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PANDAS See pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections.
panic attack A sudden episode consisting of terrifying bodily symptoms such as labored breathing, choking, dizziness, tingling in the hands and feet, sweating, trembling, heart palpitations, and chest pain. Panic attacks occur in a number of mental disorders and are common in phobias, panic disorder, and post-traumatic stress disorder (PTSD).
panic disorder An anxiety disorder characterized by repeated or disabling panic attacks. See also anxiety disorders, panic attack.
parallel distributed processing (PDP) Models of cognitive processing in which the relevant symbolic representations do not correspond to any one unit of the network but to the state of the network as a whole. See also connectionist model, distributed representation.
paranoid schizophrenia A subcategory of schizophrenia. Its dominant symptom is a set of delusions that are often elaborately systematized, usually of grandeur or persecution.
parasympathetic branch A division of the autonomic nervous system that serves vegetative functions and conserves bodily energies (e.g., slowing heart rate). Its action is often antagonistic to that of the sympathetic branch.
parietal lobe The lobe in each cerebral hemisphere that lies between the occipital and frontal lobes, and that includes the primary sensory projection area.
Parkinson's disease A degenerative neurological disorder characterized by various motor difficulties that include tremor, muscular rigidity, and slowed movement. This disease involves degeneration of dopamine-releasing neurons in the basal ganglia of the forebrain, which are crucial for motor control.
partial reinforcement A condition in which repeated responses are reinforced only some of the time.
parvo cells Ganglion cells found throughout the retina that, because of their sensitivity to differences in hue, are particularly suited to the perception of color and form. See also magno cells.
pattern recognition The process by which the perceptual system identifies the forms it encounters.
pattern theory The theory that a stimulus attribute is not coded by being sent along specific sensory fibers, but rather by a specific pattern of firing of all the relevant sensory fibers.
PDP See parallel distributed processing.
pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS) A medical condition related to streptococcus, commonly producing one or more of the OCD spectrum disorders.
penis envy In psychoanalytic theory, the wish for a penis that is assumed to ensue normally in females as part of the Electra complex.
percentile rank The percentage of all the scores in a distribution that lie below a given score.
perceptual constancies Constant attributes of a distal object, such as its shape and size, that we are able to perceive despite vagaries of the proximal stimulus.
perceptual organization A step of interpretation, provided by the perceiver, in which decisions are made about which elements of the display belong together, as parts of a larger whole, and which elements belong to different objects.
perceptual parsing The process of grouping various visual elements of a scene appropriately, deciding which elements go together and which do not.
peripheral nervous system The parts of the nervous system outside the central nervous system, including the cranial and spinal nerves that exit the skull and spinal column, respectively.
peripheral route to persuasion The processes involved in attitude change when someone does not care particularly about an issue or devotes few resources to thinking about the issue. This route depends on superficial considerations, such as the appearance of the person giving the persuasive information, and is contrasted with the central route.
permastore Near-permanent retention of some kinds of items in memory, mostly involving semantic or general knowledge (e.g., multiplication tables, names of family members).
permissive pattern A parental style in which parents try not to assert their authority and impose few restrictions or demands on their children.
perseveration The tendency to repeat the same response inappropriately, typically accompanying the defects in strategy formation often observed with prefrontal lesions.
personal space The physical region all around us whose intrusion we guard against. This aspect of human behavior has been likened to territoriality in animals.
persuasive communications Messages that openly try to convince us to act a certain way or to hold a particular belief.
PET (positron emission tomography) scan A technique for examining brain function by observing the degree of metabolic activity of different regions of the brain.
phallic stage In psychoanalytic theory, the stage of psychosexual development during which the child begins to regard his or her genitals as a major source of gratification.
phenotype The overt appearance and behavior of an organism, regardless of its genetic blueprint. See also genotype.
phenylalanine An amino acid that cannot be transformed due to an enzyme deficiency in those with phenylketonuria (PKU). In an infant with PKU, phenylalanine is converted into a toxic agent that accumulates in an infant's bloodstream and damages the developing nervous system.
phenylketonuria (PKU) A condition in which one lacks the gene that enables one to metabolize phenylalanine. If detected early enough, this condition can be treated by means of a special diet. If not detected early, this disorder can cause a severe form of retardation. See also phenylalanine.
phobia An anxiety disorder that is characterized by an intense and, at least on the surface, irrational fear. See also anxiety disorders, social phobia.
phoneme The smallest significant unit of sound in a language. In English, it corresponds roughly to a letter of the alphabet (e.g., apt, tap, and pat are all made up of the same phonemes).
photoreceptor One of the visual-pigment-filled light-sensitive cells at the back of the retina, whether rods or cones. These are the cells that transduce light energy into neural impulses, launching the processes of vision.
phrase An organized sequence of words within a sentence that functions as a unit.
phrase structure description A tree diagram that shows the hierarchical structure of a sentence. The descending branches of the tree correspond to smaller and smaller units of sentence structure.
pictorial cues The monocular depth cues (such as interposition, linear perspective, and relative size) that the eye exploits as depth cues; these cues are an optical consequence of the projection of a three-dimensional world onto a flat surface.
pitch The psychological dimension of sound that corresponds to frequency; as frequency increases, pitch appears to rise.
pituitary gland An endocrine gland that is actually a functional extension of the hypothalamus. The pituitary gland is often called the master gland because many of its secretions trigger hormone secretions in other glands.
PKU See phenylketonuria.
placebo In medical practice, a term for a chemically inert substance that produces real medical benefits because the patient believes it will help her.
placebo effect The medical or psychological benefits of a treatment produced simply because a patient believes the treatment has therapeutic powers.
place theory A theory of pitch proposed by Hermann von Helmholtz which states that different regions of the basilar membrane respond to different sound frequencies. The nervous system interprets the excitation from different basilar regions as different pitches.
plasticity The changeability of a trait or behavior with experience (e.g., eye color shows little plasticity, while hair color shows considerably more).
plateau According to some authors, one of the four stages of sexual arousal, and the stage during which orgasm occurs.
pluralistic ignorance A situation in which individuals in a group don't know that there are others in the group who share their perception (and often, their confusion), and interpret the others' inaction as reflecting knowledge that in truth is not there.
polyandry A type of mating system in which one female monopolizes the reproductive efforts of several males.
polygamy Any mating system, including polyandry and polygymy, in which one member of a sex monopolizes the reproductive efforts of several members of the other sex.
polygenic inheritance Inheritance of an attribute whose expression is controlled not by one but by many gene pairs.
polygyny A type of polygamous mating system in which one male monopolizes the reproductive efforts of several females.
pons The topmost portion of the hindbrain just above the medulla and in front of the cerebellum; it is involved in coordinating facial sensations and muscular actions, and in regulating sleep and arousal.
population The entire group of research participants (or test trials) about which the investigator wants to draw conclusions. See also sample.
positive psychology A movement within the field of psychology that seeks to emphasize in its research the factors that make people healthy, happy, able to cope, or well adjusted to their life circumstances.
positive symptoms of schizophrenia Symptoms that involve behavior or thinking that is either less pronounced or nonexistent in normal individuals, such as hallucinations, delusions, or bizarre behavior. See also negative symptoms of schizophrenia.
positron emission tomography (PET) scan See PET scan.
postsynaptic membrane The membrane of the receiving cell across the synaptic gap that contains specialized receptor sites.
postsynaptic neuron The cell receiving a neural message at the synapse.
post-traumatic stress disorder (PTSD) A chronic, sometimes lifelong disorder that has its onset some time after an especially stressful traumatic event. Symptoms include dissociation, recurrent nightmares, flashbacks, and sleep disturbances. See also acute stress disorder, anxiety disorders, dissociation.
potentiation In motivation, the tendency to make some behaviors, perceptions, and feelings more probable than others. See also long-term potentiation.
practical intelligence The intelligence required to solve everyday problems.
precursor A substance required for the chemical manufacture of some other substance.
predicate See concept.
predictive validity An assessment of whether a test measures what it is intended to measure; the assessment hinges on the correlation between the test score and some external criterion (e.g., a correlation between a scholastic aptitude test score and college grades).
prefrontal area The frontmost portion of the frontal lobes, which is involved in working memory, strategy formation, and response inhibition.
prefrontal lobotomy A neurosurgical treatment that surgically cuts the connections between the prefrontal areas of the frontal lobes and the rest of the brain. Once used widely (and mostly unsuccessfully) for many mental disorders but now performed very rarely.
preoperational period In Piaget's theory, the period from about ages two to six during which children come to represent actions and objects internally but cannot systematically manipulate these representations or relate them to each other. The child is therefore unable to conserve quantity across perceptual transformations and also is unable to take points of view other than his own.
preparedness theory of phobias The theory that phobias grow out of a built-in predisposition (preparedness) to learn to fear certain stimuli (e.g., snakes and spiders) that may have posed serious dangers to our primate ancestors.
prescriptionism The view that psychotherapeutic treatments for mental disorders may ultimately be like prescriptions for medications: tailored to both the disorder and the individual patient.
presynaptic facilitation A process that underlies many kinds of learning, documented in studies of Aplysia. It occurs when learning results in the increased readiness of presynaptic neurons to fire.
presynaptic neuron The cell that shoots a neurotransmitter across the synaptic gap.
primacy effect (1) In free recall, the tendency to recall the first items on a list more readily than those in the middle. (2) In forming an impression of another person, the tendency to give greater weight to attributes noted at the outset than to those noted later. See also recency effect.
primary messengers The neurochemicals responsible for neuron-to-neuron communication in chemical synapses, i.e., neurotransmitters. Primary messengers are contrasted with second messengers, those neurochemicals responsible for communication within neurons.
primary motor projection area A strip of cortex located at the back 0f the frontal lobe just ahead of the primary sensory projection area in the parietal lobe. This region is the primary projection area for muscular movements.
primary projection areas Regions of the cortex that serve as receiving stations for sensory information or as dispatching stations for motor commands.
primary sensory projection area Areas of the cortex that are the initial "receiving stations" for sensory information.
priming effect Phenomenon wherein giving a participant advance knowledge about or exposure to a stimulus can increase the ease of its subsequent recall or recognition.
primitive features Attributes of an object (such as its location, contour, color, and shape) that are first detected separately and then coordinated to enable identification of the object.
prisoner's dilemma A particular arrangement of payoffs in a two-person situation in which each individual has to choose between two alternatives without knowing the other's choice. The payoff structure is arranged such that the optimal strategy for each person depends upon whether she can trust the other or not. If trust is possible, the payoffs for each will be considerably higher than if there is no trust.
probability of response A common measure of the strength of conditioning, assessing the likelihood that a response will be produced.
procedural knowledge See declarative knowledge.
progesterone A female sex hormone that dominates the latter phase of the female cycle during which the uterine walls thicken to receive the embryo.
projection In psychoanalytic theory, a mechanism of defense in which various forbidden thoughts and impulses are attributed to another person rather than the self, thus warding off some anxiety (e.g., "I hate you" becomes "You hate me").
projective techniques Sometimes called unstructured personality tests. Methods of assessing personality that use relatively ambiguous stimuli in order to elicit responses that are unguarded and authentic. The most common projective techniques are the TAT and the Rorschach inkblot test.
propagation The spread of the action potential down an axon, caused by successive destabilizations of the neuronal membrane.
proposition See concept.
prosopagnosia The inability to recognize faces, usually produced by lesions in the parietal lobes.
prototype The typical example of a category of (e.g., a robin is a prototypical bird for many Americans).
prototype theory The theory that concepts are formed around average or typical exemplars rather than lists of single attributes.
proximal stimulus The stimulus information that actually reaches the sensory receptors. See also distal stimulus.
proximity (1) In perception, the closeness of two figures. The closer together they are, the more they will tend to be grouped together perceptually. (2) The nearness of people, which is one of the most important determinants of attraction and liking.
pseudohermaphroditism The most common kind of intersexuality, in which individuals have ambiguous genitalia. See also intersexual.
psychoanalysis (1) A theory of both normal and abnormal human personality development, formulated by Freud, whose key assertions include unconscious conflict and early psychosexual development. (2) A method of therapy that draws heavily on this theory of personality. Its main aim is to have the patient gain insight into her own unconscious thoughts and feelings. Therapeutic tools employed toward this end include free association, interpretation, and the appropriate use of the transference relationship between patient and analyst. See also free association, transference.
psychodynamic approach An approach to personality originally derived from psychoanalytic theory that asserts that personality differences are based on unconscious (dynamic) conflicts within the individual. See also humanistic approach, situationism, sociocultural approach, trait approach.
psychodynamic model An approach to mental disorders which holds that they are the end-products of internal psychological conflicts that generally originate in one's childhood experiences. See also learning model.
psychogenic disorders Disorders whose origins are psychological rather than organic (e.g., phobias).
psychogenic symptoms Symptoms believed to result from some psychological cause rather than from actual tissue damage.
psychological intensity The magnitude of a stimulus as it is perceived, not in terms of its physical attributes.
psychometric approach to intelligence An attempt to understand the nature of intelligence by studying the pattern of results obtained on intelligence tests.
psychopathology (1) The study of mental disorders, or (2) the mental disorder itself.
psychophysics An approach to understanding perception that relates the characteristics of physical stimuli to attributes of the sensory experience they produce.
psychosis Loss of contact with reality (most often evidenced as delusions or hallucinations), as can occur in severe cases of many kinds of mental disorders such as mania, major depression, or schizophrenia.
psychosurgery Neurosurgery performed to alleviate manifestations of mental disorders that cannot be brought under control using psychotherapy, medication, or other standard treatments. Psychosurgery can be helpful in severe cases of, for example, obsessive-compulsive disorder.
psychotherapy As used here, a collective term for all forms of treatment that use psychological rather than somatic methods.
psychotropic drugs Medications that seem to control, or at least moderate, the manifestations of mental disorder.
PTSD See post-traumatic stress disorder.
punishment A way to suppress a response by having its occurrence followed by an aversive event.
puzzle box An apparatus used by Edward Thorndike to demonstrate trial-and-error learning in cats. Animals were required to perform a simple action in order to escape the puzzle box and obtain food.
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