1. Genetic and environmental factors associated with intelligence test performance.
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2. Genetic and environmental factors associated with intelligence test performance.
including the influence of culture.
So if it is genetic, hereditary then our intelligence is purely down to our parents genes!
Those who believe in the importance of heredity draw a distinction between the genotype and the phenotype. The genotype is the genetic inheritance whereas the phenotype consists of an individual’s observable characteristics. So far as intelligence is concerned, we can’t assess the genotype. All we can do is assess the phenotype by administering an intelligence test.

3. Hereditary and the environment
However, the reality is we cannot separate out the effects of hereditary and environment because our genetic makeup influences the types of environmental experiences we have.

4. Three types of interdependence
Plomin (1990) identified three types of interdependence between genetic factors and environment:
1. Active covariation: occurs when children of differing genetic ability look for situations reinforcing their genetic differences (e.g. children of high genetic ability reading numerous books).
2. Passive covariation: occurs when parents of high genetic ability provide a more stimulating environment than parents of lower genetic ability.
3. Reactive environment: occurs when an individual’s genetically influenced behaviour helps to determine how he/she is treated by other people.

5. Twins and how they help
Monzygote (one egg). Genetically the same so should have same intelligence (genetic). If they have the same upbringing then hard to prove environmental or genetic factors but adoption or being brought up apart can show if one is more important than the other.
Zygotic twins: (50%) Different eggs. Brought up the same may show the environmental factors have greater influence or in fact that genetic predisposition does.

6. Research evidence for genetic factors
Bouchard and McGue (1981) reviewed 111 studies, and reported that the mean correlation for identical twins was +.86 compared to +.60 for fraternal twins.
McCartney, Harris, and Bernieri (1990) reported similar findings from a later analysis of numerous studies: the mean correlation for identical twins was compared to +.59 for fraternal twins.
Bouchard and McGue (1981) found that the mean correlation coefficient for identical twins brought up apart was Identical twins brought up apart should be very similar to each other in IQ if genetic factors are very important. Thus, the +.72 seems to provide fairly convincing evidence for the importance of both genetic and environmental factors. The finding that the correlation is higher than that for fraternal twins brought up together suggests the importance of genetic factors. The finding that the correlation (+.72) is lower than that for identical twins (+.86) suggests the importance of environmental factors.

7. Research evidence for genetic factors
Bouchard et al. (1990) found similar findings to the above study as they studied more than 40 adult identical twin pairs separated at a mean age of 5 months, and found their IQs correlated The similarity of the correlations supports the reliability and validity of the genetic basis of intelligence.
Mackintosh (1998) reviewed the evidence based on heritability measures. He concluded that between 30% and 75% of individual differences in intelligence in modern industrialised societies are due to genetic factors.
Brace (1996) found that the heritability of intelligence was much higher among people living in affluent white American suburbs than among people living in American urban ghettoes. This is because the favourable environment experienced by those in the suburbs meant individual differences in intelligence depended mainly on genetic factors.

8. Research evidence for genetic factors
Horn (1983) reported findings from the Texas Adoption Project, which involved almost 500 adopted children. The correlation between the adopted children and their biological mothers was +.28, and between the adopted children and their adoptive mothers was even lower at Both of these correlations are very low but they do suggest a greater role for heredity as the correlation between biological relatives was higher than between adopted relatives.
Loehlin, Horn, and Willerman (1989) found there were some differences in the findings when the adopted children were tested again 10 years later. Now the children showed an increased correlation with their biological mothers, but a reduced one with their adoptive mothers. Shared family environment between the adopted children and their adoptive mothers was reduced in importance. In contrast, genetic factors had a greater influence on the adopted children’s intelligence than 10 years earlier.

9. Research evidence against genetic factors and so for environmental factors
Loehlin and Nichols (1976) point out that the differences between MZ and DZ twins may not be solely due to genetic factors because identical twins are treated in a more similar fashion than fraternal twins. This can include parental treatment, playing together, spending time together, dressing in a similar style, and being taught by the same teachers. Thus, the differences in intelligence may be due to environmental, rather than genetic, factors.
The prenatal environment may also explain the differences in intelligence between MZ and DZ. Two-thirds of identical twins (MZ) share a placenta whereas fraternal twins (DZ) have separate placentas. This means the prenatal environment of most identical twins is more similar than that of fraternal twins and so environmental factors could explain the intelligence correlations. Identical twins sharing a single placenta are more similar in intelligence than those having separate placentas (Phelps, Davis, & Schwartz, 1997).

10. Research evidence against genetic factors and so for environmental factors
The correlation of +.28 between adopted children and their biological mothers found by Horn (1983) is much less than the correlation of between parents and children when children aren’t adopted (Bouchard et al., 1981) and so this difference must be due to environmental factors.
Bouchard and McGue (1981) found that the correlation for identical twins brought up together was +.86 compared to +.72 for identical twins brought up apart. Thus, whilst twin studies are usually used as evidence for genetic factors this difference supports environmental factors because it is due to the fact that identical twins brought up together have more similar environments than those brought up apart.

11. Research evidence against genetic factors and so for environmental factors
The Flynn effect shows the environmental factors can have a substantial effect on intelligence because Flynn (1987) found a rapid rise in average IQ in many Western countries in recent decades. Such large and rapid increases in IQ are due mainly to environmental factors, such as longer time spent in education and greater access to information.
Further evidence for environmental factors is provided by Sameroff et al. (1987) who identified 10 family risk factors related to lower IQ, which included: mother didn’t go to high school; father had a semi- skilled job. They found that at the age of 4, high-risk children were 24 times more likely to have IQs below 85 than low-risk children. On average, each risk factor reduced the child’s IQ score by 4 points.

12. EVALUATION OF THE ROLE OF GENETIC AND ENVIRONMENTAL FACTORS IN INTELLIGENCE TEST PERFORMANCE
Sample bias. Identical twins are relatively rare, and identical twins brought up in separate families are obviously even rarer. (Not enough data)
Adoption studies do not isolate genetic factors. Many identical twins brought up apart were brought up in separate branches of the same family, and so their environments may have been fairly similar. Other identical twins were brought up together for several years before being separated. Note Bouchard’s later study (Bouchard et al., 1990) addressed this, as it only involved twins separated before 5 months of age.

13. Difficult to interpret the findings from adoption studies
Difficult to interpret the findings from adoption studies. It is very hard to interpret the findings of many adoption studies because of selective placement, which is when children are placed in homes similar to those of their biological parents’ in educational and social backgrounds. Thus, the correlation between adopted children and their biological parents may be due to selective placement rather than to genetic factors. (Similar environment)
Impossible to establish that environmental risk factors cause lower intelligence. Sameroff et al.’s (1987) findings do not show that the environmental risk factors they identified were actually responsible for low IQs. It is likely that the parents of the high-risk children were less intelligent than those of the low-risk children and so there are differences in genetic potential between the low-risk and high-risk groups of children. It seems likely that the adverse environmental factors have some negative effects on children’s intelligence but it is, as always, impossible to separate out the influence of genes versus environment. (separate genes and environment)

14. Strong empirical support
Strong empirical support. Twin studies provide convincing evidence because they allow us to observe the effects of varying degrees of genetic similarity on intelligence, and so provide strong support for both the influence of genetic and environmental factors.
Genetic and environmental factors are positively correlated. Individuals with the greatest genetic potential for intelligence tend to find themselves in environments favourable for the development of intelligence (e.g. staying at school until the age of 18, going to university). This makes it hard to disentangle the effects of genetic and environmental factors.

15. Correlational evidence
Correlational evidence. Research into environmental factors is correlational because the environment cannot be manipulated. This means cause and effect cannot be established and so we cannot conclude that environmental factors cause changes in intelligence.
Validity of IQ tests. Intelligence tests are not necessarily a valid measure of intelligence. They are culture biased and narrow in scope because they fail to assess social or emotional intelligence. Consequently, the evidence is on differences in intelligence as assessed by intelligence tests, which is not necessarily a valid measure of intelligence.

16. Culture
Culture has an effect on intelligence test performance because the cognitive skills that are important vary from one culture to another. Thus, for example, language skills including reading and writing are very important within most Western cultures, but more practical skills are emphasised in other cultures. Culture is an issue in terms of IQ tests because the tests have been devised by psychologists working in the United States or in Europe. It has sometimes been claimed that American and/or Europeans are more intelligent than people from most other parts of the world. However, this is simply not true. The problem is that the IQ tests are ethnocentric, i.e. biased to favour the culture in which they were devised, and so they are not a valid measure of intelligence in other cultures.

17. Research evidence of cultural differences
Okagaki and Sternberg (1993) studied ethnic groups in San Jose, California and found concepts of intelligence varied within a culture. Asian parents emphasised the importance of cognitive skills in their conception of intelligence. In contrast, Latino parents argued that social-competence skills are of particular importance in their conception of intelligence.
Grigorenko et al. (2004) studied different aspects of intelligence in Yup’ik Eskimo children living in southwest Alaska. Some of these children lived in the towns and others lived out in the country. The study tested children’s practical intelligence (e.g. knowledge of how to travel in the virtual absence of landmarks) and also used traditional intelligence tests. The urban children performed better than the rural children on traditional intelligence tests, whereas the rural children outperformed the urban ones on the test of practical intelligence. These findings clearly represent the skills most relevant to the children in their everyday lives.

18. Sternberg et al. (2002) argued that children in many cultures perform poorly on conventional intelligence tests because they have little experience of this form of assessment. He introduced, where the individuals are tested on two separate occasions with training in the skills assessed by the tests being provided between tests. Children in Tanzania showed substantial improvements between the first and second test suggesting that they had abilities and an ability to learn not revealed on the first testing occasion. Thus, dynamic testing in developing countries can provide a better assessment of intelligence than traditional single testing.

19. EVALUATION OF THE RESEARCH INTO CULTURAL DIFFERENCES
Validity of intelligence tests. If we want to obtain a valid assessment of intelligence in any given culture we must always consider the cultural context. Research such as Grigorenko et al.’s, which has done this with the assessment of practical knowledge, provides a much more valid measure of intelligence.
Dynamic testing is less biased. Dynamic testing is potentially a very useful way of assessing intelligence. It assesses an individual’s speed of learning, which is of great importance to intelligence.

20. Conclusion
The mutant gene that led to bipedalism may be the origin, and so the development of intelligence needs to be traced back to this. The co-evolution of brain size and mental abilities may be in part due to a chance mutation. There is evidence to support co-evolution as brain size and intelligence are related. However, other factors are involved in the association. The human brain is highly complex and more organised than any other animal’s and this may be equally, if not more, relevant than total brain size. It seems likely that environmental and then social complexity are the earliest origins of human intelligence, however, these do not account for why the human brain is more advanced, at least according to EQ measures! Thus, social and ecological factors must interact with later factors, more specific to humans, such as sexual selection, language, bipedalism, and the ability to control fire.

21. Conclusion
The environmental factors that influence intelligence testing show that intelligence is not solely an evolved mechanism. Research evidence from twin, adoption, and family studies does show the role of genetic factors, however these studies can also be turned around to show the influence of environmental factors, for example the fact that intelligence correlations are lower for identical twins raised apart than those together is due to environmental factors. The influence of culture on intelligence shows quite how pronounced the effect of the environment can be as the very concept of what intelligence is depends on the cultural context.

22. Test Essay
Discuss evolutionary factors involved in the development of human intelligence.
(9 marks + 16 marks)

23. Answer
AO1 = 9 marks Outline of evolutionary factors involved in the development of human intelligence Factors involved in the evolution of human intelligence include ecological (eg bipedalism, foraging, hunting), social (group size, social complexity) and brain size. The question is on the development of intelligence, so material on, for instance, the role of diet in increasing brain size must be linked into the development of intelligence to earn marks beyond Basic. Similarly, comparative studies of brain size and the encephalisation quotient need to be presented in the context of the increase in human intelligence to earn marks beyond Basic.

25. AO2/AO3 = 16 marks Commentary on the evolution of human intelligence Research findings on the evolution of human intelligence are necessarily indirect. However the research eg of Dunbar on group size, brain size, and social intelligence in human and nonhuman primate societies, would be an excellent source of AO2/AO3 marks. Research into gender differences in types of intelligence and cognitive skills have also been discussed in an evolutionary context and would be creditworthy in this question. Comparative studies of animal intelligence in relation to, for instance, brain size, may also be made relevant. Again, however, the focus of the question is on the development of intelligence, not brain size, and implications for the question must be clear for marks to be awarded. Although unlikely, candidates may introduce research into the genetic basis of IQ. This could in theory be made relevant to the question, but this must be explicit for marks to be awarded. General commentary could include the adaptive advantage of intelligence (eg in the development of cognitive skills involved in tool use, hunting, foraging and group living). Additional issues Psychology A (PSYA3) - AQA GCE Mark Scheme 2011 June series 21 include the problems of conducting research in this area, the speculative and retrospective nature of many hypotheses, and problems of defining intelligence. Indicative issues/debates/approaches in the context of the evolution of human intelligence: evolutionary/biological approach; use of non-human animals in research; reductionism; free will/determinism; nature/nurture; cross-cultural research; social/cultural factors; gender differences. Such material must be used effectively to earn AO2/AO3 credit. AO2/AO3 material should first be placed in the appropriate band according to the descriptors. However, not all the criteria need be satisfied for an answer to be placed in a particular band. Weak performance in one area may be compensated for by strong performance in others. In order to access the top band, issues, debates and/or approaches need to be addressed effectively.