Intelligence pt. 2

Other cultures consider other behaviours as 'adaptive', desirable, or 'clever'.

Theory of successful intelligence (Sternberg, 2004): intelligence is whatever is required to meet the adaptive demands of any given culture. Sternberg also suggests that his meta-components underlie intelligence in all cultures. Current thinking suggests that using non-verbal assessments assessing fluid intelligence might be most valid.

Most intelligence tests have caveats built in for assessing individuals with 'common' special needs (e.g hearing impairment), and may use sign language. The administrator of the test should use their own judgement about the suitability of individual subtests for any individual.

People in the same family tend to be more alike in their intelligence test scores than unrelated individuals, which suggests that intelligence runs in families. The influence of genes and the environment on intelligence can be studied using twin studies. Studies can involve looking at twins who have been raised apart. Monozygotic twins who have been reared apart have just slightly lower correlations in intelligence as monozygotic twins reared together

• Plomin & Deary, 2014: heritability of intelligence ranges between .50 and .70
• Horn et al, 1983: tested 300 children who were adopted immediately after birth. When they were later tested, the correlation between their IQs and their biological mothers (whom they had never met) was 0.28. the correlation between adoptive mothers and the children was 0.15

Since monozygotic twins who were raised apart do have slightly lower intelligence correlations than mz twins reared together, it is clear that intelligence is not entirely genetic. Environmental influences must account for the remaining variance. Environment seems to account for between .50 - .30 of the variance among intelligence scores. Environmental influences can be shared and unshared. Shared = family environment, e.g some conditions in the womb. Unshared = brain damage after birth

Can a change of environment increase IQ? Children who are adopted from deprived backgrounds show an increase in IQ - about 10-12 points (Schiff & Lewontin, 1986). Children who remain in deprivation show no increase over time, and some show a decrease (Sepell, 2000).

In theory, enriched environments should have a good effect on IQ. One example is a community in East Tennessee that was quite isolated from the US mainstream in 1930 but became less and less so during the following decade. Between 1930 and 1940, the average IQ of people in this community rose by 10 points from 82-92 (Wheeler,1942)

There is no evidence that DVDs sold to better a baby's intelligence has any influence on later IQ. 

• Robb, Richert & Wartella (2009) Children between 12-15 months were randomly assigned to view baby wordsworth over 6 weeks. After every 2 weeks and 5 exposures to the DVD, children were assessed on expressive and receptive communication measures. Results indicated there was no increased growth on either outcome for children who'd viewed the DVD as compared to those in the control group
• Kirkorian et al (2009) suggests that the quality of parent-child interaction decreases even with background TV. Reliance on TV and DVDs might have a negative impact of development
• Winship & Korenman (1997) suggest that every year in school is worth about 2.7 IQ points
• Ceci & Williams (1997) school attendance raises IQ and truanting is associated with lower IQ scores

The most well-known sex difference associated with IQ is that men are better at spatial reasoning than women (Neisser et al, 1996). On the contrary, women are often thought to be better at verbal tasks than men (Hyde & Linn, 1988)

Researchers have posited that one reason for sex differences might be brain size. There is a small correlation between brain size and IQ. Males tend to have larger brains. Males and females vary considerably in their abilities on all mental tasks. Recent studies fail to find sex differences in mental abilities (Deary, 2003; Strand et al, 2006)

Socialisation could account for sex differences. 

• Crawford & Chaffin (1997): sex-typed activities in childhood.
• Hines (2005): sex hormones alter brain organisation and may extend to other behavioural differences (e.g problem-solving and aggression)

During the 'new immigration' to the US in the early 20th century, the american public wanted some "quality control" about new immigrants. In 1912, Henry Goddard started work at the Ellis Island immigrant receiving station in NY harbour. He used the Binet test. A large percentage of several immigrant groups were classed by Goddard as being 'feeble-minded', and were subsequently deported.

James Watson: "all our social policies are based on the fact that African intelligence is the same as ours - whereas all the testing says not really". While in the 1930s, black American IQ scores were lower than white Americans and people tried to argue that this did reflect a biological difference. However, they ignored the unfamiliarity with testing format, low quality of schooling due to segregation, and poor health. Flynn (2007) reported that there is still a racial IQ difference in the US, but that this difference had closed markedly since the 1940s

On June 1st 1932, everyone who was born in 1921 and was attending school was given an IQ test. 87,498 children were tested. In 1998 Deary & Whalley tested 101 people (now 77) on exactly the same test as they had done in 1932. The correlation between 1932 and 1998 was greater than .60, which is moderate to large.

Schaie's Cross-sequential study: amassed a large amount of data, and demonstrated evidence for the 'cohort effect' - later generations are doing better. Cross-sectional data shows a decline in mental abilities from 25-80 years old. Overall, verbal ability peaks in the 30s and stays fairly stable over time

James Flynn: he noted companies making mental tests needed to updates their norms every few years. New generations were doing too well on the tests and performing above the norms.

The Flynn Effect is the substantial and long-sustained increase in both fluid and crystallised intelligence scores measured in many parts of the world from roughly 1930 to today. When IQ tests are initially standardised, by convention the average of the test results is set to 100 and their standard deviation is set to 15 or 16 IQ points. When IQ tests are revised, they are again standardised using a new sample of test-takers, usually born more recently than the first. Again, the average result is set to 100. However, when the new test subjects take the older tests, in almost every case their average scores are significantly above 100. There are several explanations

• Artefact explanation: recruitment over time may have changed to include 'cleverer' people, so the norms are higher. 
• Test sophistication: successive generations might not be more intelligent - their increased test scores are due to some other reason that hasn't been worked out yet
• Others believe that we have become more familiar with IQ test type activities. Children's educational toys, computer games, magazines etc might contain materials with IQ-like properties, and so people might do better on these tests
• The Flynn effect does not completely render IQ test results useless - IQ scores can still be useful indicators of general ability for individuals

Fluid and crystallised intelligence are factors of general intelligence (g factor), originally identified by Raymond Cattell.

Fluid intelligence is the capacity to reason and solve novel problems, independent of any knowledge from the past. It's the ability to analyse novel problems, identify patterns and relationships that underpin these problems, and the extrapolation of these using logic. Fluid reasoning includes inductive reasoning and deductive reasoning.

Crystallised intelligence is the ability to use skills, knowledge and experience. It doesn't equate to memory, but it does rely on accessing information from long-term memory. Crystallised intelligence is one's lifetime of intellectual achievement, as demonstrated largely through one's vocabulary and general knowledge.

Fluid and crystallised intelligence are correlated with each other, and most IQ tests attempt to measure both varieties. Weschler's test measures fluid intelligence on the performance scale and crystallised intelligence on the verbal scale. Overall IQ is based on a combination of these 2 scales.