Intelligence

Definitions of Intelligence over the years

Spearman & “G” Factor early 1900s

• Itelligence consisted of 2 kinds of factors

  • Single, general factor “g”

  • Specific factors or s (s1-4)

• G factor was most important; s factors specific to particular tests

• Advantaged - g can be represented with IQ score

• Advantages - neglects other kinds of abilities (motor, musical, practical, creative)

Thrustone’s primary Mental Ability

• Analysed differents test of mental abilities

• Applied factor analysis to items making up intelligence tests, discovered several broad factors

Cattell-Horn: Crystalized and fluid Intelligence

• Fluid Intelligence: ability to reason abstractly, identify patterns, form concepts, use logic to solve problems, regardless of previous knowledge or experience 

• Crystallized Intelligence: requires the use of info that a person has acquired from previous experiences including verbal comprehension, social skills, and general knowledge

Gardner’s Multiple Intelligence

• Proposed intelligences theory

• Intelligence is not believed to be a single, unified concept

• Combination of different abilities or intelligences that are relatively independent of one another

Sternberg’s triarchic Theory

• Criticized spearman’s g as being too narrow (IQ tests only limited to solving skills and cognitive abilities 

• Defined intelligence by analyzing three different kinds of reasoning:

  • Analytic

  • Problem-solving

  • Practical 

Cattell-Horn-Carroll Theory of Intelligence

• Most comprehensive theory of intelligence that currently has the most scientific support

• CHC theory rests on the assumption that intelligence is made up of multiple abilities categorized through hierarchies 

• Bottom of the hierarchy are domain-specific and highly specialized abilities (eg. spelling ability)

• These specific abilities are the ones that would be measured directly

  • Clustered into several broad abilities which work together form our overall

Consistency/Reliability

• Consistency among scores

• Consistency among raters

• Consistency over time

Inter-Rater Reliability

• Measure of agreement do two raters on ratings of performance or behaviour?

• Computed in two-ways:

  • Correlated raters’ scores

  • % agreement among raters, # agreements, # possible agreements

• High Level of training is needed to ensure same judgment 

Test-Retest Reliability

• Administer same test at two separate times, find correlation between scores

• Only for traits that remain stable over time

• Concerns

  • Influenced by learning, memory, fatigue

  • Changes in participants responses for performance

Split-Half Reliability

• Test is given and items are divided into halves, scored separately 

• Concerns

  • Reliability depends on number of items in test

Validity

• Just cuz test is measuring something, consistently, does not mean it is measuring what it is supposed to measure

• Does the test measure what is intended to measure? 

Concurrent Validity

• Test and criterion can be measured at the same time

• If correlation is high, we have evidence of validity

• Criterion is a direct & independent measure of what is being tested or assessed

Measuring Intelligence

Binet-Simon Intelligence Test

• French government mandated all children attend school, Both men were commissioned to develop a scale for identifying children who would struggle

• Age Differentiation - belief that younger and older children differed intellectual ability

• Mental vs Chronological Age - eg. if your were 7 and could complete tasks of a 10 year old, you had a mental age of 10

• Idiot - most severe intellectual impairment

• Imbecile - moderate impairment

• Moron - mildest level of impairment

IQ testing in adults Wechsler Adult Intelligence Scale

• Wechsler-bellevue intelligence scale developed in 1938 in reaction to problems with 1937 Stanford-Binet

  • SB items not appropriate for use with adults

  • SB had lots of timed tests, difficult for older adults

  • SB did not consider that intellectual performance can deteriorate as a person grew older

  • SB produced only one score

Structure of the WAIS-IV 

• Mean for use with adults ages 16 years and 0 months to 90 years and 11 months

• Takes 60-90 minutes to complete the 10 core subtests

• Can be completed using paper and pen or a web-based platform

Verbal Comprehension Scale 

• Measures ability to understand and se verbal information, including vocabulary, general knowledge, and verbal reasoning skills

Perceptual Reasoning Scale

• Measures ability to reason and problem solve using visual-spatial and nonverbal information

Working Memory Scale

• The Working Memory Index Scale measures a person’s ability to temporarily hold and manipulate information in memory

Processing Speed Scale

• Measures an individual’s ability to process simple or routine information quickly and accurately in order to assess visual and motor speed

Average IQ 

• Average IQ is 100, standard deviation of 15

• 68% of people score between 18-115

• 95% of people have IQs between 70 and 130

• Nearly all people have IQs between 55 and 145

The Flynn Effect

• Steady increase in IQ scores between 1932 and 1978

• Trend continued and supported through the 2000s

• Greater gains found in nonverbal and performance based measures, not arithmetic and vocabulary scales

• May be due to education or test development

Intelligence Tests and Performance 

• Modern intelligence tests have high reliability and validity

  • Consistent measure of what is intended to measure

• Scores correlate with occupational and social achievements, income, and health-related behaviours

• Correlation does not mean causation

Nature of Nurture?

• Stronger correlation between intelligence scores of identical twins compared to fraternal twins

• Strong correlation exists between IQ scores of parents and biological children

• Heritability of IQ is around 50%

• Education may be the most consistent means of increasing IQ scores

• Enrichment and early intervention can help support intellectual development for children living in deprived environments 

Other ways to assess intelligence

• Brain size

• Neural density

• Processing Speed

• Neural efficiency

• Cortical Maturation