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Intelligence (Biological) - Coggle Diagram
Intelligence (Biological)
Different kinds of intelligence
General/Specific intelligences
Earliest/most enduring theories formulated by Spearman (2004)
He used factor analysis to examine people's scores on various mental abilities tests
He found that people who performed well on others too, Spearman suggested the tests were measuring the same underlying mental ability -> These were general intelligence (g)
Spearman also identified more specific (s) forms of intelligence. Tests include maths, vocabulary, logic.
Our ability to behave intelligently on a cognitive task relies on a combination of g and s
Fluid/Crystallised intelligences
Horn and Cattell (1966) suggested g isn't a single form but has two aspects
Fluid -> ability to reason and solve problems abstractly without experience. Independent on education
Crystallised -> ability to acquire knowledge through learning and experience. e.g. understanding learned information
Fluid declines with age, crystallised increases
Multiple intelligences - Gardner's theory
Gardner (1983) believed intelligence was made up of eight different abilities ranging in amounts from person to person
Eight intelligences were: verbal-linguistic -> use spoken and written language to achieve goals; logical-mathematical -> notice patterns, reason abstractly and think logically; bodily-kinaesthetic -> coordinate parts of your body to solve problems; musical -> identify and produce musical tones and rhythms; visual-spatial -> create mental images and manipulate them to solve problems; interpersonal -> understand other people's 'minds', their intentions and motivations; intrapersonal -> understand yourself, your own intentions, fears, motivations, etc; naturalistic -> understand the workings of the natural world (e.g. plants, animals, weather)
Need to know blend of factors to know someone's intelligence
Some factors valued differently in different cultures (e.g. verbal-linguistic high in western culture)
Biological factors in intelligence
Genes
Twin studies
McGue (1993): average concordance rate for MZ twins is +.86, for DZ twins is +.60 (significantly lower). Between 40% and 80% variation in IQ scores due to genetic inheritance
Adoption studies
IQ concordance rate of MZ twins raised separately is +.72 while DZ raised together is +.60. This shows strong evidence for heritability in intelligence and smaller role for environment
Brain structure
Brain size
Initially used head size but only small correlation between head size and IQ (+.15)
Technology advanced to measure brain and found (+.35) correlation between brain size and IQ
Brain size genetically influenced, proves genes affect intelligence further
Areas of the brain
Jung and Haier (2007): intelligence correlated with volumes of prefrontal cortex, Broca's area and Werniche's area
Suggests research looking at
specific areas may be more useful in understanding brain size and intelligence
Grey matter
Grey matter made up of neuron cell bodies -> important for processing information
White matter made up of axons -> important in communication between neurons
Higher IQ scores correlated with higher amounts of grey and white matter, as a person's capability of processing is greater (Luders et al, 2009)
Nutrition
Efficient neurotransmitter function depends on presence of certain chemicals in the diet
Absence of certain nutrients associated with intellectual impairments
Qian (2005) found deficiency of iodine linked with average decrease of 12 IQ points in China
Flynn (1987) found IQ scores in most countries increasing decade by decade since the 1930s
Improved diet means brains benefit from necessary micronutrients (neurons more efficient) so everyday and IQ performance is better
Van Leeuwen et al (2008) on the Twin family study
Background and aims
Background
Argued that studying first degree family members isn't enough to show genetic effects on intelligence and separate them from environment. Twins used because MZ share 100% genes, DZ share 50% genes
Validity of twin studies rests on two assumptions:
Parent's phenotype not correlated -> spousal IQs tend to be similar. Phenotypic assortment -> people mate with those of similar intelligence. Social homogamy -> tendency to form relationships with those who share similar environments to us
Genotype and environment (GE) are not correlated -> previous studies assumed parent's intelligence had little/no role in child's intelligence. However, more likely that parents place children in environments that match their genotype -> 'cultural transmission'
Aims
Carry out extended twin study which would consider the assumptions usually overlooked in research
Test which of two models is better explanation of variation in IQ scores - phenotypic assortment or social homogamy
Investigate whether biological factors (genotype) and/or environmental factors (phenotype) affect intelligence more
Calculate an unbiased heritability estimate for IQ
Method
Sample
Letter sent to 214 Dutch families from the Netherlands Twin Registry inviting them to take part
Families contained set of twins plus additional sibling
112 families (52%) agreed to take part. All signed consent forms. Children given present for participating
48 pairs of twins were MZ, 64 were DZ
Age of twins average 9.1 yrs, sibling average 11.9 yrs
twin-family design, correlation IQs of twins, siblings, parents
Materials
Children's intelligence measured using Raven's standard progressive matrices at the Free University of Amsterdam
Parents completed Raven's advanced progressive matrices. Both tests measured general intelligence
Procedure
Children and adults completed test in separate rooms. Took 5 hours including breaks
Twin status established using at-home swab test for parents and children
University used genetic testing technique to determine zygosity. This was standardised
Two pairs of twins didn't do this, used questionnaire instead
Results
Descriptive statistics
No significant differences in IQ measures between males/females for adults and children
Variability in IQ larger in siblings than twins, may be due to age
Inferential statistics
Correlations between pairs of IQ scores were higher for MZ twins than any other relationship
Heritability of IQ
Phenotypic assortment: 58% variation due to genetic variation, 42% due to unique, unshared environmental variation
Social homogamy: 15% variation due to genetic variation, 19% due to dominance variation, 39% due to unique, non-shared environmental variation
Heritability effect on IQ is 67%, 33% due to random environmental effects including measurement error
Conclusions
Intelligence best explained by additive genetic effects rather than environmental factors
Explaining why other studies had different results:
Van Leeuwen unable to replicate results due to considering phenotypic assortment -> earlier studies overestimated effects of shared environment and underestimated role of additive genetic effects
Results may also be due to using Raves progressive matrices which don't rely on language and the non verbal abilities used are more heritable and less influenced by shared environment than language skills
In summary:
Influence of parents on children's intelligence due to genetic factors
Cultural transmission does not exert significant influence except in children with genetic predisposition for low IQ compared to children with genetic predisposition for high IQ
Environmental factors influencing IQ generally not shared among siblings
Methods of assessing intelligence
Weschler Intelligence Scale for Children (WISC)
Most widely used IQ test for children (6-16) in the Western world
First edition 1950, updated 4 times since. Current = WISC-V
What the test measures:
5 main forms of intellectual functioning. Each called a primary index -> tested by two subtests
Produces scores for 5 ancillary indexes and gives complementary index scores which can diagnose learning difficulties
Administering the test:
Done face-to-face, duration 15 mins-3 hrs
Produces separate scores but overall score is measure of general ability (full scale IQ (FSIQ))
Usefulness
Not culturally fair due to dependence on language skills
Participants may be unfamiliar with language used in test
Leads to thought that some people are less intelligent than they are
Effectiveness
WISC-V too recent to have been assessed in many studies but previous versions are highly reliable
High degree of construct vailidity
Practicalities
Can be difficult to interpret
Revised so kept relevant and is now online
Raven's progressive matrices
Developed in 1936
Non verbal tests -> more culturally fair
Assesses fluid intelligence and doesn't depend on language ability or previous education
Description of the test:
Standard test used for children
Consists of 60 items arranged into 5 sets (A-E) of 12 items each -> non verbal reasoning
Progressively gets harder
Advanced version used for adults and adolescents of above-average intelligence. Has 48 items
Administering the test:
Takes 15-45 mins
Can be administered in groups or inidividual
No movement involved so those with physical difficulties can use this
Usefulness
Ideal for cross-cultural test:
Reliable and valid measures of intelligence
Quick to administer and provide single score so easier to interpret
Effectiveness
Split-half reliability is around +.90 and test-retest reliability is above +.80
Construct validity as g is less accepted than it used to be
Practicalities
Flexible and easy to administer
Simplicity can be a limitation as it only provides one score
Evaluation
Nature/Nurture
Nature
Biological factors of intelligence
Genes -> adoption studies -> MZ twins raised apart showed +.72 concordance IQ rate and DZ raised together showed +.60
Nature because MZ twins raised apart have higher concordance than DZ raised together, showing significant role for heritability of intelligence
Nurture
Biological factors of intelligence
Nutrition absence of certain nutrients associated with intellectual impairments -> Qian (2005) dietary deficiency of iodine linked with average IQ decrease of 12 points in China
Nurture because this is something that can be changed and diet is not determined at birth
Freewill/determinism
Freewill
Van Leeuwen
Assumption that parent's phenotypes aren't correlated and choice to mate with those of a similar IQ to ourselves -> phenotypic assortment
Freewill as choice made when choosing partner
Determinism
Van Leeuwen
Found that, assuming phenotypic assortment, 58% variation of IQ in adults/children explained by genetic variation
Shows determinism as shows child's IQ is inherited from parents
Reductionism/Holism
Reductionism
Biological factors for intelligence
Genes -> studies look at how intelligence is inherited and heritability is main reason for intelligence
Reductionist as it reduces intelligence to being due to a single factor
Holism
Van Leeuwen
Heritability estimate of 67% on IQ, shows other factors play a role
Holistic as includes possibilities for other reasons
Individual/situational
Individual
Biological factors in intelligence
Brain size is genetically influence, unless MZ twins, genes will differ
Individual as brain size will differ from person to person due to different genes
Situational
Usefulness
Ethical considerations
Ethical
Van Leeuwen
Parents and children (over 12 in Netherlands) gave written, informed consent
Ethical as considers respect as asks for informed consent
Not ethical
Van Leeuwen
May have affected participants' self esteem and caused stress to participants
Not ethical as breaks responsibility and protection of patient
Conducting socially sensitive research
Psychology as a science
Scientific
Van Leeuwen
Use of Raven's Progressive matrices, standardised procedure
Scientific as standardised and can be replicated
Not scientific
Biological factors in intelligence
Nutrition -> deficiency of iodine linked with decreased IQ (12 points)
Correlation, not cause and effect, therefore not scientific
Ethnocentrism
Ethnocentric
Not ethnocentric
Van Leeuwen
Uses Raven's progressive matrices which are non-verbal
Not ethnocentric as it is independent of language and education
Validity
Reliability
Reliable
Van Leeuwen
Standardised procedures for experiment
High because standardisation so measurements across participants are consistent
Not reliable
Van Leeuwen
Not identical -> two sessions on different days
Low because conditions weren't identical
Sampling bias
Bias
Van Leeuwen
Dutch families only used in study from the Netherlands Twin Register
Biased as only generalisable to Dutch families
No bias
Van Leeuwen
112 families used in study
Not biased as large sample used so more representative