Biological and Behaviourist Perspectives on Intelligence Flashcards
What does Intelligence help us to do?
plan
- reason
- solve problems
- quickly learn
- think on our feet
- survive
How to measure intelligence?
Intelligence Quotient (IQ) strongly correlates with life outcome
What are the advantages of higher intelligence?
socioeconomic status
- education
- social mobility
- job performance
- lifestyle choices and longevity
intelligence as a stable trait in an individual from young to old
betweeen ages of 11 and 16 correlation of 0.81 on tests of educational achievement (Deary et al., 2007)
-test taken at 11 still highly correlates when taken again at 90 (Deary et al., 2013
intelligence has a strong … component?
genetic
heritability of intelligence?
studies demonstrate heritability to be large: 50%-80% (Posthuma et al., 2001)
-one of the most heritable behaviour traits (Plomin & Deary, 2015
intelligence can…
can be measured by cognitive tests
- is stable over time
- has high heritability
- predicts major life outcome
brain size and intellgence - what did many old studies fail to do?
old studies (19th century onwards) failed to observe differences in size when dissecting brains of deceased scientists and artists-trying to see what made people have exceptional ability or talents
what assumptions were made about smarter people’s brains?
stats/studies?
that they tend to have bigger brains. - when considering multiple studies this does seem correct
advances in neuroimaging have allowed for in vivo studies-meta-analysis of 37 studies with 1500 participants found moderate positive correlation of 0.33 between brain volume and intelligence (McDaniel, 2005)
-subsequent meta-study of 88 studies with over 8000 individuals also found significant small positive correlation of 0.24 (Pietsching et at., 2015)
brain areas of intelligence - Andreasen et al 1993
Early imaging studies tried to locate area of general intelligence within the brain-also tried to link specific types of cognition to specific brain areas-
Andreasen et al. (1993) found that IQ associated with intracranial, cerebral, temporal lobe, hippocampal, and cerebellar volumes: almost all brain areas
whats Voxel-based morphemetry (VBM)
a neuroimaging analysis technique that makes it possible to test whether areas of intelligence are clustered or distributed throughout the brain
-multiple areas correlated with cortical thickness and IQ
throughout development brain structure changes throughout childhood and also in adulthood; influenced by what 4 factors?
- learning
- hormonal differences
- experience
- age
what do changes in the grey matter may involve
rearrangements of dendrites and synapses between neurons-acquisition of new skills associated with changes in the related brain regions
what else influences brain structure?
sex and age differences influence brain structure and areas associated with intelligence
-many contradictory findings in terms of associations of brain areas associated with intelligence between men and women, but the overall relationship between brain tissue volume and IQ not different
brain structure changes during normal development
gray matter increases during early ages
-thought to be result of overproduction of synapses-
strongest correlations between gray matter volume and intelligence around 10 years of age
brain structure changes during puberty
thinning occurs through adolescence and young adulthood
- synaptic pruning
- at around age 12 negative correlation between gray matter volume and intelligence emerges
differences in brains with more intelligent/higher IQ kids
pattern of cortical maturation unfolds differently in more intelligent children
-children with higher IQ seem to have a particularly plastic cortex: higher phase of cortical increase followed by higher phase of cortical thinning
2 types of intelligence?
crystallized – based on prior knowledge and experience
-fluid – adaptive reasoning in novel situation
what does fluid intelligence rely on?
on the more efficient function of distributed cortical areas
- the lateral frontal cortex is strongly associated, but also the parietal lobe and posterior cortex
- negatively correlated with the cortical metabolic rate (more efficient neural circuits)
- also associated with the structure and function of the frontal lobe region
what does crystallized intelligence rely on?
- on the cortical structure and thickness in lateral areas of temporal lobes and temporal pole
- largely relies on verbal ability, associated with areas responsible for integrating diverse semantic information
intelligence - genes
how can genetic diffs relating to intelligence between people be explored?
using Genome-wide association studies (GWAS)-used for investigating underlying variation in many traits and diseases
GWas test for associations between phenotypes and genetic variants
single-nucleotide polymorphisms (SNPs)
-usually in large groups of unrelated participants
•Most SNPs are apparently irrelevant or have very little impact on biological pathways
-some SNPs, however, have functional consequences that allow us to identify genetic underpinnings
GWAs studies/stats
GWAS studies have, over the last decade, become a useful tool for trying to identify genes relating to intelligence
•Initial studies, using smaller studies, did not provide clear results
-A meta-analysis of 31 cohorts (53,949 people) could only find about 1.2% variance in general cognitive function (Davies et al., 2015)
•More recent studies use much larger sample sizes to try to identify contributing genes
-Looking at educational attainment as proxy for intelligence increased sample size to 400,000
•Intelligence is a highly polygenic trait – many genes are involved
Intelligence as a polygenic trait
A large 2018 study has identified 206 genomic loci and implicated 1041 genes as being important for intelligence (Savage et al., 2018)
-this is 191 more genomic loci and 963 more genes than before•
Many different genes involved in intelligence
- each gene generally makes a very small difference overall
- most probably have different influences at different stages of development
•Small genetic effects at critical stages of development might have large consequences on brain development and function
-useful not only to know which genes are involved, but also when and where they are expressed within the tissues of the brain
How genes can influence intelligence
neurodevelopment, most genes relevant to intelligence appear to be active
-especially during prenatal development, genes help determine the brain’s structure and composition
•Cell-cell interactions that are beneficial to intelligence can be influenced by genes
-efficient structural and functional changes involving synapses, cytoskeleton, receptor mobility and metabolism
•The role of synaptic function and plasticity in intelligence
-influencing the efficiency of synaptic communication, plasticity and neuronal excitability, along with presynaptic organisation and vesicle release of neurotransmitters
•Supporting functions relevant to intelligence
-For example efficient energy metabolism impacting maintenance of firing during cognitive tasks
Interaction of behavioural/environmental factors
We know from twin studies that 50%-80% or intelligence is inherited (nature)-but the environment and behaviour must also play a role (nurture)
•In fact, it is not quite as simple as that: genes and the environment/behaviour actually interact-
the influence of some genes will only happen (be “activated”) when some environmental or behavioural factor is encountered
Genetic and environmental influences on intelligence
Many different environmental and behavioural factors can interact with genes, influencing intelligence, for example educational opportunities-
by being exposed to certain educational ideas, relevant genes allow for beneficial adaptive changes, enhancing intelligence
-this then allows further attainment, opening up new educational opportunities, and so on
•Trucker-Drob et al. (2013) claim “…genetic influences on cognition are the result of accumulating environmental experiences and depend on exposure to high-quality environmental contexts over time.” (p. 350)
-they go on to explore the heritability of cognition as a function of Socioeconomic Status (SES
The interaction of Socioeconomic Status and genes
Children in high SES contexts have abundant opportunities to “select and evoke positive learning experiences on the basis of their genetically influenced motivations and proclivities” (p. 252)
-those in low SES contexts have fewer opportunities for cognitively experiences, both at home and at school
- disadvantaged children may have less access to enriching books, less rigorous academic opportunities and lower quality interactions with peers and adults
- those in low SES contexts might not fully realise their genetic potential for intelligence
•Genetic influences on intelligence supressed by low SES-
for children in low SES contexts heritability of cognition approaches zero
- for children in advantaged contexts genes account for as much as 80% of individual differences in cognition
- this interaction has been found in young children, adolescents and adults
•Findings don’t always replicate in countries with strong social welfare systems…
Genes and intelligence - conclusion
Twin studies suggest that individual differences in intelligence can largely be explained by genetic influences - between 50%-80% of heritability
-GWAS studies currently can only explain 21%-22% of heritability
•Genetic influences on intelligence are attributed to tiny effects by huge number of genes
•Most intelligence genes are implicated very early on in development
-overall healthy development prerequisite for optimal cognitive function
•Environmental and behavioural circumstances also critical for activation of many genes
Biological perspective - cells
cells of intelligence
Genes influence neurons – so what properties of these are important for intelligence?
•The role of neurons or networks of neurons in information processing and thus intelligence has been known since the late 19th century (Cajal, 1893)
•So far we have the biological basis of intelligence by considering the brain at the macro level and the role of genetics
-but there are 86 billion neurons in the brain – what are their role?
•It is assumed that the activity of our neurons and the connections between them allows for coding, processing and storage of information, giving rise to cognition-we can assume that small changes in the efficiency of this process can lead to large changes in cognitive ability
Pyramidal neurons
hard to access neurons in living human brains
-recent technique is to resect tissue during surgical treatments-
possible to run cognitive tests on patient prior to surgery then test for relationship-
post-mortem tissue generally not suitable and brain imaging currently not precise enough
•Pyramidal Neurons seem to be particularly associated with intelligence
- genetic studies demonstrate key differences between structure in humans compared to other species
- humans have larger and more complex dendrites with more connected synapses
- human pyramidal neurons also recover more quickly, have faster action potentials and transfer information at a much higher rate, and are more plastic in adults
•Differences between humans and other species suggest evolutionary pressure on structure and function of higher-order association areas such as the temporal cortex
Pyramidal neurons and human intelligence
comparing pyramidal neurons show that larger temporal cortical thickness is associated with higher IQ
•Thicker temporal cortex is linked to:-larger dendrites-more complex dendrites
•Computational modelling of these factors suggest that due to larger neurons there is
:-more precise processing of synaptic information transfer
-faster action potentials resulting in improved information transfer
dendrites and intelligence
large dendrites in pyramidal cells allow for more synaptic contacts
- increases whole-brain connectivity
- allows for increased information integration
•Larger dendrites also allow for more distributed processing of information
-function as multiple semi-independent units
•Effectively larger dendrites provide many computational advantages
-allows for rapid and efficient integration of large amounts of information
•Higher IQs are associated with pyramidal cells that can receive more synaptic inputs
-transfer more information and more efficiency (use less energy) than those of lower IQs
