Assessing Intelligence

Origins of Testing Early 20 th 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 – 19 th 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: 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