Northwestern State University, Louisiana. A. Sivert, MD: "Purchase online Bactroban cheap - Cheap online Bactroban OTC".
Although loudness is directly determined by the number of hair cells that are vibrating buy cheap bactroban 5 gm line acne gel prescription, two different mechanisms are used to detect pitch order bactroban 5 gm overnight delivery acne guidelines. The frequency theory of hearing proposes that whatever the pitch of a sound wave cheap 5 gm bactroban free shipping acne around nose, nerve impulses of a corresponding frequency will be sent to the auditory nerve 5gm bactroban for sale acne is a disorder associated with. For example, a tone measuring 600 hertz will be transduced into 600 nerve impulses a second. This theory has a problem with high-pitched sounds, however, because the neurons cannot fire fast enough. To reach the necessary speed, the neurons work together in a sort of volley system in which different neurons fire in sequence, allowing us to detect sounds up to about 4,000 hertz. The cochlea relays information about the specific area, or place, in the cochlea that is most activated by the incoming sound. The place theory of hearing proposes that different areas of the cochlea respond to different frequencies. Higher tones excite areas closest to the opening of the cochlea (near the oval window). Pitch is therefore determined in part by the area of the cochlea firing the most frequently. Just as having two eyes in slightly different positions allows us to perceive depth, so the fact that the ears are placed on either side of the head enables us to benefit from stereophonic, or three- dimensional, hearing. If a sound occurs on your left side, the left ear will receive the sound slightly sooner than the right ear, and the sound it receives will be more intense, allowing you to quickly determine the location of the sound. Although the distance between our two ears is only about 6 inches, and sound waves travel at 750 miles an hour, the time and intensity differences [2] are easily detected (Middlebrooks & Green, 1991). When a sound is equidistant from both ears, such as when it is directly in front, behind, beneath or overhead, we have more difficulty pinpointing its location. It is for this reason that dogs (and people, too) tend to cock their heads when trying to pinpoint a sound, so that the ears receive slightly different signals. Hearing Loss More than 31 million Americans suffer from some kind of hearing impairment (Kochkin, [3] 2005). Conductive hearing loss is caused by physical damage to the ear (such as to the eardrums or ossicles) that reduce the ability of the ear to transfer vibrations from the outer ear to the inner ear. Sensorineural hearing loss, which is caused by damage to the cilia or to the [4] auditory nerve, is less common overall but frequently occurs with age (Tennesen, 2007). The cilia are extremely fragile, and by the time we are 65 years old, we will have lost 40% of them, [5] particularly those that respond to high-pitched sounds (Chisolm, Willott, & Lister, 2003). Prolonged exposure to loud sounds will eventually create sensorineural hearing loss as the cilia are damaged by the noise. People who constantly operate noisy machinery without using Attributed to Charles Stangor Saylor. Sounds that are 85 decibels or more can cause damage to your hearing, particularly if you are exposed to them repeatedly. Sounds of more than 130 decibels are dangerous even if you are exposed to them infrequently. People who experience tinnitus (a ringing or a buzzing sensation) after being exposed to loud sounds have very likely experienced some damage to their cilia. Taking precautions when being exposed to loud sound is important, as cilia do not grow back. While conductive hearing loss can often be improved through hearing aids that amplify the sound, they are of little help to sensorineural hearing loss. A cochlear implant is a device made up of a series of electrodes that are placed inside the cochlea. The device serves to bypass the hair cells by stimulating the auditory nerve cells directly. The latest implants utilize place theory, enabling different spots on the implant to respond to different levels of pitch. The cochlear implant can help children hear who would normally be deaf, and if the device is implanted early enough, these children can frequently learn to speak, often as well as normal children do (Dettman, Pinder, Briggs, Dowell, [6] & Leigh, 2007; Dorman & Wilson, 2004). The resulting vibrations are relayed by the three ossicles, causing the oval window covering the cochlea to vibrate. The vibrations are detected by the cilia (hair cells) and sent via the auditory nerve to the auditory cortex. The place theory of hearing suggests that we hear different pitches because different areas of the cochlea respond to higher and lower pitches. Sensorineural hearing loss, caused by damage to the hair cells or auditory nerves in the inner ear, may be produced by prolonged exposure to sounds of more than 85 decibels. Given what you have learned about hearing in this chapter, are you engaging in any activities that might cause long- term hearing loss? If so, how might you change your behavior to reduce the likelihood of suffering damage? The aging auditory system: Anatomic and physiologic changes and implications for rehabilitation. Communication development in children who receive the cochlear implant younger than 12 months: Risk versus benefits. Summarize how the senses of taste and olfaction transduce stimuli into perceptions. Although vision and hearing are by far the most important, human sensation is rounded out by four other senses, each of which provides an essential avenue to a better understanding of and response to the world around us. These other senses are touch, taste, smell, and our sense of body position and movement (proprioception). Tasting Taste is important not only because it allows us to enjoy the food we eat, but even more crucial, because it leads us toward foods that provide energy (sugar, for instance) and away from foods that could be harmful. Many children are picky eaters for a reason—they are biologically predisposed to be very careful about what they eat. Together with the sense of smell, taste helps us maintain appetite, assess potential dangers (such as the odor of a gas leak or a burning house), and avoid eating poisonous or spoiled food. The tongue detects six different taste sensations, known respectively as sweet, salty, sour, bitter, piquancy (spicy), and umami (savory). Our tongues are covered with taste buds, which are designed to sense chemicals in the mouth. Most taste buds are located in the top outer edges of the tongue, but there are also receptors at the back of the tongue as well as on the walls of the mouth and at the back of the throat. As we chew food, it dissolves and enters the taste buds, triggering nerve impulses that are transmitted to the [2] brain (Northcutt, 2004). Human tongues are covered with 2,000 to 10,000 taste buds, and each bud contains between 50 and 100 taste receptor cells. Taste buds are activated very quickly; a salty or sweet taste that touches a taste bud for even one tenth of a second will trigger a neural [3] impulse (Kelling & Halpern, 1983). On average, taste buds live for about 5 days, after which Attributed to Charles Stangor Saylor. As we get older, however, the rate of creation decreases making us less sensitive to taste. This change helps explain why some foods that seem so unpleasant in childhood are more enjoyable in adulthood.
Additional information:
The atrioventricular opening between the right atrium and right ventricle is covered by the a order bactroban 5gm with amex skin care blog. Four structures play key roles in this dance — the sinoatrial node purchase bactroban 5gm on-line acne vulgaris description, atrioventricular node buy 5 gm bactroban with visa acne 7 year old, atrioventricular bundle cheap bactroban 5 gm visa skin care zinc oxide, and Purkinje fibers. Rather than both contracting and conducting impulses as other cardiac muscle does, these structures specialize in conduction alone, setting the pace for the rest of the heart. Following is a bit more information about each one: Sinoatrial node: This node really is the pacemaker of the heart. Located at the junction of the superior vena cava and the right atrium, this small knot, or mass, of specialized heart muscle initiates an electrical impulse that moves over the musculature of both atria, causing atrial walls to contract simultaneously and emptying blood into both ventricles. Atrioventricular node: The impulse that starts in the S-A node moves to this mass of modified cardiac tissue that’s located in the septal wall of the right atrium. Also called the A-V node, it directs the impulse to the A-V bundles in the septum. Atrioventricular bundle: From the A-V node, the impulse moves into the atri- oventricular bundle, also known as the A-V bundle or bundle of His (pronounced “hiss”). The bundle breaks into two branches that extend down the sides of the interventricular septum under the endocardium to the heart’s apex. Purkinje fibers: At the apex, the bundles break up into terminal conducting fibers, or Purkinje fibers, and merge with the muscular inner walls of the ventricles. The pulse then stimulates ventricular contraction that begins at the apex and moves toward the base of the heart, forcing blood toward the aorta and pulmonary artery. One of the best ways to detect cardiac tissue under a microscope is to look for undu- lating double membranes called intercalated discs separating adjacent cardiac muscle fibers. Gap junctions in the discs permit ions to pass between the cells, spreading the Chapter 10: Spreading the Love: The Circulatory System 171 action potential of the electrical impulse and synchronizing cardiac muscle contrac- tions. Potential problems include fibrillation, a breakdown in rhythm or propagation of the impulses that causes individual fibers to act independently, and heart block, an interruption that causes the atria and ventricles to take on their own rates of contrac- tion. Left atrium Sinoatrial node (pacemaker) Purkinje fibers Atrioventricular node Figure 10-4: Right atrium The conductive Purkinje fibers system of the heart. Wolters Kluwer Health — Lippincott Williams &Wilkins A healthy heart makes a “lub-dub” sound as it beats. The first sound (the “lub”) is heard most clearly near the apex of the heart and comes at the beginning of ventricu- lar systole (the closing of the atrioventricular valves and opening of the semilunar valves). It’s lower in pitch and longer in duration than the second sound (the “dub”), heard most clearly over the second rib, which results from the semilunar valves clos- ing during ventricular diastole. Defects in the valves can cause turbulence or regurgita- tion of blood that can be heard through a stethoscope. S-A node → Purkinje fibers → Bundle of His → A-V node Riding the Network of Blood Vessels Blood vessels come in three varieties, which you can see illustrated in Figure 10-5: Arteries carry blood away from the heart. Small ones are called arterioles, and microscopically small ones are called metarterioles. Veins carry blood toward the heart; all veins except the pulmonary veins contain deoxygenated blood. Microscopically small capillaries carry blood from arterioles to venules, but sometimes tiny spaces in the liver and elsewhere called sinusoids replace capillaries. The walls of arteries and veins have three layers: the outermost tunica externa (some- times called tunica adventitia) composed of white fibrous connective tissue, a central “active” layer called the tunica media composed of smooth muscle fibers and yellow elastic fibers, and an inner layer called the tunica intima made up of endothelium that aids in preventing blood coagulation by reducing the resistance of blood flow. Arterial walls are very strong, thick, and very elastic to withstand the great pressure to which the arteries are subjected. In elastic arteries, found prima- rily near the heart, the tunica media is composed of yellow elastic fibers that stretch Chapter 10: Spreading the Love: The Circulatory System 173 with each systole and recoil during diastole; essentially they act as shock absorbers to smooth out blood flow. In muscular arteries, the tunica media consists primarily of smooth muscle fibers that are active in blood flow and distribution of blood. The larger blood vessels have smaller blood vessels, the vasa vasorum, that carry nourish- ment to the vessel wall. Venule Vein Capillaries Blood flow Figure 10-5: Arteriole The capillary Artery exchange. While larger in diameter than arteries, veins have thinner walls and are less distensible and elastic. Veins that carry blood against the force of gravity, such as those in the legs and feet, contain valves to prevent backsliding into the capillaries. Normally the blood that veins are returning to the heart is unoxygenated (contains carbon dioxide); the one exception is the pulmonary vein, which returns oxygenated blood to the heart from the lungs. Capillaries are breathtakingly tiny and capable of forming vast networks, or capillary beds. Blood from the digestive tract takes a detour through the hepatic portal vein to the liver before continuing on to the heart. Called the hepatic portal system, this circuitous route helps regulate the amount of glucose circulating in the bloodstream (see Figure 10-6). As the blood flows through the sinusoids of the liver, hepatic parenchymal cells remove the nutrient materials. Phagocytic cells in the sinusoids remove bacteria and other foreign materials from the blood. The blood exits the liver by the hepatic veins, which carry it to the inferior vena cava, which ultimately returns it to the heart. Wolters Kluwer Health — Lippincott Williams &Wilkins Beating from the Start: Fetal Circulation Because nutrients and oxygen come from the mother’s bloodstream, fetal circulation requires extra vessels to get the job done. Two umbilical arteries — the umbilical vein and the ductus venosus — fill the bill. Fetal blood leaves the placenta through the umbilical vein, which branches at the liver to become the ductus venosus before enter- ing the inferior vena cava that carries blood to the right atrium and then through a hole in the septum called the foramen ovale into the left atrium. From there it flows into the left ventricle and is pumped through the aorta to the head, neck, and upper extremities. It returns to the heart through the superior vena cava, to the right atrium, to the right ventricle, to the pulmonary trunk (lungs inactive), goes through the ductus arteriosus into the aorta, to the abdominal and pelvic viscera and lower extremities, and to the placenta through the umbilical artery. After birth, these circulation path- ways quickly shut down, eventually leaving a depression in the septum, the fossa ovale, where the hole of the foramen ovale once was. In fetal hepatic portal circulation, blood flows directly into the systemic circulation through the a. Number the structures in the correct sequence of blood flow from the heart to the radial artery for pulse. Number the structures in the correct sequence of blood flow from the forearm to the heart. Number the structures in the correct sequence of blood flow from the great saphenous vein back to the heart. Follow a drop of blood from the aortic semilunar valve of the heart to the forearm and back to the heart. Pulmonary circuit b The system for maintaining a constant internal environment in other tissues: c. Faster than that indicates the individual probably is exercising; slower than that means that the individual either is sick or is a highly trained athlete. Parietal pericardium j A tissue composed of layers and bundles of cardiac muscles: d.
O B) Steaming at 100 C It is used to sterilize media containing ingredients that would be O inactivated at temperature over 100 C and re-melt previously bottled sterile agar media generic bactroban 5 gm amex skin care gift baskets. C) Filtration It is used to sterilize additives that are heat-sensitive and can not be autoclaved bactroban 5 gm otc acne 6 year old. Turbidity in fluid media and microbial growth in solid media confirm contamination purchase bactroban 5gm with amex acne scar laser treatment. Addition of heat-sensitive ingredients Refrigerated-heat sensitive ingredients should be warmed at room temperature before added to a molten agar medium effective 5 gm bactroban skin care with peptides. Using an aseptic technique, the ingredients should be added when O the medium has cooled to 50 C, and should be distributed immediately unless further heating is required. Dispensing of culture media Media should be dispensed in a clean draught-free room using aseptic technique and sterile container. Dispensing agar media in petridish • Lay out the sterile petridishes on a level surface. Quality control • Inoculate quarter plates of the medium with a five hours broth culture for each control organism. Storage of culture media • Dehydrated culture media and dry ingredients should be stored at an even temperature in a cool dry place away from direct light. Aseptic technique during inoculation of culture media • Decontaminate the workbench before and after the work of the day. Sterlizing the Inoculating the fluid inoculating loop media with sterilized with flame loop Fig. Before inoculating a plate of culture media, dry the surface of the O media by incubating at 37 C for 30 minutes. To inoculate a plate, apply the inoculum to a small area of the plate (‘the well’) using sterile wire loop and then spread and thin out the inoculum to ensure single colony growth. Inoculation of slant media To inoculate slant media, use a straight wire to streak the inoculum down the center of the slant and then spread the inoculum in a zigzag pattern. Optimal temperature, humidity and gaseous atmosphere should be provided for microorganisms to grow best. Anaerobic atmosphere is essential for the growth of strict anaerobes, and the techniques for obtaining anaerobic conditions are the following:. Bacterial structural components and the macromolecules for the metabolism are synthesized from the elements. The four most important elements of bacteria are carbon, hydrogen, oxygen and nitrogen. Carbon Organisms require a source of carbon for the synthesis of numerous organic compounds that comprise protoplast. Autotrophs: Free-living, non-parasitic bacteria which use carbondioxide as carbon source. Heterotrophs: Parasitic bacteria require more complex organic compounds as their source of carbon and energy. Growth factors Growth factors are organic compounds that are required by micro- organisms in small amounts which the cell can not synthesize from other carbon source. Auxotrophs: Mutant bacteria, which require an additional growth factor not needed by the parental or wild type strain. Generation time It is the time taken for the size of a bacterial population to double. Bacteria grow by taking nutrients and incorporate them into cellular components; then bacteria divide into two equal daughter cells and double the number. Bacterial growth phases The pattern in cell numbers exhibited by bacterial population obtained after inoculation Of a bacterium into a new culture medium. Cell division precedes at a logarithmic rate, and determined by the medium and condition of the culture. Maximal stationary phase The period when the bacteria have achieved their maximal cell density or yield. A bacterial population may reach stationary growth when one of the following conditions occur: 1. Decline phase The period at which the rate of death of bacterial cells exceeds the rate of new cell formation. Few organisms may persist for so long time at this period at the expense of nutrients released from dying micro-organisms. Viable plate count The most common method of estimating bacterial growth which involves counting the number of bacterial colonies grown on solid media after incubation of the inoculated media for 18-24 hours. Greater than 300 colonies on a plate are too close to distinguish as an individual colony forming unit (too numerous to count). Limitation of viable plate count: It selectively in favor of a certain group of bacterial population. Direct count It involves direct microscopic counting of bacteria in the sample using counting chamber. Turbidimetric method It is the method of determination of bacterial growth in liquid media. Factors influencing bacterial growth in vitro Not all bacterial species grow under identical environmental conditions. Each bacterial species has a specific tolerance range for specific environmental parameters. Out side the tolerance range environmental conditions for a bacteria to reproduce, it may survive in dormant state or may lose viability. Rates of bacterial growth are greatly influenced by the following environmental parameters. Temperature Temperature tolerance range: The minimum and maximum temperature at which a micro-organism can grow; which is different in different species of bacteria. Optimal growth range of temperature: The temperature at which the maximum growth rate occurs; and results in the shortest generation time of bacteria. Based on different optimal growth temperature requirement, bacteria are divided into: 54 Optimal growth temperature o 0. Oxygen Base on oxygen requirements and tolerance, bacteria are divided classified as:. Microaerophiles • Obligate aerobic bacteria grow only when free oxygen is available to support their respiratory metabolism. H P <7 is acidic H P =7 is neutral H P >7 ia alkaline H • Neutrophilic bacteria grow best at near neutral P value. High salt concentration disrupts membrane transport systems and denatures proteins of bacteria but halophiles have adaptive mechanisms to tolerate high salt concentration. Pressure Osmotic pressure: The pressure exerted on bacterial cell surface as a result of difference in solute concentration between the inside and out side of a cell. High hydrostatic pressures more than 200 atmosphere generally inactivates enzymes and disrupts membrane transport process.
It can help sociation for the Advancement of Behavior Therapy free depressed children from the pervasive feelings of identify themselves as cognitive behaviorists purchase 5 gm bactroban free shipping skin care olive oil. Children in treatment are assigned to tends to be short-term (often between 10 and 20 ses- monitor their thoughts buy bactroban 5gm on-line acne 911, and the therapist points out ways sions) generic bactroban 5gm on line acne 8dpo, and it focuses on the client’s present situation in that these thoughts (such as “nothing is any fun” or “I contrast to the emphasis on past history that is a promi- never do anything right”) misrepresent or distort reality discount bactroban 5 gm visa acne tretinoin cream 005. Cognitive behavioral therapy is also used for chil- American Society for Adolescent Psychiatry. Through instruction, modeling, role playing, and other techniques, they learn to react to events in socially ap- propriate, nonviolent ways. Other childhood conditions Cognitive development for which cognitive behavior therapy has been effective include generalized anxiety disorder and attention The development of thought processes, including remembering, problem solving, and decision-mak- deficit/hyperactivity disorder. States, but they have come under increasing criticism for defining intelligence too narrowly and for being biased Cognitive therapy is generally not used for disor- with regard to race and gender. In contrast to the empha- ders, such as schizophrenia or autism, in which think- sis placed on a child’s native abilities by intelligence ing or communication are severely disturbed. The Essential Albert Ellis: Seminal Writ- ronmental factors in shaping the intelligence of children, ings on Psychotherapy. Adolescent Anger Control: Cognitive-Behav- behaviors rewarded and others discouraged. Behind the One-Way Mirror: Psy- nitive development is that of French psychologist Jean chotherapy and Children. Although Thinking: Breaking the Cycle of Depressing and Anxious Piaget was interested in how children reacted to their en- Thoughts. They also begin to are continually being modified by two complementary lose their egocentric focus, becoming able to understand processes that Piaget termed assimilation and accom- a situation from the viewpoint of another person. Assimilation refers to the process of taking in The fourth, or formal operations, stage begins in new information by incorporating it into an existing early adolescence (age 11 or 12) with the development of schema. In other words, we assimilate new experiences the ability to think logically about abstractions, including by relating them to things we already know. Ado- hand, accommodation is what happens when the schema lescents are capable of formulating and testing hypothe- itself changes to accommodate new knowledge. Accord- ses, understanding causality, and dealing with abstract ing to Piaget, cognitive development involves an ongo- concepts like probability, ratio, proportion, and analogies. Piaget’s stages of cognitive development Modern views At the center of Piaget’s theory is the principle that cognitive development occurs in a series of four distinct, In the decades since Piaget’s theory of cognitive de- universal stages, each characterized by increasingly so- velopment became widely known, other researchers have phisticated and abstract levels of thought. These stages contested some of its principles, claiming that children’s always occur in the same order, and each builds on what progress through the four stages of development is more was learned in the previous stage. It has sensorimotor, stage (birth to 24 months), knowledge is been found that children do not always reach the differ- gained primarily through sensory impressions and motor ent stages at the age levels he specified, and that their activity. Through these two modes of learning, experi- entry into some of the stages is more gradual than was enced both separately and in combination, infants gradu- first thought. However, Piaget remains the most influen- ally learn to control their own bodies and objects in the tial figure in modern child development research, and external world. The ultimate task at this stage is to many of his ideas are still considered accurate, including achieve a sense of object constancy, or permanence—the the basic notion of qualitative shifts in children’s think- sense that objects go on existing even when we cannot ing over time, the general trend toward greater logic and see them. This developing concept can be seen in the less egocentrism as they get older, the concepts of assim- child’s keen enjoyment of games in which objects are re- ilation and accommodation, and the importance of active peatedly made to disappear and reappear. The preoperational stage (ages two to six years) in- The most significant alternative to the work of Pi- volves the manipulation of images and symbols. One ob- aget has been the information-processing approach, ject can represent another, as when a broom is turned which uses the computer as a model to provide new in- into a “horsey” that can be ridden around the room, and a sight into how the human mind receives, stores, re- child’s play expands to include “pretend” games. Researchers using infor- guage acquisition is yet another way of manipulating mation-processing theory to study cognitive develop- symbols. Key concepts involved in the logical organiza- ment in children have focused on areas such as the grad- tion of thoughts—such as causality, time, and perspec- ual improvements in children’s ability to take in tive—are still absent, as is an awareness that substances information and focus selectively on certain parts of it retain the same volume even when shifted into contain- and their increasing attention spans and capacity for ers of different sizes and shapes. For example, they have found that the mains egocentric throughout both the preoperational and superior memory skills of older children are due in part sensorimotor stages. During the third, or concrete operational, stage (six or seven to 11 years of age), children can perform logical Today it is widely accepted that a child’s intellectual operations, but only in relation to concrete external ob- ability is determined by a combination of heredity and jects rather than ideas. Thus, although a child’s genetic inheri- measure, and they learn about the conservation of length, tance is unchangeable, there are definite ways that par- mass, area, weight, time, and volume. At this stage, chil- ents can enhance their children’s intellectual develop- dren can sort items into categories, reverse the direction ment through environmental factors. Other funda- mature, parents can both challenge and support the mental aspects of cognition are reasoning, the process by child’s talents. Although a supportive environment in which people formulate arguments and arrive at conclu- early childhood provides a clear advantage for a child, it sions, and problem solving—devising a useful represen- is possible to make up for early losses in cognitive devel- tation of a problem and planning, executing, and evaluat- opment if a supportive environment is provided at some ing a solution. Studies in Cognitive Growth: A Collabora- term memory provides the basis for one’s working tion at the Center for Cognitive Studies. The cognitive function that most distinctively sets Piaget, Jean, and Barbel Inhelder. The Growth of Logical humans apart from other animals is the ability to com- Thinking from Childhood to Adolescence. Of historical interest is the work of Benjamin Whorf (1897-1941), the proponent of the idea that the language people use determines the way in which they view the world. As of the late 1990s, most Cognition psychologists view the Whorfian hypothesis with skepti- A general term for the higher mental processes by cism, believing that language and perception interact to which people acquire knowledge, solve problems, influence one another. Language acquisition is another topic of debate, Cognition depends on the ability to imagine or rep- with some—including psycholinguist Noam Chomsky resent objects and events that are not physically present —arguing that all humans have innate language abilities, at a given moment. Cognitive functions include atten- while behaviorists stress the role of conditioning and so- tion, perception, thinking, judging, decision making, cial learning theorists stress the importance of imitation problem solving, memory, and linguistic ability. One of the most basic cognitive functions is the abil- Since the 1950s, cognitive psychology, which fo- ity to conceptualize, or group individual items together cuses on the relationship between cognitive processes as instances of a single concept or category, such as and behavior, has occupied a central place in psychologi- “apple” or “chair. The cognitive psychologist studies human framework for thought, allowing people to relate most perceptions and the ways in which cognitive processes objects and events they encounter to preexisting cate- operate on them to produce responses. People learn concepts by building prototypes to most cognitive psychologists is Jerome Bruner, who which variations are added and by forming and testing has done important work on the ways in which needs, hypotheses about which items belong to a particular cat- motivations, and expectations (or “mental sets”) affect egory. In the area of linguistics, the forced to deal with the opposing thoughts “I smoke” and work of Noam Chomsky has rekindled the age-old de- “smoking is dangerous” are likely to alter one of them bate over whether language exists in the mind before ex- by deciding to quit smoking. Other well-known work in cognitive psycholo- fuse dissonance by reducing its importance (discounting gy includes that of D. Berlyne on curiosity and infor- the evidence against smoking or adopting the view that mation seeking; George Kelly’s theory of personal con- smoking will not harm you personally); adding new in- structs; and investigations by Herman Witkin, Riley formation that gives more weight to one of the dissonant Gardner, and George Klein on individual perceptual and beliefs or appears to reconcile them (deciding that smok- cognitive styles. The development of the modern computer has influ- In a classic study of cognitive dissonance, subjects enced current ways of thinking about cognition through were asked to perform a dull task and then to persuade computer simulation of cognitive processes for research others that this task was interesting and enjoyable. Some purposes and through the creation of information-pro- were paid one dollar to do this, while others were paid cessing models. These models portray cognition as a sys- $20, and all of their attitudes toward the task were mea- tem that receives information, represents it with sym- sured at the conclusion of the experiment. The subjects bols, and then manipulates the representations in various who had been paid one dollar showed a marked improve- ways. The senses transmit information from outside ment in their attitude toward the task, while the more stimuli to the brain, which applies perceptual processes highly paid subjects did not.
