Unit 13: Intelligence (page 2)

Alfred Binet: Along with Theodore Simon developed the first intelligence test in France in 1904.  It was designed to measure a child's mental age in order to predict future school performance.  The test was called the Simon-Binet Intelligence Test.  It was later revised at Stanford University by Lewis Terman and is now known today as the Stanford-Binet.
Intelligence Quotient (IQ):
defined originally (Stern) as the ratio of mental age (MA) to chronological age (CA) multiplied by 100 (thus, IQ = MA/CA * 100).  On contemporary intelligence tests, the average performance for a given age is assigned a score of 100.
Wechsler Adult Intelligence Scale (WAIS) & Wechsler Intelligence Scale for Children (WISC):  These are the 2 most frequently used IQ tests in the US.  They provide a verbal IQ along with a non-verbal or performance IQ.  They also provide an overall or full-scale IQ score.  The Wechsler tests have a mean of 100 and a standard deviation of 15.
                    Principles of Test Construction
defining meaningful scores by comparison with the performance of a pretested "standardization group".
        Normal Curve: the symmetrical bell-shaped curve that describes the distribution of many physical and psychological traits (including intelligence). Most scores fall near the average, and fewer and fewer scores lie near the extremes.
Reliability: the extent to which a test yields consistent results, as assessed by the consistency of scores on two halves of the test (split-half reliability) or on retesting at a later date (test-retest reliability).
Validity: the extent to which a test measures or predicts what it is supposed to.
        a) Face Validity: the extent to which questions on a test appear to measure the construct of interest.
        b) Content Validity: extent to which a test actually measures the construct of interest.
        c) Predictive Validity: the success with which a test predicts the behavior it is designed to predict.  This is assessed by computing the correlation between
test scores and the criterion behavior (also called criterion-related validity).
Criterion: the behavior (such as college grades) that a test (such as the SAT) is designed to predict.
                  Extremes of Intelligence
Mental Retardation:
a condition of limited mental ability, indicated by an IQ score below 70 and difficulty in adapting to the demands of life; varies from mild to profound.
Down Syndrome: a condition of retardation and associated physical disorders caused by an extra chromosome in one's genetic makeup.
the proportion of variation among individuals on a particular trait that can attributed to the differences in their genes.
Twin & adoption studies show that genetics do play a role in intelligence (e.g., IQ's of identical twins correlate at about .85, while fraternal twins at about .60).

However, the same studies show how important environment is in that identical twins reared together correlate at .85, while those raised in different homes correlate at .71.

Most psychologist agree that differences in group IQ scores based on ethnic background or gender are due to environmental differences not genetics.


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