Intelligence

Psyc Week 5/6 – Intelligence

Intelligence Part 1

Brains are costly

  • 60% of energy to brain development

  • Maternal costs: “The Curse of Eve”

    • Giant human brains required a larger baby head

    • Bipedalism required a narrower pelvis

    • This creates the “Obstetrics Dilemma”: human childbirth is longer, more painful and historically more dangerous than that of other primates (up to 1% maternal mortality per birth)

  • So why didn’t the brain continue to grow?

  • Evolutionary trade-offs between:

    • Infant brain size

    • Infant dependency period

    • Female pelvic width

    • Maternal mortality (historically 1% per birth)

Two theories (what do these two theories answer?)

  • Runaway sexual selection theory

    • Males’ and females’ insatiable need for more and more intelligent mates (sexual selection) led to a runaway process resulting in our giant brains

  • The social brain hypothesis

    • Our big brains (along with language) evolved as a way to keep track of our increasingly complicated social lives

So what is intelligence?

  • Ability to use one’s mind to solve novel problems and learn from experience

So what is IQ?

  • A measure of individual differences in general cognitive ability (i.e. intelligence)

  • Intelligence quotient: originally developed to identify cognitive delays among children in school and became artificially constructed around a mean of 100 and a SD of 15

IQ history

  • Goddard – one of first to measure intelligence; used discriminatorily towards US immigrants

  • Binet & Simon – developed the first intelligence test to identify children who needed remedial education

    • Measured aptitude apart from achievement

  • Terman – developed modern IQ test

  • Ratio IQ: a child’s “mental age” (as measured by IQ test) divided by their chronological age x 100

    • IQ then was used to measure differences in intelligence between adults; had to abandon the age-based calculation

  • Deviation IQ: a person’s test score divided by the average test score of same age group x 100

    • Commonly used today

IQ: The Bell Curve

Intelligence Part 2

Intelligence Tests

  • Intelligence tests are typically used to __________

    • Do not measure “intelligence” per se, but tasks that correlate with such

  • Most widely used intelligence tests today:

    • Wechsler Adult Intelligence Scale (WAIS)

    • Wechsler Intelligence Scale for Children (WISC)

Is IQ a Valid Measure?

  • Yes, it’s a predictively valid measure of something meaningful (I predicts things we would expect it to predict)

  • Correlates positively with:

    • Academic grades (r= .5)

    • Occupational status and job performance (r = .2 to .6)

    • Income (r= .4 to .6)

  • And negatively with:

    • Arrests (r= .2)

    • Drug and alcohol use

    • Car accidents

The Hierarchy of Abilities

  • Spearman found correlations among many cognitive tasks

  • Two-factor theory of intelligence: Spearman’s theory suggesting that every task required a combination of:

    • 1) an overall single general ability (g), and

    • 2) skills that are specific to the task (s)

  • Thurstone argues for a few primary mental abilities that were stable and independent

Primary mental ability

Description

Word fluency

Ability to solve anagrams and to find rhymes

Verbal comprehension

Ability to understand words and sentences

Numerical ability

Ability to make mental and other numerical computations

Spatial visualization

Ability to visualize complex shape in various orientations

Associative memory

Ability to recall verbal material, learn pairs of unrelated words etc.

Perceptual speed

Ability to detect visual details quickly

Reasoning

Ability to induce a general rule from a few instances

A Three-Level Hierarchy

  • Both were correct; correlations between scores on different menta ability tests are best described in a three-level hierarchy

    • Spearman’s general factor (g) and specific factors (s), and between Thurstone’s group factors (m)

What are the Middle-level abilities?

  • They lie between specific & general mental abilities with regard to intelligence

    • The data-based approach connects intelligence test performance to clusters

      • Intercorrelations

      • Resulting factors (i.e. items that cluster together)

      • Confirmatory factor analysis

      • Middle-level abilities according to this approach:

        • Carroll found patterns of correlation among 8 independent middle-level abilities

        • Crystallized intelligence: retain & use knowledge that was acquired through experience (e.g. facts, vocab, trivia)

          • Increases with age

        • fluid intelligence: see abstract relationships and draw logical inferences (e.g. problem-solving)

          • Raven’s Progressive Matrices Test

      • Limitations??

    • The theory-based approach broadly surveys human abilities and then determines which one’s intelligence tests do/don’t measure

      • Three kinds of intelligence posited:

        • A_____ intelligence: finding correct answer to a defined problem

        • Creative intelligence: finding novel solutions & choosing which to apply

        • Practical intelligence: implementing solutions in everyday settings

      • What about cultural differences? Emotional intelligence?

      • Emotional intelligence: ability to identify, describe, predict and manage own emotions and those of others

      • Gardner observed many types of people and argued for 8 forms of intelligence

Why is emotional intelligence important?

  • People with higher EQs:

    • Are happier

    • Report greater life satisfaction

    • Are physically and mentally healthier

    • Have better social skills and are judged to be more socially competent

    • Have better relationships

    • More likely to be promoted

Where does intelligence come from?

  • Influenced by “nature” (innate) and “nurture” (learned)

  • Heritability: how much of observed differences between people can be attributed to genes

    • Variability must add up to 100%

    • Heritability coefficient (h^2): statistic that describes the proportion of the difference between 2+ people’s IQ scores that can be explained by differences in their genes

  • Adoption studies show:

    • Adopted siblings reared in similar environments – positively correlated IQs

      • Environment plays a role (30-50% of differences in IQ scores is due to environment

    • Identical twins reared in different environments - positively correlated IQs

      • The correlation b/w identical twins raised apart > fraternal twins raised together

    • So: genes play a role in intelligence (heritability of intelligence = .5 to .7; that is 50-70% of differences in IQ score

    • s between people is due to genetic differences

An analogy to (not mis-) understanding heritability??

Heritability

  • IQ heritability can range with SES

    • .10 to .72 in children from low vs high income households, respectively

  • Heritability changes with age

    • Higher: adults > adolescents (.70) > younger children > infancy (.25)

Environmental influences

  • Shared environment: environmental factors experienced by all relevant members of a household

  • Nonshared environment: environmental factors not experienced by all relevant members of a household

    • E.g. birth order, teachers, friends, gender roles

    • IQ scores are more similar in similar-aged siblings

  • Genes are not destinies!

  • Intelligence influenced by the environment

    • Important factors: economics and education

  • E.g. relative intelligence is generally stable over time, but absolute intelligence can change considerably

  • E.g. Flynn effect: the average intelligence test score rises about 0.3% every year

SES

  • One of the best predictors of intelligence is _________

    • +12 to +18 IQ points

    • Differences in high vs low SES at age 2 can be nearly tripled by age 16

  • Why biologically?

    • Nutrition

    • Health

    • Environmental toxins

    • Medical care

    • Daily stress

  • Why cognitively?

    • Intellectual stimulation

    • Learning opportunities

    • Vocabularies

  • What has worse outcomes for IQ: poverty in early childhood or later childhood, and why?

Education

  • The correlation between the amount of formal education and intelligence is large (r= .55 to .90)

  • School makes people smarter…

    • But, smart people tend to stay in school

    • Education may improve test-taking ability, rather than general cognitive ability

    • Educational effect on intelligence may be small and short-lived, but school produces long-lasting increases in other skills (e.g. reasoning, language, literacy)

The nature-nurture distinction

  • Nature and nurture, though separate, have a combined influence on IQ

    • They interact in complex ways

      • E.g. environmental influence on gene expression (i.e. epigenetics)

      • E.g. indirect genetic influences such as through behaviours

    • Genes and environments don’t exert an independent influence on IQ

      • It is unfeasible to unpick the distinction between the 2

The malleability of intelligence

  • E.g. research study on grade 7 students who were either taught that IQ is malleable or not

Intelligence Part 3

IQ distributions

  • Mensa: largest international high IQ society

Intellectual Developmental Disorder

  • Mild (IQ 50-69)

    • 80-85% of cases

    • “educable” level (can benefit from schooling)

    • Can lead independent lives

    • Maintain unskilled or semiskilled jobs

  • Moderate (IQ 35-49)

    • 10% of cases

    • Deficits in language development and play

    • Can care for themselves

    • Benefit from vocational training

    • May be ale to work under supervision

  • Severe (IQ 20-34)

    • 3-4% of cases

    • Basic motor and communication deficits in infancy

    • Require careful supervision and can perform basic work tasks

    • Rarely able to live independently

  • Profound (IQ<20)

    • 1-2% of cases; 70% male

    • Noticeable at birth/early infancy

    • Need structured environment and one-on-one help from caregiver

  • Severe and profound examples include:

    • Down syndrome (trisonomy 21)

    • Fragile X syndrome

    • Cretinism

    • Fetal alcohol syndrome

    • IDD from birth complications

IQ facts

  • People with high IQs are:

    • More physically healthy, lower illness rates

    • Less susceptible to MH (mental health) problems (e.g. psychosis, mood disorders, personality disorders and addictions)

    • Usually well adjusted as children

    • No more likely than those with average intelligence to contribute to their professional fields in adulthood

    • Usually gifted in a single area (i.e. middle-level or specific ability)

      • More single minded

    • Gifted children often spend more time engaged in their domain of excellence

      • But it has been said that “it takes 10000 hours of deliberate practice to become an expert”

Gender differences

  • Females and males have the same average IQ

    • Perceived that males have a higher IQ – maybe because male IQ score distribution is more spread out (SD is larger)

    • Why? Socialization = yes. Biology = ??

      • Girls at a young age can be lablled as just shy whereas males who are shy are likely to be labelled as having autism

  • Women and men have different types of intelligence

Culture, Race and IQ

  • Terman (early 1900s) involved on Binet & Simon’s work, produces Standford-Binet intelligence scale

  • Looked at group differences in IQ scores. His claims of intelligence were racist; however, between-group differences do exist

    • It’s difficult to point to the cause of group differences, but there are many theories:

      • E.g. nutritional, SES, educational, cultural specificity of IQ tests, stereotype threat

  • Between-group differences tend to be less than within-group differences

  • His facts:

    • IQ is genetic - true

    • Some racial groups outperform other groups – true

    • Thought superior genes equaled higher IQ – not a fact

The test itself as an explanation

  • Original intelligence tests were culturally biased – made by white, old, racist men

    • What does this say about the validity of these tests?

    • Cultural specificity of IQ tests: cultural differences in “correct” test answers historically

  • Now ‘unbiased’; e.g. non-verbal problems

  • Testing situations may vary

  • Stereotype threat may be exhibited

    • Fear of confirming negative beliefs that others may hold about their group

    • The more you think about not doing something, the more you’ll likely do it (ex. Skiing analogy)

    • Test done with Asian women who took a math test; they did better when they had to put their race at the top vs putting their gender at the top

    • Differences in performance doesn’t necessarily impact ability

Environmental and genetic explanations

  • Environmental differences influence intelligence

    • Higher rates of chronic illness; poorer medical care; poorer diet; lower birth weights

    • Poorer development & educational opportunities (worse schools)

    • Higher rates of single-parent families; home stress; lower incomes

    • Exposure to toxic chemicals through air pollution (faster age-related declines)

    • Exposure to more toxic messages about their innate abilities which may in turn minimize the importance of academic achievement to preserve self-esteem

  • Differences in SES influence intelligence

  • Genetic explanation is not supported

    • E.g. adoption studies; bi-racial children

HW instead of EA due Oct 17, access code: eye queue

Improving intelligence

  • Children:

    • Feeding children polyunsaturated fatty acids (in pregnancy supplements and breast milk) [+4]

    • Early educational interventions for low SES children [+6]

    • Interactive reading and conversing (earlier=better) [+6]

    • Preschool [+6]

  • Children, adults & elderly:

    • Some mental exercises (fluid intelligence)

    • Cognitive enhancers (beware their side effects) – likely short-term benefit

Keep in mind:

  • Rest is good for the brain