Heritability and Intelligence Flashcards
• To consider what heritability is and what this means in the context of intelligence • To explore the complex genetic and environmental factors that contribute to intelligence To evaluate the misuse of heritability in intelligence testing & research and the negative impact this has had more recently (89 cards)
1
Q
what are the main 2 case study considerations we’re looking at?
A
- importance of critical thinking in research
- importance of community in research and the need for this to be diverse
2
Q
first-degree relative
A
share ~50% of genes i.e. parents and siblings
3
Q
second-degree relative
A
share ~24% of genes i.e. grandparents, grandchildren, aunts, uncles, niblings
4
Q
third-degree relative
A
share ~12.5% of genes i.e. great grandparents, great-aunt, great-uncle, first cousins
5
Q
genotype
A
genetic make-up of an individual
6
Q
phenotype
A
individual’s observable traits i.e. height, eye colour, blood type and intelligence
7
Q
who is Francis Galton?
A
- first introduced nature vs. nurture (believed it was heritable but acknowledge environmental factors that may impact it) -> first to consider heritability in relation to Darwin
- started looking at familial relations and its connection to ‘eminence
- moved on to consider role of environment -> surveying total society members to explore the role of nature vs. nurture (looking at upbringing, education and opportunity on their success)
- suggested key methodology for looking at heritability -> i.e. twin and family adoption studies
8
Q
what is eminence (and the familial connection)?
A
people who hade done really successful things -> looking at family relations and whether the second-related individual was more eminence than others and whether that decreased as the degree of relation goes down -> genetic link to intelligence?
9
Q
what do we mean by genetic heritability?
A
- genotype is biologically transmitted from their two parents (50% from each)
- the genotype influences the phenotype
* this is genetic heritability -> variability between parents and child / the proportion of shared variance of the genotype that’s influencing the genotype (how much of the genotype actually influences the genotype) - child phenotype
10
Q
what happens when the proportion of shared variance is low?
A
parent and child are quite different
* variability is high
11
Q
what happens when the proportion of shared variance is high?
A
parent and child are very similar
* variability is low
12
Q
what phenotypes are entirely genetic?
A
physical characteristics particularly i.e. having a nose / eye colour are entirely genetic and determined by your genotype
13
Q
what about phenotypes that aren’t entirely genetic?
A
environment may play a role in the child’s phenotype, altering how genes are expressed i.e. intelligence
14
Q
what do we mean by heritability?
A
- genes biologically transmitted from parent to child -> 50% from each parent
- how much of the phenotype i.e. intelligence is passed from parent to child is genetic heritability
15
Q
how is genetic heritability assessed?
A
considering the variability found between parents (how much they differ) and in terms of proportion of shared variance (how much they are the same)
* presented as a %
16
Q
what are the two (broad) techniques, we can look at when looking at heritability estimates?
A
behavioural approaches and DNA / physiological approaches
17
Q
what is behavioural genetics?
A
the average estimate of the proportion of variance for intelligence thought be accounted for by genetic factors across a population
- interest in estimating genetic heritability across populations
- expressing it in terms of shared variance
18
Q
why are we estimating for a population?
A
estimates says nothing about an individual -> cannot tell a person what a proportion of their genes are contributing to their intelligence
* estimate because we can’t control for all factors
19
Q
what are three ways we can assess genetic hertiability?
A
family studies, twin studies and adoption studies
*these give natural occurrences in different groups which we can compare that differ levels in terms of shared genetic makeup and shared environment / or not shared environment
* started to tease apart how much genes influence and how much environment influences phenotype
20
Q
family studies
A
- parents-children share ~50% of genes
- can consider the associations here
- similarities may be due to shared environment
21
Q
twin studies
A
- identical (MZ) share 100% of the same genes
- non-identical (fraternal, DZ) share 50% of the same genes
- can compare (with non-twins) the influence of genetics
22
Q
adoption studies
A
- consider the role of genes and environment
- parents / adopted child
- twins or siblings raised apart
23
Q
how do these studies assess for genetic heritability?
A
NOT physiological
- look for similarties / differences in intelligence through observations, interviews, questionnaire and intelligence test measures
24
Q
what do we need to consider when using heritability estimates?
A
- they are just estimates
- do not refer to estimates for an individual -> estimates of the average heritability among a certain population of people instead
25
what do heritability estimates actually tell us?
as we reduce the level of shared genetic makeup, we get less shared variance -> suggestion of a environment contribution almost
26
by the 80s, there was a general idea that the genetic heritability of intelligence fell between...
40-80%
27
what is the percentage of genetic heritability estimates Eysenck (1979) gave?
69%
28
what is the percentage of genetic heritability estimates the Bell Curve gave?
74%
29
genome-wide association study
considers the entire set of DNA of a large group of people -> searching for small variations in a wide pool of DNA
30
single nucleotide polymorphism (SNP or 'snips')
small variations being searched for in the genome wide association studies
31
what is the use of SNPs?
sciences can look for 1000s of SNPs and potentially identify SNPs that occur more frequently in people with a certain disease or trait (scoring more highly or low on certain tests)
32
Deary looked at genetic heritability of a person's stability of intelligence across their life span (1932 and 1998).
What did he find?
slight increase in intelligence (age-related) and was quite stable (r ~.60)
33
Deary et al. (2012) investigated the genetic contribution to stability of intelligence across the lifespan in 1940 unrelated individuals. He measured intelligence at 11 year olds and then at 65, 70 or 79 years old -> combing this with a DNA analysis. He examined over half a million genetic markers to see how genetically similar these individuals were despite not being related
What did he find?
genetic contribution to the stability of intelligence across the life span but it's a lot lower than what we found in family / twin studies (38%)
34
Dear (2012) conducted a meta-analysis around heritability estimates of intelligence in different cultures. what did he find?
when considering the genetic contribution to intelligence stability across many studies, Deary found that it varied across life span and across cultures
35
Davies et al., (2011) directly considered the heritability of intelligence using
* genome-wide data looking for SNPs
* phenotype data (measures of cognitive traits associated with intelligence
Compared 3511 unrelated, middle to older adults
What did they find?
40%-50% of the variation in human intelligence is associated common SNPs
36
Deary, Cox and Hill (2021) reviewed the literature from the last 10 years that considers the heritability of intelligence through the use of direct DNA testing.
In studies that used genome-wide methods, what were heritability estimates found at?
20-30% (taking into consideration David et al., 2011 results)
37
what does it mean for genetic heritability estimates to be around 20-30%?
there's around 70-80% of variance which is not explained by the genotype (perhaps this is a vital role of environment or other factors)
38
what are the 3 traditional research methods for investigating genetic heritability?
twin studies, adoption studies and family studies
39
how did genes and environments used to be seen?
additive model
* genes + environment = phenotype
40
what is the new interactive model for looking at genes and environment?
we consider how much they interact together (how environment impacts how much genes contribute to a phenotype)
* genes x environment = phenotype
41
when using an interactive model, what are the 4 things we must keep in mind when considering genetic heritability
* conception of heritability and the environment (one we're looking at)
* different types of genetic variance
* assortative mating
* representativeness of twin and adoption studies
42
when we are considering concepts of heritability & the environment, we must consider the context within 2 concepts. what are these concepts?
abstract and population
43
abstract concepts
* theoretical concepts -> intelligence is an abstract construct
* estimates do not tell us about specific genes or environmental variables
44
population concepts
* estimates refer to a group of people (a population) ->how generalisation is it from the general population?
* cannot tell us about an individual
* more about adoption studies etc
* our genome wide studies are a bit more representative of generalisability but it's something we need to consider
45
there are different types of genetic variation (prior to environment involvement), what are they?
* additive
* dominant
* epistatic
46
additive
genes + environment = phenotype
47
dominant
process of which genes are expressed (dominant) and not expressed (recessive) -> interaction and variation in what's expressed
48
epistatic
* process of how genes interact
* how certain genes will interact with other determining whether they are expressed or suppressed
* process of how different genes in different places can interact with other genes and change what's dominant and what's recessive
* Dominant and recessive can change in the presence of other genes -> there are a lot more complex interactions that we need to consider when thinking about genes (complexity in genetic variation)
49
additive + dominant + epistatic = ?
broad heritability
50
what is assortative mating? (factor we must consider for genetic heritability)
variation in traits between mating couples is not random -> who we choose to mate with is not random, a lot goes in to our decision
51
what is meant by representativeness of twin and adoption studies? (factor we must consider for genetic heritability)
may under or overestimate heritability in the general population -> we are moving away from this with clear physiological approaches
52
what about some environmental factors we must consider when thinking about intelligence?
* biological
* family environment
* school & education
* culture
53
Environment factors which affect our Biological Processing (and development of our intelligence):
* nutrition
* toxins (i.e. lead)
* prenatal factors (i.e. smoking, drinking during pregnancy)
54
environmental factors in family environment that affect development of our intelligence:
* shared & non-shared environments (i.e. different schools, different friendship groups)
* within-family factors
* outside family factors
* socio-economic status
* birth order, family size
55
what is meant by birth order & family size? (Belmont & Marolla, 1973)
As both (birth order and family size) increase, intelligence scores decrease
56
what does family size suggest? (Rodgers et al., 2000)
no direct relationship between family size and intelligence
* previous research conflated to different population types but why:
-> conflated birth order with family size,
which is two different populations - can't put under one umbrella
* this is why a decrease was originally found
57
what is meant by birth order?
these models are suggestive towards birth order effects:
* admixture hypothesis (Rogers, 2001)
* resource dilution model (Galton, 1874)
* confluence model (Galton, 1874)
58
what does birth order research suggest?
birth order effects intelligence
* high up the birth order you are, the more the intelligence decreases
59
admixture model (in relation to birth order and intelligence)
families who have a lower SES tend to have more children -> because of a lack of different resources contribute to this finding
60
resource dilution model (in relation to birth order and intelligence)
more children, less time/resources devoted to each child -> more children, less parental resources which might help develop intelligence
61
conference model (in relation to birth order and intelligence)
includes family dynamic -> first born with siblings, might have situations where you are looking after and teaching them -> giving you more opportunities to develop your intelligence
62
how does school & education have an influence on our intelligence
* education <-> intelligence
* IQ can predict education outcomes
* but time in education can contribute to intelligence
63
how does culture have an influence on our intelligence
* decontextualisation
* quantification
* biologisation
contribute to intelligence and what kinds of intelligence develops -> linked to implicit ideas of intelligence
64
environmental influences: culture and decontextualisation
* the ability to disconnect from a situation, think about it abstractly and generalise from it
* an important skill for western industrial, capitalist societies -> this ability has therefore become a sign of intelligence and important in west society construct which is measured by these measures (but if we step out of this context, is it really?)
* we really need to think about what intelligent tests are measuring and what we see as important if we're generalising it across the whole world population
65
environmental influences: culture quantification
ability to discover or express the quantity of something
* intelligence research seeks to quantify intelligence, encapsulating a number of meanings into one word
* reification - regarding abstract ideas (like intelligence) as concrete or material (-> but maybe intelligence doesn't look like that?)
* quantifying intelligence in terms of numbers (but we need to be careful not to over-quantify)
66
environmental influences: culture biologisation
idea that prominence of biological and evolutionary theory in the last century has influenced our thinking
* gives great new insight and improve understanding. But these theories are concerned with development of traits over millions of years we've only just started looking at them -> only have a small sample of data in the evolutionary period so there may be limitations in what we're measuring.
* however, study of ourselves (intelligence is a relatively new phenomenon) and we should be careful in how we interpret data consider genetic heritability (role of environment in phenotype) over only a relatively short time period.
67
what can we assume for genetic heritability consideration?
there has been an increased complexity for genetic heritability consideration
68
how can we suggest a child's phenotype is characterised?
1. biological transmitted genes from parents -> child's phenotype
2. genetic heritability (assortative mating etc) and environmental influences -> child phenotype
69
how can we summarise heritability variance within a population?
genetics and environment (AND there's an interaction between them) (all 3 of these components feed Ito the Heritability variance within a population)
70
How can we summarise the whole of heritability variance within a population
diagram required BUT
* genetics influences development
* environment influences development
* development will also have a reciprocal interaction with genetic and environment
* we still keep assortative mating and evolution into account as well
71
summary of the hereditability variance within a population diagram
* both genetic and environmental factors influence intelligence
* interaction between genetics and environment also influence intelligence
* developmental factors influence intelligence, and this includes considering where different genes influence at different stages of development and do environmental factors influence development here as well
* assortative mating (how we choose traits) in mating partners influences as well, along with which factors were at work during the evolution of intelligence
72
what were the six assumptions Herrnstein & Murray built their Bell Curve argument on?
1. there is such a thing as a general factor of intelligence upon which humans differ
2. IQ tests are designed to measure 'g' and are mostly accurate
3. IQ scores match general ideas of what intelligence is (implicit theories)
4. IQ scores are stable, although not perfectly so
5. properly administered IQ tests are not demonstrably biased against social, ethnic, economic and racial groups
6. cognitive ability is substantially heritable, apparently no less than 40-80%
73
the bell curve proposes 4 ideas
1. the cognitive elite suggests there is an emergence of a CE within American based on separation of society through college admission and the workplace
2. socialeconomic variables and IQ suggests that an individuals's intelligence is more important than SES for predicting economic and social welfare
3. the relationship between race and intelligence describe evidence for the higher IQ of Asian-Americans and low IQ of African-American in comparison to white Americans
4. The implications for social policy
74
what were the implications for social policy?
* population of those with lower IQ is increasing as women with lower IQ tend to have more children
^ immigrants contribute towards this
* increase the societal problems (i.e. crime) with Herrnstein & Murrey suggest are associated with low IQ
* Implicit in these state arguments then is that groups of people in America with lower intelligence (immigrants & African Americans) are potentially part of this problem
75
What does Herrnstein & Murray argue are the best way to tackle these 'problems'?
* not use affirmative action as measures such as these have led to a decrease in intelligence within education and the workplace
* argue that resources should be shifted from supporting underprivileged populations to supporting the 'cognitive elite'
76
what are the issues with the 6 assumptions?
1. G exists and differs
2. IQ tests measure g and are accurate
3. IQ scores match implicit theories of intelligence
4. IQ scores stable
5. IQ test are not bias
6. Cognitive ability is substantially heritable
77
G exists and differs
* more empirical evidence of this now, research not as clear back then as they were making assumptions
* not expert consensus yet (are we sure 'g' is the only type of intelligence?)
78
IQ tests measure g and are accurate
can be some debate over this, given the context around the origins of g and around it's testing and development
79
IQ scores match implicit theories of intelligence
* maybe western ideas, but there are some differences across cultures and sub-cultures
* even within one culture are ideas can shift and change [among culture and age]
80
IQ scores stable
* quite but not perfectly (Deary 2000, r=.60)
* consider ideas around malleable and fixed intelligence -> doesn't factor in how there is some movability
81
IQ tests are not bias
the theories behind them could be bias and this is not factored in
82
cognitive ability is substantially heritable
* based on less robust research methods that were available at the time
* large estimate range (40-80%) and difficult to use to explain group differences
* in our more specificated methods it's only 20-30% which is less than they thought
83
what are some flaws in the stats and evidence used in the Bell Curve (Kamin, 1995)
Correlation DOESN'T EQUAL Causation
* correlations between SES and Intelligence
* SES can be bound up with multiple confounding factors
Often associated causation with correlation, especially when looking at SES and Intelligence -> but this can be away from genetic contribution
Measure validity
* studies using self-report measures for SES with children and no additional checks
Use measures where validity can be questioned -> basing it on studies with self-report measures in children who are less able of thinking about their SES than adult or book understanding
* No additional checks of studies -> can be questions of validity
Problematic Research Studies
* over-reliance of certain academics who omit findings showing higher IQ for Black participants -> terming this 'Inconsistent'
* If they did find black people to have high IQs, they would term it as inconsistet and emmit that evidence
Ignoring contradicting evidence
84
what did the Bell Curve book prompt?
the American Psychological Association (APA) to put together a Taskforce
* headed by Neisser who made efforts to build a Taskforce that represented a wide range if views and opinions on intelligence
85
what was one of the conclusions from the taskfoce?
while average IQ scores between African Americans and White Americans may differ, there is no definite evidence to suggest this is due to genetic -> more likely to be cultural
* highlighting importance of both a research community to support critical thinking (and a more balanced view)
86
what are some eugenics practices that intelligence was linked to?
Informed social policies
* sterilisation laws
* segregated education policies based on intelligence
* immigration policies
87
who was the father of modern eugenics
Galton -> saw intelligence as a inherited trait and artificial selection could increase intelligence in a population -> thought society was becoming weaker
88
how did Lynn put forward ideas to control the population using eugenic principals?
* argued eugenics were right in that population was 'degrading' in terms of intelligence
* proposed ways to remedy this i.e. genetically assess embryos in IVF
89
what was a general issue of the Bell Curve?
poor critical thinking skills as they are taking too much/inferring to much from the time understanding they had of genetic variability leading to racism etc etc
