What is intelligence?
Sternberg and Detterman (1986) show psychological definitions commonly include:
- Higher level abilities (e.g., abstract reasoning)
- Valued by culture
- Executive processes
- “mental abilities necessary for adaption to, as well as sharing and selection, of any environmental context”
How is intelligence measured?
IQ = a test which is standardised to a mean score of 100 and standard deviation 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).
what are the different branches of IQ (cognitive abilities) research (Deary & Caryl, 1997)
- real life impact = educational achievements, employment success, life task outcomes
- cognitive = reaction times, inspection time
- biological = brain event potentials, nerve conduction velocity, brain size, functional brain scanning
- structure of intelligence
Structure of intelligence: Psychometric IQ
- has a hierarchical structure
- general intelligence is split into learnt factors and biological potential
- learnt includes spelling, writing and oral style
- biological splits into reading speed, piagetian reasoning, sequential and inductive reasoning
what is fluid intelligence? (Gf)
- Focuses on process independent of content or knowledge domain ie. not based on prior knowledge
- includes 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 (Bugg et al., 2006)
what is crystal intelligence? (Gc)
- Gc is a product of Gf →Investment theory (Cattel).
- Gc test: vocabulary etc represent acquired knowledge.
- Knowledge (acquired) increases over lifetime.
How does Gc and Gf change over a lifetime?
- conventional wisdom is that fluid intelligence peaks relatively early in life and then declines
- This challenged by more current research suggesting heterogenous effects on different cognition domains (e.g. Hartshone and Germine, 2015)
are genetics heritable?
- heritability estimates 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?
- but problem of heritability gap as assumes genes are independent of the environment (Plomin and Deary, 2015)
Heritability of g: group differences controversies
- 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
what is Spearman’s hypotheiss?
- Noticed people’s performance of a cognitive test was correlated with their performance on other comparable cognitive tests. Hence, he proposed a common latent factor g that broadly represents cognitive capability
- Noticed that the more strongly a test correlated with IQ, the wider the difference in Black and White American’s performance on the test
- Hypothesised that Black-White differences on tests of cognitive ability correlate positively with g-loading
- extended by other authoes (e.g., Arthur Jensen, Charles Murray, J.P Rutherford, Hans Eyesneck) to suggest that racial IQ differences are genetic in origin
Eysenck’s hereditarian views on race
- Eysenck’s hereditarian views on race and intelligence were highly controversial.
- Current research has confirmed that IQ is heritable.
- Research has found no significant genetic determination of racial differences in IQ.
- Group differences in IQ may be entirely explained by envt’l factors
what is the Flynn effect?
- 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.
what environmental changes produce large changes in IQ?
- Social multipliers
- Averaging
- Gene-environment matching
how do social multipliers contribute to an IQ increase? (Rindermann et al., 2017)
- Internet and access to information
- TV?
- Gaming (reaction times and speed)?
- Education
- Group learning and studying
- Rising standards of living
- Better nutrition
how does gene environment matching contribute to an IQ increase?
gene-environment correlation
- people seek out environments that match their phenotype
- these processes by which the ability and the environment are matched produces increases on that initial ability
- Thus, environment increases genetic/biological ability
how does averaging contribute to an IQ increase?
- As an 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
how does age change IQ?
Heritability increases with age
40% in childhood, 60% in adulthood and 80% in old age
how does socio-economic status change IQ?
- Heritability high for high SES
h2 = 72% - Heritability virtually zero for low SES
h2 = 10% and environment = 60%
What may account for environmental effects on heritability of IQ?
The age effect may represent a gene-environment correlation
- 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
SES effect may reflect a gene-environment interaction
- More resources in high SES to allow genes for IQ to express.
Heritability and malleability of intelligence (Sauce & Matzel, 2017)
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 specific parties is 46%.
- Due to gene-environment interplay, IQ is more malleable than previously assumed
- Group differences in performance on IQ tests reflect cultural rather than biological effects (Kan et al., 2013).
Brain volume and IQ (McDaniel, 2005)
Higher IQ is associated with larger brain volumes
P-FIT theory (Jung & Haier, 2007)
This model tries to represent intelligence through a set of processes in the brain beginning with perception and ending with decision-making.
Step 1 – Deal with sensory information taken in from the world (smells, sights, sounds). - extra striate cortex
Step 2 – Symbolic processing and meaning making of the received information. - supramarginal gyrus
Step 3 – Parieto-frontal integration, reasoning and decision-making.
Step 4 – make decision or select a response.
Personality adds to IQ (Chamorro-Premuzic & Furnham, 2008)
- Examined FFM traits and IQ to predict 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
Intelligence as Process, Personality, Interests and Knowledge (Ackerman, 2018)
Knowledge influences
interests and this is mediated
by personality
