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Lecture 5: Introduction to Educational Psychology: Individual Differences (Parts of chapters 12 and 13) Intelligence - its measurement, components and stability Personality tests and dimensions INTELLIGENCE Definition of intelligence: definitions vary but may include generality (i.e. intelligence reflected in a wide range of tasks), problem solving, abstraction (applying theories to unfamiliar situations) and perhaps speed of processing. Heritability (twin studies): by using MZ and DZ twins, the heritability of intelligence can be estimated (although this is not an exact figure and does not tell us the effect of the environment on the intelligence of an individual). Research has shown that approx 52% of the variance in intelligence in the tested population is due to genetic differences (Bourchard & McGue, 1981). Other studies have put the figure closer to 60%. However, there are difficulties with twin studies in that MZ twins may be treated more alike than DZ twins. Interactions (parent-child) governing intelligence: because intelligence is partly heritable, intelligent parents are more likely to have intelligent children but also they are more likely to provide a rich intellectually-stimulating environment for their children (i.e. environment is positively correlated with genes). Therefore, the benefit to children of intelligent parents is twofold. Characteristics of a good intelligence test: a good test will have high reliability and validity as well as being standardised so that conditions for taking the test are the same in all individuals.
? If a test is reliable, it will yield reproducible and consistent results i.e. if the test is taken twice and the scores on the two occasions correlate highly with one another then the test can be seen to be reliable (test-retest reliability). If a test is available in two forms, the test is seen to be reliable if the results from the two different forms of test correlate highly with one another (alternate form reliability). The reliability of individual questions may be an issue in which case the score on those particular questions can be correlated with the result of the whole test - if there is a high correlation (internal consistency) then the item in question is reliable. In subjective testing (e.g. an essay paper), interjudge reliability is the correlation of scores from different examiners for the same paper and subject - a high correlation suggests reliability.
? Validity is the determination of whether a test measures what it is supposed to measure. Criterion validity is the comparison of a test score to an external factor called a validity coefficient e.g. comparison of SAT score to first year uni grades - if there is a high correlation then the SAT could be seen to be a valid test. Construct validity is especially applied to personality tests and is used in situations where there is no distinct external criterion with which the result can be applied e.g. achievement motivation. The experimenter has a theory (e.g. individuals with high achievement motivation earn higher salaries) and constructs a test to determine the achievement motivation then may correlate scores with salaries. Different tests: Sir Frances Galton was the first to investigate individual differences but his largescale study (looking at head size, visual acuity etc in 9,000 individuals) yielded no good results or correlations e.g. between head size and intelligence.
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