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Absolute Threshold
The minimum amount of sensory stimulation that can be detected 50% of the time.
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Accommodation
In vision, the flattening and bulging action of the lens as it focuses on images of objects on the retina. In learning, the process by which existing schemes are modified and new schemes are created to incorporate new objects, events, experiences or information.
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Acetylcholine
(ah-SEET-ul-KOH-leen)
A neurotransmitter that plays a role in learning new information, causes the skeletal muscle fibers to contract, and keeps the heart from beating to rabidly.
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Acquired Immune Deficiency Syndrom (AIDS)
A devastating and incurable illness that is caused by infection with the human immunodeficiency virus (HIV) and progressively weakens the body's immune system, leaving the person vulnerable to opportunistic infections that usually cause death.
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action potential
The sudden reversal of the resting potential, which initiates the firing of a neuron.
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activation-synthesis hypothesis of dreaming
The hypothesis that dreams are the brain's attempt to make sense of the random firing of brain cells during REM sleep.
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actor-observer effect
The tendency to attribute one's own behavior of others primarily to situational factors and the behavior of others primarily to dispositional factors.
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adolescence
The developmental stage that begins at puberty and encompasses the period from the end of childhood to the beginning of adulthood.
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adrenal glands
A pair of endocrine glands that release hormones that prepare the body for emergencies and stressful situations and also release corticoids and small amounts of the sex hormones.
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aerobic exercise
Exercise that uses the large muscle groups in continuous, repetitive action and increases oxygen intake and breathing and heart rates.
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afterimage
A visual sensation that remains after a stimulus is withdrawn.
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agression
The intentional infliction of physical or psychological harm to others.
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agoraphobia
An intense fear of being in a situation from which escape is not possible or in which help would not be available if one experienced overwhelming anxiety or a panic attack.
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alarm stage
The first stage of the general adaptation syndrome, in which the person experiences a burst of energy that aids in dealing with the stressful situation.
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algorithm
A systematic, step-by-step procedure, such as a mathematical formula, that guarantees a solution to a problem of a certain type if applied appropriately and executed properly.
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alpha wave
The brain-wave pattern associated with deep relaxation.
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altered state of conciousness
Changes in awareness produced by sleep, meditation, hypnosis, and drugs.
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alternative medicine
Any treatment or therapy that has not been scientifically demonstrated to be effective.
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alttruism
Behavior that is aimed at helping another, requires some self-sacrifice, and is not performed for personal gain.
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Alzheimer disease
An incurable form of dementia characterized by progressive deterioration of intellect and personality, resulting from widespread degeneration of brain cells.
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amnesia
A partial or complete loss of memory due to loss of consciousness, brain damage, or some psychological cause.
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amplitude
The measure of loudness of a sound; expressed in the unit called decibel.
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amygdala
a structure in the limbic system that plays an important role in emotion, particularly in response to unpleasant or punishing stimuli.
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analogy heuristic
A rule of thumb that applies to a solution that solved a problem in the past to a current problem that shares many features with the past problem.
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anorexia nervosa
An eating disorder characterized by an overwhelming, irrational fear of gaining weight or becoming fat, compulsive dieting to the point of self-starvation and excessive weight loss.
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anterograde amnesia
The inability to form long-term memories of events occurring after a brain injury or brain surgery, although memories formed before the trauma are usual intact and short-term memory is unaffected.
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antidepressant drugs
Drugs that act as mood elevators for severely depressed people and are also prescribed to treat some anxiety disorders.
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antipsychotic drugs
Drugs used to control severe psychotic symptoms, such as delusions, hallucinations, disorganized speech, and disorganized behavior, by inhibiting dopamine activity; also known as neuroleptics.
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anxiety disorders
Psychological disorders characterized by frequent fearful thoughts about what might happen in the future.
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aphasia
A loss or impairment of the ability to use or understand language, resulting from damage to the brain.
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applied research
Research conducted specifically to solve practical problems and improve the quality of life.
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approach-approach conflict
A conflict arising from having to choose between equally desirable alternatives.
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approach-avoidance conflict
A conflict arising when the same choice has both desirable and undesirable features.
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aptitude test
A test designed to predict a person's achievement or performance at some future time.
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archetype
Existing in the collective unconscious, an inherited tendency to respond to universal human situations in particular ways.
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arousal
A state of alertness and mental and physical activation.
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arousal theory
A theory of motivation suggesting that people are motivated to maintain an optimal level of alertness and physical and mental activation.
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artificial intelligence
The programming of computer systems to simulate human thinking in solving problems and in making judgments and decisions.
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artificial neural networks (ANNs)
Computer systems that are intended to mimic the human brain.
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assimilation
The process by which new objects, events, experiences, or information is incorporated into existing schemes.
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association areas
Areas of the cerebral cortex that house memories and are involved in thought, perception, and language.
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attachment
The strong affectionate bond a child forms with the mother or primary caregiver.
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attention
The process of sorting through sensations and selecting some of them for further processing.
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attitude
A relatively stable evaluation of a person, object, situation, or issue, along a continuum ranging from positive to negative.
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attribution
An assignment of a cause to explain one's own or another's behavior.
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audience effects
The impact of passive spectators on performance.
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audition
The sensation and process of hearing.
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authoritarian parents
Parents who make arbitrary rules, expect unquestioned obedience from their children, punish transgressions, and value obedience to authority.
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authoritative parents
Parents who set high but realistic standards, reason with the child, enforce limits, and encourage open communication and independence.
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availability heuristic
A cognitive rule of thumb that says that probability of an event or the importance assigned to it is based on its availability in memory.
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aversion therapy
A behavior therapy in which an aversive stimulus is paired with a harmful or socially undesirable behavior until the behavior becomes associated with pain or discomfort.
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avoidance learning
Learning to avoid events or conditions associated with aversive consequences or phobias.
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avoidance-avoidance conflict
A conflict arising from having to chose between undesirable alternatives.
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babbling
Vocalization of the basic speech sounds (phonemes), which begins between 4 & 6 months.
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