability of a win to the value of a loss times the probability of a loss in order to make a decision.
Experiential intelligence -  The ability to adapt to new situations and produce new ideas.
Experiment -  A research method that provides information about causal relationships between variables.
Experimental group -  A group of subjects in an experiment for whom the independent variable is manipulated.
Experimenter bias -  A source of error that arises when researchers’ preferences or expectations influence the outcome of research.
Explicit attitudes -  Conscious beliefs that can guide decisions and behavior.
Explicit memory -  Conscious, intentional remembering of information.
Exposure therapies -  Therapies that aim to eliminate anxiety responses by having clients face real or imagined versions of feared stimuli.
Expressive language -  The ability to use language to communicate.
External attribution -  An inference that a person’s behavior is due to situational factors. It is also called situational attribution.
External locus of control -  The tendency to believe that circumstances are not within one’s control but rather are due to luck, fate, or other people.
Extinction -  In classical conditioning, the gradual weakening and disappearance of a conditioned response when a conditioned stimulus is not followed by an unconditioned stimulus. In operant conditioning, it’s the gradual disappearance of a response after it stops being reinforced.
Extraneous variable -  A variable other than the independent variable that could affect the dependent variable. It is not part of the hypothesis.
Extrinsic motivation -  The motivation to act for external rewards.
Eye movement desensitization and reprocessing (EMDR) -  A type of exposure therapy in which clients move their eyes back and forth while recalling memories that are to be desensitized.

F

Facial-feedback hypothesis -  The idea that the brain uses feedback from facial muscles to recognize emotions that are being experienced.
Factor analysis -  A statistical procedure that clusters variables into dimensions depending on similarities among the variables.
Falsifiability -  The ability of a theory or hypothesis to be rejected.
Family studies -  Studies in which researchers examine trait similarities among members of a family to figure out whether that trait might be inherited.
Family therapy -  A type of therapy in which a therapist sees two or more members of a family at the same time.
Feature detectors -  Specialized neurons that are activated by specific features of the environment.
Fee for service -  An arrangement for health care in which people pay providers for health care services.
Feigned scarcity -  Implying that a product is in scarce supply, even when it is not, in order to increase demand for it.
Fetal alcohol syndrome -  A collection of symptoms that may be present in babies of alcoholic mothers who drank heavily in pregnancy.
Fetal stage -  The last stage of prenatal development, lasting from two months after conception until birth.
Figure -  What stands out when people organize visual information.
Fixation -  An inability to progress normally from one psychosexual stage of development into another.
Fixed-interval schedule -  A reinforcement schedule in which reinforcement happens after a set amount of time.
Fixed-ratio schedule -  A reinforcement schedule in which reinforcement happens after a set number of responses.
Flashbulb memories -  Vivid, detailed memories of important events.
Flooding -  A type of exposure therapy in which the client is exposed to a feared stimulus suddenly rather than gradually.
Flynn effect -  Phenomenon showing that people’s performance on IQ tests has improved over time in industrialized countries.
Foot-in-the-door phenomenon -  The tendency to agree to a difficult request if one has first agreed to an easy request.
Forebrain -  The biggest and most complex part of the brain, which includes structures such as the thalamus, the hypothalamus, the limbic system, and the cerebrum.
Forgetting curve -  A graph that shows how quickly learned information is forgotten over time.
Fovea -  The center of the retina, where vision is sharpest.
Free association -  A psychoanalytic technique that involves having the client verbalize all thoughts that come to mind.
Frequency -  The number of times per second a sound wave cycles from the highest to the lowest point.
Frequency theory -  A theory explaining how people discriminate low-pitched sounds that have a frequency below 1000 Hz.
Frustration -  The experience of being thwarted in the process of achieving a goal.
Frustration-aggression hypothesis -  A hypothesis stating that aggression is always caused by frustration.
Functional fixedness -  The tendency to think only of an object’s most common use in solving a problem.
Fundamental attribution error -  The tendency to attribute other people’s behavior to internal factors such as personality traits, abilities, and feelings. It is also called correspondence bias.

G

GABA -  The main inhibitory neurotransmitter in the brain.
Galvanic skin response -  An increase in the skin’s rate of electrical conductivity. It is also known as an electrodermal response.
Gambler’s fallacy -  The false belief that a chance event is more likely if it hasn’t happened recently.
Gate-control theory -  States that pain signals traveling from the body to the brain must go through a gate in the spinal cord.
Gender -  A learned distinction between masculinity and femininity.
Gender stereotypes -  Societal beliefs about the characteristics of males and females.
General adaptation syndrome -  The stress response of an organism, described by Hans Selye. The response has three stages: alarm, resistance, and exhaustion.
General intelligence factor (g) -  An ability that underlies all intelligent behavior, proposed by Charles Spearman.
Generalized anxiety disorder -  A disorder involving persistent and excessive anxiety or worry that lasts at least six months.
Generative -  The characteristic symbols of a language that can be combined to produce an infinite number of messages.
Genes -  Segments of DNA that function as hereditary units.
Germinal stage -  The two-week period after conception.
Gestalt psychology -  A German school of thought that studies how people organize visual information into patterns and forms.
Glial cells -  Cells that give structural support to neurons and nourish and insulate them.
Glucose -  A simple sugar that acts as an energy source for cells.
Glutamate -  The main excitatory neurotransmitter in the brain.
Grandiose delusion -  A belief centered around the idea that one is very important or famous.
Ground -  The background in which a figure stands when people organize visual information.
Group -  A social unit composed of two or more people who interact and depend on one another in some way.
Group cohesiveness -  The strength of the liking and commitment group members have toward one another and to the group.
Group polarization -  The tendency for a dominant point of view in a group to be strengthened to a more extreme position after a group discussion.
Groupthink -  The tendency of a close-knit group to emphasize consensus at the expense of critical thinking and rational decision making.

H

Hallucinations -  Sensory or perceptual experiences that happen without any external stimulus.
Hallucinogens -  Drugs that cause sensory and perceptual distortions.
Health psychology -  A branch of psychology that focuses on the relationship between psychosocial factors and the emergence, progression, and treatment of illness.
Heritability -  A mathematical estimate that indicates how much of a trait’s variation in a population can be attributed to genetic factors.
Heuristic -  A general rule of thumb that may lead to, but doesn’t guarantee, a correct solution to a problem.
Hierarchical classification -  The ability to classify according to more than one level.
Hierarchy of needs theory -  The idea, proposed by Abraham Maslow, that people are motivated by needs on four levels. Maslow believed people pay attention to higher needs only when lower needs are satisfied.
Higher-order conditioning -  In classical conditioning, the process by which a neutral stimulus comes to act as a conditioned stimulus by being paired with another stimulus that already evokes a conditioned response.
Hindbrain -  Portion of the brain consisting of the medulla, the pons, and the cerebellum.
Hindsight bias -  The tendency to interpret the past in a way that fits the present.
Hippocampus -  A part of the limbic system involved in memory.
Histogram or bar graph -  A plot that shows how data are distributed.
Histrionic personality -  A personality type characterized by a desire to be the center of attention and the tendency to be self-focused, excitable, highly open to suggestion, very emotional, and dramatic.
Histrionic personality disorder  -  A disorder characterized by attention-seeking behavior and shallow emotions.
Homeostasis -  Maintenance of a state of physiological equilibrium in the body.
Hormones -  Chemicals that are produced in glands and released into the bloodstream, involved in regulating body functions.
Humanism -  A school of thought that encourages seeing people’s lives as those people would see them.
Humanistic therapies -  Therapies aimed at helping people accept themselves and free themselves from unnecessary limitations.
Hypnosis -  A procedure in which suggestions are made to a person.
Hypochondriasis -  A disorder in which a person has constant fears of having a serious disease.
Hypothalamus -  A part of the forebrain that helps to control the pituitary gland, the autonomic nervous system, body temperature, and biological drives.
Hypothesis -  A testable prediction of what is going to happen given a certain set of conditions.

I

Iconic memory -  Visual sensory memory.
Id -  The component of the personality that contains instinctual energy.
Identity achievement -  A state in which a person commits to an identity after considering alternative possibilities.
Identity diffusion -  A state of confusion when a person lacks a clear sense of identity and hasn’t yet begun exploring issues related to identity development.
Identity foreclosure -  A state in which a person has prematurely committed to values or roles prescribed by others.
Identity moratorium -  A state in which commitment to an identity is delayed while a person experiments with various roles and values.
Illusion -  A misinterpretation of a sensory stimulus.
Immune system -  The body’s defense against harmful agents such as bacteria, viruses, and other foreign substances.
Implantation -  The process by which the embryo becomes embedded in the wall of the uterus.
Implicit attitudes -  Beliefs that are unconscious but that can still influence decisions and behavior.
Implicit memory -  Unconscious retention of information that affects thoughts and behavior.
Incentive -  An environmental stimulus that pulls people to act in a particular way.
Inclusive fitness -  The reproductive fitness of an individual organism plus any effect that the organism has on increasing reproductive fitness in related organisms.
Incongruence -  According to Carl Rogers and other humanistic therapists, a disparity between the self-concept and reality.
Independent variable -  The variable that is manipulated in an experiment.
Individual psychology -  Alfred Adler’s school of thought, which maintains that the main motivations for human behavior are not sexual or aggressive urges but strivings for superiority.
Inductive reasoning -  The drawing of a general conclusion from certain premises or statements.
Inferential statistics -  Statistics used to determine the likelihood that a result is just due to chance.
Inferiority complex -  An exaggerated sense of inferiority.
Informational social influence -  An individual’s tendency to conform because a group provides one with information.
Informed consent -  A subject’s voluntary agreement to participate in a research study, given after he or she has learned enough about the study to make a knowledgeable decision to participate.
Infradian rhythms -  Biological cycles that take longer than twenty-four hours.
Ingroup -  A group to which one belongs.
Inhibitory postsynaptic potential -  A negative change in voltage that occurs when a neurotransmitter binds to an inhibitory receptor.
Innate abilities -  Abilities that are present from birth.
Insanity -  A legal term that refers to the mental inability to take responsibility for one’s actions.
Insight therapies -  Treatments involving complex conversations between therapists and clients. The treatments aim to help clients understand the nature of their problems and the meaning of their behavior, thoughts, and feelings.
Insomnia -  A chronic problem with falling or staying asleep.
Instinctive drift -  The tendency for conditioning to be hindered by natural instincts.
Insulin -  A hormone secreted by the pancreas.
Integrative approach -  Therapy approaches that combine the ideas and techniques of several different schools of psychology.
Intelligence -  The capacity to acquire and apply knowledge. It includes the ability to benefit from past experience, act purposefully, solve problems, and adapt to new situations.
Intelligence quotient (IQ) -  A person’s mental age divided by his or her chronological age and multiplied by 100.
Interference theory -  States that people forget information because of interference from other learned information.
Intermittent reinforcement -  A reinforcement schedule in which reinforcement happens only on some of the occasions a particular response occurs. It is also called partial reinforcement.
Internal attribution -  An inference that an event or a person’s behavior is due to personal factors such as traits, abilities, or feelings. It is also called dispositional attribution.
Internal locus of control -  The tendency to believe that one has control over one’s circumstances.
Interpersonal attraction -  Positive feelings about another person.
Interpretation -  A psychoanalytic technique that involves suggesting the hidden meanings of free associations, dreams, feelings, memories, and behavior to the client.
Interval schedule -  The schedule in which reinforcement happens after a particular time interval.
Intimacy -  The warm, close, caring aspect of a romantic relationship.
Intrinsic motivation -  The motivation to act for the sake of the activity alone.
Ions -  Positively and negatively charged atoms and molecules.
Iris -  A ring of muscle that surrounds the pupil in the eye.
Irreversibility -  The inability to mentally reverse an operation.

J

James-Lange theory -  The idea that people experience emotion because they perceive their bodies’ physiological responses to external events.
Justification of effort -  The idea that if one works hard to reach a goal, one is likely to value that goal.
Just world hypothesis -  The tendency to believe that the world is fair and that people get what they deserve.

K

Kinesthesis -  The sense of the position and movement of body parts.

L

Laboratory observation -  An observational research method in which information about subjects is collected in a laboratory setting.
Language -  A system of symbols and rules used for meaningful communication.
Latent content -  The hidden meaning of a dream.
Lateralization -  The difference in specialization between the two hemispheres of the brain.
Law of effect -  A law proposed by Edward Thorndike stating that any behavior that has good consequences will tend to be repeated, and any behavior that has bad consequences will tend to be avoided.
Learned helplessness -  A tendency to give up passively in the face of unavoidable stressors.
Learning -  A change in behavior or knowledge that results from experience.
Learning model -  The idea that psychological disorders result from the reinforcement of abnormal behavior.
Learning model of addiction -  The idea that addiction is a way of coping with stress.
Lens -  Part of the eye behind the pupil and iris. It can adjust its shape to focus light from objects that are near or far away.
Leptin -  A hormone secreted by fat cells.
Lesioning studies -  An invasive method of studying the brain in which a specific, small area of the brain is destroyed.
Lie scales -  Statistics used to provide information about the likelihood that a subject is lying in a test.
Light -  A kind of electromagnetic radiation emitted by the sun, stars, fire, and lightbulbs.
Light adaptation -  The process by which receptor cells become less sensitive to light.
Light intensity -  The amount of light emitted or reflected by an object.
Limbic system -  A part of the forebrain involved in emotional experience and memory.
Linguistic relativity hypothesis -  A theory proposed by Benjamin Lee Whorf that claims that language determines the way people think.
Link method -  The process of associating items with one another in order to remember them.
Lithium -  A drug prescribed for treating bipolar disorders.
Lobotomy -  A surgical procedure that severs nerve tracts in the frontal lobe, formerly used to treat certain psychological disorders but now rarely performed.
Locus of control -  People’s perception of whether or not they have control over circumstances in their lives.
Long-term memory -  A memory system that stores an unlimited amount of information permanently.
Long-term potentiation -  A lasting change at synapses that occurs when long-term memories form.
Lowball technique -  The act of making an attractive proposition and revealing its downsides only after a person has agreed to it.
Lucid dreams -  Dreams in which people are aware that they are dreaming.

M

Magnetic resonance imaging (MRI) -  A method for studying the brain that uses magnetic fields and radio waves to produce pictures of the brain.
Major depressive disorder -  A disorder diagnosed after at least one major depressive episode.
Major depressive episode -  A period of at least two weeks marked by sadness or irritability and loss of interest in activities. Other symptoms may include changed sleeping or eating patterns, low energy, feelings of worthlessness or guilt, difficulty concentrating, and recurrent thoughts about suicide.
Managed care -  An arrangement for health care in which an organization, such as a health maintenance organization, acts as an intermediary between a person seeking care and a treatment provider.
Manifest content -  The plot of a dream.
Massed practice -  The process of learning material over a short period; also called cramming.
Matching hypothesis -  The idea that people tend to pick partners who are about equal in level of attractiveness to themselves.
Maturation -  Genetically programmed growth and development.
Mean -  The arithmetic average of a set of scores.
Measures of central tendency -  The mean, median, and mode.
Median -  The middle score in a set when all scores are arranged in order from lowest to highest.
Medical model -  A way of describing and explaining psychological disorders as if they are diseases.
Meditation -  The practice of focusing attention.
Medulla -  A part of the hindbrain that controls essential functions that are not under conscious control, such as breathing.
Melatonin -  A hormone that regulates the sleep cycle.
Memory -  The capacity for storing and retrieving information.
Menarche -  A woman’s first menstrual period.
Menopause -  The gradual, permanent cessation of menstruation.
Mental age -  The chronological age that typically corresponds to a particular level of performance. It is used as a measure of performance on intelligence tests.
Mental hospitals -  Medical institutions that specialize in providing treatment for psychological disorders.
Mental set -  A tendency to use only solutions that have worked in the past.
Mere exposure effect -  The tendency to like novel stimuli more if one encounters them repeatedly.
Metalinguistic awareness -  The capacity to think about how language is used.
Method of loci -  The process of imagining oneself physically in a familiar place in order to remember something.
Midbrain -  The part of the brain between the hindbrain and forebrain that is involved in locating events in space and that contains a dopamine-releasing system of neurons.
Midlife crisis -  A time of doubt and anxiety in middle adulthood.
Minnesota Multiphasic Personality Inventory (MMPI) -  A test developed to help clinical psychologists diagnose psychological disorders.
Misinformation effect -  The tendency for recollections of events to be distorted by information given after the event occurred.
Mnemonics -  Strategies for improving memory.
Mode -  The most frequently occurring score in a set of scores.
Monoamine oxidase inhibitors (MAOIs) -  A class of antidepressant drugs that increase the level of norepinephrine and serotonin.
Monocular cues -  Depth perception cues that require only one eye.
Monogenic traits -  Traits determined by a single gene.
Mood disorders -  Disorders characterized by marked disturbances in emotional state, which affect thinking, physical symptoms, social relationships, and behavior.
Moral reasoning -  The reasons and processes that cause people to think the way they do about right and wrong.
Morpheme -  The smallest meaningful unit in a language.
Motivated forgetting -  The idea that people forget things they don’t want to remember; also called psychogenic amnesia.
Motivation -  An internal process that makes a person move toward a goal.
Motive -  An impulse that causes a person to act.
Motor development -  The increasing coordination of muscles that makes physical movements possible.
Muller-Lyer illusion -  Illusion in which two lines of the same length appear to be different lengths because of different diagonal lines attached to the end of each line.
Mutations -  Small changes in genes.
Myelin sheath -  The fatty coating around some axons that increases the speed of neural impulse transmission.

N

Name calling -  A strategy of labeling people in order to influence their or others’ thinking.
Narcissistic personality disorder -  A disorder in which a person has an exaggerated sense of importance, a strong desire to be admired, and a lack of empathy.
Narcolepsy -  A tendency to fall asleep periodically during the day.
Narcotics -  Drugs that can relieve pain; also called opiates.
Narrative method -  The process of making up a story in order to remember something.
Naturalistic observation -  A method of collecting information about subjects in a natural setting without interfering with them in any way.
Negative correlation -  A relationship between two variables in which one variable increases as the other one decreases.
Negatively skewed distribution -  A data distribution with a few very low scores.
Negative punishment -  In operant conditioning, the removal of a stimulus after a response so that the response will be less likely to occur.
Negative reinforcement -  In operant conditioning, the removal of a stimulus after a response so that the response will be more likely to occur.
Negative symptoms -  Indicated by an absence or reduction of normal behavior.
NEO Personality Inventory -  A test that measures the Big Five traits: extraversion, openness to experience, agreeableness, conscientiousness, and neuroticism.
Nerves -  Bundles of axons extending from many neurons.
Nervous system -  A complex, highly coordinated network of tissues that communicate via electrochemical signals.
Neurons -  Nervous system cells that communicate via electrochemical signals.
Neurotransmitters -  Chemicals that are released from a neuron and activate another neuron.
Nocturnal emissions -  Signal of the onset of puberty for boys; also called wet dreams.
Norepinephrine -  A neurotransmitter involved in learning, memory, dreaming, awakening, emotion, and responses to stress.
Normal distribution -  A symmetrical bell-shaped curve that represents how characteristics such as IQ are distributed in a large population.
Normative social influence -  An individual’s tendency to conform because of a need to be accepted or not rejected by a group.
Norms -  Data that provide information about how a person’s test score compares with the scores of other test takers.
Nucleotides -  Biochemical units that make up DNA and genes.

O

Obedience -  Compliance with commands given by an authority figure.
Objective personality tests -  Tests that usually consist of self-report inventories. Commonly used objective tests include the MMPI-2, the 16PF, and the NEO Personality Inventory.
Objective test -  Generally a pencil-and-paper-type standardized test used to assess a psychological disorder.
Object permanence -  The ability to recognize that an object exists even when the object is not present and not perceived.
Object relations -  The relationships that people have with others, who are represented mentally as objects with certain attributes.
Observational learning -  A change in behavior or knowledge that happens by watching others. It can also be called vicarious conditioning.
Obsessions -  Persistent ideas, thoughts, impulses, or images that cause anxiety or distress.
Obsessive-compulsive disorder -  A disorder involving obsessions, compulsions, or both.
Occam’s razor -  See principle of parsimony.
Oedipus complex -  In psychoanalytic theory, a male child’s sexual desire for his mother and his hostility toward his father, whom he considers to be a rival for his mother’s love.
Operant conditioning -  A type of learning in which responses come to be controlled by their consequences.
Operational definition -  A way of stating precisely how a variable will be measured.
Opponent process theory -  A theory of color vision that states that the visual system has receptors responding in opposite ways to wavelengths associated with three pairs of colors.
Optic disk -  The point in the retina at which the optic nerve leaves the eye. This point is also called the blind spot.
Optic nerve -  A bundle of ganglion cell axons that originate in the retina.
Optimism -  The tendency to expect positive outcomes.
Ossicles -  Three bones in the middle ear called the hammer, the anvil, and the stirrup.
Outgroup -  A group to which one does not belong.
Overlearning -  Continuing to practice material even after it is learned in order to increase retention.
Overcompensation -  According to Alfred Adler, the attempt to cover up a sense of inferiority by focusing on outward signs of superiority such as status, wealth, and power.
Overconfidence effect -  The tendency for people to be too certain that their beliefs, decisions, estimates, and accuracy of recall are correct.

P

Panic attack -  A period in which a person has uncomfortable and frightening physical and psychological symptoms, including heart palpitations, trembling, fear of dying, and a perceived loss of control.
Panic disorder -  A disorder characterized by recurrent, unexpected panic attacks.
Papillae -  Small bumps on the skin that hold taste buds, which in turn hold the taste receptors in the tongue and throat, on the inside of the cheeks, and on the roof of the mouth.
Paranoid type -  A subtype of schizophrenia characterized by marked delusions or hallucinations and relatively normal cognitive and emotional functioning.
Parasympathetic nervous system -  Part of the autonomic nervous system that keeps the body still and conserves energy. It is active during states of relaxation.
Parental investment -  The sum of resources spent in order to produce and raise offspring.
Partial reinforcement effect -  Phenomenon in which responses resist extinction because of partial or intermittent schedules of reinforcement.
Passionate love -  Sexual desire and tenderness for, and intense absorption in, a person with whom one is romantically involved.
Peg word method -  Process of remembering a rhyme that associates numbers with words and words with the items to be remembered.
Penis envy -  In psychoanalytic theory, a sense of discontent and resentment that Freud thought women experience, resulting from their wish for a penis.
Percentile score -  A score that indicates the percentage of people who achieved the same as or less than a particular score.
Perception -  Organization and interpretation of sensory information.
Perceptual constancy -  The ability to recognize that an object is the same even when it produces different images on the retina.
Perceptual set -  The readiness to see in a particular way that’s based on expectations, experiences, emotions, and assumptions.
Perceptual speed -  The amount of time a person takes to accurately perceive and discriminate between stimuli.
Peripheral nervous system -  The part of the nervous system outside the brain and the spinal cord that includes the somatic nervous system and the autonomic nervous system.
Persecutory delusion -  A belief centered on the idea that one is being oppressed, pursued, or harassed.
Personality -  The collection of characteristic thoughts, feelings, and behaviors that make up a person.
Personality disorders -  Disorders characterized by stable patterns of experience and behavior that differ noticeably from patterns considered normal by a person’s culture.
Personal unconscious -  An individual’s unconscious, unique to him or her.
Person-centered theory -  A theory, proposed by Carl Rogers, stating that the self-concept is the most important feature of personality.
Person perception -  The process of forming impressions about other people.
Phi phenomenon -  An illusion of movement that arises when a series of images is presented very quickly one after another; also called stroboscopic movement.
Phoneme -  The smallest distinguishable unit in a language.
Phonemic encoding -  A way of encoding verbal information that emphasizes how words sound.
Photoreceptor -  Cells that are specialized to receive light stimuli.
Physical dependence -  Addiction based on a need to avoid withdrawal symptoms.
Pineal gland -  A gland that secretes melatonin.
Pinna -  The visible part of the ear.
Pituitary -  The master gland of the endocrine system, which regulates the function of many other glands.
Placebo effect -  The effect on a subject of receiving a fake drug or treatment. Expectations of improvement contribute to placebo effects.
Placenta -  The tissue that passes oxygen and nutrients from the mother’s blood into the fetus and removes waste materials from the fetus.
Place theory -  Explains how people discriminate high-pitched sounds that have a frequency greater than 5000 Hz.
Pleasure principle -  The drive to achieve pleasure and avoid pain. It is the operating principle of the id.
Polygenic traits -  Traits influenced by several genes.
Polygraph or lie detector -  A device that detects changes in autonomic arousal.
Polygyny -  A mating system in which a single male mates with many females.
Pons -  A part of the hindbrain involved in sleeping, waking, and dreaming.
Population -  The collection of individuals from which a sample is drawn.
Positive correlation -  A relationship between two variables in which as one variable increases, the other does too.
Positively skewed distribution -  A data distribution with a few very high scores.
Positive punishment -  In operant conditioning, the presentation of a stimulus after a response so that the response will be less likely to occur.
Positive reinforcement -  In operant conditioning, the presentation of a stimulus after a response so that the response will be more likely to occur.
Positive symptoms -  Symptoms indicated by the presence of altered behaviors.
Positron emission tomography (PET) -  A method for studying the brain that involves injecting a radioactive substance, which collects in active brain areas.
Postsynaptic neuron -  At a synapse, the neuron that receives a neurotransmitter.
Postsynaptic potential -  The voltage change that occurs at a receptor site of a postsynaptic neuron when a neurotransmitter molecule links up with a receptor molecule.
Posthypnotic amnesia -  The phenomenon that occurs when a person who has been hypnotized and instructed to forget what happened during hypnosis accordingly claims not to remember what happened.
Post–traumatic stress disorder (PTSD) -  A disorder in which a person constantly re-experiences a traumatic event, avoids stimuli associated with the trauma, and shows symptoms of increased arousal.
Preconscious -  The part of the mind that contains information that is outside of a person’s attention, which is not currently being attended to, but which is readily accessible if needed.
Prejudice -  A negative belief or feeling about a particular group of individuals.
Prenatal period -  The time between conception and birth.
Pressure -  A sense of being compelled to behave in a particular way because of expectations set by oneself or others.
Presynaptic neuron -  At a synapse, the neuron that releases a neurotransmitter.
Primary auditory cortex -  In the temporal lobe of the cerebrum, the brain part involved in processing auditory information.
Primary motor cortex -  In the frontal lobe of the cerebrum, the brain part involved in controlling muscle movement.
Primary process thinking -  Thinking that is irrational, illogical, and motivated by a desire of immediate gratification of impulses.
Primary punisher -  In operant conditioning, a consequence that is naturally unpleasant.
Primary reinforcer -  In operant conditioning, a consequence that is naturally satisfying.
Primary somatosensory cortex -  In the parietal lobe of the cerebrum, the brain part involved in handling touch-related information.
Primary visual cortex -  In the occipital lobe of the cerebrum, the brain part involved in handling visual information.
Priming -  The retrieval of a particular memory by activating information associated with that memory.
Principle of closure -  The Gestalt psychology principle that states that people tend to interpret familiar incomplete forms as complete by filling in gaps.
Principle of continuity -  The Gestalt psychology principle that states that people tend to perceive interrupted lines and patterns as continuous by filling in gaps.
Principle of parsimony -  The principle of applying the simplest possible explanation to any set of observations; also called Occam’s razor.
Principle of proximity -  The Gestalt psychology principle that states that people tend to perceive objects as a group when they are close together.
Principle of similarity -  The Gestalt psychology principle that states that people tend to group similar objects together.
Principle of simplicity -  The Gestalt psychology principle that states that people tend to perceive forms as simple, symmetrical figures rather than as irregular ones.
Prison study -  A famous study done by Philip Zimbardo that showed the influence of roles.
Proactive interference -  The forgetting of new information because of previously learned information.
Problem solving -  The active effort people make to achieve a goal that cannot be easily attained.
Procedural memory -  Memory of how to do things. Procedural memory is usually considered implicit.
Prognosis -  A prediction about the probable course and outcome of a disorder.
Projection -  A defense mechanism that involves attributing one’s own unacceptable thoughts or feelings to someone else.
Projective hypothesis -  The idea that people interpret ambiguous stimuli in ways that reveal their concerns, needs, conflicts, desires, and feelings.
Projective personality tests -  Tests that require subjects to respond to ambiguous stimuli, such as pictures and phrases, that can be interpreted in many different ways.
Projective test -  A test that requires psychologists to make judgments based on a subject’s responses to ambiguous stimuli. It is used to assess a psychological disorder.
Prototype -  A typical example of a concept.
Proximity -  The tendency to perceive objects that lie close together as groups.
Psychoactive drugs -  Drugs that have effects on sensory experience, perception, mood, thinking, and behavior.
Psychoanalysis -  A technique developed by Sigmund Freud to treat mental disorders. It is also a theory of personality developed by Freud that focuses on unconscious forces, the importance of childhood experiences, and division of the psyche into the id, ego, and superego.
Psychodynamic model -  The idea that psychological disorders result from maladaptive defenses against unconscious conflicts.
Psychodynamic theories -  Theories based on the work of Sigmund Freud. These theories emphasize unconscious motives and desires and the importance of childhood experiences in shaping personality.
Psychological dependence -  Addiction based on cravings for a drug.
Psychological test -  An instrument that is used to collect information about personality traits, emotional states, aptitudes, interests, abilities, values, or behaviors.
Psychometric approach -  A method of understanding intelligence that emphasizes people’s performance on standardized aptitude tests.
Psychophysics -  The study of the relationship between physical properties of stimuli and people’s experience of the stimuli.
Psychotherapy -  The treatment of psychological problems through confidential verbal communications with a mental health professional.
Puberty -  The beginning of adolescence, marked by menarche in girls and the beginning of nocturnal emissions in boys.
Pubescence -  The two years before puberty.
Punishment -  The delivery of a consequence that decreases the likelihood that a response will occur.
Pupil -  An opening that lets light into the back of the eye.
Pure light -  Light of a single wavelength.

R

Random assignment -  A way of placing subjects into either an experimental or a control group such that subjects have an equal chance of being placed in either one group or the other.
Range -  The difference between the highest and lowest scores in a set of scores.
Rapid eye movement (REM) sleep -  A stage of deep sleep in which brain wave activity is similar to that in the waking state. It is also called paradoxical sleep.
REM rebound effect -  The tendency to spend more time in the REM stage of sleep after a period of REM sleep deprivation.
Rational-emotive therapy -  A type of cognitive-behavioral therapy, developed by Albert Ellis, that aims to identify catastrophic thinking and to change the irrational assumptions that underlie it.
Rationalization -  A defense mechanism that involves using incorrect but self-serving explanations to justify unacceptable behavior, thoughts, or feelings.
Ratio schedule -  A schedule in which reinforcement happens after a certain number of responses.
Reaction formation -  A defense mechanism that involves behaving in a way that is opposite to behavior, feelings, or thoughts that are considered unacceptable.
Reaction range -  The limits that heredity places on characteristics such as IQ.
Reaction time -  The amount of time a subject takes to respond to a stimulus.
Reality principle -  The awareness that gratification of impulses has to be delayed in order to accommodate the demands of the real world. It also acts as the operating principle of the ego.
Recall -  The process of remembering without any external cues.
Receptive language -  The ability to understand language.
Reciprocal determinism -  The process of interaction between a person’s characteristics and the environment. This interaction results in personality.
Reciprocity norm -  An implicit rule in many societies that tells people they should return favors or gifts given to them.
Recognition -  The process of identifying learned information by using external cues.
Reflex -  An innate response to a stimulus.
Regression -  A defense mechanism that involves reverting to a more immature state of psychological development.
Regression toward the mean -  The tendency for extreme states to move toward the average when assessed a second time.
Rehearsal -  The process of practicing material in order to remember it.
Reinforcement -  The delivery of a consequence that increases the likelihood that a response will occur.
Reinforcement schedule -  The pattern in which reinforcement is given over time.
Relearning -  A method for measuring forgetting and retention, which involves assessing the amount of time it takes to memorize information a second time.
Reliability -  The ability of a test to produce the same result when administered at different times to the same group of people.
Replicability -  The ability of research to repeatedly yield the same results when done by different researchers.
Representativeness heuristic -  A rule-of-thumb strategy that estimates the probability of an event based on how typical that event is.
Representative sample -  A sample that corresponds to the population from which it is drawn in terms of age, sex, and other qualities on the variables being studied.
Repression -  A defense mechanism that involves keeping unpleasant thoughts, memories, and feelings shut up in the unconscious.
Reproductive advantage -  The outcome of a characteristic that helps an organism mate successfully and thus pass on its genes to the next generation.
Resistance -  A client’s usually unconscious efforts to block the progress of treatment.
Response tendency -  A learned tendency to behave in a particular way.
Resting potential -  The slight negative charge inside an inactive neuron.
Resting state -  The period during which the inside of a neuron has a slightly higher concentration of negatively charged ions than the outside does. A neuron during this time is inactive.
Retention -  The proportion of learned information that is retained or remembered.
Reticular formation -  A structure that includes parts of the hindbrain and midbrain and that is involved in sleep, wakefulness, pain perception, breathing, and muscle reflexes.
Retina -  A thin layer of neural tissue in the back of the eye.
Retinal disparity -  The difference between the images picked up by the two eyes.
Retrieval -  The process of getting information out of memory.
Retrieval cues -  Stimuli that help to get information out of memory.
Retroactive interference -  Forgetting of old information because of newly learned information.
Retrograde amnesia -  An inability to remember events that occurred before a brain injury or traumatic event.
Reuptake -  The process by which neurotransmitter molecules return to presynaptic neurons.
Reversibility -  The ability to reverse actions mentally.
Reversible figure -  An ambiguous drawing that can be interpreted in more than one way.
Risky shift -  The tendency for a dominant, risky point of view in a group to be strengthened to an even riskier position after a group discussion.
Rods -  Photoreceptor cells in the retina that allow people to see in dim light.
Rorschach test -  A series of ten inkblots that subjects are asked to describe. Psychologists then use complex scoring systems to interpret the subjects’ responses.

S

Sample -  A collection of subjects, drawn from a population, that a researcher studies.
Sampling bias -  A source of error that arises when the sample is not representative of the population that the researcher wants to study.
Scalloped response pattern -  The phenomenon in which responses are slow in the beginning of the interval and faster just before reinforcement happens. It occurs as a result of a fixed-interval schedule.
Schema -  A mental model of an object or event that includes knowledge about it as well as beliefs and expectations.
Schizoid personality disorder -  A disorder characterized by social withdrawal and restricted expression of emotions.
Schizophrenia -  A disorder involving a loss of contact with reality and symptoms that may include some of the following: hallucinations, delusions, disorganized speech or behavior, emotional flatness, social withdrawal, decreased richness of speech, and lack of motivation.
Scientific method -  A standardized way of making observations, gathering data, forming theories, testing predictions, and interpreting results.
Secondary process thinking -  Thinking that is logical and rational.
Secondary punisher -  In operant conditioning, a consequence that is unpleasant because it has become associated with a primary punisher. It is also called a conditioned punisher.
Secondary reinforcer -  In operant conditioning, a consequence that is satisfying because it has become associated with a primary reinforcer. It is also called a conditioned reinforcer.
Secondary sex characteristics -  Sex-specific physical traits that are not essential to reproduction, such as breasts, widened hips, facial hair, and deepened voices.
Sedatives -  Drugs that slow down the nervous system.
Selective attention -  The ability to focus on some pieces of sensory information and ignore others.
Selective serotonin reuptake inhibitors (SSRIs) -  A class of antidepressant drugs that increase the level of serotonin.
Self-actualization -  The need to realize one’s full potential. According to Maslow, this is human beings’ highest need, which arises after the satisfaction of more basic needs.
Self-concept -  According to Rogers, the most important feature of personality. The self-concept includes all the thoughts, feelings, and beliefs people have about themselves.
Self-effacing bias -  The tendency of people in certain cultures to attribute their successes to situational factors rather than to personal attributes and to attribute their failures to lack of effort.
Self-efficacy -  Confidence in one’s ability to meet challenges effectively.
Self-help groups -  Groups that are similar to therapy groups except that they do not have a therapist.
Self-report data -  Information that people being surveyed give about themselves.
Self-report inventory -  A paper-and-pen test that requires people to answer questions about their typical behavior.
Self-serving bias -  The tendency to attribute successes to internal factors and failures to situational factors.
Semantic encoding -  A way of encoding verbal information that emphasizes the meaning of words.
Semantic memory -  Remembering of general facts.
Semantic slanting -  A way of making statements so that they will evoke specific emotional responses.
Semicircular canals -  Three fluid-filled tubes that are the main structures in the vestibular system. They are located in the inner ear.
Sensation -  Occurs when physical energy from objects in the world or in the body stimulates the sense organs.
Sensory adaptation -  The decrease in sensitivity to an unchanging stimulus.
Sensory memory -  A memory system that stores incoming sensory information for an instant.
Separation anxiety -  The emotional distress babies show when separated from their caregivers.
Serotonin -  A neurotransmitter involved in sleep, wakefulness, appetite, aggression, impulsivity, sensory perception, temperature regulation, pain suppression, and mood.
Set point -  A genetically influenced determinant for body weight.
Sex -  A biological distinction between males and females.
Sexual script -  A set of implicit rules that allow a person to judge what sexual behavior is appropriate in a given situation.
Sexual selection -  Process in which females choose their mates based on certain characteristics that will then be passed on to their male offspring.
Shaping -  In operant conditioning, a procedure in which reinforcement is used to guide a response closer and closer to a desired response.
Short-term memory -  A memory system that stores a limited amount of information for a brief period.
Signal detection theory -  A theory used to predict when a weak signal will be detected.
Similarity -  The tendency to group similar objects together.
Simplicity -  The tendency to perceive forms as simple, symmetrical figures rather than as irregular ones.
Single-blind -  A procedure in which subjects don’t know whether they are in an experimental or control group.
Sixteen Personality Factor Questionnaire (16PF) -  A test that assesses sixteen basic dimensions of personality.
Skinner box -  A device used to study operant conditioning.
Sleep apnea -  A condition in which a person stops breathing many times during a night’s sleep.
Sleep spindles -  Short bursts of brain waves that occur during stage 2 sleep.
Smooth muscles -  Involuntary muscles that help organs such as the stomach and bladder carry out their functions.
Social clocks -  Social and cultural norms that indicate the typical ages at which people experience particular life events, behaviors, and issues.
Social desirability bias -  The tendency of some people to describe themselves in socially approved ways.
Social exchange theory -  A theory arguing that people help each other because they want to gain as much as possible while losing as little as possible.
Social facilitation -  The tendency for individuals to perform better in the presence of other people.
Social loafing -  The reduced effort people invest in a task when they are working with other people.
Social norms -  Societal rules about appropriate behavior.
Social phobia -  A disorder characterized by intense anxiety when exposed to certain kinds of social or performance situations.
Social responsibility norm -  A societal rule that tells people they should help others who need help even if doing so is costly.
Social roles -  Patterns of behavior that are considered appropriate for a person in a particular context.
Social schemas -  Mental models that represent and categorize social events and people.
Social skills training -  A behavioral therapy that aims to enhance a client’s relationships with other people.
Social trap -  A situation in which one harms oneself and others by acting in one’s self-interest.
Soma -  The central area of a neuron; also called the cell body.
Somatic nervous system -  The part of the peripheral nervous system that is connected to the skeletal muscles and sense organs.
Somatization disorder -  A disorder characterized by a wide variety of physical symptoms, such as pain and gastrointestinal, sexual, and pseudoneurological problems. The disorder begins before age thirty and continues for many years. It is also called hysteria or Briquet’s syndrome.
Somatoform disorders -  Disorders characterized by real physical symptoms that cannot be fully explained by a medical condition, the effects of a drug, or another mental disorder.
Sound waves -  Changes in pressure generated by vibrating molecules.
Source amnesia -  Inaccurate recall of the origin of information in memory. It is also called source misattribution or source monitoring error.
Specific phobia -  A disorder in which a person feels intense anxiety when exposed to a particular object or situation.
Spinal cord -  Connects the brain to the rest of the body.
Spinal reflexes -  Automatic behaviors that require no input from the brain.
Split-brain surgery -  A surgical operation in which the corpus callosum is cut, separating the two hemispheres of the brain.
Spontaneous recovery -  In classical conditioning, the reappearance of an extinguished conditioned response.
Stable attribution -  An inference that an event or behavior is due to stable, unchanging factors.
Stage -  A period in development when people show typical behavior patterns and capacities.
Standard deviation -  A statistic that indicates the degree to which scores vary around the mean of a distribution.
Standardized tests -  Tests with uniform procedures for administration and scoring.
Standardization -  The use of uniform procedures when administering and scoring tests.
Standardization sample -  A large group of people that is representative of the entire population of potential test takers.
States -  Temporary behaviors or feelings.
Statistical significance -  The likelihood that a result was not due to chance.
Statistics -  The analysis and interpretation of numerical data.
Stereotypes -  Beliefs about people based on their membership in a particular group.
Stimulants -  Drugs that stimulate the central nervous system.
Stimulus discrimination -  In classical conditioning, the tendency not to have a conditioned response to a new stimulus that’s similar to the original conditioned stimulus. In operant conditioning, it’s the tendency for a response to happen only when a particular stimulus is present.
Stimulus generalization -  In classical conditioning, the tendency to respond to a new stimulus as if it’s the original conditioned stimulus. In operant conditioning, it’s the tendency to respond to a new stimulus as if it’s the original discriminative stimulus.
Storage -  The process of maintaining information in memory.
Strange Situation -  An experiment devised for studying attachment behavior.
Stress -  The experience of being threatened by taxing circumstances. It also sometimes refers to circumstances that threaten well-being, to the response people have to threatening circumstances, or to the process of evaluating and coping with threatening circumstances.
Stressors -  Circumstances or events that are psychologically or physically demanding.
Structural encoding -  A way of encoding verbal information that emphasizes how words look.
Subject -  An individual person or animal that a researcher studies.
Subject bias -  Bias that results from the subject’s expectations or the subject’s changing of his or her behavior.
Subjective utility -  The process of making a decision by estimating the personal value of a decision’s outcome.
Subjective well-being -  The perception people have about their happiness and satisfaction with life.
Sublimation -  A defense mechanism that involves channeling unacceptable thoughts and feelings into socially acceptable behavior.
Substance abuse -  According to the DSM, a maladaptive pattern of drug use that results in repeated negative consequences such as legal, social, work-related, or school-related problems.
Superego -  The moral component of the personality.
Suprachiasmatic nucleus -  The main biological clock regulating circadian rhythms of sleep in humans.
Survey -  A method of getting information about a specific behavior, experience, or event by means of interviews or questionnaires, using several participants.
Survival advantage -  The outcome of a characteristic that helps an organism to live long enough to reproduce and pass on its genes.
Symbol -  A sound, gesture, or written character that represents an object, action, event, or idea.
Symbolic thought -  The ability to represent objects in terms of mental symbols.
Sympathetic nervous system -  Part of the autonomic nervous system that prepares the body for action and expends energy.
Synapse -  The junction between the axon of one neuron and the cell body or dendrite of a neighboring neuron.
Synaptic cleft -  The gap between two cells at a synapse.
Synaptic vesicles -  Small sacs inside a neuron’s terminal buttons, in which neurotransmitters are stored.
Syntax -  A system of rules that governs how words can be meaningfully arranged to form phrases and sentences.
Systematic densensitization -  A behavioral treatment that uses counterconditioning to decrease anxiety.

T

Tardive dyskinesia -  A serious side effect of antipsychotic drugs. It is usually a permanent condition, characterized by involuntary movements.
Telegraphic speech -  Speech that contains no articles or prepositions.
Temperament -  Innate personality features or dispositions.
Teratogen -  An agent such as a virus, a drug, or radiation that can cause deformities in an embryo or fetus.
Terminal buttons -  Bumps at the end of axons that release neurotransmitters.
Test-retest reliability -  The ability of a test to produce the same results when given to the same group of people at different times.
Thalamus -  The part of the brain through which almost all sensory information goes on its way to the cerebrum.
Thematic Apperception Test (TAT) -  A psychological test that requires people to make up stories about a set of ambiguous pictures. It is often used to measure the need for achievement.
Theory -  An explanation that organizes separate pieces of information in a coherent way.
Theory of natural selection -  A theory that explains the process of evolution. It states that inherited characteristics that give an organism a reproductive or survival advantage are passed on more often to future generations than other inherited characteristics.
Therapeutic window -  The amount of a drug that is required for an effect without toxicity.
Theta waves -  The type of brain waves present when a person is lightly asleep.
Timbre -  The particular quality of a sound.
Token economy -  A behavior modification program based on operant conditioning principles.
Tolerance -  The need over time for more and more of a drug to get the same effect.
Traits -  Characteristic behaviors and feelings that are consistent and long lasting.
Transcranial magnetic stimulation (TMS) -  A noninvasive procedure for treating severe depression that involves stimulation of the brain by means of a magnetic coil.
Transference -  The process by which clients relate to their psychoanalyst or therapist as they would to important figures in their past.
Transformation -  Making a series of changes to achieve a specific goal.
Trial and error -  Trying out different solutions until one works.
Triarchic theory of intelligence -  A theory proposed by Robert Sternberg that distinguishes among three aspects of intelligence.
Trichromatic theory -  A theory of color vision that states that there are three different types of cones in the retina, which are sensitive to light of three different wavelengths. It is also called the Young-Helmholtz theory.
Tricyclics -  A class of antidepressant drugs that increase the level of norepinephrine and serotonin.
Twin studies -  Studies in which researchers examine trait similarities between identical and fraternal twin pairs to figure out whether that trait might be inherited.
Two-factor theory -  The idea that people’s experience of emotion depends on two factors: physiological arousal and the cognitive interpretation of that arousal. When people perceive physiological symptoms of arousal, they look for an environmental explanation of this arousal.
Type A personality -  A personality type characterized by competitiveness, impatience, time pressure, anger, and hostility.
Type B personality -  A personality type characterized by relaxed, patient, easygoing, amiable behavior.

U

Ultradian rhythms -  Biological cycles that occur more than once a day.
Unconditional positive regard -  A therapist quality that is considered crucial in client-centered therapy. It involves nonjudgmental acceptance of the client.
Unconditioned response -  A naturally occurring response that happens without previous conditioning.
Unconditioned stimulus -  A stimulus that evokes an innate response.
Unconscious -  The part of the mind that contains thoughts, feelings, desires, and memories of which people have no awareness but that can influence people’s behavior.
Undifferentiated type -  A subtype of schizophrenia diagnosed if a patient does not meet criteria for paranoid, disorganized, or catatonic subtypes of schizophrenia.
Unstable attribution -  An inference that an event or behavior is due to unstable, temporary factors.

V

Validity -  The ability of a test to measure the characteristic it is supposed to measure.
Values -  Perceptions of what is important in life.
Variable -  An event, characteristic, behavior, or condition that researchers measure and study.
Variable-interval schedule -  A reinforcement schedule in which reinforcement happens after a particular average amount of time.
Variable-ratio schedule -  A reinforcement schedule in which reinforcement happens after a particular average number of responses.
Vestibular system -  The sensory system involved in balance.
Vulnerability-stress model -  The idea that individuals who have a biological vulnerability to a particular disorder will have the disorder only if certain environmental stressors are present.

W

Wavelength -  The distance between the peaks of waves.
Wernicke’s area -  A part of the brain, in the left temporal lobe, that is involved in understanding language.
Withdrawal symptoms -  Symptoms such as sweating, nausea, or shakiness that occurs when drug usage ceases.
Womb envy -  In Karen Horney’s view, the discontent and resentment that men experience because of their inability to bear children.
Working memory -  An active memory system that holds information while it’s processed or examined.

Z

Zygote -  A cell that results from the combination of a sperm cell and an egg during conception.

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