Intelligence and Cognition

Abilities related to intelligence

• Reasoning

• Planning

• Solving problems

• Thinking abstractly

• Comprehending complex ideas

• Learning quickly

• Learning from experience

Can intelligence be taught?

It is not:

• Book learning; a narrow academic skill; or test‑taking smarts.

It reflects a broader and deeper capability for comprehending our surrounding

• ‘Catching on’

• ‘Making sense’ of things

• ‘Figuring out’ what to do.

Francis Galton

• Made the first attempt at creating a standardised test for rating a person's intelligence

• Created the statistical concept of correlation

• First to apply this to the study of human differences and the inheritance of intelligence.

Galton’s main theories

Intelligence should correlate with observable traits such as reflexes, muscle grip, and head size.

• “Hereditary” Genius (1869)

  • How genius clusters in families > count eminent relatives of eminent men

• “The history of twins” (1875)

  • Better to study the similarity between twins reared in either similar or dissimilar environments > than the nature/nurture debate.

Galton (1883) - Eugenics

Concerned with “race betterment” and conscious efforts to “improve the race”.

• State involvement.

• First, by encouraging healthy, capable people of above-average intelligence to bear more children (so-called ‘positive eugenics’).

• Later, it aimed at removing the related genes from the population

  • Policies included involuntary sterilisation or institutionalisation (so-called ‘negative eugenics’).

• Policies specifically targeted minority women, immigrants, the physically and mentally ill, and the poor.

Buck v. Bell

US Supreme Court

• A woman was alleged to be “feebleminded” and promiscuous, following her rape and the birth of a child.

• Legitimised eugenic sterilisation laws across the U.S. led to the sterilisation of tens of thousands of individuals.

• Has never been explicitly overturned, though later cases like Skinner v. Oklahoma (1942) limited its application.

• Widely condemned today as a violation of human rights and an example of the dangers of pseudoscience influencing law.

Factor Analysis of Intelligence - Spearman

Charles Spearman

• Noticed that there were positive correlations between students’ performance in lots of very different subjects

• He compared scholastic performance with the ability to discriminate weights and pressures

  • Found that these correlated as well

What is a factor analysis (FA)?

• A method of dimension reduction

• Seeks to identify underlying unobservable variables (i.e. latent variables) that are reflected in the observed variables.

• You are looking for a simple structure.

• The starting point is a correlation matrix (i.e. the intercorrelations between the observed variables).

Factor Analysis & Intelligence

• Vast array of different tasks with some element of cognitive difficulty

• Exhibit a manifold of positive correlations.

• Posited that a latent factor exists that explains these correlations.

• Spearman’s analysis confirmed this, and this latent factor is known as g (or Spearman’s g).

Spearman’s g

• IQ (intelligence quotient)

• General intelligence

• General cognitive and mental ability

• g factor (g = general)

G factor and IQ tests

• The g factor typically accounts for ~50 per cent of the variance in IQ test performance

• IQ scores are typically regarded as estimates of individuals' g factor

Alfred Binet (1857-1911)

• Physician. France – Universal Elementary Education

• Sought to find an objective way to identify children who needed additional help

• Constructed the Simon-Binet Intelligence Scale (with Theodore Simon)

• Mental vs Chronological Age

Important Realisations from Binet

• Recognised limitations of Intelligence Scales

• Importantly, he believed that measures of intelligence were not always generalisable

• Could only apply to children with similar backgrounds and experiences

The WAIS (Wechsler Adult Intelligence Test)

A modern intelligence test battery

• 15 different tests

WAIS - Matrix reasoning task

Measures nonverbal abstract problem-solving ability

• Shown a series of pictures

• For each picture, there is an aspect missing

• Choose missing part from five choices

WAIS - Block Design Test (Kohs, 1920)

Measures spatial visualisation and constructional skills

• Shown a two-dimensional geometric pattern.

• Given a set of red and white blocks (typically with solid or diagonally divided colours).

• They must reproduce the pattern using the blocks within a time limit.

WAIS - Figure Weights

Measure of quantitative and analogical reasoning

• Scale or balance with shapes or weights on one or both sides.

• One side of the scale may be missing a piece or have a question mark (? symbol).

• Choose the missing weight from multiple-choice options

• Shapes have implied weights or values, deduce them based on balance logic

WAIS - Digit Span Backward Test

Measures Working memory, Attention and Cognitive Flexibility

• Psychologist reads series of numbers

• Examinee replies with numbers in reverse

WAIS - Letter-number sequencing

Measures Working memory, Attention and Cognitive Flexibility

• Psychologist reads series of numbers and letters

• Examinee replies with numbers and letters in reverse

WAIS - Coding test - Deary (2020)

A.k.a Digit Symbol Substitution Test (DSST)

Measures processing speed, visual-motor coordination, and attention to detail

• Refer to the key

• Find the matching symbol

• Write it in the correct place — quickly and accurately.

WAIS - Vocabulary test

Measures verbal knowledge and expressive language abilities

• Define the word as precisely as possible in your own word

• Starts simple and gets more advanced/abstract

WAIS - Similarities Test

Measures abstract verbal reasoning and comprehension

• Describe what two words have in common, not how they are different.

• Starts simple and gets more advanced/abstract

The WAIS-IV - Development and Marketing

The Psychological Corporation

• 2200 people tested in the USA for the WAIS-IV

• Aged 16 to 90

• Ethnic, sex and regional mix reflective of US population

• Good spread of educational backgrounds

Every person sat the 15 tests that make up the WAIS-IV

Evaluation of the WAIS

• Observed substantial correlations between scores on…

• …all of the tasks

• 105 correlations, all significant, lowest 0.21 and highest 0.74.

• The average of the correlations was 0.45

• Full-scale IQ, our best estimate of g, is a weighted average of all of them

Standardisation of IQ scores

• Have a Mean of 100

• Standard Deviation of 15.

• Normal distribution

WAIS-IV IQ Levels and Rank

130 → Very Superior → 98-99.9 percentile

90-109 → Average → 25-73 percentile

69 and below → Intellectual disability → .01-2 percentile

Statistical Associations Amongst the Individual Tests

Three-level hierarchy of mental ability test scores (WAIS-IV)

• Optimal way of presenting associations

Level III of Three-level hierarchy (WAIS-IV)

General intelligence (g)

Level II of Three-level hierarchy (WAIS-IV)

Cognitive domains

• Verbal comprehension

• Perceptual reasoning

• Working memory

• Processing speed

Level I of Three-level hierarchy (WAIS-IV)

Individual cognitive traits (15 tests)

Individual Level/Specific factors

• The combination of general ability (Level 3, g) and group factor (Level 2, Cognitive Domain) is not enough to account for how well people perform on the individual tests.

• There seems to be very specific ability (s) (Level 1, Individual Test) needed to do well on each test

• Something that is not shared with any other test even where the material in the test is quite similar to that in other tests.

Hierarchical Structure

• This hierarchical structure has been known for over a century

• It means that talking about a single general intelligence is supported to some extent

• This finding has been replicated in hundreds of dataset

Salthouse (2004) - Method

The Hierarchical Structure of Intelligence

33 studies;

• n = approximately 7000;

• age range 18-95 years

• 16 cognitive tests – coalesce into five factors (broad domains)

• All five factors/domains have high associations with g

Salthouse (2004) - Findings

• LEVEL 3: Approx 50% variance among this group of participants could be attributed to a general mental ability required for all the tests

  • Spearman’s g (i.e. the shared variance across sets of intercorrelating cognitive tasks)

  • General Intelligence

  • General Cognitive Ability

• LEVEL 2: Narrower types of mental ability that relate to the specific type of mental work

• LEVEL 1: Specific ability to do well on a specific task

Warne & Burningham (2019)

• Spearman’s g is robustly observed in Western populations

Spearman’s g as an cross-cultural phenomenon?

• Used exploratory factor analysis to analyse 97 samples from 31 non-Western, non-industrialised nations (totalling 52,340 individuals).

• Found that a single factor emerged unambiguously from the majority of the samples.

• The first factor explained an average of 45.9% of observed variable variance, which is similar to what is seen in Western samples.

• Spearman’s g is likely a universal phenomenon in humans.

Arden & Adams (2015)

Dogs exhibit a general intelligence factor that influences performance in various cognitive tasks

• 68 Border Collies were selected to minimise variability due to breed and environmental factors

• Three-factor Hierarchy Model accounted for 68% of the variance in task performance

• 17% of the variance with the general intelligence factor alone