The definition of intelligence has been widely debated in psychology. One definition that has been well accepted is the one proposed by David Wechsler (the individual who brought us the Wechsler intelligence scales discussed in class - the WAIS, WISC, and WPPSI). He defined intelligence as follows:

"The global capacity to act purposefully, to think rationally, and to deal effectively w/ the environment."

Other psychologists/researchers would say that the definition of intelligence needs to expressly mention things about memory span or problem-solving, but this definition is pretty widely accepted.

When researchers are studying intelligence, they use an operational definition of it (see Chapter 2). In intelligence research, psychologists define intelligence by the types of questions that they ask. And intelligence tests usually have questions that cover things like verbal fluency, memory, reasoning, and spatial skills.

Your book has a great diagram to show the ranges that aptitudes and intelligence covers. You may also see the same diagram by clicking here.

• An aptitude is a capacity for learning certain abilities - a knack for picking up certain skills. An aptitude isn't the same thing as intelligence. A great example to illustrate this is Billy Bob Thornton's character is Slingblade. Billy Bob's character was dumb as a rock, but he was a real whiz at fixing lawn-mowers. While Billy Bob's character was not particularly intelligent, he possessed an aptitude: a mechanical aptitude. He was great at fixing things.
• An aptitude test will test someone in a specific area, to find out how they perform in that area. They predict a person's success in that area.
• Special aptitude test: tests one single area.
• Ex: a typing test. When we're looking to hire secretaries where I work, we need to know that they can type - and type well. So, what do we do? Do we take their words for it? Nope! We administer them an aptitude test to measure their typing ability. In this case, they take a typing test.
• My friend who applied for the job at JC Penney took a special aptitude test covering her ability to use a cash register.
• Multiple aptitude test: tests multiple areas. Can be much broader than a special aptitude test. It can look somewhat like an intelligence test. Some examples you should be familiar with are the ASVAB and SAT.
• General Intelligence Test: measures a variety of mental abilities. Tasks range from putting puzzles together and transcribing symbols to doing arithmetic problems and answering questions about vocabulary of life's social problems.
• Examples of intelligence tests materials can be seen in the glass case on the second floor of Girard Hall.

To be a good test, it has to be both reliable and valid.

• Reliability - a measure of consistency. Do you get pretty much the same score every time?
• If you hopped on your bathroom scale and it said 105 lbs and the next day it said 129 lbs and the next day it said 45 lbs then your scale would not be reliable - it is not giving you consistent answers. You probably wouldn't lend much credence to your scale's results.
• Different ways to look for reliability:
• Test-retest - give the test two times and compare the results. Does everyone get pretty much the same scores?
• Split-half reliability - give test, compare results from one half to the other. Scores on one half should pretty much be the same as the scores from the other half.
• Equivalent forms: make up different forms of the test, administer them, and compare results. If it's reliable, people should perform pretty much the same on all forms.
• Ex: ACT - not everyone took the same form on test day
• Validity - does this test measure what it is supposed to measure?
• A depression test should measure depression, not intelligence. Your math test should have math questions on it, not English.

Other terms:

• Objective test - results are the same, no matter who scores it. If monkeys score your test or if I score your test, you will get the same score. Ex: multiple guess tests.
• Test standardization - everyone is tested & graded the same way. Like in the ACT - you went in, everyone sat so many feet apart, everyone got the same time limits, everyone got the same instructions, everyone had the same kind of text booklet and answer sheets.
• With test standardization, norms can be found. Norms are the typical performance. They can tell you if a person's score was high, low, or average.
• Think about when you got your ACT/SAT/SRA/CAT (whatever standardized test you took) results in the mail. You opened it up and there was a chart on the back. It should you your score. Then it also showed you how the rest of the people taking the test performed. Your score meanings nothing unless you know the norms - that's why they give you that chart. You know how you performed when compared to everyone else.
• You made a 45 on your math test. Sounds pretty bad, right? Well, it sounds pretty good when I tell you that everyone else made a 36 on the test. Suddenly you don't feel so stupid. So your scores can only be interpreted accurately if you know the norms.

Intelligence testing began in France with Alfred Binet. He administered questions to children to find out what the typical 5, 7, 9, etc year old kids were capable of. What can the typical 17 year old do? Terman (at Stanford) brought Binet's work to the U.S. So that's why the test is now called the Stanford-Binet Intelligence Test - IV.

• Originally, IQ calculated MA/CA * 100 - mental age/chronological age *100.
• Now, there are deviation scores - how far above or below average is this person relative to his/her peers. Now we're no longer comparing 25 year olds to 80 year olds. So if you have an IQ of 100, then you are considered to be perfectly average - tracking right along with the majority of other 25 year olds.

• Stability Over time
• IQ begins to stabilize around age 6. Slowly & steadily increases until around age 40.
• According to some researchers, there is a terminal decline - a dropping of IQ about 5 years before death. Probably related to the changes in the body as it prepares to die.
• IQ can change. Injury, illness, chronic substance use (this includes alcohol) can all affect intelligence. Remember: if it can kill your brain cells, then it can affect your intelligence.
• Beer! Cliff's theory of intelligence that we discussed in class just isn't true!

SB-IV was originally designed for kids and extended upward. Wechsler 1st to design a test for adults. Downward versions of the test were later made.

• Wechsler Adult Intelligence Scale (WAIS) - 17 and up.
• For use with adults or particularly precocious children
• Wechsler Intelligence Scale for Children (WISC) - 6 to 16
• For use with children, adults with mental impairments, or really really really sharp wee-ones
• Wechsler Preschool and Primary Scale of Intelligence - 6 & under
• For use with the wee-ones

Wechsler scales yield three IQ scores:

• Verbal IQ: test of verbal abilities
• Performance IQ : test of nonverbal abilities - spatial skills, etc.
• Full scale IQ: a combination of the two above IQ scores
• Average is 100, MR starts at 70, and gifted begins at 130.

WWI necessitated the development of group tests - tests that could be administered to a large group of people to quickly classify them.

• Army Alpha - a verbal test
• Army Beta - a nonverbal test - for illiterates and non-English speakers

IQ is distributed normally in the population - a normal distribution - a bell curve. This means that most people fall in the middle - in the hump of the curve. This means that most people are average. As you progress to the tails - the extremes of the distribution, you find less and less people.

• SEX & IQ
• Overall - no differences
• Small differences: women slightly stronger in verbal skills, vocabulary, and memorization. Men tend to be stronger in spatial abilities & math.
• Due to different learning opportunities, environment, differential encouragement, and biology
• IQ & Achievement
• .5 correlation w/ school achievement. This means, as a generality, the more intelligent you are, the better success you will have in school.

• IQ 130 and up - usually considered gifted
• Terman did long-term study to disprove myths that gifted are weak, inept, nerds
• Giftedness & achievement
• Usually related.
• Giftedness isn't just an IQ score
• GATE (GT) programs tailor to gifted kids' needs

• Criteria: A person must have an IQ of 70 or less & have some sort of impairment in the performance of adaptive behaviors. By adaptive behavior, we mean basic skills such as dressing yourself, preparing food for yourself, going to work, etc.
• There are different levels: see textbook.
• Causes: Organic & Familial
• Organic - biological cause
• Birth injuries - such as lack of oxygen supply
• Fetal damage - could result from exposure to harmful substances like alcohol
• Metabolic disorders - like PKU
• Genetic abnormalities - missing, extra, or defective genes, like w/ Down's Syndrome
• PKU
• Hydrocelphaly, Microcephaly, Down's Syndrome
• Familial - no specific biological cause
• These cases usually appear as the result of an impoverished environment, malnutrition, and occurs mostly in exceptionally destitute households.

What is responsible for intelligence? Biology? Or Environmental factors?

• Twin studies
• Twin studies focus on comparisons of identical twins & fraternal twins. The rationale for these studies is that both identical & fraternal twins are exposed to similar environmental conditions as they age. However, identical twins, who are genetically the same, share more of a genetic kinship than fraternal twins, who are no more similar genetically than any other set of siblings. Hence, if pairs of identical twins are more similar in intelligence than pairs of fraternal twins, it's presumably because of their greater genetic similarity.
• The chart on page 391 helps summarize information from these studies.