Week Eight - Genes Flashcards
Genes
General Information..
We have seen how evolution can provide a framework for understanding human behaviour: now we will take a brief look at how genes provide the link between evolution and the biological factors that more directly underlie criminal behaviour
The debate over the importance of genes in behaviour has always been intense, from the eugenics movement at the start of the twentieth century right through to the present. Critics, some from within biology, have attacked the implication that genes largely determine our behaviour as well as the interpretation of the data from some of the methods that form the cornerstone of the genetic approach
For most of the twentieth century the ‘nature versus nurture’ debate in which one side argued that biology, especially genes, determined our behaviour and the other that the environment determine how we behaved, was how disagreements were presented
More recently it has become clear that the evidence makes sense only if the biosocial interaction model is used (Raine, 2002).
No serious biologists think that there is ‘a criminal gene’: they are looking for genes that make criminal behaviour more probable. If genes can influence our impulsivity and we know impulsivity makes you more likely to become an offender (Morgan and Norris, 2010) then those genes increase the probability that you will perform criminal acts
We now have compelling evidence that genes are important in establishing the likelihood that we will display particular anti-social and criminal behaviour
The combination of sustained criticism and improved understanding has resulted in the recognition that the impact of genes depends on the social and physical environment that the person lives in
Investigating the contribution genes make to a behaviour also reveals the importance of the environment
Behavioural Genetics
What does Behavioral Genetics try to identify..
Behavioural Genetics tries to identify how important genes are, in particular behaviours using methods that rely on comparing how similar different relatives are on that behaviour.
Behavioural Genetics
Explanations..
Different relatives share different, predictable proportions of their genes. Humans share about 99 percent of their genes because most are for crucial biological systems such as your heart and liver. Humans all need genes to do the same tasks, so we may all seem to have the same set of genes. However, remember that there will be a variety of versions of the same gene so we will end up with different genotypes.
Almost all genes we have do not appear to be relevant to how likely we are to be anti-social or criminal; that leaves a much smaller number where variations in the versions, alleles, that we inherit may alter our predisposition to criminality. If you share half of your alleles in general with a relative then you will also be likely to share half of those alleles relevant to criminal behavior
Identical twins share all their genes; non-identical twins and other brothers and sisters share half their genes; parents share half their genes with each child; an aunt or uncle shares 25 percent of their nieces or nephews genes and so on.
This means that by studying families we can compare how similar they are on, say, having a criminal record and see whether those who share more genes are also more alike in criminality
Genes are more important in males than females. Perhaps this is because of the genes are on the Y sex chromosome that only the male inherits. Or maybe there is less reproductive advantage in females in carrying these genes and therefore female adult criminals are more likely to behave like that either because of biological damage or because of their past or present environment
In summary the genes you inherit do put you at more or less risk of anti-social and criminal behaviour but their impact depends on the environment you grow up in
Behavioural Genetics
Evidence..
Twin studies have shown that genes are relevant to anti-social and criminal behaviour. If we ignore those with small sample sizes (as a rule the larger the sample the more valid the results) there are two early projects that stand our: Dalgaard and Kringlen (1976) and Christiansen (1977). They both compared identical twins and non-identical twins on how alike each type of twin was on adult criminal behaviour. This similarity is called concordance, and can range from 0 per cent to 100 per cent. If we combine their results, the concordance for identical twins was 31 per cent and for non-identical twins was 12.9 per cent.
Cloninger and Gottesman (1987) added more subjects to Christiansen’s set and reanalysed the data. Now the concordance for identical twins for 74 per cent against 47 per cent for non-identical twins. This was then used to calculate the importance of genes in adult crime, also called its heritability. They found that 54 percent of the differences between adults in criminal behaviour were due to genetic differences
Osborn and West (1979) - 2/5 of boys whose fathers had criminal records had criminal records themselves (cfd 1/8 of boys whose fathers did not). But this isn’t evidence in itself. It could indicate environmental factors too (e.g. socialisation, peer group). Also 3/5 of the boys with fathers who had criminal records did not have criminal records themselves
There were also adoption studies. Bohman (1995) found that there was a 40% chance of a child developing a criminal record where the biological and adoptive parents had a criminal record and 12% where adoptive parents had no criminal record. There are some complications with adoption studies - adopted children were sometimes placed in environments similar to those they have been taken from, children not always adopted after birth, in early studies before easy genetic testing, potential for misclassifying twins and dispute about the nature of official data used
Genetics Influencing behavior
Researchers now looking at more indirect connections
Alcoholism - Genetic predisposition to alcoholism (Bohman, 1978)
ADHD - Maybe some genetic basis for ADHD and impulsivity (Sherman et al, 1997)
Schizophrenia - Genetic pre-disposition towards the illness. It’s onset is triggered when certain environmental factors are present (Ainsworth, 2000)
Molecular Genetics
What is Molecular Genetics?
Molecular genetics involves the use of sophisticated laboratory-based methods to identify precisely which genes, and which alleles, are linked to particular traits and behaviors.
This connects the findings of behavioural genetics to the functioning of brain systems and structures
Genes Connecting Criminal Behaviour to Serotonin Systems
Evidence and explanation..
Low serotonin activity has repeatedly been associated with criminality, for example conduct disorder (Coccaro et al, 1997), anti-social personality disorder (Dolan et al, 2002)and young adult offending (Moffit et al, 1998)
Other analyses have show a clear link between low serotonin and high levels of impulsive violence, with changing serotonin activity altering human aggression (Berman et al, 2008). Therefore, it is not surprising to find that genes involved in different aspects of serotonin function have been linked with various types of anti-social and criminal behaviour.
Genes Affecting Dopamine Function
Explanation..
The other transmitter system that has been researched with encouraging results is the dopamine system.
One part of the brain’s dopamine system is known to be involved in experiencing reward, or in the motivation to get a reward.
One type of transmitter will be used in several systems in the brain, each carrying out a distinct function. There are also several different receptor types for each transmitter, and we assume that these create different results in the neurons that carry them. The Dopamine 4 receptor (D4) has been implicated in characteristics relevant to criminal behaviour, with different versions creating different tendencies to act in particular ways.
Epigenetics
Explanations…
“The development and maintenance of an organism is orchestrated by a set chemical reactions that switch parts of the genome off and on at strategic times and locations”
Epigenetics is the study of these reactions and the factors that influence them
Epigenetics and the Environment - “The genome dynamically responds to the environment. Stress, diet, behaviour, toxins and other factors activate chemical switches that regulate gene expression”
Practical Implications..
There is already a genuine debate about using genetic information to show that an offender has a predisposition towards anti-social or criminal behaviour, and on that basis altering the sentence they receive.
We could intervene biologically by altering the diets of children with low levels of a transmitter and increasing the amount of the ‘building blocks’ of that transmitter, or the chemicals involved in making it.
