Methods in behavioural genetics. Behavioural genetics and practical facets

Июль 27, 2022

Главная
Психология
Methods in behavioural genetics. Behavioural genetics and practical facets

Содержание

2. Heredity and intelligence Psychologists measure intelligence using a range of tests called IQ (Intelligence Quotient). However,
3. However, IQ tests come in a variety of forms. Some require an individual to engage in
4. One of implications now accepted by most testers of IQ, is that the statistical technique of
5. Adoption studies have also provided evidence for genetic influences on IQ (Loehlin, 1997). Children given up
6. Heredity and personality The dominant view at present is that the number of independent personality traits
12. It is known that a large number of genes affect the function of the brain, moreover,
13. Heredity and antisocial behaviour Concerning crime and antisocial behaviour it is widely accepted that they are
14. Criminologists conceptualise antisocial behaviour as one that is against the law. As a result, their definitions
15. Estimates of heritability for antisocial behaviour from recent research in quantitative genetics cluster around 0.50. The
16. Heredity and sexual orientation There has always been a significant interest in the biological explanations of
17. Theoretically, there are many ways of the biological characteristics influence to sexual orientation. For example, they
18. A number of studies have calculated the rate of homosexual orientation among siblings where one is
19. The findings in the area of research into sexual orientation has led some commentators to conclude
20. An often made argument against the likelihood that homosexuality is of genetic origin is that such
21. Another suggestion is that homosexual family members contribute to the reproductive success of an extended family
22. If it possible to change? Methods in behavioural genetics
23. There are some possible ways of impact on human traits to correct them tenderly. They are
24. The second type of gene therapy is called germline gene therapy (it is also referred to
25. Medical interventions It seems more likely that if new interventions aimed at changing behavioural traits in
26. Environmental interventions The third type of intervention involves environmental strategies for changing behaviour. We already have
27. Thank you for your attention!
29. Скачать презентацию

Слайд 2

Heredity and intelligence
Psychologists measure intelligence using a range of tests called

IQ (Intelligence Quotient).
However, there is considerable disagreement about whether or not these tests measure intelligence, and whether intelligence can even be measured at all by a test.
Many critics believe that intelligence is too complex to be measured using such tests:
‘IQ psychologists ... like to think that intelligence can be measured, as if it were ... a simple scalar quantity ... Unfortunately, for psychologists IQ is not so ... Intellect ... is a complex and multi-sided business. Among its elements are speed and span of grasp , the ability to see implications and conversely to discern a non sequitur and other fallacies, to discern analogies and formal parallels between outwardly dissimilar phenomena or thought structures, and much else besides. One number is not do for all of these’ (Medawar, 1982).

Слайд 3

However, IQ tests come in a variety of forms.
Some require

an individual to engage in reasoning in order to solve novel problems, which may be presented in verbal, numerical or diagrammatical form.
Others test general knowledge or the extent of an individual’s vocabulary.
Yet others measure how quickly an individual can solve a series of very simple problems, as well as whether they are capable of solving seriously difficult problems regardless of time pressure.
The very diversity of questions asked in the various IQ tests makes it hard to accept that none of them succeeds in measuring any aspect of intelligence.
But the important observation is that scores on all these different kinds of test are positively correlated.

Слайд 4

One of implications now accepted by most testers of IQ, is

that the statistical technique of factor analysis, when applied to scores on a variety of IQ tests, will always yield a substantial general factor ‘g ’ ( for general intelligence), that the reason IQ tests correlation is they all mainly measure a single underlying psychological or even neurological process (Spearman, 1927).
Different types of IQ test may all be partly measuring a factor of general intelligence as well as distinct cognitive abilities.
Both testers of IQ and researchers in behavioural genetics agree that the heritability of IQ is relatively high (Devlin et al., 1997, Plomin et al., 2000, Chipuer et al., 1990).
That there is a genetic influence on IQ is suggested by two findings:
(i) Monozygotic (MZ) twins resemble one another more closely than dizygotic (DZ) twins or siblings, and full siblings resemble one another more closely than half siblings.
(ii) Individuals who are genetically-related continue to resemble one another even when living apart.
Two other observations suggest that environmental factors have an effect:
(i) For all kinship categories, those living together resemble one another more closely than those living apart.
(ii) Unrelated people living together, adoptive parents and their adopted children or two adopted children living in the same family, show a modest correlation in IQ

Слайд 5

Adoption studies have also provided evidence for genetic influences on IQ

(Loehlin, 1997).
Children given up for adoption before the age of 6 months continue to resemble their biological mother in IQ (Plomin et al., 1997).
There is some evidence that the heritability of IQ increases with age.
The most simple supposal is that an infant’s or young child’s intelligence is affected by their genetic make-up, and that the cumulative effect of environmental experience should be stronger as children grow older.
It is also possible that some of the genes associated with variations in IQ are not ‘switched on’ until adolescence.
Another possibility is that the genetic effects on IQ is that we actively select environments that is more complement to our genotypes, and that the environment different influence to us depends on our genotypes.
If this is true, it could mean that the effects of our genes are reinforced over time and thus appear to be more important as we get older

Слайд 6

Heredity and personality
The dominant view at present is that the number

of independent personality traits are five; this is called the ‘Big Five’ model of personality.
They are: Neuroticism, Extraversion, Agreeableness, Conscientiousness and Openness to Experience.
These five traits, or factors, are commonly referred to as ‘dimensions of personality’.
Across a range of traits, heritability estimates from twin studies lie in the range 0.30–0.505 (Bouchard, Loehlin, 2001).
This is the result obtained for Neuroticism, Extraversion, Conscientiousness, Openness to Experience and Agreeableness.
Sensation-seeking has been reported to have somewhat higher heritability, about 0.60.
Thus, the genetic contribution to personality is thought to be substantial and appears to be roughly equal across all aspects of personality.
Future research combining genetic and factor-analytic methods may be able to improve this alignment.

Слайд 7

Слайд 8

Слайд 9

Слайд 10

Слайд 11

Слайд 12

It is known that a large number of genes affect the

function of the brain, moreover, a hypothesis can be constructed so as to link virtually any of the known genes with almost any aspect of personality. And many other genes that affect the brain have yet to be clarified in future.
There are many reasons to believe that levels of anxiety, psychoticism or impulsivity may in part reflect the different levels of functioning of certain neurotransmitters in the brain, such as dopamine, serotonin and noradrenaline.
Future research in behavioural genetics in the field of personality traits is likely to focus on the use of molecular genetic research techniques to identify candidate genes and regions of DNA that have an effect.
If such genes are identified, they could provide the basis for experiments aimed at determining the neurobiological pathways by which genetic influences are brought to bear.
Detailed knowledge of the genes that affect personality would then, in turn, provide the basis for investigation of non-genetic influences on personality

Слайд 13

Heredity and antisocial behaviour
Concerning crime and antisocial behaviour it is widely

accepted that they are the results of many different influences, include deprivation and poverty.
Mental health clinicians interested in pathological behavior consider antisocial behavior as a mental disorder. As a result, their definitions order that behavior is seriously harmful to others, it involves a number of different types of antisocial actions, or have persisted for a long period of time.
The primary labels assigned to antisocial pathology are:
conduct disorder, in young people under 18;
antisocial personality disorder, in adults;
and psychopathy, also in adults.
These definitions tend to be relevant to less than 5–10% of the population, depending on age.
Such mental disorders are typically measured as diagnostic categories (either presence of the criteria of the disorder, or not).

Слайд 14

Criminologists conceptualise antisocial behaviour as one that is against the law.
As

a result, their definitions do not require there to be serious harm, a variety of acts or persistence. In practice most criminologists apart the minor one-off offender and proficient or persistent recidivists.
These legal definitions tend to apply to between 20–30% of the population, depending on age. These constructs are sometimes measured as legal categories (either the individual has been convicted at court, or not).
Personal psychologists consider antisocial traits in terms of attitudes, beliefs, interests, and preferences that indicate a tendency to take advantage of or harm others, or a willingness to break the law. As a result, their definitions do not describe that any anti-social act has occurred.
The main labels assigned are hostility, which relates to character, socialisation (includes level of conscientiousness and honesty) or aggression.
Definitions of personality traits tend to be relevant for the entire population; the upper limit of the “aggression” scale may indicate enthusiasm for aggression, while the lower limit may indicate timidity.

Слайд 15

Estimates of heritability for antisocial behaviour from recent research in quantitative

genetics cluster around 0.50.
The most reliable estimates come from contemporary studies in the Netherlands, Britain, Norway, Sweden, Australia and the US, because these studies examine large, representative samples using sophisticated quantitative modelling techniques.
A complementary meta-analysis of 51 twin and adoption studies yielded an estimate of heritability of 0.41 for the genetic influence on antisocial behaviour (Rhee, Waldman, 2002).
Subsequent studies will help find out how the environment of young people interacts with their genetic vulnerability, exacerbate or protect them from the risk of antisocial behavior.
Since the ‘crime’ itself is not inherited, researchers are working to find out which personality and cognitive features may be associated with anti-social behavior.

Слайд 16

Heredity and sexual orientation
There has always been a significant interest in

the biological explanations of homosexuality, as well as in other aspects of human behavior.
Until the 1970s, homosexuality was classified as a mental disorder in many western countries, which meant that many studies focused on the development of 'cures' for the 'disease'.
Today, the vast majority of countries do not classify homosexuality as a disorder.
However, attitudes to homosexuals are often negative, hostile and discriminatory, and there are more than 40 countries in Africa, Asia, Europe, the Middle East and Americas, where homosexual behavior remains illegal and in some is punished by death.
There remains a significant debate about whether sexual orientation is a matter of choice and whether it is possible to change one’s sexual orientation.

Слайд 17

Theoretically, there are many ways of the biological characteristics influence to

sexual orientation.
For example, they can directly impact this by affecting the physical development of the brain.
Alternatively, they could operate indirectly by influence to personality and temperament, which in turn could affect an individual’s development and interaction with environmental factors.
These biological influences need not be genetic, they could be chemical or hormonal. However, it should be remembered that the control of hormones is largely mediated through genetic factors.
The rate of homosexual orientation in the general population has been variously estimated between 2% and 10% depending on the criteria used, with 4–5% being the most common estimate for males, and around 2–4% for females (Le Vay, 1993).
Calculations of the rate of homosexuality are made difficult by the fact that some individuals may not wish to disclose their sexual orientation to a third person, and because of the various ways in which sexual orientation can be defined and measured.

Слайд 18

A number of studies have calculated the rate of homosexual orientation

among siblings where one is homosexual (Bailey, Pillard, 1995).
Most studies show that the rate of brother's homosexuality appears to be around 9%, though one study found a much higher rate of 22%.
The rate of homosexuality among the sisters of a homosexual brother appears to be around 5%.
Findings of the rate of homosexuality among the sisters of a homosexual female range from 6% to 25% (Pillard, Weinrich, 1986 ).
The rate of homosexuality among the brothers of a homosexual female appears to be around 10%.
These results indicate that homosexual males may be more likely to have homosexual brothers than sisters.
Homosexual females may be more likely to have homosexual sisters than brothers.
This suggests that the factors influencing homosexual orientation may be different in sexes.

Слайд 19

The findings in the area of research into sexual orientation has

led some commentators to conclude that hormones have a key role in sexual orientation: ‘The “gay gene” … is widely expected to turn out to be a series of genes that affect the sensitivity of certain tissues to testosterone‘ (Ridley, 1993).
A fundamental conceptual difficulty in this field is a question whether are there two or three distinct categories of sexual orientation or is there a spectrum of orientation?
Another problem is that there is no consensus about whether homosexuality in men and women is the same type of trait or has the same origin in both sexes.
All of these uncertainties contribute to inconsistencies between research projects that make replication and comparison difficult and allow large differences in the interpretation of results.

Слайд 20

An often made argument against the likelihood that homosexuality is of

genetic origin is that such genes do not “survive” evolutionarily, since gay couples usually have no children.
Various possible explanations for the survival of genes that affect homosexuality have been proposed.
One of them is that the gene or genes in question have a beneficial effect on the fertility of women, which means that women with the corresponding genes are likely to have more children.
Another possibility is that the genes are part of the female mitochondrial DNA. If this were so, they would be inherited by both male and female offspring, but only the offspring of the female could reproduce.
As a result, reduced competition for resources among the extended family could contribute to the reproductive success of women (Ridley, 1993).

Слайд 21

Another suggestion is that homosexual family members contribute to the reproductive

success of an extended family by assisting with raising offspring.
Finally, it has been proposed that homosexuality may be associated with another trait which is linked with improved reproductive success.
It should be recognized that all these hypotheses are basically assumptions: it is extremely difficult to guess how evolution can work in relation to a particular genetic variant.

Слайд 22

If it possible to change?
Methods in behavioural genetics

Слайд 23

There are some possible ways of impact on human traits to

correct them tenderly. They are genetic, medical or environment interventions.
Genetic interventions
Genetic interventions can be of two types, depending on the cells in the body to which they are applied.
Somatic gene therapy is the process of changing the genotype of an individual by modifying the DNA in the cells of their body. This type of therapy is currently being studied as a potential cure for genetic disorders such as haemophilia and cystic fibrosis.
The aim is to replace, in the relevant parts of the body, the mutated DNA that causes the disease. For example, a person with cystic fibrosis might receive gene therapy that was targeted at the lungs.
An individual who has received this type of gene therapy would, however, be unlikely to pass on the genetic changes to their children, because the therapy would not affect the cells that are important in reproduction, namely the egg and sperm cells.

Слайд 24

The second type of gene therapy is called germline gene therapy

(it is also referred to as germline genetic engineering). This involves modifying the germline cells, those are transmitted to children by their parents.
Thus, germline gene therapy would change not only the characteristics of the individual who received the therapy, but also the characteristics of their children and future generations.
There is a general consensus that, at present, the consequences are not well enough understood for this procedure to be attempted safely, and thus that germline gene therapy should not currently be attempted.

Слайд 25

Medical interventions
It seems more likely that if new interventions aimed at

changing behavioural traits in the normal range are developed as a result of research in behavioural genetics, they will take the form of drugs, or of environmental interventions such as changes in diet or in social policies.
Medicines such as anti-depressant drugs and substances that claim to alleviate shyness are already in use, and it may be that additional medicaments will be developed that can alter normal behaviour.
Predictions that there will be medicines to enhance our memories, improve our cognitive function, or change our personalities are often made when scientists, journalists and others speculate on future advances.
Research in behavioural genetics might lead in this direction by suggesting which genes might be the best targets for new drugs.

Слайд 26

Environmental interventions
The third type of intervention involves environmental strategies for changing

behaviour.
We already have some clear examples of such interventions. For example, it seems likely that improving the diet and standard of living of children also improves their IQ.
There is also good evidence that exposure to chemicals such as lead (Pb) can adversely affect behavioural traits.
Other social policies such as the provision of free education and schemes such as Sure Start (a programme run by the UK Government that aims to improve the physical, social and intellectual development of babies and young children) are specifically premised on the capacity to change or enhance various traits in the population.

Слайд 27

Methods in behavioural genetics. Behavioural genetics and practical facets

Содержание

Heredity and intelligencePsychologists measure intelligence using a range of tests called

However, IQ tests come in a variety of forms. Some require

One of implications now accepted by most testers of IQ, is

Adoption studies have also provided evidence for genetic influences on IQ

Heredity and personalityThe dominant view at present is that the number

It is known that a large number of genes affect the

Heredity and antisocial behaviourConcerning crime and antisocial behaviour it is widely

Criminologists conceptualise antisocial behaviour as one that is against the law.As