Py 1: Exam 2: Intelligence

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Intelligence

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the capacity to acquire and apply knowledge. Refers to predicting behavior, not merely evaluating it.

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Achievement tests

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are designed to measure acquired skills.

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Aptitude tests

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are designed to measure a capacity to acquire a skill or body of knowledge. Most aptitude tests must end up measuring achievement as well.

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The development of IQ tests:

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In 1895 the French government asked psychologist Alfred Biknet to design a test to diagnose children with intelligence problems. He came up with two important notions in his task:
An intelligence test should sample a wide variety of cognitive abilities
Intelligence is developmental (strongly related to age). So, if children grow mentally, and if growth rate varies, then at each age there will be a different distribution of mental performances.

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Basic scheme of test

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develop test items that would vary from easy to difficult and would distribute results based on age. Mental age- the level of difficulty that an individual achieves as designated by the performance of a given age cohort on the test items. We can place this value over physical/chronological age x 100 to get the IQ. If a 10 year old performs like a 12 year old, his IQ would be 120. An example: a seven year old should be able to know which way a saw cuts wood.

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Mental age-

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the level of difficulty that an individual achieves as designated by the performance of a given age cohort on the test items.

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Wechsler Adult Intelligence Scale (WAIS)

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However, Binet’s definition of IQ stops working after teenage years. So, for adults, IQ is measure not relative to age but to average performance of all adults. Wechsler Adult Intelligence Scale (WAIS) produces a rank based on performance on many cognitive test items: information, comprehension, arthimatic reasoning, memory span, similarity tests, picture arrangement, block design, object assembly, and vocabulary. Mean = 100. Standard deviation = 16.

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Reliability

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does the test give a similar value when it is repeated on the same individual at a later time? r is the Pearson correlation coefficient at it varies from –1 to 0 to 1; a score of 1 (or –1) implies perfect correlation. IQ tests have reliability (relative performance at different ages stays roughly the same- r value of .7) after 6 years of age. Note: correlation does not always imply causation.

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Validity

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do scores measure what they intend to measure? For example, does IQ match up to school grades? (Answer: low IQs= low grades but high IQs don’t always = high grades.)

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Genetic abnormality

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results in low IQ (Huntington’s choria, Down’s syndrome, PKU), which causes abnormal brains. But, for the genetically normal population, the question of nature vs. nurture is more sticky.

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Heritability and heritability ratio:

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: how much can we quantitatively attribute IQ to genetic factors? The H ratio: a statistical index that estimates the contribution of genetic factors to variations of intelligence (or another trait) who make up a specified population at a given time. Measure IQs of fraternal and identical twins then note the differences. Note: fraternal twin (environmental + genetic) scores vary more than identical twins (environmental) scores. H= 1 would be all variance is due to genetic factors. H = 0 would be all variance is due to environmental factors. For intelligence, H = .7 (but different studies place different values on H).

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racial differences

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There are racial differences in test scores, but such differences cannot be extended to mean that races are unequal. The H score only applies WITHIN groups and can’t be applied to different groups.

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Stereotype threat

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when people believe that a negative stereotype is relevant to a testing situation their behavior is affected.