1
Q
What is intelligence?
A
- Most people have a ‘folk’ concept of intelligence
- Sternberg and Detterman (1986) show psychological definitions commonly include:
a) Higher level abilities (e.g., abstract reasoning)
b) Valued by culture
c) Executive processes (regulating flow of information toward goal achievement, e.g., attentional control, working memory) - Intelligence comprises the “mental abilities necessary for adaptation to, as well as shaping and selection, of any environmental context
- What is measured by an intelligence (IQ) test?
- Usually assess IQ which is standardised to a mean score of 100 and standard deviation (SD) of 15
- Norming involves administering IQ test to a representative sample of a population to obtain norms or referential scores for different sub-groups (e.g., age groups)
2
Q
Concepts and theories
A
- IQ has dominated the intelligence research agenda. In this lecture we will examine some key concepts and issues in IQ research. We will also explore an alternative perspective on the nature of intelligence
a) General Intelligence (g)
b) Crystal vs Fluid Intelligence
c) Heritability of intelligence
d) Relationship between personality and IQ
e) Gardner’s theory of multiple intelligences
3
Q
Structure of intelligence: Psychometric IQ
A
- Gc (crystallized intelligence)
- Learnt (83-93% of IQ tests)
- Culture specific - Gf (fluid intelligence)
- Biological potential (7-17% of IQ test)
4
Q
Fluid Intelligence (Gf)
A
- The ability to reason, solve new problems without relying on prior knowledge
- Focuses on process independent of content or knowledge domain
- Seen to include executive control and working memory tasks (may also be referred to as fluid cognition)
- Seen as biologically instantiated in the pre-frontal cortex
- Declines in later life
5
Q
Crystal Intelligence (Gc)
A
- Knowledge and skills acquired through education and experience
- Gc test: vocabulary etc represent acquired knowledge
- Gc is a product of Gf
- Investment theory (Cattel) – investment of fluid intelligence in a specific body of knowledge
- Knowledge (acquired) increases over lifetime
6
Q
Gc and Gf over the lifetime
A
- Gf helps build Gc
- Gf peaks in adolescence to early adult and then slowly declines overtime (your ability to reason)
- Gc slowly increase overtime and starts to level out at old age (because we constantly accumulate information)
- Conventional wisdom is that fluid intelligence peaks relatively early in life and then declines
- This is challenged by more current research suggesting heterogenous effects on different cognition domains
7
Q
Behavioural genetics
A
- Heritability estimates for IQ range from .42 to .62 (up to .80)
- This means between 48% and potentially up to 80% of the variability in IQ scores is attributed to genetic variation?
- Mind the heritability gap!
8
Q
Heritability of g: group differences controversies
A
- Behavioural genetics assumes independence of genes and environment.
- Also tends to assume that fluid intelligence is fixed and crystallised intelligence less so.
- Spearman’s hypothesis:
1. People’s performance on a cognitive test was correlated with their performance on other comparable cognitive tests. Hence, Spearman proposed a common latent factor g that broadly represents cognitive capability
2. Noticed that the more strongly a test correlated with IQ, the wider the difference in Black and White Americans’ performance on the test.
3. Hypothesized that Black-White differences on tests of cognitive ability correlate positively with a test’s g-loading
4. Extended by other authors to suggest that racial IQ differences are genetic in origin
9
Q
What does contemporary evidence tell us about racial group differences in IQ?
A
- Fagan & Holland (2002, 2007): No performance differences between Black and White Americans given equal prior exposure to test-relevant information. Group differences reflect unequal opportunity to acquire information, not differences in cognitive processing capacity
- Nisbett et al. (2012): A review by 16 leading intelligence researchers concluded that evidence for a genetic basis for group differences is weak, and that environmental factors (SES, schooling quality, stereotype threat, health disparities) are sufficient to account for observed gaps
- Genome-wide evidence (Bird, 2021): Large-scale polygenic analyses find no evidence that intelligence was under divergent selection across ancestral populations, suggesting genetic differences between racial groups are not a meaningful driver of IQ gaps
- Key principle: heritability within groups tell us nothing about the causes of differences between groups
10
Q
Why genetic determinism cannot be the whole story: The Flynn effect
A
- Generation rise in IQ by average of 10 percentage points (range 5 – 20 points)
- This is seen across at least 14 countries
- It is more substantial for Gf than Gc
- Stronger among adults than children
- Highest in the Netherlands, below average in the UK, ceased in Sweden and reversed in Norway
11
Q
The heritability paradox: the Flynn effect
A
- If heritability is so strong and environmental effects so little, how can environmental changes produce large changes in IQ?
a) Social multipliers
b) Averaging
c) Gene-environment matching
12
Q
The Flynn effect: social multipliers
A
- Environmental factors potentially contributing to an increase in IQ
a) Internet and access to information
b) TV?
c) Gaming (reaction times and speed)?
d) Education
e) Group learning and studying
f) Rising standards of living
g) Better nutrition
13
Q
The Flynn effect: averaging
A
- As individuals’ ability rises, this will also influence those around them.
- Small effects over time will influence the population more widely
- The population average will increase
14
Q
The Flynn effect: matching
A
- Gene-environment correlation
- People seek out environments that match their phenotype
- The process by which the ability and the environment are matched produces increases in that initial ability
- Thus, environment increases genetic/biological ability
15
Q
Environmental toxins
A
- US Americans born in the 60s lost up to six IQ points on average due to lead exposure
- Removal of lead from petrol was followed by measurable population-level IQ increases across multiple countries
16
Q
Gene-environment interaction in heritability of IQ
A
- Socio-economic status:
a) Heritability high for high SES (72%)
b) Heritability virtually zero for low SES (10%) - Why?
- Genetic primacy is a phenomenon of relative privilege. Genes can only express potential once basic environmental conditions are met
17
Q
Gene-environment correlation: The Wilson effect
A
- Heritability increases with age:
a) 40% childhood
b) 60% adulthood
c) 80% old age - Why?
- Genes need the appropriate environment to express
- High IQ people will seek out high IQ contexts and as they get older their intelligence will show
18
Q
Heritability and malleability of intelligence
A
- Heritability is not the same as genetic influence
- Some traits are genetically determined with low heritability: Heritability of number of human fingers is next to zero. Main predictors of variance are environmental (e.g., traumatic amputations, birth defects)
- Some traits are highly heritable but are not genetically determined: In the US, heritability of voting is 53% and heritability of voting for specific parties is 46%
- Due to gene-environment interplay, IQ is more malleable than previously assumed
- The most heritable subtests are also the most culturally loaded i.e. the g factor itself partly reflects cultural experience and education, not just biological potential
19
Q
More on heritability of g
A
- Hereditarian views on race and intelligence were highly controversial
- Current research has confirmed that IQ is heritable
- There is no evidence of significant genetic determination of racial differences in IQ
- Group differences in IQ may be entirely explained by envt’l factors
20
Q
Intelligence as process, personality, interests & knowledge
A
- Adult intelligence is best understood as an integration of:
a) Process (how we think) - basic cognitive abilities, similar to Gf
b) Personality (how we typically behave)
c) Interest (what we are motivated to learn) – guides where knowledge develops
d) Knowledge (what we have learned) – similar to Gc - Process + motivation + interest = knowledge accumulated
21
Q
Personality adds to IQ
A
- Examined FFM traits and IQ to predict performance in university exams a year later
- Conscientiousness explains an extra 27% of performance on
- University exams once IQ (Gf) is controlled for, and openness an
- Extra 4%. Thus, being hardworking, methodical and organized add
- Significantly to exam performance above IQ
22
Q
Big 5 personality traits and IQ
A
- Openness to Experience (r ≈ .20–.30 with g): Strongest Big Five correlate of IQ. Consistent with investment theory: curious individuals invest more cognitive effort and build greater Gc over time
- Intelligence compensation hypothesis: observed small negative correlation between conscientiousness and Gf suggests lower-ability individuals may develop greater diligence as an adaptive strategy
- Neuroticism (r ≈ -.09 to -.18 with g): Small negative association with Gc and Gf; predicts steeper age-related cognitive decline
- Extraversion & Agreeableness: Near-zero correlations with overall g
- Practical implication: IQ predicts learning speed; Conscientiousness and Emotional Stability predict occupational functioning; Openness predicts creative achievement. A full picture of human potential requires both cognitive and personality assessment
23
Q
Gardner’s theory of multiple intelligences
A
- Concerned by the tendency to focus only on linguistic and logical-mathematical symbolism in educational settings
- Argued that g (general intelligence) is most closely aligned with linguistic and logical mathematical intelligences (2 out of 8 forms of intelligence he proposed)
- His definition of intelligence recognises biological and cultural influences
- Intelligence: logical-mathematical, linguistic, musical, spatial, bodily-kinesthetics, interpersonal, intrapersonal
- An eighth dimension – naturalistic intelligence was added later. This refers to human perceptiveness of and sensitivity to the natural world
24
Q
Applications of multiple intelligences theory
A
- Project Zero (Gardner, Harvard): The Spectrum Project assessed children across MI domains through naturalistic observation and performance tasks rather than standardised tests
- Differentiated instruction (Kornhaber, 2001): Teachers applying MI principles diversify pedagogy through project-based learning, cooperative tasks, multimodal presentations
- Clinical and counselling applications: Therapists integrating MI report enhanced therapeutic alliance and more flexible intervention strategies, particularly for clients whose strengths lie outside verbal-linguistic domains
25
Empirical challenges to Gardner’s theory of multiple intelligences
- The eight intelligences intercorrelate positively (consistent with a general factor)
- Many studies of MI effects in teaching did not follow standard scientific practices or explore alternative explanations
- Some studies show support for distinct neural bases of multiple intelligences
- Neuroscience research overwhelmingly refutes Gardner’s suggestion that the brain is organised in modules dedicated to specific forms of cognition
26
Intelligence summary
- Intelligence is a multidimensional construct
- g captures meaningful variance but Gc and Gf have distinct developmental trajectories that are shaped by biology and experience
- Heritability of IQ is substantial, but heritability statistics cannot tell us why groups differ
- The Flynn effect shows that IQ is environmentally malleable at the population level
- Personality and intelligence are distinct but interacting systems (e.g., openness amplifies intellectual development through investment in knowledge acquisition)
- Gardner’s MI challenges the cultural narrowness of g-centric approaches to intelligence, though its psychometric foundations remain contested
