Testing and Individual Differences
Francis Golton was one of the first to study human intelligence and testing, and initiated the use of surveys to collect data, along with creating and applying statistics towards its analysis.
Standardisation and Norms
A test that is standardised is a test that has been piloted on a group of people similar to the population that is supposed to take the test, where achievement norms have been established. An easy one for many students planning on studying in the US is the SAT. At the end of the SAT, students take an extra set of questions that aren’t graded. These questions are developed so the Educational Testing Service can continue to standardise coming exams. Since the students taking the SAT are representative of the groups taking the SAT as a whole, they are known as the standardisation sample. People who make tests (known as psychometricians) at ETS use the achievement of students on the experimental section of the exam to decide how the next exam will be formulated. Questions nearly everyone gets right or wrong are discarded as they aren’t useful for differentiating between students.
In order for a test to be taken seriously, it needs reliability and validity.
Reliability is the consistency of the test as a means of measurement. For instance, if you take an IQ test and score 99 the first time, 115 the next time, and 160 the third time, the test isn’t very reliable. There are many ways to measure a tests reliability. Split-half reliability involves randomly splitting a test into two different sections and correlating someone’s performance on the two halves. The closer the correlation coefficient is to +1, the greater the split-half reliability. Equivalent-form reliability is the correlation between someone’s performance on two different but equivalent forms of the same test. Finally, test-retest reliability is the correlation between 2 different administrations of the same test.
A test is valid if it measures what it’s supposed to measure. If Albert Einstein took an IQ test and got 99 all 3 times, you can say the test is reliable, but it’s clearly not very valid. A test cannot be valid if it is not reliable, however it can be reliable without being valid. There are multiple different kinds of validity, for example, face validity is a superficial measure of accuracy- it is the degree to which a test appears effective. If you’re looking for a chef, a cake baking test has high face validity. Face validity is considered a type of content validity- This is how well a measure reflects the entire range of material is is supposed to be testing. The cake baking test doesn’t have great content validity if the chef needs to cook things other than cake. There is also criterion-related validity- the extent to which a measure is related to an outcome. There are two kinds of criterion-related validity: Concurrent validity which measures how much of a characteristic a person has now, and predictive validity which is a measure of future performance. Finally, construct validity, which is a measure of whether a test measures a construct accurately.
Two common types of tests are aptitude tests and achievement tests. Aptitude tests measure potential while achievement tests measure what someone has learnt. Making a test that exclusively measures one of these qualities is nearly impossible. For example, take a Math Aptitude test- you can have two people, each with equal potential to do well in the subject, but one of the test-takers has spent years studying math, while the other has barely done it at all- it’s obvious who will score better. On a Chemistry Achievement exam, you can have two students who studied an equal amount, however one may have a higher test-taking aptitude and score better than the other.
There are also speed and power tests. Speed tests consist of a large number of questions asked in a short amount of time- typically time that is insufficient to complete the problems, and power tests typically gauge the difficulty level of problems that someone can solve.
Finally, there are group and individual tests. Group tests are given to groups of people at one time and have little to no interaction between the examiner and test-takers. Individual tests involve more interaction with the examiner and study one person at a time.
Intelligence is another one of those words that get thrown around constantly but are surprisingly difficult to define. A medical doctor would look like an idiot when talking to a group of quantum physicists about string theory, but logically we would still call him intelligent. Many psychologists draw a distinction between fluid intelligence and crystallised intelligence. Fluid intelligence is our ability to solve abstract problems and learn new things while crystallised intelligence involves using the knowledge we accrue over time.
Charles Spearman- Charles Spearman argued that intelligence can be expressed as a single factor. He used factor analysis to conclude that underlying the many different specific abilities (s) that people regard as types of intelligence is actually a single factor that he named g.
Howard Gardner- Howard Gardner subscribed to the idea of multiple intelligences. What made his theory unique was that the intelligences that he named encompass a much larger range of human activities than most other psychologists. For example, he named linguistic, mathematical, and spatial intelligence which line up with what most psychologists use, however, added: musical, bodily-kinesthetic, intrapersonal, interpersonal, and naturalist intelligence.
Daniel Goleman: Daniel Goleman is one of the main proponents of EQ, or emotional intelligence. These are related to Gardner’s intrapersonal and interpersonal intelligence.
Robert Sternberg- Sternberg has offered a nontraditional definition of intelligence. His triarchic theory defines 3 types of intelligences. Componential or analytic intelligence describes our ability to compare, contrast, explain, and analyse. Experiential, or creative intelligence observes how people use their knowledge in innovative ways. Thirdly, is contextual or practical intelligence. These are people who are able to apply their knowledge to the real world. Sternberg’s theory also raises another question- does intelligence depend on context? Sternberg would say yes. Most intelligence tests however view intelligence as ability based rather than context based.
There are two widely used individual tests- the Stanford Binet and Wechsler, however there are as many different types of intelligence tests as there are theories for what intelligence actually is.
Alfred Binet wanted to make a test to identify the children who needed extra help in school. His test was based on the idea of mental age, supposing that intelligence increases as someone ages. A normal 10 year old has the mental age of a 10 year old. Louis Terman, a professor at Stanford university used this system to measure IQ (intelligence quotient), and create the Stanford-Binet IQ test. A score on this test is formulated by dividing their mental age by their chronological age and multiplying by 100. The 10 year old would have an IQ of 100- (10/10 x 100). This test gets a bit weirder with adults. To rectify this, Terman assigned all adults an arbitrary age of 20.
David Wechsler took a bit of a different approach. There are 3 different Wechsler tests- there is the Wechsler adult intelligence scale (WAIS), the Wechsler intelligence scale for children (WISC), which is given to children from ages 6 to 16, and the Wechsler preschool and primary scale of intelligence (WPPSI). These tests yield an IQ score based on deviation IQ. The tests are standardised so that the mean is 100, and the standard deviation is 15. Scores are found based on how many standard deviations they fall away from the mean. Someone who scores at the 15.87th percentile falls one standard deviation below the mean, and would receive a score of 85. Someone who scores at the 97.72nd percentile scored 2 standard deviations above the mean and would get a 130. Wechsler’s tests also provides scores on a number of sub-scales along with a total IQ score. The WAIS has 11 sub-scales. 6 produce a verbal IQ score, 5 produce a performance IQ score.
The accusation that tests like the SAT are biased is not a new one. Researchers looking into the SAT say that although different races and sexes score differently on these tests, they have the same predictive validity for all groups. Other researchers argue that both the tests and college grades are significantly biased due to the advantages white middle and upper class students benefit from.
Here we are, back again on this debate which seems to appear everywhere throughout Psychology. Research suggests that both genetics and environment contribute to molding intelligence. When discussing the effects of nature and nurture, researchers use the term heritability- this is a measure of how much of a trait’s variation is explained by genetic factors. Heritability of 0 implies that the environment is completely in control of differences in the trait, while 1 implies that genetics is totally responsible. So how heritable is intelligence? Answering this question is extremely difficult as effectively studying this question would require studying a controlled population, rather than an individual which would bring up serious ethical questions. There have been some interesting findings, however.
The Flynn Effect is a finding that suggests environmental factors like nutrition, education, and even entertainment like TV can play a role in intelligence
Monozygotic/identical twins score much more similarly on intelligence tests than dizygotic/fraternal twins, however, bias may play a role in this as monozygotic twins tend to be treated more similarly than dizygotic twins.
To avoid this bias, researchers look to monozygotic twins separated at birth. There have been strong correlations in intelligence, however, bias may still be present as the twins may be placed in similar environments.
Some people (including the bloke who made the SAT) point to racial differences to prove that intelligence is genetically based. Carl Brigham used his test to “prove” that white people were superior to people of colour, while ignoring factors like poverty and lack of education, and English fluency when scoring his exams.