Dictionary of Terms


Pacinian Corpuscle A specialized, encapsulated somatosensory nerve ending, which detects mechanical stimuli, especially vibrations.

Panic A feeling of fear mixed with hopelessness or helplessness.

Panic Disorder Unpredictable attacks of acute anxiety that are accompanied by high levels of physiological arousal and that last from a few seconds to a few hours.

Papilla A small bump on the tongue that contains a group of taste buds.

Parallel Processor A computing device that can perform several operations simultaneously.

Paranoid Schizophrenia A form of schizophrenia in which the person suffers from delusions of persecution, grandeur, or control.

Parasympathetic Branch The portion of the autonomic nervous system that activates functions that occur during a relaxed state.

Parental Investment The resources including time, physical effort, and risks to life that a parent spends in procreation and in the feeding, nurturing, and protecting of the resulting offspring

Parietal Lobe The region of the cerebral cortex behind the frontal lobe and above the temporal lobe; contains the somatosensory cortex; is involved in spatial perception and memory.

Passionate Love An emotional, intense desire for sexual union with another person. Sometimes called "romantic love."

Peg word Method A mnemonic system in which items to be remembered are associated with a set of mental pegs that one already has in memory, such as key words of a rhyme.

Perception A rapid, automatic, unconscious process by which we recognize what is represented by the information provided by our sense organs.

Period of Concrete Operations The third period in Piagetís theory of cognitive development, during which children come to understand the conservation principle and other concepts, such as categorization.

Period of Formal Operations The fourth period in Piagetís theory of cognitive development, during which individuals first become capable of more formal kinds of abstract thinking and hypothetical reasoning.

Peripheral Nervous System The cranial and spinal nerves; that part of the nervous system peripheral to the brain and spinal cord.

Perseverance The tendency to continue to perform a behavior even when it is not being reinforced.

Person Variables Individual differences in cognition, which, according to Mischel, include competencies, encoding strategies and personal constructs, expectancies, subjective values, and self-regulatory systems and plans.

Personality A particular pattern of behavior and thinking prevailing across time and situations that differentiates one person from another.

Personality Psychology The branch of psychology that attempts to categorize and understand the causes of individual differences in patterns of behavior.

Personality Trait An enduring personal characteristic that reveals itself in a particular pattern of behavior in a variety of situations.

Personality Types Different categories into which personality characteristics can be assigned based on factors such as developmental experiences or physical characteristics.

Phallic Stage The third of Freudís psychosexual stage, during which the primary erogenous zone is the genital area. During this time, children become attached to the opposite-sex parent.

Phantom Limb Sensations that appear to originate in a limb that has been amputated.

Pharmacotherapy The treatment of psychological problems with chemical agents.

Phenotype The outward expression of an organismís genotype; an organismís physical appearance and behavior.

Phenylketonuria A genetic disorder caused by a pair of homozygous recessive genes and characterized by the inability to break down phenylalanine, an amino acid found in many high protein foods. The resulting high blood levels of phenylalanine cause mental retardation.

Phi Phenomenon The perception of movement caused by the turning on of two or more lights, one at a time, in sequence; often used on theater marquees; responsible for the apparent movement of images in movies and television.

Phobia Unreasonable fear of specific objects or situations, such as insects, animals, or enclosed spaces, learned through classical conditioning.

Phobic Disorder An unrealistic, excessive fear of a specific class of stimuli that interferes with normal activities. The object of the anxiety is readily identifiable: It may be a snake, an insect, the out-of-doors, or closed spaces.

Phoneme The minimum unit of sound that conveys meaning in a particular language, such as /p/.

Phonetic Reading Reading by decoding the phonetic significance of letter strings; "sound reading."

Phonological Dyslexia A reading disorder in which people can read familiar words but have difficulty reading unfamiliar words or pronounceable nonwords because they cannot sound out words.

Phonological Short-Term Memory Short-term memory for verbal information.

Photopigment A complex molecule found in photoreceptors; when struck by light, it bleaches and stimulates the membrane of the photoreceptor in which it resides.

Photoreceptor A receptive cell for vision in the retina; a rod or a cone.

Physiological Psychology The branch of psychology that studies the physiological basis of behavior.

Pituitary Gland An endocrine gland attached to the hypothalamus at the base of the brain.

Placebo An inert substance that cannot be distinguished from a real medication by the patient or subject; used as the control substance in a single-blind or double-blind experiment.

Pleasure Principle The rule that the id obeys: Obtain immediate gratification, whatever form it may take.

Polyandry The mating of one female with more than one male.

Polygraph An instrument that records changes in physiological processes such as brain activity, heart rate, and breathing.

Polygynandry The mating of several females with several males.

Polygyny The mating of one male with more than one female.

Pons The part of the brain stem just anterior to the medulla; involved in control of sleep.

Positive Reinforcement A consequence that increases the frequency of a response that is regularly and reliably followed by an appetitive stimulus.

Positive Symptoms Symptoms of schizophrenia that may include thought disorder, hallucinations, or delusions.

Postconventional Level Kohlbergís third and final level of moral development, in which people come to understand that moral rules include principles that apply across all situations and societies.

Posthypnotic Amnesia A failure to remember what occurred during hypnosis; induced by suggestions made during hypnosis.

Posthypnotic Suggestibility The tendency of a person to perform a behavior suggested by the hypnotist some time after the person has left the hypnotic state.

Postsynaptic Neuron A neuron with which the terminal buttons of another neuron form synapses and that is excited or inhibited by that neuron.

Posttraumatic Stress Disorder An anxiety disorder in which the individual has feelings of social withdrawal accompanied by untypically low levels of emotion caused by prolonged exposure to a stressor, such as a catastrophe.

Preconventional Level Kohlbergís first level of moral development, which bases moral behavior on external sanctions, such as authority and punishment.

Prefrontal Cortex The anterior part of the frontal lobe; contains the motor association cortex.

Prejudice An attitude or evaluation, usually negative, toward a group of people defined by their racial, ethnic, or religious heritage or by their gender, occupation, sexual orientation, level of education, place of residence, or membership in a particular group.

Prenatal Period The nine months between conception and birth. This period is divided into three developmental stages: the zygote, the embryo, and the fetal stages.

Preoperational Period The second of Piagetís periods, which represents a 4- to 5-year transitional period between first being able to think symbolically and then being able to think logically. During this stage, children become increasingly capable of speaking meaningful sentences.

Preoptic Area A region at the base of the brain just in front of the hypothalamus; contains neurons that appear to control the occurrence of slow-wave sleep.

Presynaptic Neuron A neuron whose terminal buttons form synapses with and excite or inhibit another neuron.

Preventive Psychology Any attempt to forestall the development of psychological problems by altering the sociocultural variables predictive of psychological distress.

Primacy Effect The tendency to remember initial information. In the memorization of a list of words, the primacy effect is evidenced by better recall of the words early in the list.

Primary Auditory Cortex The region of the cerebral cortex that receives information directly from the auditory system; located in the temporal lobes.

Primary Motor Cortex The region of the cerebral cortex that directly controls the movements of the body; located in the back part of the frontal lobes.

Primary Punisher A biologically significant aversive stimuli, such as pain.

Primary Reinforcer A biologically significant appetitive stimulus, such as food or water.

Primary Somatosensory cortex The region of the cerebral cortex that receives information directly from the somatosensory system (touch, pressure, vibration, pain, and temperature); located in the front part of the parietal lobes.

Primary Visual Cortex The region of the cerebral cortex that receives information directly from the visual system; located in the occipital lobes.

Proactive Interference Interference in recall that occurs when previously learned information disrupts our ability to remember newer information.

Problem-Focused Coping Any coping behavior that is directed at reducing or eliminating a stressor.

Process Schizophrenia According to Bleuler, a form of schizophrenia characterized by a gradual onset and a poor prognosis.

Progressive Relaxation Technique A relaxation technique involving three steps: (1) recognizing the bodyís signals that indicate the presence of stress; (2) using those signals as a cue to begin relaxing; and (3) relaxing groups of muscles, beginning with those in the head and neck and then those in the arms and legs.

Projection A defense mechanism in which oneís unacceptable behaviors or thoughts are attributed to someone else.

Projective Personality Tests Unstructured personality measures in which a person is shown a series of ambiguous stimuli, such as pictures, inkblots, or incomplete drawings. The person is asked to describe what he or she "sees" in each stimulus or to create stories that reflect the theme of the drawing or picture.

Prosody The use of changes in intonation and emphasis to convey meaning in speech besides that specified by the particular words; an important means of communication of emotion.

Prosopagnosia A form of visual agnosia characterized by difficulty in the recognition of peopleís faces; caused by damage to the visual association cortex.

Protanopia A form of hereditary anomalous color vision; caused by defective "red" cones in the retina.

Prototype A hypothetical idealized pattern that resides in the nervous system and is used to perceive objects or shapes by a process of comparison; recognition can occur even when an exact match is not found.

Protoword A unique string of phonemes that an infant invents and uses as a word.

Proximate Causes Immediate environmental events and conditions that affect behavior.

Psychoactive Substance Use Disorders Disorders are characterized by addiction to drugs or by abuse of drugs.

Psychoanalysis A form of therapy aimed at providing the client insight into his or her unconscious motivations and impulses.

Psychodynamic A term used to describe the Freudian notion that the mind is in a state of conflict among instincts, reasons, and conscience.

Psychogenic Amnesia A dissociative disorder characterized by the inability to remember important events or personal information.

Psychogenic Fugue Amnesia with no apparent organic cause accompanied by a flight away from home.

Psycholinguistics The branch of psychology devoted to the study of verbal behavior.

Psychology The scientific study of the causes of behavior; also, the application of the findings of psychological research to the solution of problems.

Psychoneuroimmunology Study of the interactions between the immune system and behavior as mediated by the nervous system.

Psychophysics A branch of psychology that measures the quantitative relation between physical stimuli and perceptual experience.

Psychophysiology The measurement of physiological responses, such as blood pressure and heart rate, to infer changes in internal states, such as emotions.

Psychosurgery Surgical destruction of brain tissue in the absence of any evidence of disease or damage in an attempt to treat mental disturbances.

Psychoticism The tendency to be aggressive, egocentric, and antisocial.

Puberty The period during which the reproductive systems mature, marking the beginning of the transition from childhood to adulthood.

Punishment A consequence that decreases the frequency of a response that is regularly and reliably followed by an aversive stimulus.

Pure Word Deafness The ability to hear, to speak, and (usually) to write, without being able to comprehend the meaning of speech; caused by bilateral temporal lobe damage.

Pursuit Movement The movement that the eyes make to maintain an image upon the fovea.

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