Chapter 9: Intelligence & Psychological Testing

Key Concepts in Psychological Testing

Psychological Test

It is a standardized measure of a sample (potentially not representative) of a person’s behaviour. These tests are measurement instruments that measure the individual differences that exist among people in abilities, aptitudes, interests & aspects of personality.

Two Principal Types of Tests

Mental Ability Tests - Measure general mental ability. 3 Principle Sub-Categories:

  • Intelligence Tests - Measure general mental ability and intellectual potential.
  • Aptitude Tests - Assess specific types of potential mental ability. Differential Aptitude Tests assess verbal reasoning, numerical ability, abstract reasoning, perceptual speed & accuracy, mechanical reasoning, space relationships, spelling, language use, etc.
  • Achievement Tests - Assess a person’s master & prior knowledge of various subjects, such as mid-term tests.

Personality Tests - Measure aspects of personality, including motives, interests, values & attitudes.

  • Traits (such as introversion versus extroversion) are systematically assessed with these tests.
  • Psychologists prefer to call these tests personality scales, since there’s no right or wrong answer.

Both personality scales & mental ability tests are standardized measures of behaviour.


Refers to the uniform procedures used in the administration & scoring of a test. Same instructions, same questions, same time limits so scores can be compared meaningfully.

Test Norms

Test norms provide information about where a score on a psychological test ranks in relation to other scores on that test. They’re needed because in psychological tests, everything is relative. Usually, test norms allow you to convert your raw score into a percentile.

Percentile Score

A percentile score indicates the percentage of people who score at or below the score obtained.

Standardization Group

Test norms are based on a sample of people who are known as the standardization group. Ideally, this group must be representative of the people who are expected to take the test.


It is an intelligence test in Canada that stands for Wechsler Adult Intelligence Scale.


Refers to the measurement consistency of a test (or of other kinds of measurement techniques).

Checking a Psychological Test’s Reliability

There are several ways to test correlation coefficient (degree relationship between two variables). Here’s one of them:

Test-Retest Reliability - Which is estimated by comparing subjects’ scores on two administrations of a test.

Different Types of Validity of Psychological Tests

Refers to the ability of a test to measure what is was designed to measure. The term is also used to refer to the accuracy or usefulness of the inferences or decision based on a test.

Content Validity - Refers to the degree to which the content of a test is representative of the content it’s supposed to cover. Achievement tests & educational tests such as classroom exams should be valid.

Criterion-Related Validity - This is estimated by correlating subjects’ scores on a test with their scores on another measure of the trait assessed by the test. For example, you can check the validity of your airplane pilot test by correlating their scores to performance ratings. Basically, the test should be predictive of performance.

Construct Validity - When measuring hypothetical constructs (creativity), construct validity matters. The extent to which there is evidence that a test measures a particular hypothetical construct.

The Evolution of Intelligence Testing

Sir Francis Galton and the Study of Intelligence Testing

Sir Francis Galton, in the late 1800s, studied family trees & concluded in his book Hereditary Genius that intelligence is passed down generations through genetic inheritance. He is the one who coined the phrase nature versus nature, came up with correlation & percentile test scores!

He believed that mental ability could be assessed by measuring simple sensory processes (sensitivity to high-pitched sounds, colour perception, reaction time, etc). However, turns out that this is not a good way to assess mental ability.

The Binet-Simon Scale of Intelligence

In 1905, Alfred Binet & Theodore Simon, published the first useful test of mental ability. The test required abstract reasoning skills rather than sensory skills. It was inexpensive, easy to administer, objective & predictive of children’s school performance.

Mental Age

A child’s mental age (or mental level) indicates that they’re displaying the mental ability of the typical child of that chronological age (actual age). Binet revised this model twice before dying.

Stanford-Binet Intelligence Scale (IQ)

In 1916, Lewis Terman at Standford University made a major expansion to Binet’s test. The scale incorporated William Stern’s suggestion of an intelligence quotient. An intelligence quotient (IQ) is a child’s mental age divided by chronological age, multiplied by 100:

IQ=(IQ = (Mental Age)/()/(Chronological Age)×100) \times 100

This made it possible to compare children of different ages.

Current versions of the test assess 10 subsets of intelligence!

Wechsler Adult Intelligence Scale (WAIS)

In 1939, David Wechsler at New York’s Bellevue Hospital published the first high-quality IQ test designed for adults. 2 Major Innovations in WAIS:

  • Less dependent on subjects’ verbal ability, by including items that required non-verbal reasoning. To highlight this distinction, he would compute 3 separate IQ scores:
  • Verbal IQ
  • Performance IQ: Nonverbal IQ
  • Full-Scale IQ: Total IQ
  • Did not use the intelligence quotient but rather used a new scoring system based on the normal distribution. Nowadays, though we use the word IQ, no tests actually use an intelligence quotient.

The Debate about Structure of Intelligence

The debate regarding the structure of intellect was launched by Charles Spearman.

Factor Analysis & Spearman’s View of Intelligence

A statistical procedure invented by Charles Spearman, British psychologist. In factor analysis, correlations among many variables are analyzed to identify closely related clusters of variables. If many variables are highly correlated, the assumption is that a single factor is influencing them all.

Spearman used factor analysis to correlate many specific mental abilities. He concluded that all cognitive abilities share one important factor: general mental ability (g). However, he did recognize that people due have ‘special abilities’ but still believed that g largely influenced it.

L.L. Thurstone’s View of Intelligence

L.L. Thurstone developed the test that evolved into the Scholastic Aptitude Test (SAT). Thurstone believed that intelligence involves multiple abilities, and argued that Spearman put too much emphasis on g. He carved intelligence into 7 Primary Mental Abiltiies.

Primary Mental Abilities

  1. Word Fluency
  2. Verbal Comprehension
  3. Spatial Ability
  4. Perceptual Speed
  5. Numerical Ability
  6. Inductive Reasoning
  7. Memory

J.P. Guilford went a step further & divided intelligence into ~150 distinct mental abilities & got rid of g.

Fluid & Crystallized Intelligence

In the 1980s, IQ tests began moving in a new direction. In order to give educators more specific information, g was divided into 2 subsections:

Fluid Intelligenc - Reasoning, memory, speed of info processing.

  • Prefrontal cortex is more involved in problem solving using fluid intelligence but less involved with crystallized.

Crystallized Intelligence - Knowledge & skill application in problem solving.

Modern IQ tests are now typically subdivide g into 10-15 specific & distinct mental abilities!

This means that both views of Thurstone & Spearman are used today!

Basic Questions about Intelligence Testing

Normal Distribution

Normal distribution is a symmetric, bell-shaped curve that represents the pattern in which many human traits (such as height) are dispersed in the population. When a trait is normally distributed, most cases fall near the centre of the distribution (an average score).

Deviation IQ Scores

Since intelligence is normally distributed, Wechsler was able to devise a new scoring system. Raw scores are translated into deviation IQ scores that locate subjects precisely within the normal distribution, using the standard deviation as the unit of measurement. Mean of distribution is usually set at 100 (to have continuity with the old definition) & standard deviation is 15.

Modern IQ Scores

Modern IQ scores indicate exactly where you fall in normal distribution of intelligence.

IQ Tests Reliability

They are statistically reliable (they have a correlation of above 0.90). However, they sample behaviour & a specific testing may yield an unrepresentative score. Sometimes, anxiety or other external factors can produce misleading scores.

IQ Tests Validity

IQ tests are valid measures for a specific academic type of intelligence, and they’re good at predicting school performance. However, Robert Sternberg found that 3 types of intelligence:

  1. Verbal Intelligence - IQ tests generally only validly measure this type of intelligence.
  2. Practical Intelligence
  3. Social Intelligence

Although tests focus on cognitive abilities, Keith Stanovich argues that they do not predict rational thinking & effective decision making in the real world.

A Person’s IQ Score Over Time

IQ scores are not stable during pre-school years & don’t predict IQ scores in the future. However, around the age of 7-10, IQ scores become more stable & their predictive value increases. IQ tends to be stable but they’re not concrete.

Intelligence Tests Predicting Occupational Success

Yes. People who score high on IQ tests are more likely to end up in high-status jobs. However, the correlation is moderate (around 0.37). The relationship between IQ & income is weaker.

IQ Tests Usage in non-Western Cultures

Very little. Maybe because Western IQ tests do not translate well into the language & cognitive frameworks of many non-Western cultures. Different cultures are used to different ways of having tests administered, and other cultures value different types of mental skills differently.

Extremes of Intelligence

Intellectual Disability

  • formerly known as Mental Retardation

Subnormal general mental ability accompanied by deficiencies in adaptive skills, originating before age 18.

3 Broad Domains of Adaptive Skills

  1. Conceptual Skills - Managing money or writing a letter.
  2. Social Skills - Making friends or coping with others’ demands.
  3. Practical Skills - Preparing meals, using transportation or going shopping.

The IQ criterion of subnormality is arbitrary. Once the AAMR (now known as the American Association on Intellectual & Developmental Disorders) set the cutoff at 70-75.

The requirement of testing deficits in everyday living skills is included to make sure that decisions are not based off of a single test score. This is why the Diagnostic & Statistical Manual (DSM-5) from the American Psychiatric Association includes items to test these skills.

Different Levels of Intellectual Disability

Roughly ~1% of people are intellectually disable. Some estimates go as high as ~3%.

Origins of Intellectual Disability

Down Syndrome - Most children with this syndrome carry an extra chromosome. They have distinctive physical characteristics (slanted eyes, stubby limbs & thin hair). Occurs in 1/800 births in Canada. Probability of Down Syndrome increases with increasing age of mother.

Fragile X Syndrome (FXS) - The FRM 1 gene contributes to the development of this syndrome due to mutation. Kim Cornish says that FXS is characterized by an inhibitory control deficit.

Phenylketonuria - A metabolic disorder due to an inherited enzyme deficiency, but can be treated in infancy.

Hydrocephaly - An excessive accumulation of cerebrospinal fluid in the skull destroys brain tissue.

There are ~1000 other organic syndromes, more discovered each year. However, ~50% of these cases are unable to be correctly diagnosed. This may because of difficult-to-detect physiological defects or unfavourable environmental factors (marital instability, parental neglect, poverty, etc).


Savants are people will low IQs but exceptional ability in certain domains (like artistic pursuits). Kim Peek is an example of a savant, who has memorized 9000 books. Another example, Daniel Tammet has memorized 22 thousand digits of Pi & is a best-selling author.

Gifted Kids

Definitions of giftedness vary greatly. Experts say that giftedness should not be equated with high intelligence & IQ. However, often times, that’s exactly how gifted kids are identified.

Personal Qualities of the Gifted

Lewis Terman’s 1921 study (which is still on-going almost 100 years later) of gifted kids found that they were above average on height, weight, strength, mental & physical health, emotional adjustment & social maturity. In adulthood, they exhibited above average physical health, emotional stability & social satisfaction.

However, Ellen Winner says that moderately gifted kids (IQ of 130-150) & profoundly gifted kids (IQ of 180+) are different. She says that profoundly gifted kids are often introverted & socially isolated. She estimates that interpersonal & emotional problems in this group is twice as high as other kids. People who are exceptionally creative have higher levels of mental illness.

Joseph Renzulli theorizes that profound giftedness depends on 3 Factors:

  1. High Intelligence - Exceptional intelligence or ability in specific domain.
  2. High Creativity
  3. High Motivation

‘Hidden Gifted’

Gifted children who, for a variety of reasons (learning disabled, cultural minority, gifted females), may not be properly identified as gifted as they are underperforming academically.

Drudge Theory

The theory states eminence primarily depends on determination; practice & mentoring/training.

Heredity/Environment as Intelligence Determinants

Types of Evidence Suggesting that Intelligence is Inherited

  • Twin Studies - Identical twins share more genetic makeup than fraternal. If pairs of identical twins are more similar in intelligence than pairs of fraternal twins, it’s presumable because of greater genetic similarity. Studies show that identical twins have a stronger intelligence correlated (0.86) than fraternal twins (0.6), however they’re both relatively strong. Even when reared apart, identical twins have a correlation of 0.72.
  • Adoption Studies - Adopted children’s intelligence is similar to their biological parents, though they didn’t raise them.

Heritability Estimates & Ratios

A heritability ratio is an estimate of the proportion of trait variability in a population that is determined by genetics.

Example \rightarrow Height’s heritability is 90%.

Heritability of Intelligence

Arthur Jensen says 80%. Others go as low as 40%. However, consensus tends to be 50%.

Three Limitations of Heritability

  1. Can’t be applied to individuals - Heritability estimates are based on trait variability in a specific group.
  2. Heritability may vary from one group to another - It depends on a multiple factors, like environment diversity.
  3. There is fixed value of heritability - Heritability ratios are sample-specific estimates.

The Evidence of Environmental Influence on Intelligence

Adoption Studies - Adopted children show resemblance to their adoptive parents in terms of IQ. Siblings (& identical twins) reared together are more similar than children reared apart. Unrelated children reared together are similar.

Environmental Deprivation & Enrichment - The cumulative deprivation hypothesis states that children reared in substandard circumstances should experience gradual declines in IQ. This turns out to be true. The reverse is also true; children who are placed in enriching environments should gradually experience increases in IQ.

Generational Changes (Flynn Effect) - Using military data, James Flynn noticed that performance on IQ tests steadily increases over generations. He found that IQ of the entire world has been increasing in the last 90 years.

Heredity & Environment Intelligence Interaction

Sandra Scarr’s reaction-range model says that heredity may set certain limits (max & min) on intelligence & environmental influences decide where individuals fall within these limits. Reaction range refers to these genetically determined limits on IQ (or other traits).

Genes and General Mental Ability

We don’t know which genes influence mental ability, there could be 100s. The strongest links found between genes & intelligence account for less than 0.5% of variations in intelligence.

Explanations of IQ Differences Between Different Ethnic Groups

Heritability - Arthur Jensen argues that cultural differences in IQ are largely due to heredity because he had evidence that heritability of intelligence is about 80%.

  • Richard Herrnstein & Charles Murray, in The Bell Curve, said races have IQ differences due to genetics.
  • Leon Kamin has come up with an analogy to rebut this line of thinking; you fill two sacks with corn seeds with a variety of genes. One planted in barren soil will not grow as tall as the other sack, planted in fertile soil. This analogy shows that within-group differences are highly heritable but between-group differences could be environmental.
  • The Flynn Effect also show that, even though intelligence is heritable, there can be environmental increases to IQ.

Socioeconomic Disadvantage - Certain ethnic groups are disproportional socioeconomically disadvantaged which can cause detriment to a person’s intellectual development.

  • Poor kids come from large families which can cause them to receive less parental attention & parental assistance.
  • Poor kids are less exposed to knowledge, have less learning supplies & don’t have adequate privacy to study.
  • Poor kids tend to have poor role models for language development, experience less pressure to work hard on intellectual pursuits, attend poorer-quality schools, are more likely to be affected by crime, live in areas where ‘street smarts’ are emphasized more than academic intelligence.
  • Poor kids tend to suffer from malnutrition or be exposed to environmental toxins.

Stereotype Threat - Claude Steele, psychologist from University of California-Berkeley, has argued that derogatory stereotypes create feelings of stereotype vulnerability.

  • Stereotype Vulnerability - A self-fulfilling prophecy. When people feel like they can’t do well, they don’t. Or when people worry that their failure will be blamed on their gender, race, etc. This can cause a lack of motivation.
  • Belonging Uncertainty - People move away from academics if they feel their pursuit of it will make them an outcast.

Cultural Bias on IQ Tests- Critics say that IQ tests are constructed by white, middle-class psychologists & this biases the test. Cultural disparities reflect differences in knowledge, not ability.

New Directions in Study of Intelligence

Cognitive Perspective of Intelligent Behaviour

The cognitive perspective, as opposed to the testing perspective, are concerned more about how people use their intelligence. The interest in information-processing strategies rather than amount.

Exploring Biological Correlates of Intelligence

  • Studies suggest that breastfeeding has positive effects on IQ.
  • Large brains are somewhat predictive of greater intelligence (0.35 to 0.4). Intelligence is positively correlated with amount of both grey & white matter in the brain.
  • People with high IQs in their youth tend to have longer lives and better health. This may be because the genes that cause higher intelligence cause healthier bodies. Or it may be because intelligent people are better prepared to take care of themselves. Or it may be that intelligent people tend to be richer which allows them better access to health care.

Sternberg’s Triarchic Theory of Human Intelligence

Robert Sternberg’s Triarchic theory of human intelligence consists of 3 parts:

Contextual - Intelligence is culturally defined, and different manifestations of intelligence are valued differently.

Experiential - Relationship between experience & intelligence.

Two Hallmark Factors of Intelligent Behaviour:

  1. The ability to deal effectively with novelty.
  2. The ability to learn how to handle familiar tasks automatically & effortlessly.

Componential - Three Types of Mental Processes that intelligent thought depends on

  1. Metacomponents - Control, monitor & evaluate cognitive processing.
  2. Performance Components - Execute strategies assembled by metacomponents.
  3. Knowledge - Acquisition Components: Encode, combine & compare information.

‘Successful Intelligence’

There are 3 aspects/facets of successful intelligence:

  1. Analytical Intelligence - Involves abstract reasoning, evaluation & judgement. IQ tests usually assess this type.
  2. Creative Intelligence - Ability to generate new ideas & be inventive in dealing with novel problems.
  3. Practical Intelligence - Ability to deal effectively with everyday problems, such as on the job or at home.

Sternberg maintains that all 3 are independent & can be measured reliably.

Gardner’s 8 Types of Intelligence

Howard Gardner believes that IQ tests put too much emphasis on verbal & mathematical skills. Logical

  1. Mathematical - Sensitive & able to discern logical/numerical patterns; handle long chains of reasoning.
  2. Linguistic - Sensitive to sounds, rhythms & meaning of words; sensitive to different functions of language.
  3. Musical - Ability to produce & appreciate rhythm, pitch & timbre; appreciates forms of musical expressiveness.
  4. Spatial - Able to perceive visual-spatial world accurately; perform transformations on one’s initial perceptions.
  5. Bodily-Kinesthetic - Ability to control one’s body movements & handle objects skillfully.
  6. Interpersonal - Ability to respond appropriately to moods, temperaments, motivations & desires of other people.
  7. Intrapersonal - Access to one’s own feelings & be able to control them to guide behaviour; knowledge of self.
  8. Naturalist - Ability to recognize & categorize objects/processes in nature.

Emotional Intelligence

Emotional intelligence was first developed by Peter Salovey & John Mayer, but popularized by Daniel Goleman. Emotional Intelligence is ability to perceive & express emotion effectively.

Four Components

  1. People need to accurately perceive emotions in themselves & others. Able to express them, too.
  2. People need to be aware of how emotions shape their thinking, decision-making & coping with stress.
  3. People need to understand & analyze their emotions.
  4. Be able to regulate their emotions.

Measuring Emotional Intelligence

It can be measured using the Multifactor Emotional Intelligence Scale (MEIS).

Emotional Intelligence Critics

Skeptics question whether sophistication about emotion should be viewed as an intelligence. They note that definitions of emotional intelligence tend to vary & be fuzzy. They claim that its real-word impact has been exaggerated.



Creativity involves the generation of ideas that original, novel & useful.

  • Creativity occur in a burst of insight, but not always. Creativity tends to be natural & logical extensions of existing idea, involving hard work & multiple steps. Creative ideas come from a deep understanding of a specific area.

Convergent vs divergent Thinking

J.P. Guilford first made the distinction between the two types of thinking.

Convergent thinking - One narrows down a list of alternatives to converge on a single answer. Most training in school encourages this type of thinking.

Divergent Thinking - One expands the range of alternatives by making many possible answers. Divergent thinking contributes to creativity.

Fallacy - A mistake or error in the process of reasoning.

‘Appeal to Ignorance’

It is a fallacy that involves misusing a lack of knowledge on an issue to support an argument.


Reification occurs when a hypothetical/abstract concept is given a name & then treated as though it were a concrete/tangible object. Intelligence has been “reificated”.

Featured Study: Racial Stereotypes & Test Performance


Participants were 114 black & white undergraduates. The study compared black and white students with high and roughly equal ability and preparation (based on their SAT scores) to rule out cultural disadvantage as a factor.

The participants were asked to take a challenging, 30-minute test of verbal ability comprising items from the verbal subtest of the Graduate Record Exam (GRE). In one condition, the issue of stereotype vulnerability was not made salient, as the test was presented to subjects as a device to permit the researchers to analyze participants’ problem-solving strategies. In another condition, the spectre of stereotype vulnerability was raised, as the test was presented as an excellent index of one’s general verbal ability. The principal dependent variable was subjects’ performance on the verbal test.


When the black students’ stereotype vulnerability was not made salient, the performance of the black and white students did not differ. However, when the same test was presented in a way that increased blacks’ stereotype vulnerability, the black students scored significantly lower than their white counterparts.

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