The science of getting your own back

Martha Gill's "Irrational Animals" column.

There’s a fantastic scene at the end of Quentin Tarantino’s film Death Proof. Three young girls are being hunted by Kurt Russell, a psychopath with a stunt car and a foot fetish. We have watched him torture and kill his way through the film, and, as he wends his way towards this group, their naivete is used as a foil to his ever increasing menace. In the last three minutes they beat him to death with an iron pole. It’s a great ending.

Outside Hollywood, the idea of revenge is often pushed into the background, especially when explaining our motives. We call it “justice” or “righting a wrong” or “balancing the scales”, but these notions don’t do much for us biologically, and don’t show up in an obvious way in the brain (it’s a grey area). Revenge, on the other hand, has a very clear neural signal, and that signal is pleasure.

A classic psychology scenario - the prisoner's dilemma - can be combined with neuroimaging to show this quite clearly. In the dilemma, two people have committed a crime and are being held in separate cells. They can either confess and get a reasonable sentence or blame the other, and get a light one. If both blame the other, though, they get the longest sentence of all.

In a study published in 2006, by Tania Singer at UCL, researchers asked two “prisoners” to play this out in front of an audience. Then members of the audience were then put inside fMRI machines while they witnessed each prisoner receiving electric shocks to his hands. As they watched, they showed increased activity in neural pain areas – evidence of empathy. Surprisingly, though, this empathy was present only when watching one of the “silent partners”. If a “confessor” was punished, the activity died down considerably. It looked like the brain cared much less about the pain of those who had betrayed their partner.

There was another finding that Singer didn’t expect. Watching “bad” prisoners get punished gave members of the audience pleasure: there was activation in reward-related areas of the brain, such as the ventral striatum and the nucleus accumbens. (This was limited to male subjects.)

So, we - or at least the men among us - get pleasure from revenge. According to similar studies, we also get activity in the left prefrontal cortex of the brain, which relates to goal planning. Revenge, then, seems to be not only a passing delight, but a craving, something we need, that we plan for. The desire increases when we are mistreated in front of others – we need to show people we’re not to be pushed around – and decreases when we’ve got more to lose by exacting it. In other words, the emotion has a logic to it.

Does it have an evolutionary function? Literature is littered with sayings about revenge and how it never pays, or is better expressed by forgiving the other person, or is exacted by “living well” (with gritted teeth). Yet our neurobiology feels otherwise. Which is right?

Well, let’s return to the prisoner’s dilemma. The dilemma itself is whether or not to trust your partner, but this issue figures only in the beginning. As the game plays out, round after round, prisoners seek petty revenge on each other, punishing the other for betraying them. Eventually, burned out, the two settle on a compromise. And this may be the lesson. Fear of retribution keeps us behaving fairly to others, making co-operation possible. This is why we love watching people get their comeuppance in Singer's test, and why we love watching Quentin Tarantino's films. Revenge is a sweet necessity.

Actress Emily Vancamp from the US drama Revenge. Photograph: Getty Images

Martha Gill writes the weekly Irrational Animals column. You can follow her on Twitter here: @Martha_Gill.

This article first appeared in the 11 February 2013 issue of the New Statesman, Assange Alone

Davide Restivo at Wikimedia Commons
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Scientists have finally said it: alcohol causes cancer

Enough of "linked" and "attributable": a new paper concludes that alcohol directly causes seven types of cancer.

I don't blame you if you switch off completely at the words "causes cancer". If you pay attention to certain publications, everything from sunbeds, to fish, to not getting enough sun, can all cause cancer. But this time, it's worth listening.

The journal Addiction has published a paper that makes a simple, yet startling, claim: 

"Evidence can support the judgement that alcohol causes cancer of the oropharynx [part of the throat], larynx, oesophagus, liver, colon, rectum and [female] breast"

So what's especially significant about this? 

First, scientists, unlike journalists, are very wary of the word "causes". It's hard to ever prove that one action directly led to another, rather than that both happened to occur within the same scenario. And yet Jennie Connor, author of the paper and professor in the Preventive and Social Medicine department at the University of Otago, New Zealand, has taken the leap.

Second, alcohol not only causes cancer of one kind – the evidence supports the claim that it causes cancer at seven different sites in our bodies. There was weaker evidence that it may also cause skin, prostate and pancreatic cancer, while the link between mouth cancers and alcohol consumption was the strongest. 

What did we know about alcohol and cancer before?

Many, many studies have "linked" cancer to alcohol, or argued that some cases may be "attributable" to alcohol consumption. 

This paper loooks back over a decade's worth of research into alcohol and cancer, and Connor concludes that all this evidence, taken together, proves that alcohol "increases the incidence of [cancer] in the population".

However, as Connor notes in her paper, "alcohol’s causal role is perceived to be more complex than tobacco's", partly because we still don't know exactly how alcohol causes cancer at these sites. Yet she argues that the evidence alone is enough to prove the cause, even if we don't know exactly how the "biologial mechanisms" work. 

Does this mean that drinking = cancer, then?

No. A causal link doesn't mean one thing always leads to the other. Also, cancer in these seven sites was shown to have what's called a "dose-response" relationship, which means the more you drink, the more you increase your chances of cancer.

On the bright side, scientists have also found that if you stop drinking altogether, you can reduce your chances back down again.

Are moderate drinkers off the hook?

Nope. Rather devastatingly, Connor notes that moderate drinkers bear a "considerable" portion of the cancer risk, and that targeting only heavy drinkers with alcohol risk reduction campaigns would have "limited" impact. 

What does this mean for public health? 

This is the tricky bit. In the paper, Connor points out that, given what we know about lung cancer and tobacco, the general advice is simply not to smoke. Now, a strong link proven over years of research may suggest the same about drinking, an activity society views as a bit risky but generally harmless.

Yet in 2012, it's estimated that alcohol-attributable cancers killed half a million people, which made up 5.8 per cent of cancer deaths worldwide. As we better understand the links between the two, it's possible that this proportion may turn out to be a lot higher. 

As she was doing the research, Connor commented:

"We've grown up with thinking cancer is very mysterious, we don't know what causes it and it's frightening, so to think that something as ordinary as drinking is associated with cancer I think is quite difficult."

What do we do now?

Drink less. The one semi-silver lining in the study is that the quantity of alcohol you consume has a real bearing on your risk of developing these cancers. 

On a wider scale, it looks like we need to recalibrate society's perspective on drinking. Drug campaigners have long pointed out that alcohol, while legal, is one of the most toxic and harmful drugs available  an argument that this study will bolster.

In January, England's chief medical officer Sally Davies introduced some of the strictest guidelines on alcohol consumption in the world, and later shocked a parliamentary hearing by saying that drinking could cause breast cancer.

"I would like people to take their choice knowing the issues," she told the hearing, "And do as I do when I reach for my glass of wine and think... do I want to raise my risk of breast cancer?"

Now, it's beginning to look like she was ahead of the curve. 

Barbara Speed is a technology and digital culture writer at the New Statesman and a staff writer at CityMetric.