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.
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.
Kinesthesis – The sense of the position and movement of body parts.
Zygote – A cell that results from the combination of a sperm cell and an egg during conception.
SparkNotes Editors. (2005). SparkNote on Psychology Glossary. Retrieved November 17, 2016, from http://www.sparknotes.com/psychology/psych101/glossary/