Assessing Intelligence
Origins of Testing
• Early 20th Century France requires all children
attend school
• How to determine who would benefit? Were
they “dull” or just unprepared
Origins of Testing
• Alfred Binet – Predicting School Achievment
– Binet assumes all children follow same
development and develops test
– “Dull” would be like a child younger
– “Bright” would score like older child
– He measured “mental age” – level of average
child at that age
– Test was not to “measure” intelligence, but to
identify French children that needed educational
help
Origins of Testing
• Lewis Terman – The Innate IQ
– Stanford professor
– Binet’s French test didn’t work for California kids
– Modified Binet’s test, extended from teens to
“superior adults”
– Still known as Stanford-Binet test
– US government used it on immigrants and WWI
army recruits
Origins of Testing
• Francis Galton
– Eugenics – 19th century movement to measure
human traits and encouraging only smart/fit
people to reproduce
– Terman thought IQ testing would “curtail the
reproduction of feeblemindedness and eliminate
crime and poverty”
– Eventually showed how science can be value
driven
Intelligence Quotient
• Original way to compute:
– IQ =
Mental Age
x 100 (no decimal)
Chronological Age
– If your mental & chronological age is same, your
IQ is 100 (average)
• What happens if a 40 year old take the test?
How does that score work?
• It is not computed this way any longer, but still
called IQ
Modern Tests
• Achievement Tests
– designed to assess what a person has learned
• Aptitude Tests
– designed to predict a persons future performance;
aptitude is the capacity to learn
Modern Tests
• David Wechsler
– Wechsler Adult Intelligence Scale (WAIS) – most
widely used IQ test
• Wechsler Intelligence Scale for Children (WISC) and another
for preschoolers
– WAIS consist of 15 subtests, including these:
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•
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Similarities – reasoning the commonality of 2 objects
Vocabulary – Naming items or defining words
Block Design – Visual abstract processing
Letter-number sequencing – on hearing a series of
numbers/letters, repeat numbers in ascending order
and letters in alphabetical (R-2-C-1-M-3)
– Gives overall score and separate scores
Test Construction
• Standardization
– Defining uniform testing procedures and
meaningful scores by comparison with the
performance of a pretested group
– One person’s score means nothing until compared
against other
Test Construction
• Normal Curve
– Bell curve
– Tests are re-standardized to keep avg at 100
Test Construction
• Reliability
– Extent to which a test yields consistent results
– How to check?
• Retest people
– Use same test or maybe just use odds or evens
– If scores generally correlate, it’s reliable
– Stanford-Binet, WAIS, and WISC have reliabilities
of about +.9
Test Construction
• Validity
– Extent to which test actually measures what it
predicts or promises
• Content Validity
– Extent to which a test samples the behavior of
interest
– Ex. Driver’s test
• Predictive Validity
– Success that a test predicts behavior it’s designed
to predict