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SAD See seasonal affective disorders.
sample A subset of a population selected by the investigator for study. A random sample is constructed such that each member of the population has an equal chance of being picked. A stratified sample is constructed such that every relevant subgroup of the population is randomly sampled in proportion to its size. See also population.
sample mean The mean for a particular group of observations; often contrasted with the population mean, which is the mean of every possible observation. The population mean can also be obtained by obtaining the sample mean for sample after sample after sample, and then taking the mean of these means.
saturation A perceived dimension of visual stimuli that describes the "strength" of a color — the extent to which it appears rich or pale (e.g., light pink vs. hot pink).
savant syndrome A syndrome in a mentally retarded person who has some remarkable talent that seems out of keeping with his low level of general intelligence. Previously idiot savant, a term now abandoned as derogatory.
scaling A procedure for assigning numbers to a subject's responses. See also categorical scale, interval scale, nominal scale, ordinal scale, ratio scale.
scatter diagram See scatter plot.
scatter plot A graph depicting the relationship between two interval- or ratio-scale variables, with each axis representing one variable; often used to graph correlation data.
schedule of reinforcement The pattern of occasions on which responses are to be reinforced. Commonly, reinforcement is scheduled after a stipulated number of responses occurs or when a response occurs after a preset time interval has elapsed. See also fixed-ratio schedule, fixed-interval schedule.
schema (1) In theories of memory and thinking, a term that refers to a general cognitive structure in which information is organized. (2) In Piaget's theory of development, a mental pattern.
schizophrenia A group of severe mental disorders characterized by at least some of the following: marked disturbance of thought, withdrawal, inappropriate or flat emotions, delusions, and hallucinations. See also catatonic schizophrenia, disorganized schizophrenia, negative symptoms of schizophrenia, paranoid schizophrenia, positive symptoms of schizophrenia.
SD See standard deviation.
seasonal affective disorder (SAD) A mood disorder that shows reliable fluctuations with the time of year. One example is a depression that ensues in the fall when the days become shorter and ends in the spring when the days lengthen.
second messengers Neurochemicals within the neuron that regulate such mechanisms as the creation of receptor sites for specific neurotransmitters and the synthesis of the neuron's own neurotransmitter, thus determining the neuron's overall responsiveness. See also primary messengers.
second-order conditioning A form of learning in which a stimulus is first made meaningful or consequential for an organism through an initial step of learning, and then that stimulus is used as a basis for learning about some new stimulus. For example, an animal might first learn to associate a bell with food (first-order conditioning), but then learn to associate a light with the bell (second-order conditioning).
selection task A commonly used research task in which participants must decide which cards to turn over in order to determine if a rule has been followed or not.
selective serotonin reuptake inhibitors (SSRIs) Medications such as Prozac, Zoloft, and Paxil that increase serotonin turnover in the brain and find wide use as treatments for depression, obsessive-compulsive disorder, panic disorder, and many other disorders.
self-actualization According to Abraham Maslow and some other adherents of the humanistic approach to personality, the full realization of one's potential. See also hierarchy of needs.
self-concept Generally, the sum of one's beliefs about and attitudes toward oneself. For Carl Rogers, the sense of oneself as both agent and object.
self-control The ability to pursue a goal while adequately managing internal conflicts about it, or to delay pursuing a goal because of other considerations or constraints.
self-disclosure The act of revealing personal information; usually occurs reciprocally and facilitates intimacy.
self-efficacy The sense a person has about what things he can plausibly accomplish.
self-handicapping A self-protective strategy in which one arranges for an obvious and nonthreatening obstacle to one's own performance, such that any failure can be attributed to the obstacle and not to one's own limitations.
Self-Monitoring Scale A personality measure that seeks to determine the degree to which a person alters or adjusts their behavior in order to act appropriately in new circumstances.
self-perception theory The theory that we know our own attitudes and feelings only indirectly, by observing our own behavior and then performing much the same processes of attribution that we employ when trying to understand others.
self-report data Data supplied by the research participant describing herself (usually, ratings of attitudes or moods, or tallies of behavior), rather than that collected by the experimenter.
semantic feature The smallest significant unit of meaning within a word (e.g., male, human, and adult are semantic features of the word man).
semantic memory The component of generic memory that concerns the meaning of words and concepts.
semantic priming The enhanced performance on verbal tasks that occurs when the items being considered have similar meanings.
semantic role The part that each word plays in the "who did what to whom" drama described by a sentence; one word takes the role of being the cause of the action, another, the source of the action, and so on.
sensations According to the empiricists, the primitive experiences that emanate from the senses (e.g., greenness, bitterness).
sensation seeking A predisposition to seek novel experiences, look for thrills and adventure, and be highly susceptible to boredom.
sensitive period See critical period.
sensorimotor intelligence In Piaget's theory, intelligence during the first two years of life, consisting mainly of sensations and motor impulses, with little in the way of internalized representations.
sensory coding The process through which the nervous system represents the qualities of the incoming stimulus — whether auditory or visual, for example, or whether a red light or a green one, a sour taste or a sweet taste.
sensory neurons Neurons that convey information from sense organs to other portions of the nervous system.
sensory quality A distinguishing attribute of a stimulus (e.g., brightness or hue or pitch).
sentence A sequence of words constructed in accord with the rules of syntax. "The boy hit the ball" is a sentence, but "Ball the hit boy the," is not. Sentences do not have to be meaningful: "The green idea tripped" is a sentence, although "Tripped idea green the" is not.
serotonin (5HT) A neurotransmitter involved in many of the mechanisms of sleep, arousal, aggression, and mood.
setpoint A general term for the level at which negative feedback tries to maintain stability. An example is the setting of a thermostat.
sex flush One of the bodily states achieved during the plateau stage of sexual activity; in this stage, changes in blood flow can cause the skin on many surfaces to redden.
sexual dimorphism The state of affairs, observed in many species, in which the sexes differ in form (such as deer antlers or peacock tail feathers) or size. Sexual dimorphism is minimal among monogamous animals and maximal among polygamous ones.
sexual orientation A person's predisposition to choose members of the same or the opposite sex as romantic and sexual partners. See also bisexuality, heterosexuality, and homosexuality.
shadowing The procedure, often used in dichotic presentations, in which a participant is asked to repeat aloud, word for word, only what she hears through one earphone.
shallow processing The encoding of a stimulus using its superficial characteristics, such as the way a word sounds or the typeface in which it is printed.
shape constancy The tendency to perceive objects as retaining their shapes despite changes in our angle of regard that produce changes in the image projected on the retina.
shaping An instrumental learning procedure in which an animal (or human) learns a rather difficult response through the reinforcement of successive approximations to that response. See also successive approximations.
short-term memory See stage theory of memory.
signal-detection theory The theory that the act of perceiving or not perceiving a stimulus is actually a judgment about whether a momentary sensory experience is due to background noise alone or to the background noise plus a signal. The theory also includes a procedure for measuring sensory sensitivity.
signs In psychopathology, what the diagnostician observes about a patient's physical or mental condition (e.g., tremor, inattentiveness). See also symptoms, syndrome.
similarity In perception, a principle by which we tend to group like figures, especially by color and orientation.
simple reaction time A measurement of the speed with which a research participant can respond to a stimulus.
simultaneous color contrast The effect produced by the fact that any region in the visual field tends to induce its complementary color in adjoining areas. For example, a gray patch will tend to look bluish if surrounded by yellow and yellowish if surrounded by blue.
sine waves Waves (e.g., sound waves or light waves) that correspond to the plot of the trigonometric sine function.
single-case experiment A study in which the investigator manipulates the values of some independent variable, just as she would in an experiment with many participants, and then assesses the effects of this variable by recording a single participant's responses. See also case study.
situationism The view that human behavior is largely determined by the characteristics of the situation rather than personal predispositions. See also humanistic approach, psychodynamic approach, sociocultural perspective, trait approach.
size constancy The tendency to perceive objects as retaining their size, despite the increase or decrease in the size of the image projected on the retina caused by moving closer to or farther from the objects.
skewed A term used to describe distributions of experimental results that are asymmetrical (tending to have outlying values at one end).
skin senses The group of senses, including pressure, warmth, cold, and pain, through which an organism gains information about its immediate surround.
sleep paralysis The phenomenon of waking up unable to move for several seconds, due to the persistence of the loss of muscle tone that occurs during REM sleep. While sleep paralysis is sometimes frightening, it is harmless.
sleep-wake cycle A daily rhythm in which the body moves from alert vigilance to sleep and back again.
slow-wave sleep Type of sleep characterized by slow, rolling eye movements, an EEG indicative of low cortical arousal, slowed heart rate and respiration, and recall of "boring," mostly verbal dreams.
smooth muscles The nonstriated muscles controlled by the autonomic nervous system that constrict the blood vessels to help regulate blood pressure and that line many internal organs such as those that produce peristalsis in the digestive tract.
social cognition The way in which we interpret and try to comprehend social events.
social-cognitive approach A perspective on personality which argues that in explaining behavior, we should emphasize neither the person's traits by themselves nor the situation by itself. Instead, we should examine how people and situations change, moment by moment, in their interactions.
social comparison A process of reducing uncertainty about one's own beliefs and attitudes by comparing them to those of others.
social development A child's growth in his or her relations with other people.
social exchange A theory that asserts that each partner in a social relationship gives something to the other and expects to get something in return.
social facilitation The tendency to perform better in the presence of others than when alone. This facilitating effect works primarily for simple or well-practiced tasks.
social impact theory The theory that the influence others exert on an individual increases with their number, their immediacy, and their strength (e.g., status).
socialization The process whereby the child acquires the patterns of behavior characteristic of his or her society.
social learning theory A theoretical approach to socialization and personality that is midway between radical behaviorism and cognitive approaches to learning. It stresses learning by observing others who serve as models and who show the child whether a response he already knows should or should not be performed.
social loafing An example of the diffusion of social impact in which people working collectively on a task generate less total effort than they would had they worked alone.
social phobia A fear of embarrassment or humiliation that causes people to avoid situations that might expose them to public scrutiny. See also anxiety disorders, phobia.
sociocultural perspective Within social psychology and personality psychology, the view that many psychological phenomena, some of which have been presumed to be universal, result from or are affected substantially by cultural norms. See also humanistic approach, psychodynamic approach, trait approach, situationism.
sociopathy See antisocial personality disorder.
soma See cell body.
somatic division A division of the peripheral nervous system primarily concerned with the control of the skeletal musculature and the transmission of information from the sense organs.
somatization disorder A mental disorder in which the patient reports miscellaneous aches and pains in various bodily systems that do not add up to any known syndrome in physical medicine.
somatoform disorders The generic term for mental disorders in which bodily symptoms predominate despite the absence of any known physical cause; included are conversion disorder, hypochondriasis, somatization disorder, and somatoform pain disorder.
somatoform pain disorder A mental disorder in which the sufferer describes chronic pain for which there is no discernible physical basis.
somatogenic hypothesis The hypothesis that mental disorders result from organic (bodily) causes.
somatosensory area See primary sensory projection area.
sound waves Successive pressure variations in the air that vary in amplitude and wavelength.
source confusion A type of memory error in which information acquired in one context is remembered as having been encountered in another (e.g., a person's recalling that she had chocolate cake on her last birthday when she actually had it two birthdays ago).
spatial summation The process whereby two or more stimuli that are individually below threshold will elicit a reflex if they occur simultaneously at different points on the body.
spatial thinking The mental computations engaged in when we must locate objects and discern the spatial relationships among them.
specificity theory An approach to sensory experience which asserts that different sensory qualities are signaled by different neurons. These neurons are somehow labeled with their quality, so that whenever they fire, the nervous system interprets their activation as that particular sensory quality.
specific language impairment A syndrome in which individuals are very slow to learn language and throughout their lives have difficulty in understanding and producing many sentences, even though these individuals seem normal on most other measures, including measurements of intelligence.
spectral sensitivity The pattern of a receptor's (or pigment's) reactions to different wavelengths of light.
spectral sensitivity curve A graphical representation of a receptor's spectral sensitivity.
spontaneous recovery The reappearance of a previously extinguished response after a time interval in which neither the conditioned stimulus (CS) nor the unconditioned stimulus (US) is presented.
SSRIs See selective serotonin reuptake inhibitors.
stage theory of memory An approach to memory that proposes several memory stores. One is short-term (or working) memory, which holds a small amount of information for fairly short intervals; another is long-term memory, which can hold vast amounts of information for extended periods. According to the theory, information can only be transferred to long-term memory if it has first been in short-term memory.
standard deviation (SD) A measure of the variability of a frequency distribution, calculated as the square root of the variance (V) – SD = √V. See also variance (V).
standardization sample The group of individuals to which a test is given to decide what "normal" performance on the test looks like.
standard score (z-score) A score that is expressed as a deviation from the mean in standard deviations (SDs), which allows a comparison of scores drawn from different distributions; if M is the mean, then z = (score – M)/SD.
statistical reliability The degree to which an observed difference in sample means reflects a real difference in population means and is not attributable to chance.
statistics The process of quantitatively describing, analyzing, and making inferences about numerical data.
stereotypes Schemas by which people try to categorize complex groups. Group stereotypes are often negative, especially when applied to minority groups. See also out-group homogeneity effect.
stereotype threat A hypothesized mechanism through which a person's performance on a test (e.g., a test of intelligence) is influenced by her perception that the test results may confirm others' stereotypes about her.
stimulant An influence (typically, a drug) that has activating or excitatory effects on brain or bodily functions (e.g., amphetamines, Ritalin, cocaine).
stimulus generalization In classical conditioning, the tendency to respond to stimuli other than the original conditioned stimulus (CS). The greater the similarity between the CS and the new stimulus (CS+), the greater generalization will be. An analogous phenomenon in instrumental conditioning is a response to stimuli other than the original discriminative stimulus.
storage capacity The amount of information that can be retained in memory. See also magic number.
strategic retrieval A deliberate effort to recall information by supplying one's own retrieval cues (e.g., "Let's see, the last time I remember seeing my wallet was . . .").
stratified sampling An experimental procedure in which each subgroup of the population is sampled in proportion to its size.
stress In psychopathology, the psychological or physical wear-and-tear that, together with a preexisting vulnerability, may lead to mental disorder.
Stroop effect A marked decrease in the speed of naming the colors in which various color names (such as green, red, etc.) are printed when the colors and the names are different. An important example of automatization.
structured personality test A personality test (e.g., the MMPI or CPI) that asks specific questions and requires specific answers.
subcortical structures Usually the forebrain structures, such as those comprising the limbic system and extrapyramidal motor system, that lie beneath the cortex.
subjective contours Perceived contours that do not exist physically. We tend to complete figures that have gaps in them by perceiving a contour as continuing along its original path.
subroutines In a hierarchical organization, lower-level operations that function semiautonomously but are supervised by higher-level ones.
successive approximations The process of shaping a response by rewarding closer and closer versions of the desired response. See also shaping.
superego In Freud's theory, reaction patterns that emerge from within the ego, represent the internalized rules of society, and come to control the ego by punishment with guilt. See also ego, id.
syllogism A logic problem containing two premises and a conclusion that may or may not follow from them.
symbolic representation A type of mental representation that does not correspond to the physical characteristics of that which it represents. Thus, the word mouse does not resemble the small rodent it represents. See also analogical representation.
symmetrical distribution A distribution of numerical data in which deviations in either direction from the mean are equally frequent.
sympathetic branch The division of the autonomic nervous system that mobilizes the body's energies for physical activity (e.g., increasing heart rate, sweating, and respiration). Its action is typically antagonistic to that of the parasympathetic branch.
symptoms In psychopathology, what the patient reports about his physical or mental condition (e.g., nervousness, hearing voices). See also signs, syndrome.
synapse The juncture of two neurons, consisting of the presynaptic and postsynaptic membranes, and — in nonelectrical synapses — the synaptic gap between them.
synaptic gap The space between two communicating neurons; neurotransmitters are released by the presynaptic neuron, cross the synaptic gap, and trigger a response in the postsynaptic neuron.
synaptic reuptake The process through which neurotransmitters are reabsorbed by the presynaptic neuron, so that they can be released again, sending a new signal, the next time that axon fires.
synaptic vesicles Tiny sacs within a presynaptic membrane that contain the neurotransmitter; when the presynaptic neuron fires, some of these vesicles burst and eject their contents into the synaptic gap.
syndrome A pattern of signs and symptoms that tend to co-occur.
systematic desensitization A behavior therapy that tries to remove anxiety connected to various stimuli by gradually counterconditioning to them a response incompatible with fear, usually muscular relaxation. The stimuli are usually evoked as mental images according to an anxiety hierarchy, whereby relaxation is conditioned to the less frightening stimuli before the more frightening ones.
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