Thousands took the Gender Lab test, designed to work out what goes on in the minds of men and women. Here, psychologist Anne Campbell's reveals her analysis of the results of the experiment.

Have you taken the test yet!

What were all those tests and questions about?
There were 24 questions that assessed your self-control. This means your ability to withhold your real feelings or to fake emotions you don't really feel in order to avoid conflict with others. The questions looked like this:

In conversations, I sometimes blurt things out before I have thought them through.
[ ] Very true of me
[ ] Often true of me
[ ] Rarely true of me
[ ] Not at all true of me

We also asked you to do two computer-based games. These were tests of your ability to inhibit or check your desire to react 'automatically' to a stimulus. This is called cognitive inhibition by psychologists. One of two different pictures appeared on the computer screen and you had to react to one of them but not the other.

We set up the first game, called the 'Go/No-Go Task', so that the first 10 trials required you to press the space bar – this set up a strong 'Go' tendency. We then inserted 'No-Go' pictures randomly. You had to mentally inhibit your desire to respond.

In the second game, called the 'Stop Signal Task', we quickly replaced the 'Go' picture with the 'No-Go' picture. This is even harder because you have to cancel a motor message that has already been sent to your hands. One important question we wanted to answer is whether self-control and cognitive inhibition are really the same thing.

We asked you to fill in a questionnaire about your emotions that was designed to find out how you think about aggression. The questions looked like this:

During a physical fight, I feel out of control.
[ ] Strongly agree
[ ] Agree
[ ] Neither agree nor disagree
[ ] Disagree
[ ] Strongly disagree

Some people see aggression as a loss of self-control (expressive). Others see it as a means of controlling others (instrumental). You got a score on each of these two scales.

We also asked you about how often you had actually behaved aggressively during the last year. We asked about indirect, verbal and physical aggression.

What was the theory you were testing?
People with high self-control (which we predict will be women more than men) rarely act aggressively because they are so good at controlling their behaviour. But when these people snap, they will be at a very high level of anger because that is the only thing that can break through their self-control. Because of this, they actually experience their aggression quite accurately as 'losing control'.

People with lower self-control (which we predict will be men more than women) express their anger long before it gets to the point of explosion. Because they are less emotional and angry at the time they behave aggressively, they are able to monitor their behaviour and use it to control others (more instrumentally).

Who responded?
The analysis below is based on the first 5426 people who responded during November and December 2002. There were 3114 men and 2312 women. We still have several thousand more responses to analyse, so the results we give below are provisional.

Were there gender differences in aggression?
The only gender difference was on indirect aggression, and women scored higher. This is what other researchers have found. Indirect aggression is spreading rumours, gossiping and excluding others as punishment.

We were very surprised that there were no gender differences in verbal and physical aggression. Worldwide criminal statistics tell us that this is one of the most robust sex differences. Here are two reasons why we think we didn't find any.

An average gender difference can be the result of a very few members of one sex scoring incredibly high and 'pulling' their sex's average aggression score upwards. Because we know that about 5% of male offenders commit about 50% of all crime, it's likely that highly aggressive men don't often log on to Channel 4 web sites!

It might also be that respondents were thinking about episodes of partner aggression. We know that there are no gender differences in the frequency with which cohabiting men and women verbally and physically attack one another (though there are of course big differences in the injuries suffered).

Are self-control and cognitive inhibition really the same thing?
No. The measures are unrelated. Knowing how high your self-control is in social situations does not predict how good you are at the games involving inhibitory control.

Were there gender differences in self-control?
Yes, women reported significantly higher self-control than men.

Were there gender differences in cognitive inhibition?
No. There were no gender differences on either task.

Were there gender differences in the way people think about aggression?
Yes. These were big effects, in line with previous data we have collected from USA, Japan, Philippines and Spain. Women are more likely then men to think that their aggression comes from losing their self-control (expressive aggression). Men are more likely then women to think it's about controlling other people (instrumental aggression).

Does the way you think about aggression affect how aggressive you are?
Yes. Most people score higher on expressive (loss of self-control) than on instrumental (controlling others). But people who reported more than six episodes of physical aggression last year, are more instrumental than expressive in their thinking.

Does self-control affect how aggressive you are?
Yes. As self-control drops, the number of episodes of aggression reported rises.

Does cognitive inhibition affect how aggressive you are?
Yes. On the computer games, the more times you 'Go' when you shouldn't (errors of commission), the more physical aggression you report. However, the effect is much weaker than for self-control.

What's the take-home message?
Below we have listed the factors that are associated with high physical aggression. They are listed in order of importance, but all of them are statistically significant effects.

The more times you engaged in physical aggression last year:

• the more verbally aggressive you are
• the more strongly you believe that aggression is about controlling others
• the less strongly you believe that your aggression is about loss of self-control
• the lower your self-control
• the more likely you are to be male
• the more indirectly aggressive you were
• the more incorrect 'Go' responses you made on the 'Go/No-Go Task'
• the more incorrect 'Go' responses you made on the 'Stop Signal Task'

So what?
It's really useful that we have confirmed other work showing that self-control and cognitive inhibition are not the same thing. Children suffering from attention deficit hyperactivity disorder (ADHD) tend not to do so well on tests of cognitive inhibition. Some have suggested that their raised levels of aggression might result from this. Others think that their deficits in cognitive inhibition chiefly effect concentration, learning and memory. Cognitive inhibition is necessary to be able to focus on one thing and to refuse to attend to competing thoughts. Without this, inattention and distractibility slows down learning.

We find that cognitive inhibition is less important than self-control in explaining aggression. Other studies have also found that conduct disorder in children and criminality in adolescents and young adults is better predicted by self-control (sometimes called impulsivity) than by cognitive inhibition. Self-control is now the strongest predictor of gender differences in aggression.

For many years, my colleagues and I have been trying to explain the gender difference in beliefs about aggression. We assumed that these beliefs must be picked up from other members of one's own sex, so that there's a kind of contagion effect that ripples through society. But the fact that the gender difference is found in many cultures made us wonder if we were wrong. It looks like we might have been. It seems that our beliefs are grounded in our lived experience at the moment of aggression. Aggression truly feels different for different people.

People with high self-control experience a much greater emotional intensity when they erupt. So strong in fact that it disrupts their usual information processing. This may explain why in some murder cases, especially of female defendants, the attacker says that she cannot recall what happened. She acknowledges that she must have killed him (and often phones the police) but 'blanks out' at the precise moment when she lost control.

So self-control is a double-edged sword. We need enough to prevent us from lashing out every time we get angry but not so much that we cannot control our behaviour when we do. On a day-to-day basis, low self-control is more problematic because we erupt too often over minor issues. We are currently looking at men undergoing treatment for domestic violence to see if there are changes not only in their violence but in the way they experience it.

Why are women higher on self-control than men?
Women are better at faking 'nice' emotions and suppressing negative ones. (One experimenter gave participants a foul-tasting drink and asked them to pretend it was nice – women fooled observers much more successfully than men). They are also more likely to consider the long-term rather than short-term benefits of their behaviour and are better at 'deferring gratification' (selecting a bigger reward next week rather than a smaller one now). Why? The usual answer has been that we train our sons and daughters differently. In fact, boys are punished for aggression more often than girls are – so they ought to acquire stronger self-control over aggression!

Some psychologists are looking at the possibility that there may be a sex-linked genetic effect as a result of evolutionary pressure. Men who were impulsive and unrestrained may have achieved aggressive dominance over other males, acquired more mates and consequently left behind male-linked genes for impulsivity. Women may have been under a different kind of selection pressure. As mothers, they had to consider the survival of their offspring. A mother who risked her own life by over-impulsive behaviour also jeopardised her children's survival too. For women, a more cautious approach may have been the best strategy.

Finally
Thanks to everyone who took part. It's unheard of for a humble psychologist to obtain a sample size of this magnitude. The work will be published shortly in academic journals.

Further information about the experiment can be found here.

Resources

Channel 4 is not responsible for the content of third party sites

Websites

A Conversation with Steve Jones
www.houghtonmifflinbooks.com/catalog/
authordetail.cfm?textType=interviews&authorID=8016
Steve Jones, author of Darwin's Ghost, reveals his thoughts on male and female genetic history and differences: 'It is hard to deny that the ten times greater murder rate by men compared to women world-wide has something to do with genes.'

Human Social Order, Aggression and Social Order
www.rand.org/publications/MR/MR1139/MR1139.appc.pdf
Document featuring a presentation by Richard Wrangham, Professor of Zoology at Harvard University, on evolutionary psychology and the origins of male violence.

Mean Girls
http://observer.guardian.co.uk/focus/
story/0,6903,660933,00.html
An article investigating a new aggression sweeping through schools that's affecting not boys but girls. Escalating from the traditional cliques and hierarchies, some psychologists claim there is a new form of non-physical cruelty spreading through schools so extreme it has been given a new name – relational aggression.

Aggression and Violent Behaviour, A Review Journal
www.elsevier.com/inca/publications/store/3/0/8/4/3/
In-depth multidisciplinary journal that publishes reports of innovative ongoing clinical research programs. Includes a wide range of topics in the field of aggression and violent behaviour.

Science of self-control
www.bbc.co.uk/science/humanbody/mind/
articles/personalityandindividuality/selfcontrol.shtml
Informative area of the BBC's science site, investigating the various areas of research in to, and understanding of, obsessive compulsive disorder.

The truth about lie detection
www.timesonline.co.uk/printFriendly/
0,,1-7-746178,00.html
Article highlighting research by Dr Sean Spence into the effort we need to apply if we want to avoid telling the truth: 'Lying may be the mark of sophistication and intelligence – but it takes an effort to lie. The brain has to suppress the instinct to tell the truth.'

Go to Find Out More for details of further websites.

Books

	Men, Women and Aggression by Anne Campbell (Basic Books, 1994) Why are men more aggressive than women? Campbell shows how men and women's different views of anger and restraint profoundly affect their actions – from rage in marriage to violence in the streets. Buy this book from Amazon
	Sex Differences in Antisocial Behaviour: Conduct disorder, delinquency, and violence in the Dunedin longitudinal study by TE Moffitt, A Caspi, M Rutter, PA Silva (Cambridge University Press, 2001) A fresh approach to sex differences in the causes, course and consequences of antisocial behaviour. The book presents all-new findings from a landmark investigation of 1000 males and females studied from ages 3 to 21 years. Buy this book from Amazon
	The Two Sexes: Growing up apart, coming back together (The family and public policy) by Eleanor E Maccoby (Harvard University Press, 1999) How does being male or female shape us? This book explores how individuals express their sexual identity at successive periods in their lives. Buy this book from Amazon
	Pro- and Anti-social Behaviour by David Clarke (Routledge, 2003) Humans have the capacity to help others and be altruistic yet also to be aggressive and uncooperative. The author considers both of these types of behaviour and the theories psychologists use to explain them. Buy this book from Amazon
	Attention Deficit Disorder (ADHD) by Thom Hartmann (Newleaf, 1999) Can drugs cure attention deficit disorder? Why are some ADHD children and adults more successful that their peers? Thom Hartmann explains that rather than being a problem, ADHD may actually be beneficial. When correctly approached, their characteristics can be harnessed to create an overall positive effect. Buy this book from Amazon
	A Mind of Her Own: The evolutionary psychology of women by Anne Campbell (Oxford University Press, 2002) 'Readable and thought-provoking ... this book will stimulate an important debate and ensure that evolution cannot be ignored': Times Literary Supplement. Buy this book from Amazon
	The Science of Self-Control by Howard Rachlin (Harvard University Press, 2000) Claiming that insight and self-knowledge are insufficient for controlling one's behaviour, the author argues that the only way to achieve such control, and ultimately happiness, is through the development of harmonious patterns of behaviour. Buy this book from Amazon

Go to Find Out More for details of further books.