This cheat sheet covers major ideas in intelligence and IQ testing, including how psychologists define intelligence, measure it, and interpret test scores. Students need this topic to understand what IQ tests can show and what they cannot prove. It also helps students evaluate claims about intelligence in school, research, and society.
The core ideas include general intelligence, multiple intelligences, emotional intelligence, standardization, reliability, validity, and cultural bias. A common historical formula is IQ = mental age / chronological age x 100, but modern IQ tests usually use standard scores. Most modern IQ tests have a mean of 100 and a standard deviation of 15.
Test results should be interpreted with context, because motivation, language, culture, health, and opportunity can affect performance.
Key Facts
- The historical IQ formula is IQ = mental age / chronological age x 100.
- Modern IQ tests usually use standard scores with a mean of 100 and a standard deviation of 15.
- A score of 115 is one standard deviation above the mean on many IQ tests because 100 + 15 = 115.
- Reliability means a test gives consistent results across time, versions, or scorers.
- Validity means a test measures what it claims to measure and supports accurate interpretations.
- Standardization means the test is given and scored the same way for everyone using a comparison group.
- A percentile rank shows the percentage of people in the norm group who scored at or below a given score.
- Cultural bias can occur when test content or testing conditions advantage one group over another for reasons unrelated to intelligence.
Vocabulary
- Intelligence
- Intelligence is the ability to learn from experience, solve problems, adapt to new situations, and use knowledge effectively.
- IQ
- IQ is a score used to summarize performance on certain standardized tests of cognitive ability.
- General intelligence
- General intelligence, or g, is the idea that one broad mental ability influences performance across many cognitive tasks.
- Standardization
- Standardization is the process of giving, scoring, and comparing a test in a consistent way using a norm group.
- Reliability
- Reliability is the degree to which a test produces stable and consistent results.
- Validity
- Validity is the degree to which evidence supports the intended use and interpretation of a test score.
Common Mistakes to Avoid
- Treating IQ as a complete measure of a person is wrong because IQ tests measure selected cognitive skills, not creativity, character, motivation, wisdom, or life potential.
- Confusing reliability with validity is wrong because a test can be consistent but still fail to measure the intended ability.
- Using the old IQ formula for all modern tests is wrong because most current IQ tests are based on standard scores, not mental age divided by chronological age.
- Ignoring the norm group is wrong because an IQ score only has meaning when compared with the population used to standardize the test.
- Assuming group score differences are purely genetic is wrong because environment, schooling, nutrition, stress, discrimination, language, and testing conditions can influence results.
Practice Questions
- 1 A 10-year-old child has a mental age of 12 on an older-style test. Using IQ = mental age / chronological age x 100, what is the IQ?
- 2 On a modern IQ test with mean 100 and standard deviation 15, how many standard deviations above the mean is a score of 130?
- 3 A student scores in the 84th percentile on a cognitive ability test. What does this percentile rank mean?
- 4 Why should psychologists consider culture, language, and testing conditions when interpreting IQ test scores?