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Internet Service Provider Company (ISP)

Service Provider, company that sells computer access to the Internet, also called Internet service provider (ISP) or access provider. A user buys a subscription to a service provider, which gives the user an identifying username and password and a phone number. With his or her computer and modem, the user calls, connects to, and logs on to the service provider's computer. The user's computer then lets the service provider's computer take over, acting like a dumb terminal. The user can then utilize any of the tools the service provider's computer furnishes, which can give access to the World Wide Web (WWW), electronic mail (e-mail), File Transfer Protocol (FTP), Telnet, and other Internet services. Some service providers limit the amount of time a user can spend connected to the service provider's computer or charge more money for extra time.

Speech And Speech Disorders, Language Impairments

Speech and Speech Disorders. Speech is a learned system of communication requiring the coordinated use of voice, articulation, and language skills. Although many animals are physiologically able to use the voice for communicating a wide range of simple messages to others of their species, only humans are able to produce true speech (as opposed to the skills in speech mimicry of such birds as parrots and mynae). In a broad sense, speech is synonymous with language.


Voice, or phonation, is the sound produced by the expiration of air through vibrating vocal cords (see Larynx). Voice is defined in terms of pitch, quality, and intensity, or loudness. Optimum pitch, which means the most appropriate pitch for speaking, varies with each individual. Both optimum pitch and range of pitch are fundamentally determined by the length and mass of the vocal cords; within these limits, pitch may be varied by changing the combination of air pressure and tension of the vocal cords. This combination determines the frequency at which the vocal cords vibrate; the greater the frequency of vibration, the higher the pitch.

Another aspect of voice is resonance. After voice is produced, it is resonated in the chest, throat, and cavities of the mouth. The quality of the voice is determined by resonance and the manner in which the vocal cords vibrate; intensity is controlled by resonance and by the strength of the vibrations of the vocal cords.


Articulation refers to the speech sounds that are produced to form the words of language. The articulating mechanism comprises the lips, tongue, teeth, jaw, and palate. Speech is articulated by interrupting or shaping both the vocalized and unvocalized airstream through movement of the tongue, lips, lower jaw, and soft palate. The teeth are used to produce some specific speech sounds.


Language is an arbitrary system of abstract symbols agreed upon by any group of people to communicate their thoughts and feelings. Symbols may be verbal or nonverbal, that is, either spoken or written; additionally, nonverbal symbols may be gestures and body movements (See also Sign Language). In spoken language the skills of articulation are used; in written language, spelling is substituted for articulation. Both auditory and visual skills are essential to the comprehension and expression of language.

Rate and rhythm also should be considered in the evaluation of speech. Connected speech should not be so rapid or so slow that it interferes with comprehension. Rhythm is judged mostly in terms of fluency. Good or so-called normal speech cannot be exactly measured or described, however; it can be judged essentially only as it seems to be suitable to the sex, size, age, personality, and needs of the speaker.


Because speech is a learned function, any interference with learning ability may be expected to cause a speech impairment. The most common interfering conditions are certain neuroses and psychoses, mental retardation, and brain damage, whether congenital or acquired. Articulation itself may be impaired by such physical disabilities as cleft palate, cerebral palsy, or loss of hearing; it may likewise deteriorate as a result of paralysis of any part of the articulating mechanism. Impairment may also be the consequence of unconscious imitation of poor speech models or inadequate perception of auditory stimuli.

Voice disorders, so-called dysphonias, may be the product of disease or accidents that affect the larynx. They may also be caused by such physical anomalies as incomplete development or other congenital defect of the vocal cords. The most frequent cause, however, is chronic abuse of the vocal apparatus, either by overuse or by improper production of the voice; this may result in such pathological changes as growths on or thickening and swelling of the vocal cords.

Disorders of rate and rhythm are generally either psychogenic or have a basis in some neurological disturbance. A notable example of a neurological condition is Parkinson disease.


A speech therapist is a specialist who has been trained to diagnose and treat the various disorders of speech, language, and voice. Because physical, neurological, or psychological conditions often are either responsible for or are related to the speech disorder, the therapist often works as a member of a team, which may include a neurologist, an otolaryngologist, a psychiatrist, a psychologist, a psychiatric social worker, and a speech pathologist.

Speech disorders caused by disease, injury, or malformation fall in the province of the physician and surgeon. Once these defects are remedied, the speech therapist is responsible for teaching the speech-impaired person to hear and monitor speech accurately, to think appropriately in verbal terms, and to exercise control over speech disordered by incoordination or emotional influences.

Inasmuch as a hearing loss (see Deafness) will prevent learning by imitation of essential speech patterns and sounds and prevent the individual from monitoring his or her own errors, one of the therapist's most valuable techniques is the measurement of hearing. Because intellectual capacity and the ability to handle language are closely related, the therapist must also understand how intelligence develops in a young child. The most obvious emotional speech disorder is stuttering, which is often caused by anxiety. The speech therapist uses a program of speech exercise to reduce this disability. Where necessary, the aid of a psychologist is enlisted; in extreme cases, a psychiatrist assists with psychotherapy.

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Slide Rule, (Mathematics)

slide-rule-mechanical-deviceSlide Rule, mechanical device formerly used by engineers and scientists for rapid and approximate multiplication, division, extraction of roots, raising to powers, and other simple computations. The slide rule has been almost totally superseded by the small hand-held electronic calculator. The principle of the slide rule is the translation of all computations to equivalent additions or subtractions that can be carried out on a set of scales sliding over each other. Thus, two uniformly graduated marked scales can be used for addition or subtraction as shown in Fig. 1 for 2 + 4 = 6. If 2 and 3 are to be multiplied, it follows from the definition of logarithm that log 2 + log 3 = log 6. Accordingly, a scale which is laid out logarithmically (Fig. 2) can be used to add (or subtract) logarithms and therefore to multiply or divide. Powers or roots (fractional powers) can be represented on a set of scales by a further extension of logarithms. Thus, 42 = 16 becomes 2 × log 4 = log 16. If the logarithm is taken once more, log 2 + log (log 4) = log (log 16). Thus, the combination of the normal (logarithmic) slide-rule scale with a so-called log-log scale leads to the evaluation of powers and roots. Other scales, such as for sine, cosine, and tangent, and logarithm and for calculations involving p (pi) are also found on the usual rectilinear slide rule. This consists of an upper and lower fixed part with various imprinted scales and a movable center slide on which further scales are given (see illustration). A glass runner or cursor with a finely engraved vertical line is provided for easier alignment of the scales.
The computational accuracy possible depends on the size of the slide rule and on the care with which the scales are printed. The commonly used 10-in. slide rule permits multiplications and divisions to be made with an accuracy of about 1/10th percent, which suffices for many engineering calculations. Both the rectilinear and the less commonly used circular slide rule were invented by the English mathematician William Oughtred shortly after the discovery of logarithms. Various special slide rules have been devised for the solution of widely applicable engineering formulas, or for business calculations, such as the determination of interest, compound interest accumulation, and depreciation.

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Facts and Figures About Costa Rica,(History of Costa Rica)

Facts and Figures About Costa Rica,(History of Costa Rica)Costa Rica, republic in southern Central America, bounded on the north by Nicaragua, on the east by the Caribbean Sea, on the southeast by Panama, and on the southwest and west by the Pacific Ocean. The uninhabited and densely wooded tropical Cocos Island, about 480 km (about 300 mi) to the southwest in the Pacific Ocean, is under Costa Rican sovereignty. The total area of Costa Rica is 51,060 sq km (19,714 sq mi). The country’s capital is San José.


 Most of Costa Rica is rugged highlands, about 900 to 1,800 m (about 3,000 to 6,000 ft) above sea level. Several mountain ranges extend nearly the entire length of the country. These include the Cordillera de Talamanca, Cordillera Central, and Cordillera de Guanacaste. The highest peaks are Chirripó Grande (3,819 m/12,530 ft) and the active volcano of Irazú (3,432 m/ 11,260 ft). A central plateau, the Meseta Central, is located between the ranges and contains the bulk of the population. Wide lowlands extend along the almost unindented Caribbean coast. The lowlands along the Pacific are narrower. Here the coast is broken by a number of bays, the chief ones being the landlocked Gulf of Nicoya, the deep, open Gulf of Dulce, and Coronado Bay. The principal stream of Costa Rica is the San Juan River, which forms part of the country’s boundary with Nicaragua to the north.

A  Climate 

The climate of Costa Rica ranges from tropical on the coastal plains to temperate in the interior highlands. Average annual temperatures range from 31.7°C (89°F) on the coast to 16.7°C (62°F) inland. A rainy season lasts from April or May to December. Annual precipitation in the country averages about 3,000 to 3,500 millimeters (120 to 140 inches).

B  Natural Resources

Good agricultural soils in Costa Rica are concentrated in the Meseta Central and in the river valleys. About one-third of the total land area is covered by forest, much of which is commercially productive. Mineral resources, including bauxite, are believed to be extensive but remain largely undeveloped. Fishing for tuna, sharks, and turtles is carried out along the coast. Waterpower is abundant and is used to generate electricity for industrial operations.

C  Plants and Animals
Costa Rica’s forests contain rich stands of ebony, balsa, mahogany, and cedar. More than 1,000 species of orchids are found in Costa Rica. Wildlife is abundant and includes puma, jaguar, deer, monkeys, and 600 species of birds.

D  Environmental Issues
Costa Rica’s land is protected by one of the most ambitious conservation programs in Central America. Costa Rica was one of the first, and most active, countries to participate in debt-for-nature swaps, which cancel some national debt in exchange for the protection of a specified amount of land from environmental degradation. In an effort to bolster its economy while remaining responsible to the environment, Costa Rica has also established a booming ecotourism business. This form of tourism encourages travelers to learn more about the country’s natural wonders and to respect the environment in the course of their exploration.

Despite Costa Rica’s efforts to protect its valuable forest resources, much of what lies outside the country’s protected reserves is subject to deforestation. Land is cleared for cattle ranching and for harvesting valuable tropical timber for export. In addition, because some of Costa Rica’s protected lands are privately owned, their protection from future deforestation is not guaranteed. Deforestation places Costa Rica’s rich biodiversity in danger. The country’s location on the cusp between North and South America and its abundance of tropical forests make it home to a great variety of species, many of them rare and threatened. Deforestation also contributes to the country’s problematic rate of soil erosion.

Costa Rica is party to international treaties concerning biodiversity, climate change, endangered species, hazardous wastes, marine dumping, and wetlands.


A majority of the people of Costa Rica are of European (largely Spanish) descent. Whites and mestizos (people of mixed Spanish and Native American ancestry) account for about 96 percent of the population; the small black community is largely of Jamaican origin. About 50 percent of the population is defined as rural. Spanish is the official language, but English is also spoken by many educated people and some of the ethnic Jamaicans. Roman Catholicism is the state religion, but freedom of worship is guaranteed by the constitution.

A  Population Characteristics
The population of Costa Rica (2004 estimate) is 3,956,507, giving the country an overall population density of 78 persons per sq km (202 per sq mi).

B  Political Divisions
Costa Rica is divided into seven provinces: San José, Alajuela, Cartago, Puntarenas, Guanacaste, Heredia, and Limón. Each of the provinces has a governor appointed by the president.

C  Principal Cities
The capital is San José, with an estimated population in 2000 of 309,672. Important cities are Puerto Limón (84,986), a trading center and one of the country’s principal ports; Puntarenas (102,504), a major Pacific seaport; and Alajuela (222,853), a center for the production of coffee and sugar.

D  Education

Costa Rica has one of the highest rates of literacy in Latin America, estimated at 96 percent. Primary and secondary education is free, and attendance is compulsory between the ages of 6 and 15. In 2000, 551,465 pupils were enrolled in 3,711 primary schools and 255,600 students attended public and private secondary schools. The prominent University of Costa Rica, in San José, was founded in 1843, and has an annual enrollment of about 29,000.

E  Culture

Costa Rica, with a relatively small Native American population, has been strongly influenced by the culture and traditions of Spain. Native American and African American influences have had relatively little impact. The Roman Catholic cultural pattern of Spain, with emphasis on the family and the church, has evolved into a national style of life. Festivals in honor of patron saints are a colorful part of village and town life. The guitar, accordion, and mandolin have traditionally been the most popular musical instruments, and the music reflects a Spanish heritage. Traces of the Native American culture survive in designs used in jewelry, leather goods, and clothing. The national sport is soccer.


The economy of Costa Rica remains basically agricultural, although manufacturing industries have been expanding since the early 1960s. In an effort to introduce economic diversity, more emphasis has been given to the raising of livestock. Overall living conditions are high by Latin American standards, and the country has a large middle class. Between 1970 and 1987, Costa Rica received about $1.2 billion in loans and grants from the United States. In 2001 annual budget figures showed revenues of $ 3.6 billion and expenditures of $ 3.9 billion.

A  Agriculture

Some 10.3 percent of Costa Rica’s land area is under cultivation or used for plantation agriculture. Apart from banana plantations, most of the agricultural landholdings are small. Coffee, one of the most valuable crops, is cultivated mainly in the central plateaus. In 2003, 132,000 metric tons of coffee was produced. Bananas are raised in the tropical coastal regions on plantations. In the late 19th and early 20th century a United States firm, the United Fruit Company (now United Brands), opened the largest banana plantation in the world on the Pacific coast of Costa Rica and constructed the ports of Quepos and Golfito as banana-shipping points. Cacao, sugarcane, and pineapples are also raised primarily for export. Corn, rice, vegetables, tobacco, and cotton are generally cultivated throughout the country. In 2003 livestock included 1.2 million cattle, 500,000 hogs, and 115,000 horses.

B  Mining and Manufacturing

Gold and silver are mined in the western part of Costa Rica. Deposits of manganese, nickel, mercury, and sulfur are largely unworked. Petroleum deposits have been found in the south, but not exploited. Salt is produced from seawater.

Most of the country’s industry is of small-scale enterprises such as coffee-drying plants, cheese factories, sawmills, woodworking factories, breweries, and distilleries. Costa Rica has factories that produce petroleum products, furniture, paper, textiles, chemicals, pharmaceuticals, plastics, candles, boots, and cigars and cigarettes. Costa Rica produced 6.8 billion kilowatt-hours of electricity in 2001; 82 percent of the power was generated in hydroelectric facilities.

C  Currency and Foreign Trade

The unit of currency is the colón, consisting of 100 centimos (359.82 colones equal U.S.$1; 2002 estimate). The Banco Central, established in 1950, is the bank of issue and administers foreign reserves. In 2002 the value of imports was $6.9 billion and of exports, $5 billion. The chief exports included coffee, bananas, beef, textiles, and sugar. Principal imports were manufactured goods, machinery, transportation equipment, chemicals, crude petroleum, and foodstuffs. Chief purchasers of exports are the United States, Germany, Italy, Guatemala, El Salvador, the Netherlands, the United Kingdom, and France. Leading suppliers of imports were the United States, Japan, Mexico, and Guatemala. The entry in 1963 of Costa Rica into the Central American Common Market brought about major increases in trade in that region although its importance has since waned. In 1995 Costa Rica joined in the formation of the Association of Caribbean States (ACS). A free-trade organization, the ACS comprises the members of the Caribbean Community and Common Market (CARICOM) as well as 12 Latin nations bordering the Caribbean.

D  Transportation

Railroad lines in Costa Rica total 424 km (263 mi) and link San José with both coasts. Roads total 35,881 km (22,295 mi); some 680 km (some 425 mi) of roadway forms a portion of the Inter-American Highway. San José is linked by road with the cities of the surrounding plateau region. Several domestic airlines provide service within the country. Juan Santamaría Airport, which is located near San José, is served by the Costa Rican national airline and several foreign airlines.

E  Communications

In 2001 Costa Rica had 8 daily newspapers. There were 3,045 radio receivers and 930 televisions for every 1,000 residents. In 2002 Costa Rica had 251 telephone mainlines for every 1,000 people.

F  Labor
Agriculture employs 16 percent of the labor force while industry employs 23 percent. The remainder was employed in the public and private service sectors. Labor unions are relatively weak in Costa Rica.


Costa Rica is a republic governed under a constitution of 1949.

A  Executive

Executive power is vested in a president and two vice presidents, each of whom is elected by direct popular vote for single four-year terms. Each candidate must receive more than 40 percent of the total vote. Voting is compulsory for all citizens over 18 years of age. The president is assisted by a cabinet of some 20 ministers.

B  Legislature

Legislative power in Costa Rica is vested in a single-chamber Legislative Assembly, with 57 deputies, elected for four-year terms.

C  Political Parties

The leading political groups in Costa Rica are the National Liberation Party (Partido de Liberación Nacional, or PLN), a reformist organization, and the Social Christian Unity Party.

D  Judiciary

Judicial power in Costa Rica is vested in a Supreme Court, appellate courts, a court of cassation (highest appeals court), and subordinate provincial courts. Capital punishment has been banned.

E  Social Services

The average life expectancy in Costa Rica is 77 years, the highest in the western hemisphere. A national health plan was established in the 1970s. Health services are concentrated in urban areas. A social security program has been in operation since 1942, with participation compulsory for all employees under 65 years of age.

F  Defense

Costa Rica has had no armed forces since 1948, when the PLN came to power and abolished the army. The only security forces are the 4,500-member Civil Guard and the 3,200-member Rural Guard.

Human habitation of Costa Rica dates from at least 5000 bc, but in comparison with the great civilizations of pre-Columbian America the Native Americans of Costa Rica were neither numerous nor highly developed. When confronted by Spanish soldiers and missionaries, they resisted violently. Those who did not succumb to the epidemics that swept over the isthmus either died fighting or fled to remote areas.

A  The Colonial Period

Christopher Columbus sailed along Costa Rica’s Caribbean shore in 1502 and gave it its name (“rich coast”). Spanish conquest, however, came later than in most of the rest of Central America, delayed by the hostility of the natives and the absence of obvious wealth. After Juan de Cavallón led the first successful colonizers into Costa Rica in 1561, Juan Vásquez de Coronado followed from 1562 to 1565 with the establishment of Cartago and other settlements in the central valley, where most of the population is still concentrated. Within the kingdom of Guatemala (in the viceroyalty of Mexico, called New Spain) from 1570 forward, Costa Rica was principally a small dependency of Nicaragua throughout its colonial period. Such circumstances as its remoteness from Guatemala City and its lack of wealth allowed it to develop with less direct interference and regulation than the other provinces of Central America. Costa Rica’s relative obscurity gave it some of its unique characteristics. The Europeans were unable to subjugate a sedentary native population, nor could they afford to import African slaves, as was done in areas of more apparent commercial agricultural or mining potential. Costa Ricans consequently turned to subsistence farming on small land grants, without the extremes of wealth and poverty that characterized so much of Latin America. Government and church officials were fewer than in the centers of authority and production. Thus, Costa Rica played only a minor role in the kingdom of Guatemala, and it developed to a large degree apart from the mainstream of Latin American history. It was first in the late 18th century, when Spanish emphasis on commercial agriculture led to the growth of tobacco as a major export, that the colony became of some importance to the Guatemalan authorities.

Child Development Advice And Help For Parents(Develop Skills)

Child Development Advice And Help For Parents(Develop Skills)Child Development, physical, intellectual, social, and emotional changes that occur from birth to adolescence. Although people change throughout their lives, developmental changes are especially dramatic in childhood. During this period, a dependent, vulnerable newborn grows into a capable young person who has mastered language, is self-aware, can think and reason with sophistication, has a distinctive personality, and socializes effortlessly with others. Many abilities and characteristics developed in childhood last a lifetime.

Some developments in behavior and thought are very similar for all children. Around the world, most infants begin to focus their eyes, sit up, and learn to walk at comparable ages, and children begin to acquire language and develop logical reasoning skills at approximately the same time. These aspects of individual growth are highly predictable. Other aspects of development show a much wider range of individual differences. Whether a child becomes outgoing or shy, intellectually advanced or average, or energetic or subdued depends on many unique influences whose effects are difficult to predict at the child’s birth. 

A variety of factors influence child development. Heredity guides every aspect of physical, cognitive, social, emotional, and personality development. Family members, peer groups, the school environment, and the community influence how children think, socialize, and become self-aware. Biological factors such as nutrition, medical care, and environmental hazards in the air and water affect the growth of the body and mind. Economic and political institutions, the media, and cultural values all guide how children live their lives. Critical life events, such as a family crisis or a national emergency, can alter the growth of personality and identity. Most important of all, children contribute significantly to their own development. This occurs as they strive to understand their experiences, respond in individual ways to the people around them, and choose activities, friends, and interests. Thus, the factors that guide development arise from both outside and within the person.

Why is the study of child development important? One reason is that it provides practical guidance for parents, teachers, child-care providers, and others who care for children. A second reason is that it enables society to support healthy growth. Understanding early brain development, for example, means that parents can provide better opportunities for intellectual stimulation, and society can reduce or eliminate obstacles to healthy brain growth. Third, the study of child development helps therapists and educators better assist children with special needs, such as those with emotional or learning difficulties. Finally, understanding child development contributes to self-understanding. We know ourselves better by recognizing the influences that have made us into the people we are today.


A  Early Views of Children

People have thought very differently about children in different historical eras. In ancient Rome and throughout the Middle Ages, for example, childhood was brief: A boy or girl was considered an “infant” until the age of six, but soon afterward worked alongside adults in the fields, workshop, or home. Children were thought to be born in a state of sin and were viewed as the property of their fathers. Such beliefs contributed to strict discipline of children and neglect of their special needs.

These harsh attitudes softened during the Renaissance and Enlightenment as the humanistic spirit of the times caused a rediscovery of the special qualities of childhood. In paintings, for example, young children were depicted more realistically as they played, nursed, and did other childish things, rather than being shown as miniature adults. The importance of childhood as a unique period of development was understood more fully in the 17th and 18th centuries, as reflected in the writings of two important European thinkers. The English philosopher John Locke argued that the newborn infant comes into the world with no inherited predispositions, but rather with a mind as a tabula rasa (Latin for “blank slate”) that is gradually filled with ideas, concepts, and knowledge from experiences in the world. He concluded that the quality of early experiences, particularly how children are raised and educated, shapes the direction of a child’s life. Later, the French philosopher Jean Jacques Rousseau claimed that children at birth are innately good, not evil, and that their natural tendencies should be protected against the corrupting influences of society. The sympathetic, romantic attitude toward children inspired by Rousseau had an important influence on society. For example, the novelists Charles Dickens and Victor Hugo decried the exploitation of child labor and highlighted the need for educational and social reform.

B  Scientific Study

In the late 19th century, interest in the characteristics and needs of children produced more systematic efforts to study their development. The modern theory of evolution, conceived by British naturalist Charles Darwin, contributed to this interest by arguing that human behavior is best understood through knowledge of its origins—in both the evolution of the species and the early development of individuals. Darwin himself studied children’s growth by writing one of the first “baby biographies,” consisting of careful observations of his children. In the early 1900s, the theory of psychoanalysis focused on the importance of early childhood experiences. American psychologist G. Stanley Hall at Clark University began large-scale investigations of child development through surveys and interviews with the adults who cared for them. For the first time, children warranted scientific attention because of society’s interest in their development and well-being.

In the 1920s developmental scientists at other American universities began large-scale observational studies of children and their families, including the Berkeley Growth Studies at the University of California, the Fels Growth Study at Antioch College, and the Harvard Growth Studies at Harvard University. Each investigation studied a large number of children repeatedly over many years to identify changes and consistencies in their behavior and thinking. At Stanford University, psychologist Lewis Terman created the Stanford-Binet Intelligence Scale, which remains one of the most widely used assessments of children’s intellectual capabilities (see Intelligence). Terman also started his own long-term study of highly intelligent children. At Yale University, psychologist Arnold Gesell established a research institute devoted to identifying age norms for a wide variety of behaviors and characteristics. While Gesell believed in the importance of maturation on children’s development, other psychologists emphasized the role of learning from environmental influences. One of these, John B. Watson of Johns Hopkins University, advised parents to treat their offspring in an objective, consistent manner to encourage the development of desired characteristics. Watson believed that all human behaviors could be explained as learned responses to stimuli in the environment, an approach known as behaviorism. This approach to the study of child development remained dominant for the first half of the 20th century.
Although behaviorists contributed much to the study of children, their concepts eventually were viewed as being overly narrow. In the early 1960s scholars began to focus more attention on the work of Swiss psychologist Jean Piaget, who had been studying children’s cognitive development since the 1920s. Piaget claimed that children construct new knowledge by applying their current knowledge structures to new experiences and modifying them accordingly. His perspective, called constructivism, emphasized the active role children play in their own mental growth as inquisitive thinkers.

Piaget’s theories led to other approaches to the study of child development. In the 1960s and 1970s British psychologist John Bowlby and American psychologist Mary Ainsworth introduced the concept of attachment. They proposed that infants and young children form emotional bonds to their caregivers because, throughout human evolutionary history, close attachments to adults promoted the survival of defenseless children. In the 1970s and 1980s American psychologist Urie Bronfenbrenner sought to describe child development in terms of ecological and cultural forces. In his model, environmental influences on the child extend well beyond the family and peer group, and include schools and other community agencies, social institutions such as the media, political and economic conditions, and national customs. Other developmental scientists have studied how cultural values guide the skills and attitudes that children acquire as they mature, and how brain maturation influences the development of thinking and feeling.


A  Nature and Nurture
Scholars have long debated the relative importance of nature (hereditary influences) and nurture (environmental influences) in child development. It was once assumed that these forces operated independently of each other. Today developmental scientists recognize that both influences are essential and are mutually influential. For example, how a child responds to parenting—an environmental influence—is partly determined by the child’s temperament and other inherited characteristics.

Likewise, the environment influences how hereditary characteristics develop and are expressed. During the past century, for example, there have been significant increases in average height because of improved nutrition and medical care, even though individual differences in height are strongly influenced by heredity. The conclusion that strongly inherited characteristics are changeable has important practical implications. For instance, even though many features of personality are based on inherited temperament, the family environment is an important influence on a child’s personality development. Thus, even a child with a difficult temperament can develop positively in a warm and caring family environment.

B  Continuity or Stages
Does childhood growth occur continuously and gradually, or is it instead a series of distinct stages? People often think of childhood as a sequence of age-related stages (such as infancy, early childhood, and middle childhood), and many developmental theories portray childhood growth in this manner. Such a view recognizes that each period of growth has its own distinct changes, challenges, and characteristics. But many aspects of childhood development are more gradual and continuous, such as the development of physical skills, social abilities, and emotional understanding. Even some milestones that seem to denote a new stage of growth—such as a child’s first word—are actually the outcome of a more gradual developmental process.

C  Stability and Change
Are a person’s characteristics primarily shaped by early influences, remaining relatively stable thereafter throughout life? Or does change occur continuously throughout life? Many people believe that early experiences are formative, providing a strong or weak foundation for later psychological growth. This view is expressed in the popular saying “As the twig is bent, so grows the tree.” From this perspective, it is crucial to ensure that young children have a good start in life. But many developmental scientists believe that later experiences can modify or even reverse early influences; studies show that even when early experiences are traumatic or abusive, considerable recovery can occur. From this vantage point, early experiences influence, but rarely determine, later characteristics.

Like other basic questions about development, whether early experiences are a determining force or fading influence has practical implications. For example, belief in the importance of early experiences is the basis of efforts to strengthen early childhood education programs, especially for children from disadvantaged backgrounds, to reduce later difficulties in school achievement.

A theory is an organized set of principles that is designed to explain and predict something. Over the years, psychologists and other scientists have devised a variety of theories with which to explain observations and discoveries about child development. In addition to providing a broader framework of understanding, a good theory permits educated guesses—or hypotheses—about aspects of development that are not yet clearly understood. These hypotheses provide the basis for further research. A theory also has practical value. When a parent, educator, therapist, or policymaker makes decisions that affect the lives of children, a well-founded theory can guide them in responsible ways.

Theories can also limit understanding, such as when a poor theory misleadingly emphasizes unimportant influences on development and underestimates the significance of other factors. It is therefore essential that theories are carefully evaluated and tested through research, whose results often lead to improvements in theoretical claims. In addition, when theories are compared and contrasted, their strengths and limitations can be more easily identified.

There are four primary theories of child development: psychoanalytic, learning, cognitive, and sociocultural. Each offers insights into the forces guiding childhood growth. Each also has limitations, which is why many developmental scientists use more than one theory to guide their thinking about the growth of children.

A  Psychoanalytic Theories
At the end of the 19th century, Austrian physician Sigmund Freud developed the theory and techniques of psychoanalysis; it formed the basis for several later psychoanalytic theories of human development. Psychoanalytic theories share an emphasis on personality development and early childhood experiences. In the psychoanalytic view, early experiences shape one’s personality for an entire lifetime, and psychological problems in adulthood may have their origins in difficult or traumatic childhood experiences.

In addition, psychoanalytic theories emphasize the role of unconscious, instinctual drives in personality development. Some of these drives are sexual or aggressive in quality, and their unacceptability to the conscious mind causes them to be repressed in the unconscious mind. Here, they continue to exert a powerful influence on an individual’s behavior, often without his or her awareness.

Most psychoanalytic theories portray development as a series of stages through which all children proceed. According to Freud, child development consists of five psychosexual stages in which a particular body region is the focus of sensual satisfactions; the focus of pleasure shifts as children progress through the stages.

During the oral stage, from birth to age 1, the mouth, tongue, and gums are the focus of sensual pleasure, and the baby develops an emotional attachment to the person providing these satisfactions (primarily through feeding). During the anal stage, from ages 1 to 3, children focus on pleasures associated with control and self-control, primarily with respect to defecation and toilet training. In the phallic stage, from ages 3 to 6, children derive pleasure from genital stimulation. They are also interested in the physical differences between the sexes and identify with their same-sex parent. The latency phase, from ages 7 to 11, is when sensual motives subside and psychological energy is channeled into conventional activities, such as schoolwork. Finally, during the genital stage, from adolescence through adulthood, individuals develop mature sexual interests.

An American psychoanalyst, Erik Erikson, proposed a related series of psychosocial stages of personality growth that more strongly emphasize social influences within the family. Erikson’s eight stages span the entire life course, and, contrary to Freud’s stages, each involves a conflict in the social world with two possible outcomes. In infancy, for example, the conflict is “trust vs. mistrust” based on whether the baby is confident that others will provide nurturance and care. In adolescence, “identity vs. role confusion” defines the teenager’s search for self-understanding. Erikson’s theory thus emphasizes the interaction of internal psychological growth and the support of the social world.

Psychoanalytic theories offer a rich portrayal of personality growth that emphasizes the complex emotional—and sometimes irrational—forces within each person. These theories are hard to prove or disprove, however, because they are based on unconscious processes inaccessible to scientific experimentation.

B  Learning Theories
Learning theorists emphasize the role of environmental influences in shaping the way a person develops. In their view, child development is guided by both deliberate and unintended learning experiences in the home, peer group, school, and community. Therefore, childhood growth is significantly shaped by the efforts of parents, teachers, and others to socialize children in desirable ways. According to learning theories, the same principles that explain how people can use a bicycle or computer also explain how children acquire social skills, emotional self-control, reasoning strategies, and the physical skills of walking and running.

One kind of learning occurs when a child’s actions are followed by a reward or punishment. A reward, also called a reinforcer, increases the probability that behavior will be repeated. For example, a young child may regularly draw pictures because she receives praise from her parents after completing each one. A punishment decreases the probability that behavior will be repeated. For example, a child who touches a hot stove and burns his fingertips is not likely to touch the stove again. American psychologist B. F. Skinner devoted his career to explaining how human behavior is affected by its consequences—a process he called operant conditioning–and to describing the positive and constructive ways that reinforcement and punishment can be used to guide children’s behavior.

Another kind of learning, classical conditioning, occurs when a person makes a mental association between two events or stimuli. When conditioning has occurred, merely encountering the first stimulus produces a response once associated only with the second stimulus. For example, babies begin sucking when they are put in a familiar nursing posture, children fear dogs whose barking has startled them in the past, and students cringe at the sound of school bells that signal that they are tardy. Classical conditioning was first studied by Russian physiologist Ivan Pavlov in the early 1900s and later by American psychologist John B. Watson.

A third kind of learning consists of imitating the behavior of others. A boy may acquire his father’s style of talking, his mother’s tendency to roll her eyes, and his favorite basketball player’s moves on the court. In doing so, he also acquires expectations about the consequences of these behaviors. This type of learning has been studied extensively by American psychologist Albert Bandura. His social learning theory emphasizes how learning through observation and imitation affects behavior and thought.

Learning theories provide extremely useful ways of understanding how developmental changes in behavior and thinking occur and, for some children, why behavior problems arise. These theories can be studied scientifically and practically applied. Critics point out, however, that because of their emphasis on the guidance of the social environment, learning theorists sometimes neglect children’s active role in their own understanding and development.

Opioids and Morphine Derivatives Facts and Effects

Drug and Alcohol Derivatives,
Opioids and Morphine Derivatives Effects, Drug IndependenceDrug Dependence, psychological and sometimes physical state characterized by a compulsion to use a
Tolerance, a form of physical dependence, occurs when the body becomes accustomed to a drug and requires ever-increasing amounts of it to achieve the same pharmacological effects. This condition is worsened when certain drugs are used at high doses for long periods (weeks or months), and may lead to more frequent use of the drug. However, when use of the drug is stopped, drug withdrawal may result, which is characterized by nausea, headaches, restlessness, sweating, and difficulty sleeping. The severity of drug withdrawal symptoms varies depending on the drug involved.

Habituation, a form of psychological dependence, is characterized by the continued desire for a drug, even after physical dependence is gone. A drug often produces an elated emotional state, and a person abusing drugs soon believes the drug is needed to function at work or home. Addiction is a severe craving for the substance and interferes with a person’s ability to function normally. It may also involve physical dependence.

Scientists often measure a drug’s potential for abuse by conducting studies with laboratory animals. Drugs that an animal administers to itself repeatedly are said to have powerful reinforcing properties and a high potential for abuse. These drugs include some commonly abused substances like opium, alcohol, cocaine, and see barbiturates. Other drugs, such as marijuana and the hallucinogens (see Psychoactive Drugs), appear to produce habituation in humans even though they are not powerful reinforcers for laboratory animals.

The drugs that are commonly abused, except alcohol and tobacco, can be grouped into six classes: the opioids, sedative-hypnotics (see Sedative), see stimulants, hallucinogens, cannabis, and inhalants.

II  OPIOIDS This class includes drugs derived from opium, such as morphine and heroin, and synthetic substitutes such as methadone. Medically, morphine is a potent pain reliever; indeed, it is the standard by which other pain-relieving drugs are measured (see Narcotics). Morphine and other opium derivatives also suppress coughing, reduce movements of the intestine (providing relief from diarrhea), and induce a state of psychological indifference. Heroin, a preparation synthesized from morphine, was introduced in 1898 as a cough suppressant and nonaddictive substitute for morphine. The addictive potential of heroin, however, was soon recognized, and its use was prohibited in the United States, even in medical practice. Users report that heroin produces a “rush” or “high” immediately after being taken. It also produces a state of profound indifference and may increase energy.

Opioids produce different effects under different circumstances. The drug user’s past experience and expectations have some influence, as does the method of administering the drug (by injection, ingestion, or inhalation). Symptoms of withdrawal from opioids include kicking movements in the legs, anxiety, insomnia, nausea, sweating, cramps, vomiting, diarrhea, and fever.

In the 1970s scientists isolated substances called enkephalins, which are naturally occurring opiates in the brain. They discovered what many believe is the reason behind physical dependence on opioids—that is, the drugs may mimic the action of enkephalins. If true, this hypothesis suggests that physical dependence on opioids may develop in people who have a deficiency of these natural substances.


The drugs most commonly abused in this class are the barbiturates, which have been used since the early 1900s to relieve anxiety and induce sleep. They are also used medically in the treatment of epilepsy. Some people who abuse barbiturates ingest large amounts daily but never appear intoxicated. Others use the drugs for binges of intoxication, and still others use them to boost the effects of heroin. Many people who abuse these drugs, especially those who do so daily, routinely obtain the drugs from physicians.

Barbiturates produce severe physical dependence, closely resembling the dependence and effects produced by alcohol. Abrupt withdrawal results in similar symptoms: shaking, insomnia, anxiety, and sometimes, after a day, convulsions and delirium. Death can occur when use of barbiturates is suddenly discontinued. Toxic doses, which may be little more than what is required to produce intoxication, are often taken accidentally. Barbiturates are particularly lethal when combined with alcohol.

Other sedative-hypnotics include the benzodiazepines, which are marketed under such trade names as Valium and Librium. These are the so-called minor tranquilizers (see Tranquilizer) used in the treatment of anxiety, insomnia, and epilepsy. They are generally safer than the barbiturates and are now the preferred drug for treatment of these conditions. Consequently, tranquilizer addiction has become a problem.

Commonly abused stimulants are cocaine and drugs of the amphetamine family. Cocaine, a white, crystalline powder with a bitter taste, is extracted from the leaves of the South American coca bush. It is used medically to produce anesthesia for surgery of the nose and throat and to constrict blood vessels and reduce bleeding during surgery. Abuse of cocaine, which increased considerably in the late 1970s, can lead to severe physiological and psychological problems. A highly addictive, smokable form of cocaine called “crack” appeared in the 1980s.

Amphetamines, introduced in the 1930s for the treatment of colds and hay fever, were later found to affect the nervous system. For a while people trying to lose weight commonly used them as appetite suppressants. Today, use is restricted primarily to the treatment of narcolepsy, a sleep disorder characterized by sudden sleep attacks during the day, and hyperactivity in children, for whom amphetamines produce a calming effect. For adults, however, amphetamines rightfully earn the street name “speed.” These drugs heighten alertness, elevate mood, and decrease fatigue and the need for sleep, but they often make users irritable and talkative. Both cocaine and amphetamines, after prolonged daily use, can produce a psychosis similar to acute schizophrenia.

Tolerance to both the euphoric and appetite-suppressing effects of amphetamines and cocaine develops rapidly. Withdrawal from amphetamines, particularly if the drug has been injected intravenously, produces depression so unpleasant that the user is compelled to keep taking the drug until he or she collapses.

These drugs are not used medically in the United States except occasionally in the treatment of dying patients, the mentally ill, drug abusers, and alcoholics. Among the hallucinogens widely abused during the 1960s were lysergic acid diethylamide, or LSD, and mescaline, which is derived from the peyote cactus. Although tolerance to these drugs develops rapidly, no withdrawal syndrome is apparent when they are discontinued.

Phencyclidine, or PCP, known popularly by such names as “angel dust” and “rocket fuel,” has no medical purpose for humans but is occasionally used by veterinarians as an anesthetic and sedative for animals. It became a common drug of abuse in the late 1970s, and is considered a menace because it can easily be synthesized. Its effects differ from those of other hallucinogens. LSD, for example, produces detachment and euphoria, intensifies vision, and often leads to a crossing of senses (colors are heard, sounds are seen). PCP, by contrast, produces a sense of detachment and a reduction in sensitivity to pain, and may trigger or produce symptoms so like those of acute schizophrenia that professionals confuse the two states. The combination of this effect and indifference to pain has sometimes resulted in bizarre thinking, occasionally marked by violently destructive behavior.

The plant Cannabis sativa is the source of both marijuana and hashish. The flowering tops of the Cannabis plant secrete a sticky resin that contains the active ingredient of marijuana and hashish. Hashish is comprised of only the flowering tops of the plant, whereas marijuana is made up of flowering tops and leaves. Both drugs are usually smoked. Their effects are similar: a state of relaxation, accelerated heart rate, perceived slowing of time, and a sense of heightened hearing, taste, touch, and smell. These effects can differ, however, depending on the amount of drug consumed and the circumstances under which it is taken. Marijuana and hashish do not produce psychological dependence except when taken in large daily doses. The drugs can be dangerous, however, especially when smoked before driving. Although the chronic effects have not been clearly determined, marijuana is probably injurious to the lungs in much the same way as tobacco. A cause for concern is the regular use by children and teenagers, because intoxication markedly alters thinking and interferes with learning. A consensus exists among physicians and others who work with children and adolescents that use of marijuana and hashish is undesirable and may interfere with psychological and possibly physical maturation.

Cannabis has been used as a folk remedy for centuries. Its active ingredient, delta-9-tetrahydrocannabinol (THC), has been used experimentally for treating alcoholism, seizures, pain, the nausea produced by anticancer medications, and glaucoma. Glaucoma patients have used THC successfully, but the disorienting effects limit its usefulness for cancer patients.


This class includes substances that are usually not considered drugs, such as glue, gasoline, and aerosols like nasal sprays. Most such substances sniffed for their psychological effects depress the central nervous system. Low doses can produce slight stimulation, but higher amounts cause users to lose control or lapse into unconsciousness. The effects, which are immediate, can last as long as 45 minutes. Headache, nausea, and drowsiness follow. Sniffing inhalants can impair vision, judgment, and muscle and reflex control. Permanent damage can result from prolonged use, and death can result from sniffing highly concentrated aerosol sprays. Although physical dependence does not seem to occur, tolerance to some inhalants develops. Another source of medical concern is the widespread misuse, for a supposed aphrodisiac effect, of so-called “poppers”—chemicals such as isoamyl nitrite that have legitimate medical functions as blood vessel dilators (vasodilators). Continued sniffing of these easily obtainable substances can damage the circulatory system and have related harmful effects.


With the exception of treatment of opioid dependence, medical attention to the problems of the drug abuser is largely confined to dealing with overdoses, acute reactions to drug ingestion, and the incidental medical consequences of drug use such as malnutrition and medical problems caused by unsterilized needles. Abusers of barbiturates and amphetamines may require hospitalization for detoxification, as is common among alcoholics. Others, such as those arrested repeatedly for possession of marijuana, may, in lieu of imprisonment, be forced to undergo treatment designed primarily for opioid abusers. Whatever the substance abused, the goal of most treatment programs is to foster abstinence in the patient.

Two types of treatment programs are used for most opioid users. Therapeutic communities require the drug abuser to take personal responsibility for his or her problem. Typically, the idea behind this treatment is that the drug abuser is emotionally immature and must be given a second chance to grow up. Harsh encounters with other members of the community are typical; the support of others, together with status and privilege, are used as rewards for good behavior.

The other model for opioid abuse treatment is the use of heroin substitutes. One such substitute is methadone, which acts more slowly than heroin but is still addictive. The idea is to help the user gradually withdraw from heroin use while removing the need for finding the drug on the street. A more recent treatment drug, naltrexone, is nonaddictive but does not provide an equivalent “high;” it also cannot be used by persons with liver problems, which are common among addicts.


Drug use for nonmedical purposes occurs throughout society. For this reason the 1978 President’s Commission on Mental Health did not recommend health and mental-health assistance except to persons whose drug use was intense and compulsive. The commission identified heroin as the number one drug problem because heroin addiction may lead to criminal behavior to pay for the drug. Adding to the problem is the fact that chemically similar drugs can be synthesized and sold on the street because they are not yet classified as controlled substances.
In a 1999 household survey by the Substance Abuse and Mental Health Services Administration an estimated 14.8 million people in the United States classified themselves as current illicit drug users. Among youths aged 12 to 17, close to 8 percent of respondents were regular users of marijuana. The percentage of youths in the same age range who used cocaine at least once a month was 49.8 percent. The survey also reported an estimated 1.6 million U.S. residents used prescription drugs for nonmedical purposes in 1998. The state with the highest rates of dependence on illicit drugs was Alaska with 2.8 percent of its 12 and older population dependent on illicit drugs and 7.3 percent dependent on illicit drugs or alcohol. drug to experience psychological or physical effects. Drug dependence takes several forms: tolerance, habituation, and addiction.