In the history of psychology one of the oldest arguments is the Nature-Nurture debate with regard to what makes us human beings different from each-other: our genes or our environment, and which one of these sides contributes more to a person's psychological and physical development.
The Nature -Nurture debate was introduced in the late IX Century by one of the first experimental psychologists Francis Galton in his "English men of science: Their Nature and Nurture" (1874). In this work he calls nature and nurture, "a convenient jingle of words, for it separates under two distinct heads the innumerable elements of which personality is composed. Nature is all that a man brings with himself into the world; nurture is every influence that affects him after his birth" (p. 12).
Philosophers in ancient times, such as Plato, believed that a child was born with some innate knowledge. Locke however, was an empiricist and believed that the mind at birth was a "blank slate"-with an empty brain and no abilities.
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Certain physical characteristic are biologically determined by genetic inheritance such as pigmentation of skin and color of eyes which are gathered by the genes we inherit. Additional physical characteristics such as height, weight, hair loss even some illnesses (e.g. breast cancer in women) appear to be influenced by the genetic make-up of our parents. These facts have made many to ask the question whether psychological characteristics such as intelligence, gender, personality and behavior are product of our genes or they are influenced by the environment.
The following debate looks at whether we acquire many of our traits through nature, or through our environment- nurture concerning our intelligence and gender.
The case of heredity (nature) as an argument to the debate can be traced back to Charles Darwin's theory of evolution and the idea of "survival of the fittest" influencing the Biological approach in Psychology which focuses on genetic and hormonal explanation of behavior and tends to favor the nature side of the nature-nurture debate. The nature approach view claims that many human skills and actions are result of genetically inherited urges (e.g. intelligence, personality, maternal instinct) and it is supported by nativists. On the other hand the view that supports the belief that human main skills and characteristics are socially learned and developed through experience is the view of empiricists, according to whom whatever we learn we learn trough perception.
The topic of Intelligence is one of the major interests within Psychology and very difficult to define as it is subject of many psychological factors as: ability to cope with all aspects of daily living, problem solving skills, learning and benefiting from previous experiences, predicting likely outcomes and many more skills that humans use to adapt themselves to their environment. Good reasoning abilities, rationalization and cognitive skills seem to further develop intelligence.
An influential theory of the biological bases of intelligence is the idea that the base of intelligence is in the brain (Donald Hebb 1949). This theory suggests the necessity of distinguishing among different intelligences: Intelligence A as innate potential which is biologically determined and represents the capacity for development. Intelligence B is the functioning of the brain and is generated when intelligence A interacts with the environment. Philip E. Vernon (1979) elaborated this definition to include intelligence C, which is the score one obtains on an intelligence test. Hebb's point of view is that the basic potential for intellectual development is provided by the genes and the stimulation for this potential to be reached is environmentally provided.
Early psychologists, such as Sir Francis Galton, defined intelligence in terms of simple sensory, perceptual, and motor responses, as opposed to higher mental processes such as thinking and problem solving. Galton's main contribution was that he raised questions about individual differences in intelligence and how it should be assessed.
He believed that intelligence is innate something we are born with.
In 1905 Alfred Binet and his student Theofile Simon introduced one of the first measuring intelligence test called the Binet-Simon scale. They developed the concept of mental age to measure the individual's level of mental development relative to others. For example a child with a mental ability of a normal five year old has a mental level (age) of five, so an eight year old with a mental age of five is 'deficient'. Using Binet's concepts and calculations, William Stern developed the intelligence quotient (IQ). The IQ is a concept measured by dividing a person's mental age by his/her chronological age and multiplying by 100.
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The current version of the original IQ test is called the Stanford-Binet and it can be administered as early as age 2 and through adulthood. It has been revised to assess abilities in four areas: verbal reasoning, quantitative reasoning, abstract/visual reasoning, and short-term memory. Intelligence quotient is the most common measure of intelligence, but is it the most accurate and can it measure all the types of intelligence that people possess. Is it valid and reliable concerning different cultures and environmental factors. Perhaps not, for example intelligent tests designed for middle class white children do not reflect the values and early experiences of children in other cultures, which means that they are culturally biased. However it is proved that most intelligence tests have high reliability with a correlation coefficient of +90 and IQ scores are a good predictors of success in school, e.g. the verbal scale of the Weschler tests correlated with school grades.
Twin studies are probably the best way to assess the influence of genes and the environment in determining individual differences in intelligence. Because identical twins (MZ) come from a single fertilized egg that splits in two, they share virtually the same genetic code which means they are of the same sex and they should look very much alike. By comparing fraternal twins (DZ), (who come from separate eggs and share on average half their DNA) with identical twins, researchers can identify the extent to which our genes affect our intelligence. If identical twins have more similar IQ scores than fraternal twins, there would be a reasonable conclusion that heredity influences intelligence. The various studies carried by researchers regarding intelligence use the aforementioned different degrees of genetic relationship as a basis for their hypothesis. It should be the case that the closer the kinship the more similar individuals should be, if the particular characteristic investigated is inherited.
Some of the evidence supporting the genetically inherited intelligence comes from the twin studies. For instance, by reviewing many twin studies Bouchard and Mc Gue(1981) found that identical twins raised in different environment tend to have more similar IQ scores than the fraternal twins reared together. These findings suggest that there is a strong genetic component to IQ and supports the heredity point of view. If the environment was an important factor, the fraternal twins' IQ scores should have had closer correlation. However there is few criticisms of the twin studies, Leon Kamin for example criticizes Shield's twin study claiming that the twins in the study were actually raised by members of the family e.g. one twin by the mother and the other by the grandmother, aunt or other relation. They shared the same environment by going to the same school and living in the same neighborhood. Another more general criticism of the twin studies would be the small samples of twins actually used in the studies and the method of recruiting them e.g. advertisements in the media therefore each sample was self-selected. Last criticism would be that MZ twins are not exactly identical, partly because of small genetic differences and also because they create their own microenvironment.
The Adoption studies provide an alternative option to investigate the effects of heredity and environment in intelligence, by comparing adopted children's intelligence to that of their adoptive family and of their biological parents. Adopted children share half of their biological parents' genetics and none of their environment, while they share no genes and some environment with their adoptive parents. Hence any similarity detected between adopted children's IQ and either their real or adoptive family would indicate which one of these factors nurture or nature, plays more important role in human's intelligence.
The Texas Adoption Project-Horn(1983) involved almost 500 children, the findings of wich showed that adopted children's IQ's were more closely correlated with their biological rather than adoptive mother(0.28 compared with 0.15)though differences were small. Years later when the children were older they were tested again and the results showed, increased IQ correlation with their biological mothers and decreased one with the adopted family especially during late adolescence (Bouchard, 1997; McGue, Bouchard, Iacono, & Lykken, 1993) . The adoption studies show that shared environment became less important and genetic factors turned out to be more important as the children became older.The outcome of this study outlines the importance of the family environment and the influence it gives on the development of children's intelligence.
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Another essential study to note is the Project Headstart which was desighned to improve intelligence of disadvantaged children, through environmental imput and tended to provide more stimulating culturaly enriched program for them and compare their IQ before and after the program. It was argued however that such children lacked some of the early benefits enjoyed by more of the middle-class children. For example intellectual stimulation and health and therefore they were disatvantiged even before they started school. Such disatvantages may lead to possible failure. When the childrens were compared with a control group they showed modest intellectual improvements, however these gains were short- lived. The outcomes of Project Head Start provide strong support for the short-term effectiveness, demonstrating how important is the intellectuall stimulation at home and indicates that intelligence can be affected by environmental factors.
Gender is a psychological term which defines several charachteristics or traits and determines what a woman or a man is in social and biological aspect. In other words gender refers to the personal concept of being male or female regardless of an individual's biological and outward sex. Although we are born with our sex which is the more obvious biological difference between a male and a female, we have to learn about our gender.
Biological sex is determined at conception by the pairing of chromosomes that can either be XX for females and XY for males. Gender however is a socially influenced term very much determined by culture,ideas, expectations, stereotipes and attitudes regarding someone's sex. In addition to the nature nurture debate , the subject of gender and sex is widely discussed , where the belief that gender differences are determined by genes and hormones is in favorof the the nature side of the debate and it is supported by the biological and psychoanalitical approach.Thus any gender differences are assumed to be innate. On the other hand nurture refers to the idea that gender differences are a result of cultural and social factors. Hence these differences are due to the environment. This is the behaviorist's and cognitive approaches.
Sex hormones determine the physical development of males and females. The main female hormones are called
estrogens, and androgens are the main male hormones.
A study carried by Money and Ehrhardt (1972) on females who were exposed to high levels of male sex hormones prenatally, noted that they were acting more like a boys rather than girls. They preferred to play with blocks and cars rather than with dolls even though their parent treated them as girls. These findings provide proof for biological influences in the differences between the sexes.
However Money and Ehrhardt (1972)concluded from further twin studies that gender is socially rather than biologically constructed .They studied male identical twins, one of whom sexual organ's was severely damaged, due to surgical intervention. Money advised the parents of the boy, that the best solution would be to raise the boy as a girl, with additional supply of female hormones at puberty. The parents raised the boy as a girl calling him Brenda and rewarding him with a gender appropriate behavior. Money reported that Brenda played with dolls and behaved like a girl whereas his twin brother preferred boy's toys. Although Money used the aforementioned study to argue that social factors can domineer biology, later reports Colapinto(2000)( Brenda chose to be a male and married) showed that nature may be more important in determining gender.
Criticism of the above studies, which are in favor of the nurture side of the debate, would be the lack of explanation of the impact of social factors and environment on gender development, such as woman's surroundings and health nutrition during her pregnancy. Also the attained findings from Money and Ehrhardt (1972) cannot be universal for the general population, e.g. the evidences have been obtained from very unusual cases.
An opposing to the nature view of biological inheritance in gender is the cross-cultural study of anthropologist Margaret Mead. She researched various societies in New Guinea the findings of which support the sociobiological theory. Margaret mead discovered a different pattern of male and female behavior in each of the cultures she studied, noticing some gender differences, but also gender similarities. The Aparesh Indians both males and females were responsive, gentle and cooperative which in western society would be more commonly associated with females way of behavior. Among the Mundugumor tribe, both males and females were violent and aggressive, seeking power and position. For the Tchambuli the females behaved in a self-confident and independent manner, being in charge and oppositely the males were less responsible and more emotionally dependent. Mead's finding contribute to the suggestion that environment or social learning in developing gender roles plays crucial part in favor of the nurture side of the debate, even if there are genetic or hormonal differences between the sexes. However Mead's work has been criticized for the validity of her study and whether the findings she reported were not made, so they can support her theory.
In contradiction with Mead's theory, John Bowlby argues that some differences in the attitudes and behavior of males and females are genetically transmitted instincts. For example Bowlby argued that females must have maternal instincts and "the role of caregiver is simply something which girls are born with" (p.277).
The psychoanalytical theory of Sigmund Freud indicated biological factors and the social environment as determining influences on the child gender-role development. Biological factors - sexual energy which is channeled to the various zones of the body during the course of development. Social environment - the way in which the child is treated by the parents.
According to Freud gender role development begins during the phalic phase (3-6 years). During that stage a child experiences a biologically based love for the parent of the opposite gender-the Oedipus complex in boys and Electra complex in girls. However the child experiences conflict and anxiety as a result of these forbidden wishes and in an attempt to resolve the conflict he or she identifines with the parent of the same gender.Therefore gender -role
Development begins as a result of children's identification with the same gender parent. This process according to F occurs on the unconscious level and therefore can't be controlled by either the parent or the child. F argued that if the mother or the father behaved in an unappropriate for their gender model the child respectively would not acquire appropriate gender role
According to social learning theory children learn gender appropriate behaviour trough observation and modeling (imitation) of others in their society(e.g. Bandura, 1977) and from that society media exposure. Many parents encourage their children to behave appropriately and reinforce them when they do so. An example in support that view is
Beverly Fagot's (1989) longtitudinal study on children as young as age of 2.Their parents had to encourage gender appropriate behavior and on the other hand to discurrage gender inapropriate behaviour.For example girls were encouraged to play with dolls and discouraged to climb trees. The findings of the study showed that some parents did teach their children how to behave in gender-sterotyped way.