Genes and Personality Workshop Scheme (notes and
materials)
Context
The aim of this workshop is to stimulate thought and discussion about reductionist positions
that exist/are assumed to exist in science. A key outcome of this workshop is to introduce
young people to the notion that a plurality of views exist on this matter.
Genetics has become an important area in which reductionist thought holds sway in some
quarters amongst biologist but also, more importantly, amongst non-scientists and in the
presentation of genetics in the popular media. The narrative example that will be used here to
open the dialogue is from a popular drama series and draws on the increasing field of
behavioural genetics in which individual genes, or groups of genes, are being linked with
often complex behaviours, including: musical ability, happiness, voting patterns, sexuality,
depression and risk taking. One such gene produces the monoamine oxidase (MAOA)
enzyme which is important in the transmission of nerve impulses. Too little of this enzyme
has been linked to increased aggression and the allele (variant) responsible for this (MAOAL) has become termed the “Warrior Gene” because of this possible link to greater levels of
aggression
The story of Jono is presented in which his actions are linked to the “Warrior Gene” and
some initial points for discussion are offered to allow young people to consider the issue of
responsibility, what they think the programme makers were trying to show and to invite them
into the courtroom and decide what further information they would like to know.
Introduction
Introduce the session and incorporate the following points to orientate the students:
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In trying to understand what it is to be human one of the important aspects is our
genetic make-up.
What we want to think about in this session is how important our genes are when we
are thinking about how we behave – are they all we need to know? Are they
unimportant? Are they part of a bigger story?
We will look at a couple of crimes and then look at some evidence to decide if genes
were important in these cases.
Our first case will be the story of Jono…
Offering school students the Jono story as a discussion activity to prompt them thinking
about personality.
Jono Story:
Offer the students the Jono story text and invite them to read through. (should only take 2-3
mins)
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First question: Is Jono responsible for what he’s done?
a. Depending on group numbers it will probably be best to give them a couple of
minutes to ‘think-pair-share’ with a partner before taking answers in the wider
group.
b. Probe: if answers come back as simply ‘yes’ or ‘no’ ask them to share why
they hold the position that they do.
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Second Question: What do you think the producers of the TV programme were
trying to get us to think?
a. Think, pair, share.
b. If they struggle with this question a possible re-frame might be “Why do you
think they chose this topic for a programme?”
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Third question. Invite them to think that they are members of the jury and thay
had the ability to ask for more information before they made their decision.
What witnesses would you like to call and what questions would you like
answered?
a. Invite them to think through the information they need to come to a decision,
who might provide it, how much detail they might need.
Activity
The aim of this activity is to introduce the notion of dynamic systems and the regulation role
of enzymes, in particular to visualise the role of MAOA in the transmission of nerve
impulses. Students will be placed into groups, at least two. Each team will then be split into
“forwards” and “backwards” teams. Their task of the forwards team will be to carry balls
from the start to the finish bucket. The task of the backwards team will be to take them out of
the finish bucket and put them back into the start bucket. In one group the forwards team can
be more or less equal in numbers to the backwards team but in the other there should be an
imbalance with a greater number (say 2:1) in the forward team.
Place the start and finish buckets as far apart as possible. Establish that within a group they
need to move in an up lane and a down lane, to avoid collisions. Give them a set time (60-90
seconds should be enough and say there will be a prize for the team that gets the most into
their target bucket (you could give two prizes – one for the most in a start bucket, one for the
most in a finish bucket).
The aim here is to show how quickly a small imbalance can lead to a major difference in
outcome. We will use this to lead into thought on the nature of transmission of nerve
impulses and the potential impacts of low levels of MAOA on behaviour.
Supporting Material for the role of MAOA in transmission of nerve impulses and
linking it with the ball game above.
Below is a brief description of the role of MAOA in the transmission of nerve impulses
across synapses. Students could be given this to read or have it presented to them in a brief
talk. The image at the bottom is of a synapse and could be used as a visual aid in
communicating what happens at a synapse.
This can be used to expand on the principle looked at in the ball game.
The ‘Warrior Gene’ – some background information
How the brain works and what makes us behave the way we do is a complex process but one
thing that does seem pretty clear is that our nerves have a big part to play, whether they are in
our brain or elsewhere in the body.
Nerves – it’s the gaps that are important!
The way impulses are transmitted along nerves is electrical but is different from the
electricity that runs through our mains circuits at home. The impulses along our nerves can
be seen as more like a line of dominoes that topple when someone pushes the first one over.
If there is nothing to stop the line toppling it will just keep going. This is why people put
breaks in lines of dominoes until the very last minute when they attempt records. In a similar
way, if our nerves were just unbroken wires that transmitted every impulse completely we
would be soon overwhelmed with information – a gentle breeze moving our hair would feel
just the same as hitting our thumb with a hammer! We simply couldn’t cope. To prevent this
we have a system that regulates whether an impulse is passed along a chain of nerve cells and
that place where this happens is at the point where the nerves meet – the Synapse.
Where two nerve cells meet there is a gap. For the message of the impulse to be carried
across this gap, and to ‘tip’ the next line of dominoes, the cell carrying the impulse produces
chemicals called neurotransmitters that cross the gap and fit into ‘receptors’ on the other side.
If enough transmitters are produced and make it to the receptors then the impulse is fired on
the other side and the impulse passed on. The number of impulses we receive can influence
the amount of pain, heat, pressure or pleasure we experience. Also, the number of impulses
in the cells in our brain affect the intensity of feelings we have, such as happiness, sadness
and anger. The ability of the transmitters to pass the message across the synapse is very
important in how we experience the world and how we feel about it.
There a many different types of transmitters and each person has different levels of them at
different times. This can affect our moods and the functioning of these transmitters is linked
with conditions like depression. They can also affect our levels of anger, aggression or fear.
If you are threatened your body produces increased levels of nerve impulse to help you fight
or run away.
To help control things at the synapse you also produce some enzymes, chemicals whose job it
is to break down the transmitters to prevent them building up to the point where your nerves
keep firing and to help recycle the chemicals in the transmitters. A very important enzyme
that does this is called MAO-A. This enzyme keeps nerve transmission in balance and it has
been found that too much of the enzyme is linked with depression, as not enough impulse
occur, and too little of the enzyme can lead to increased levels of aggression and risk taking.
Importantly, it does seem that higher levels of aggression associated with this enzyme are on
significant when combined with a history of abuse in childhood.
Every enzyme in our body is produced from a template held in our DNA that is found in
every cell. It has been found that some people have a variation of the gene that produces a lot
less of MAO-A than normal (MAOA-L). This doesn’t mean that they don’t produce it but
that a piece of DNA (a promoter region) nearby that acts to help start the production of the
enzyme isn’t as efficient at starting the process. This means that people with the variation
produce MAO-A less quickly and so when there is a high demand, such as in situations of
stress or fear, this can lead to transmitters being produced faster than the enzyme can break
them down. In such situation these people are less likely to be able to control their nervous
responses and may act in more extreme ways. For this reason the variation in the gene has
been called the ‘Warrior Gene’.
Research has indicated that when people with the ‘warrior gene’ are given the chance to
punish people for wrongdoing they will do so more severely (see paper in handout pack). An
interesting phenomenon is that at low levels of stimulus (i.e. small theft levels) they show no
difference from those with high levels of MAOA (i.e. those with the MAOA-H variant) but at
higher levels of stimulus they show much higher levels of punishment. This is predictable as
they do produce some MAOA but are unable to produce more quickly when under higher
demand conditions. This would suggest a range of response depending on the level of
MAOA present and the level of stimulus. A ‘tipping point’ for each individual may therefore
exist and this can be expected to follow a bell-shaped curve pattern. For those with MAOAL we can expect the tipping point, on average, to be lower than for those with MAOA-H.
Discussion Points:
Do you think that this one change in body chemistry can make enough difference in our
behaviour and choices to mean that we can’t make choices freely?
The link between higher levels of aggression and the gene only seem to occur when there is
also a history of abuse in childhood? Do you think we can still link behaviour to the gene if a
persons history can have such an effect?
There is a difference of opinions in the media over whether having the ‘Warrior Gene’ is
enough reason to reduce someone’s responsibility for their acts.
Case Study: A bit like the story of Jono, a real life case from the United States. Bradley
Waldroup was convicted of murder but his defence successfully argued against the death
penalty on the basis that he had the Warrior Gene and had been abused in childhood.
In the pack are some articles that are for and against this outcome.
Discussion Point:
Having seen this evidence. Do you believe in Warrior Genes? Can they be enough to
explain aggressive behaviour?
What do you think about the way the science is reported in the different articles?
Discovering the notion of ‘environment’ in genetic studies
In the functioning of the MAOA gene and the cases above we have touched on the idea that
‘environment’ can be an important factor in the way genes work, and so possibly affect our
behaviour.
Quick think: get students to think-pair-share what sort of things in the ‘environment’ might
affect how genes work.
Aim: to recognise that environment has a broad definition in terms of the interaction with
genetics. At this point try to introduce the notion of Free Will and culture as a possible
environmental factor. Also, that genes interact and so any one feature (whether physical or
behavioural) is rarely controlled by a single gene.
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Students are encouraged to find out more about what ‘environment’ in this context
means:
o Influences of sibling interactions?
o The moderating effects of parents?
o What we choose (for example where we choose to go)?
Some remarks about the notion of environment:
o In ‘genes and the environment’ language, environment includes anything apart
from genes effect
o Environment has a broad sense.
o Environment may include Culture and Free will.
o Environment in its broad sense has a significant role in shaping personality.
o The idea of one gene, one trait is not quite useful. There are not many
monogenic traits (A monogenic trait is one which is encoded by a single gene.
e.g. - cystic fibrosis in humans).
o Most of the time a trait is determined by a combination of genes (polygenic)
that interact with environment in its broad sense
Activity: Look at the Daily Mail and Daily Telegraph reports on ‘nature and nurture’ in
personality. (see below)
Discussion: Is there much difference between saying ‘nature’ or ‘nurture’? Don’t they both
suggest that something other than free will if controlling our behaviour?
More about ‘free will’
 Scientists cannot tell whether free will exists or not, maybe because of the following
reasons:
o It is unethical to do the kind of experiment that restricts people’s choices
(ethical issue)
o It is too complicated (practical issue)
o It may be beyond science to investigate, may be something not testable
(methodological issue)
o Remember: Environment includes aspects of life that may be related to free
will.
Discussion: From what we have thought about so far, how do you think Free Will fits into
the way we behave?
The bread metaphor, recipe for a human
One possible way of thinking about the roles of genes, environment and free will is to
think about our personalities and behaviour like bread:
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The ‘flour’ of genetics, the ‘water’ of the environment, the ‘yeast’ of agency and the
heat of development makes the bread, bread
Not all of the ingredients are apparent in the finished product (where is the yeast in
the bread? Where is free will?), but all are essential:
o No flour, no bread!
o No water, no bread!
o No yeast, no bread!
We are vastly more complex than a bread!
The bread as a whole has emergent properties which are non-reducible to its initial
components; similarly our personality is not reducible to our genes or other elements.
Five guidelines to avoid misconceptions about genetic findings (take home messages):
1. ‘Environment’ in its widest sense has a key role.
2. Environment-Gene interactions are important.
3. Usually, no individual gene contributes in major way.
4. Genetics does not say that our genes determine our personality, that is Geneticism!
5. The question of the existence of free-will is beyond the scope of Genetics
Final Question:
Going back to the story of Jono, now that you’ve though about these things. If you were in
the jury, would you find him guilty or not guilty?
Additional Activity after session:
Look through the scientific papers looking at genes and different forms of behaviour.
Do you think they indicate that genes are the main factor in our behaviour?
Can science, maybe not now, but in the future, tell us everything about personality?
Bradley Waldroup Case
https://www.psychologytoday.com/blog/the-human-beast/201007/pity-the-poor-murderer-hisgenes-made-him-do-it
Pity the poor murderer, his genes made him do it
Did his genes make him murder?
Post published by Nigel Barber Ph.D. on Jul 13, 2010 in The Human Beast
A criminal defense attorney has many arrows in his/her quiver. The latest is the "warrior
gene." Having this gene saved Bradley Waldroup from a first degree murder conviction.
The charges stemmed from a bloody rampage in which Waldroup shot his wife's friend Leslie
Bradshaw, eight times, killing her before attempting to kill his wife by chopping her up with
a machete.
Waldroup had been drinking as he waited for his estranged wife and their four children who
were to spend the weekend at his trailer home in the mountains of Tennessee. When his wife
said that she was leaving with her friend, he removed the key from Penny Waldroup's van to
ensure that they could not leave, thereby establishing criminal intent. Waldroup then
launched his deadly attack on the pair.
The "warrior gene"
Waldroup's defense attorneys ordered a test and established that he had the warrior gene. Like
most such biological defenses, there is a germ of scientific truth combined with a hefty dose
of junk science, including clever labeling. The warrior gene might be called other things,
such as the gambling gene, the depression gene, the irritability gene, or, even the live-in-atrailer gene because its effects are contingent on an abusive childhood.
The scientific rationale for diminished responsibility is that a variant of the relevant gene,
known as MAO-A is linked to an under active prefrontal cortex, this being a key area of the
brain that inhibits antisocial impulses. The gene is also associated with antisocial behavior in
European Americans (but not others) but only if they were abused as children (1).
The gene has recently acquired some evidence linking it to impulsive aggression. In an
experiment where subjects were provoked by having money winnings taken from them,
people with the MAO-A variant proved slightly more vengeful but only if they lost the higher
of two amounts of money(2). They asked for the provoker to drink a larger amount of hot
sauce as punishment. Whether this experiment is more relevant to homicidal aggression, or
sensitivity to the taste of hot sauce is anybody's guess.
So far, a skilled defense lawyer might weave a tale that the bad gene had gotten the better of
the European American defendant. The key scientific problem is that about 34 percent of
Europeans have the warrior gene. Yet, homicide is extremely rare at a population level with
only about one person in 100 committing a homicide during their lives. If the gene were used
to predict homicide, it would be wrong more than 33 times for every one occasion that it was
right (3).
Just the facts
This brings us back to the Waldroup case tried in March, 2009, where the warrior gene
formed the kernel of a diminished responsibility defense. This defense received enthusiastic
endorsement in a recent NPR report by Barbara Bradley Haggerty ("Can Your Genes Make
You Murder (link is external)?")
Waldroup's defense was not a simple genetic defense because it was combined with the
normally ineffective abuse excuse. Defense expert William Bernet of Vanderbilt University
argued that the combination of the warrior gene and being abused as a child was a dangerous
cocktail that increased the likelihood of committing a violent offense.
Some of the jurors were persuaded by this defense. According to one, Debbie Beatty: "A
diagnosis is a diagnosis, it's there. A bad gene is a bad gene."
Junk science is also junk science. There is no getting away from that either, especially if it
helps the defense to save a defendant's life.
1. Crampton, P., & Parkin, C. (2007, March 2). Warrior genes and risk-taking science.
Journal of the New Zealand Medical Association, 120 (1250).
2. McDermot, R., et al. (2009). Monoamine oxidase A gene (MAOA) predicts behavioral
aggression following provocation. Proceedings of the National Academy of Sciences, 106,
2118-2123.
3. Caspi, A. et al. (2002). Role of genotype in the cycle of violence in maltreated children.
Science, 297, 851-854.
Npr (national public radio) website and radio report
http://www.npr.org/templates/story/story.php?storyId=128043329
When the police arrived at Bradley Waldroup's trailer home in the mountains of Tennessee,
they found a war zone. There was blood on the walls, blood on the carpet, blood on the truck
outside, even blood on the Bible that Waldroup had been reading before all hell broke loose.
Assistant District Attorney Drew Robinson says that on Oct. 16, 2006, Waldroup was waiting
for his estranged wife to arrive with their four kids for the weekend. He had been drinking,
and when his wife said she was leaving with her friend, Leslie Bradshaw, they began to fight.
Soon, Waldroup had shot Bradshaw eight times and sliced her head open with a sharp object.
When Waldroup was finished with her, he chased after his wife, Penny, with a machete,
chopping off her finger and cutting her over and over.
"There are murders and then there are ... hacking to death, trails of blood," says prosecutor
Cynthia Lecroy-Schemel. "I have not seen one like this. And I have done a lot."
Prosecutors charged Waldroup with the felony murder of Bradshaw, which carries the death
penalty, and attempted first-degree murder of his wife. It seemed clear to them that
Waldroup's actions were intentional and premeditated.
"There were numerous things he did around the crime scene that were conscious choices,"
Lecroy-Schemel says. "One of them was [that] he told his children to 'come tell your mama
goodbye,' because he was going to kill her. And he had the gun, and he had the machete."
A machete that Bradley Waldroup used to wound his estranged wife. At right is the Bible
Waldroup had been reading before his wife and her friend arrived at his home.
Police crime scene image from the 10th District Police Department in Cleveland, TN
It was a pretty straightforward case. Even Waldroup said so during his trial last year. He said
on the murderous night, he just "snapped," and he admitted that he killed Leslie Bradshaw
and attacked his wife. "I'm not proud of none of it," Waldroup said.
"It wasn't a who done it?" says defense attorney Wylie Richardson. "It was a why done it?"
A Dangerous Mix
Richardson says he realized that the testimony at trial would be "very graphic." The defense
team, he says, did not try to dismantle the graphic evidence but rather sought to "give a
broader and fuller picture of what that was."
How to do that? The answer, it turned out, lay in Bradley Waldroup's genes.
Immediately, Richardson went to forensic psychiatrist William Bernet of Vanderbilt
University and asked him to give Waldroup a psychiatric evaluation. Bernet also took a blood
sample and brought it to Vanderbilt's Molecular Genetics Laboratory. Since 2004, Bernet and
laboratory director Cindy Vnencak-Jones have been analyzing the DNA of people like
Waldroup.
They've tested some 30 criminal defendants, most of whom were charged with murder. They
were looking for a particular variant of the MAO-A gene — also known as the warrior gene
because it has been associated with violence. Bernet says they found that Waldroup has the
high-risk version of the gene.
"His genetic makeup, combined with his history of child abuse, together created a
vulnerability that he would be a violent adult," Bernet explains.
Over the fierce opposition of prosecutors, the judge allowed Bernet to testify in court that
these two factors help explain why Waldroup snapped that murderous night.
"We didn't say these things made him become violent, but they certainly constituted a risk
factor or a vulnerability," Bernet says.
Bernet cited scientific studies over the past decade that found that the combination of the
high-risk gene and child abuse increases one's chances of being convicted of a violent offense
by more than 400 percent. He notes that other studies have not found a connection between
the MAO-A gene and violence — but he told the jury that he felt the genes and childhood
abuse were a dangerous cocktail.
"A person doesn't choose to have this particular gene or this particular genetic makeup,"
Bernet says. "A person doesn't choose to be abused as a child. So I think that should be taken
into consideration when we're talking about criminal responsibility."
i
A jury was asked to weigh genetic evidence in the case against Bradley Waldroup, accused of
murder and attempted murder. A forensic psychiatrist testified that Waldroup carried a gene
associated with violence.
Genetics, Or Smoke And Mirrors?
The genetic testing was only one piece of Waldroup's defense. His attorneys also argued that
Waldroup was depressed, suffered from "intermittent explosive disorder" and acted in the
heat of passion. Still, defense co-attorney Shari Tayloe Young says the genetic evidence was
critical.
"I think if that wasn't out there, then all the jury would have seen are all these terrible pictures
where he took a machete and hacked at his wife," she says. "And they would have thought,
he's the worst of the worst, and that's what the death penalty is for — the worst of the worst.
But because they heard all the mental issues, they understood what was going on in him and
understood why he did what he did."
Prosecutor Drew Robinson thinks this genetic evidence is "smoke and mirrors," aimed at
confusing the jury.
"The more of this information that you put before a jury, the [greater the] chances of
confusing them and drawing their attention away from the facts and onto some other aspects
of the case," Robinson says. "You always run that risk. And I just think that's asking the jury
to grasp ahold of a little bit too much."
To rebut Bernet's testimony, Robinson called in his own expert: psychiatrist Terry Holmes,
the clinical director of Moccasin Bend Mental Health Institute in Chattanooga, Tenn. Holmes
urged the jury to ignore it.
"This was somebody who was intoxicated and mad and was gonna hurt somebody," Holmes
says. "And it had little to nothing to do with his genetic makeup."
Holmes says it's way too early to use this research in a court of law. And he believes Bernet
is spinning the data.
But jurors say they weren't spun. Sheri Lard, one of the 12, says it was just one piece of
evidence that weighed heavily for some — and for others, not at all.
"We had your good old boys who wanted to stick it to him," Lard says, laughing. "You had
your grandmother types who felt sorry for him. And then you had the medical ones. The
medical ones were the ones who wanted to do due diligence."
Genetic Evidence A Factor
But Lard says the genetic evidence did figure into a major decision — whether to find
Waldroup guilty of murder and impose the death penalty. The jurors concluded that his
actions were not premeditated and agreed with the defense argument that Waldroup just
exploded.
"I remember when we were talking as a jury, the comment was brought up, 'You know, if I
were in this situation, I would snap.' But there was more to it. There was more to his whole
life that led to that moment," Lard says.
Including his genes?
"Oh I'm sure," Lard says. "And his background — nature vs. nurture."
Psychiatrist Terry Holmes says it's too early to use this kind of genetic evidence in a court of
law, and testified that Waldroup was simply drunk and mad. The attacks "had little do with
his genetic makeup," Holmes says.
Another juror, Debbie Beaty, says the science helped persuade her that Waldroup was not
entirely in control of his actions.
"Evidently it's just something that doesn't tick right," Beaty says. "Some people without this
would react totally different than he would."
And even though prosecutors tried to play down the genetic evidence, Beaty felt it was a
major factor.
"A diagnosis is a diagnosis, it's there," she says. "A bad gene is a bad gene."
After 11 hours of deliberation, the jury convicted Waldroup of voluntary manslaughter — not
murder — and attempted second-degree murder.
Prosecutor Drew Robinson was stunned.
"I was just flabbergasted. I did not know how to react to it," Robinson says.
Nor did fellow prosecutor Cynthia Lecroy-Schemel. She worries that this sort of defense is
the wave of the future.
"Anything that defense attorneys can have to latch onto to save their client's life or to lessen
their client's culpability, they will do it," Lecroy-Schemel says.
Waldroup's attorney, Wylie Richardson, says she's right.
"I would use it again" under the right circumstances, he says. "It seemed to work in this
case."
The judge in the case sentenced Waldroup to 32 years in prison. At the hearing, Judge Carroll
Ross told Waldroup he should think twice about appealing. The state might not mind trying
this again and asking for the death penalty, the judge said. You might not be as fortunate with
a jury the next time.
Scientists and legal experts expect to see more cases like this as neuroscience makes inroads
into the courtroom, and presents guilt and innocence — not in terms of black and white —
but in shades of gray.
Daily Mail
Is personality determined by nature or
nurture? New research suggests
environment is stronger than genes
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Personality traits are inherited through observed
behaviour, not genetics
Foster parents have greater influence on personality
development than birth parents in zebra finches
Study raises questions about the inheritance of
personality in humans
By Nicola Rowe
Published: 23:00, 4 June 2013 | Updated: 23:00, 4 June 2013
The debate over whether nature or nurture defines personality has taken a
further twist after scientists found foster parents have a greater impact on
personality than directly inherited genes from parents.
Researchers at the University of Exeter and the University of Hamburg used
the zebra finches to investigate how personality is transferred between
generations.
They found that foster parents have a greater influence on the personalities of
fostered offspring than the genes inherited from birth parents.
The zebra finch has shown that personality is environmentally-determined, not based on
genetics
''This research shows that personality variation can be more
rapidly transmitted across generations than previously thought' Dr Nick Royle
The research measured personality by placing the zebra finches in a new
environment and counting the number of features they visited.
Some were shy, staying mainly in one place while others explored widely
demonstrating a more outgoing personality. Male and female birds were then
paired up and allowed to breed.
Each clutch of eggs was fostered by another pair just prior to hatching.
Offspring personality was measured once they were adults.
Offspring size was also measured and was found to be primarily genetically
inherited and not significantly influenced by foster parent size.
Dr Nick Royle from the University of Exeter said: 'This is one of the first
experiments to show that behaviour can be non-genetically transmitted from
parents to offspring.
Researchers found that foster parents have a greater influence on the personalities of fostered
offspring than the genes inherited from birth parents
NATURE OR NURTURE - WHAT IS IT?
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'Nature' refers to your innate qualities - 'wired in' traits that occur
without having to think about them
Focuses on genetically and neurologically-based behaviour
'Nurture' refers to the needs we develop based on our surroundings
Believes that all behaviour is learned from our environment
Our study shows that in zebra finches, personality traits can be transmitted
from one generation to another through behaviour, not just genetics.'
Speaking to MailOnline, Dr. Royle said, 'It's important to understand more
about the mechanisms underlying the inheritance of personality.
'Most previous studies have found personality to be genetically heritable, but
few studies have looked at the potential for personality to be non-genetically
transmitted.
'Our research findings are therefore surprising because they show that, for
zebra finches, personality is primarily determined by the environment they
experience after hatching.
'We know this because we cross-fostered eggs just before hatching, so any
genetic parent effects on personality were limited to the time before
hatching.'
He added: 'Although this study considers personality inheritance in zebra
finches, it raises questions about the inheritance of personality in other
species, including humans.
'Do adopted children inherit the personality characteristics of their birth
parents or their adoptive parents? Is the environment more important than
genetic inheritance in the development of personality? '
The research was published in the journal Biology Letters.
Daily Telegraph
It's nature, not nurture: personality lies in
genes, twins study shows
Nature rather than nurture is responsible for creating
your personality, according to a study of twins which
found that character is something you are born with.
Researchers studied sets of twins to learn whether genetics or upbringing has a greater effect
on how successful people are in life Photo: REX
By Nick Collins, Science Correspondent
16 May 2012
Genes play a greater role in determining key personality traits like social skills and learning
ability than the way we are brought up by our parents, researchers claimed.
The findings contradict the existing belief among psychologists that the environment we
grow up in plays a larger role than genetics in shaping our personality.
Researchers from Edinburgh University studied more than 800 sets of identical and nonidentical twins to learn whether genetics or upbringing has a greater effect on how successful
people are in life.
Twins are useful in such studies because almost all twins share the same home environment
as each other, but only identical twins share exactly the same genetics.
Participants were asked a series of questions about how they perceive themselves and others,
such as "are you influenced by people with strong opinions?"
By applying their answers to a well-established scale of psychological scale, researchers
could assess and categorise different personality traits for each person.
Writing in the Journal of Personality, the researchers found that identical twins were twice as
likely as non-identical twins to share the same personality traits, suggesting that their DNA
was having the greatest impact.
Genetics were most influential on people's sense of self-control and also affected their social
and learning abilities and their sense of purpose.
Prof Timothy Bates, who led the study, said: "Previously, the role of family and the
environment around the home often dominated people's ideas about what affected
psychological wellbeing. However, this work highlights a much more powerful influence
from genetics."
The study was focused on personality traits which contribute to our chances of success in life
by dictating whether, for example, how determined we are to overcome challenges.
Prof Bates said: "If you think of things that people are born with you think of social status or
virtuoso talent, but this is looking at what we do with what we've got.
"The biggest factor we found was self control. There was a big genetic difference in [people's
ability to] restrain themselves and persist with things when they got difficult and react to
challenges in a positive way.