New DNA technique means pointing the finger at the right identical twin just got easier

Won't get fooled again (posed by models). twins by iofoto/www.shutterstock.com

DNA profiling (or genetic fingerprinting) has proved a revolutionary tool for forensic investigators as a means to identify potential suspects, exonerate the innocent and convict the guilty. But, like any forensic technique, it has its limitations. One limitation is in cases involving identical twins, something that has raised technical, legal and ethical problems – until now.

The more closely related one human is to another, the more similar their DNA profiles. For example, the probability of a DNA match between two random, unrelated individuals is in the region of one in a billion. For two full siblings, the probability drops to one in 10,000. Identical twins present the same DNA profile.

In forensic investigations, this presents problems. Under the ethical premise that it is better to let ten guilty men go free than to imprison one innocent man, if the courts cannot decide which twin is responsible then both must go free. There have in fact been a small number of high-profile cases where the suspects were identical twins, leading forensic genetics researchers to explore how this could be addressed. Now we’ve come up with a solution, recently published in the journal Analytical Biochemistry.

Finding a difference between equals

One method is mutation analysis, where the whole genome of both twins is sequenced to identify mutations that might have occurred to one of the twins. If such a mutation is identified at a particular location in the twin, then that same particular mutation can be specifically searched for in the crime scene sample. However this is very expensive and time-consuming, and is unlikely to be paid for by cash-strapped police forces.

The Forensic Genetics Research Group has demonstrated proof of principle of a cheaper, quicker technique. The basic principle behind this test is the concept of DNA methylation. This is effectively the molecular mechanism that turns on and off various genes.

For example, a blood-specific gene is also present in brain cells, but the cells in the brain do not produce the blood-specific component, because the gene is “switched off”. Many mechanisms affects the methylation status – whether a particular gene is “on” or “off” – of the DNA, but in the case of identical twins, the significant factor is environmental effects on them since birth.

As the twins grow older, the degree of difference between them grows as they are subjected to increasingly different environments. For example, one might take up smoking, or one might have a job outdoors and the other a desk job. This will cause changes in the methylation status of the DNA.

Methylation and melt

In order to analyse this, the DNA is extracted from the sample and then undergoes a process called bi-sulfite treatment. This reaction targets the methylated areas of the DNA and changes the sequence of its component nucleotide bases, known as A, C, G, and T.

DNA sequence, showing GATC nucleotides. Sjef

If a section of DNA is heavily methylated and then subjected to bi-sulfite treatment, the DNA sequence becomes heavily changed, so that for example C becomes T. The new characteristics of the DNA could be discovered by further sequencing – but again, this is expensive. Instead we carry out what is called high resolution melt curve analysis (HRMA).

Graph showing the different melt temperatures of DNA samples taken from two identical twins. Stewart et al./Analytical Biochemistry, Author provided

Human double stranded DNA is held together by hydrogen bonds that link these ACGT nucleotide bases. Guanine (the G of the ACGT nucleotides) is bound to cytosine (C) by three hydrogen bonds, and thymine (T) is bound to adenine (A) by two hydrogen bonds. If one sequence is predominantly made up of GC bonds that are methylated, then following bi-sulfite treatment, these GC bonds become AT bonds and the number of hydrogen bonds in that sequence decreases.

What HRMA does is to subject the DNA to increasingly high temperatures until the hydrogen bonds break, known as the melting temperature. The more hydrogen bonds that are present in the DNA, the higher the temperature required to melt them. Consequently, if one DNA sequence is more methylated than the other, then the melting temperatures of the two samples will differ – a difference that can be measured, and which will establish the difference between two identical twins.

Forensic biochemistry

Our studies have demonstrated that it’s possible to distinguish between identical twins using this method. However, there are some limitations.

It relies on there being a differing level of methylation between the twins' DNA. So for example young twins, or twins raised in highly similar environments may not have yet developed sufficient methylation differences. There is also irregularity in the level of methylation in DNA taken from different body fluid samples – for example, between saliva and blood – which means the same sample fluid is needed from the suspects to be tested as is found at the crime scene. The third limitation is that the technique requires a high sample quantity (around 100 nanogrammes) for DNA methylation studies, and this may not be present at the crime scene.

Nevertheless, we have demonstrated substantial progress towards a relatively cheap and quick test for differentiating between identical twins in forensic case work.

Forensic evidence offers only probabilities, not guarantees that justice will be served

This is science, not clairvoyance. fingerprint by Torsak Thammachote/www.shutterstock.com

Scientific evidence and expert witness testimony are integral to criminal trials worldwide. Yet while we live in a scientific age of increasingly specialised expert knowledge, a growing reliance on forensic evidence is a double-edged sword.

There is no doubting that forensic science techniques provide near-miraculous abilities to detect, investigate and prosecute crime. But any powerful medicine can have strong side-effects, if administered in excessive dosages or to the wrong patients. Forensic scientific evidence has won for itself an aura of credibility that verges on infallibility. This leaves flawed expert evidence as a potent source of potential injustice.

Is forensic science evidence fit for justice? Science and technology constantly evolve; forensic tests become ever more discriminating, cheaper and easier to use, and more freely available to law enforcement. Courts and legislators must not be complacent if they are to keep pace with scientific innovation. Unfortunately austerity-blighted Britain may be storing up serious trouble for the future.

Forensics and miscarriages of justice

It shouldn’t surprise us that forensic science is associated with miscarriages of justice. All forms of judicial evidence are inherently fallible: witnesses are sometimes dissembling or forgetful, or sincere and credible yet wrong. Confessions may be false or made under duress. As reliance on scientific evidence grows so too will the number of miscarriages of justice that stem from forensic science. It’s also fair to say that injustice occurs when the scientific evidence and techniques available are not exploited to their maximum. Scientific evidence is in some areas peculiarly vulnerable to unreliability and misinterpretation.

To begin with, scientific evidence is circumstantial. It may constitute strong evidence of the offender’s identity, his presence at the crime scene, or association with incriminating objects such as the murder weapon or stolen property. But it has at best very little, and generally no value in proving other elements of criminal liability such as intent, grounds of excuse, justification, or the absence of the victim’s consent. In other words, it typically leaves considerable scope for interpretation.

Scientific samples are prone to degradation and contamination, as demonstrated by recent high-profile cases in the UK and Australia in which contaminated samples falsely incriminated innocents. Presented in court, there is a constant danger that it will be misrepresented or misunderstood by lawyers, judges, or jurors. These difficulties are compounded whenever scientific evidence offered by one legal team is contradicted, or given a different interpretation, by counter-expertise advanced by the opposing side.

There will always be a risk of error, attributable to human fallibility, that must be accepted regardless of our efforts to detect miscarriages of justice. But one aspect of modern forensic science evidence is genuinely novel. Starting with the invention of fingerprinting about a century ago, forensic science has operated on the basis that it is possible to identify suspects or physical objects uniquely – an exclusively “matching” fingerprint, tool mark, hair sample, carpet fibre, bite mark would indicate the particular offender (or murder weapon, location of fibres or whatever). But the arrival of DNA profiling in the mid-1980s has seriously disrupted this way of thinking.

DNA evidence is powerful, but should redefine how we think about evidence. DNA by The Biochemist Artist/www.shutterstock.com

DNA profiles

DNA profiles, derived from only small samples of a person’s entire genetic code, do not claim to point the finger so uniquely. They are statements of random match probability (RMP), the probability that a person would match the DNA at the crime scene? if they were not its donor. The conventional RMP for fully matching DNA profiles in England and Wales has been one in a billion – a tiny probability, but one which concedes the possibility that DNA profiles are not unique.

It was soon realised that, far from a weakness of DNA profiling in contrast to other well-established techniques, in fact DNA profiling represents a truly scientific approach, whereas orthodox forensic practice rested on a fallacy. It is never possible to conclusively identify a person from sets of matching characteristics, unless the characteristics measured are known to be absolutely unique in the population. This kind of uniqueness probably does not exist in the real world – as graphically demonstrated by recent fingerprint miss-attributions in Scotland and in the US.

So with DNA profiling as the new forensic science model, nobody should assert or believe that a matching fingerprint or other forensic trace means “it’s definitely him”. Yet the impression is that many forensic scientists have failed to grasp these radical implications, and continue to make claims for their evidence that lack foundation in either logic or science.

In search of a remedy

For an effective prescription for institutional reform there needs to be an intelligent diagnosis of the existing ailments. Simplistic solutions, or those predicated on superficial misunderstandings of criminal procedure, are liable to do more harm than good. Modest but effective reforms include greater pre-trial dialogue between legal teams, only putting disputed facts before a jury, reinforcing professional ethics among lawyers and expert witnesses, proper scrutiny of scientific evidence before admitting it, and educational initiatives such as the Royal Statistical Society’s guides for interpretation of statistics.

print by polygraphus/www.shutterstock

Unfortunately, in a moment of penny-pinching madness that future governments may regard with incomprehension, the UK coalition government closed down the world-famous Forensic Science Service, arguing – quite improbably – that the private sector would fill the gap.

There are now serious worries, expressed by a parlimentary select committee and in a National Audit Commission report, that this move to free-market forensics is not meeting the justice system’s need for high-quality scientific support and has put in jeopardy long-term forensic research, development and training.

The closure stands against a landscape of “austerity justice”, across which swingeing cuts to legal aid raises serious questions about the viability of effective criminal defence in England and Wales. Meanwhile, the Forensic Science Regulator, professional bodies such as the Chartered Society of Forensic Sciences and other key stakeholders such as academic departments must do what they can to pick up the slack, in an effort to ensure that forensic evidence generated and presented in criminal proceedings remains fit for justice.

The price of failure will be paid not by politicians in Westminster, nor by prosecutors, nor by free-market forensic practitioners, but by the victims of miscarriages of justice and through damage to public confidence in the legal system. Something that, in an all-too-familiar historical pattern, may not become apparent for many years, or even decades, to come.

Some shape-shifting animals that can morph to fool others

Pretty impressive, mimicry octopus, but you don't fool us. Klaus Stiefel/flickr, CC BY-NC

Animals come in all different shapes and sizes, but only a few can change their shapes. Researchers in Ecuador recently reported a new species of frog that can change its skin texture from spiny to smooth – the first ever case of a shape-shifting vertebrate.

When an animal is about to be attacked by a predator, it has two choices: run or hide. Sometimes, though, running might actually make the animal more obvious to its attacker. An animal that happens to look the same as its environment, however, may survive by being camouflaged from the attacker, such as moths that resemble fallen leaves, or even help to attract prey – a tactic the orchid mantis uses.

Many animals have evolved such permanent adaptations that help them to mimic their environments. However, along with the newly classified mutable rain frog, there are just a few animals known to be capable of changing their shape.

1. The mutable rain frog

The mutable rain frog - blink and it may have changed form. Zoological Journal of the Linnean Society, Author provided

This frog was discovered in the Ecuadorian rain forest in 2006 but was only recently reported in the Zoological Journal of the Linnean Society as it took several years to find a second specimen, and only then did the shape-shifting ability become apparent.

The frog visibly changes its skin in a matter of seconds, completely changing texture from spiny to smooth in a few minutes. This change is so rapid that when the first researcher captured the frog to photograph it she thought she had mistakenly taken the wrong frog specimen – the spines had disappeared. The researchers put moss in the container with the frog until they could return it to the wild, but when they checked on it later it had changed its skin texture to spiny again.

The team also identified a second frog species, the Sobetes robber frog, capable of the same shape-shifting behaviour. This indicates that this phenomenon could be present in many species of amphibian and is possibly just unrecorded as it happens so quickly. This is the first known vertebrate to shape-shift over such a rapid time frame – apart from werewolves and J.K Rowling’s Professor McGonagall of course.

2. The golden tortoise beetle

It’s either this or shiny gold. Kenneth ng/flickr, CC BY-NC-ND

This species of beetle is capable of changing its colour when mating or to blend in with its background and avoid predation, just as specialist colour changers such as chameleons do. But it can also change the finish of its colour, for example from a shiny gold to a dull red colour. It does this through an optical illusion whereby tiny grooves in the shell can create a shiny surface when filled with liquid and a dull one when drained.

The golden tortoise beetle also undergoes a metamorphosis from the larval to the adult stage (in the same way that caterpillars morph into butterflies). This process of metamorphosis occurs through cells growing and specialising as the beetle grows to maturity and is brought about by hormonal change.

3. Cuttlefish

The same cuttlefish filmed only seconds apart. Klaus Stiefel/flickr, CC BY-NC

Cuttlefish are capable of mimicking their background environment by changing the colour, pattern and texture of their skin. They do this by altering pigments in their skin to change the way it reflects light. This is all controlled by neurons in the brain that transmit impulses and information to the rest of the body.

As well as camouflaging themselves, cuttlefish can alter their skin to startle predators or to communicate with other cuttlefish. Some cuttlefish have even been dubbed as cross-dressers: the males have been known to imitate females in order to sneak past other males to mate with the females.

4. The mimic octopus

This octopus was discovered in 1998 off the coast of an Indonesian island, and is perhaps the greatest shape-shifter of all. Similar to the cuttlefish, it is capable of mimicking its background environment by changing the colour and texture of its skin. However, impressively, it is the only animal able to mimic a diverse range of species – at least 13 have been recorded so far – including lion fish, sea snakes, jellyfish and sea anemones.

Most of the impersonated species are poisonous, giving the mimic octopus protection from predators, but it is also known to imitate members of the opposite sex in crabs, luring them in before feasting on them. The mimic octopus has remarkable dexterity, being capable of changing its colour, behaviour, shape and texture, and can alter its mimickry according to the circumstances.

5. Pufferfish

Watch out, he’s about to puff! Benjamin Jakabek/flickr, CC BY-NC-ND

Porcupinefish and pufferfish are a group of fish that puff themselves up rapidly when threatened. These fish can more than double their size by inflating their stomachs with water or air, making themselves much less attractive as a meal to predators – would you want to eat a large spiky ball? – and too large to be eaten by predators with smaller mouths.

Most porcupinefish and pufferfish also contain a deadly toxin, far more poisonous than cyanide, so if they are taken unaware the predators often won’t last for long. The meat from these fish are considered a delicacy in Japan, where it is carefully prepared by trained chefs, although it seems several customers still die each year.

Exoskeleton boot makes for more efficient walking

Walking on a trail becomes a bit easier with a pair of unpowered exoskeleton boots.

Stephen Thrift

Some boots are made for walking, and some are made for walking more efficiently.

Scientists have developed an unpowered exoskeleton "boot" that reduces the amount of energy spent while walking by about 7 percent. The boot has a passive clutch that activates a spring in parallel with the Achilles tendon when the foot is on the ground. That offloads the effort of the calf muscles, making walking easier, researchers report April 1 in Nature.

Seven percent doesn't seem like much of an energy savings. But humans have been walking for a long time, and finding that a slight energy savings is still possible suggests there's still much more to learn about walking, the team says.

Does civic society need Martha Lane Fox as online champion?

There needs to be more to the net than just data scraping and surveillance. heyrocker, CC BY

In his iconic Discworld series, the late Terry Pratchett offered two useful social observations: first, that dragons affect the value of personal property and, second, that in order to avoid tyranny we should always question who guards the guards.

The second is relevant to the points made by Martha Lane Fox who, in her recent Richard Dimbleby Lecture, called for the creation of an civic institute to “examine the ethical and moral issues posed by the internet”.

Martha Lane Fox. The Cabinet Office/Crown Copyright

Lane Fox envisages her institute as guardians to watch over us everyday users of the world wide web, and to guard against the domination of corporations, government censorship, and self-serving EU legislative agendas that provide only weak data regulation and protection.

These concerns are not new, and are shared by many who care about the future of the internet. Grandees such as Sir Tim Berners-Lee and his Web Foundation and the W3C, have already campaigned for a more “pro-human” web as it passes its 25th birthday, one that is better suited to digital rights. What’s been called a Web We Want where users have influence over a digital future intended for everyone.

Free people pull in many directions

This is all very well, but the internet is relatively ungoverned: virtual, supranational territory that falls outside the boundaries of nation-states, and which lacks the democratic mechanisms and social protections that they afford.

Claims of a flat, open, and egalitarian internet are misguided. Where there is one rule for one user and one rule for another, social Darwinism – the survival of the fittest – ensues. The web echoes and magnifies the world’s gross cultural relativity and widespread inequality. Its transformative power has reached only half the world’s population, a fact that reinforces the power, money, gender, and class-based inequalities rife offline. Any civic internet institute without major financial support and global political backing will struggle to make a difference.

Such an institute would be forced to consider how the many free-ranging individuals, from many levels of society, which shape the web may react to proposed changes to a platform that is a major part of their lives. Increasingly, online behaviour defines us as individuals, yet direction and control of the internet is held by a technical oligarchy.

So Lane Fox’s call is not limited to the implications of what the web could bring, or what it has already brought – good or bad. It is also an investigation of the scope of human imagination, looking towards what we want the web to be by establishing a set of rules and agreements on decision-making – what Berners-Lee has called an online magna carta. The implications of the internet of things, of the rapid growth of government surveillance, and surveillance-based, data-trawling business models all play in to this.

An institute that aimed to provide a civic counterweight to corporate and government power would have to evaluate where that power lies on the web, the different views of digital privacy and ownership and use of data.

A user’s right to control their data and privacy might require laws or regulation to support that right, ensuring that one is never allowed to treat another as merely a means to their own ends. Then again, users could agree to surrender their data in exchange for services – a deal that need not be Faustian, merely utilitarian. The fact that the mechanisms for this exchange – cash for data, essentially – already exist means the services get built and we all benefit.

Even benevolent, technocratic tyranny must be watched for. davidmasters, CC BY

Standing on the shoulders of giants

Importantly, Lane Fox’s call is concerned with more than technicalities, and is focused on how to strengthen individual freedoms on the web. After all, citizenship emerges from civil, social and political rights and responsibilities – extending this to the web is not such a great leap, but will require wide support and agreement. In fact this may be more important than any institute – an antidote to the concerns of power and dominance that could be as important as movements for gender equality and universal suffrage.

If the internet has technocratic forums such as the W3C, IETF and Internet Society, perhaps society at large should have a representative body to compare to these technocratic ones, to push participatory governance and keep digital citizenry alive to reflect the very human rights of the billions of internet users.

There are already organisations striving to bring understanding to the tangle of power and rights online, including the University of Southampton’s Web Science Institute, the Oxford Internet Institute, and others in the Web Science Trust network.

So perhaps another new institute is not what we need, but instead greater support for those that already exist, and better links between industry, academia and government. This needs to be strengthened against a background of increasing individual digital freedoms, because only this way are we going to be able to innovative and educate our way to a better web for all. These together can engineer new digital leaders for tomorrow, creating online champions for our human rights.

Air pollution may be damaging children's brains – before they are even born

Hold your breath. Radharani/Shutterstock

Exposure to air pollutants during pregnancy may contribute to childhood abnormalities in the brain, a new study suggests.

The research, from the Children’s Hospital of Los Angeles, measured the exposure of the mothers to PAH air pollution and used brain imaging to look at the effects on their children’s brains.

PAHs, or polycyclic aromatic hydrocarbons, are widespread pollutants formed when organic materials are incompletely burned. They originate from vehicle exhausts, burning coal and oil, waste incineration, and wildfires. They can also be found inside the home, for example from tobacco smoke or open fires and stoves.

We need our white matter

The researchers began looking at the effects of prenatal exposure to PAH on brain development in the 1990s. The initial study recruited more than 600 women in the third trimester of pregnancy from New York City minority communities. They completed questionnaires and were given portable pollution monitors for 48 hours to allow researchers to determine their exposure.

Their children were then assessed between the ages of three and seven, and the team found that exposure was associated with symptoms of ADHD (attention deficit hyperactivity disorder) and other cognitive and behavioural problems including reduced IQ, anxiety and depression.

For the latest study, 40 of the same children had their brains scanned, revealing a strong link between PAH exposure in the womb and a reduction of white matter in the brain. Brain white matter is made of millions of cells called axons that allow rapid connections between different regions of the brain.

The study found an association of areas of reduced white matter with the processing speed of that part of the brain. Yellow, red and orange show areas where white matter had affected the processing speed of that part of the brain. There was a stronger correlation in the left side of the brain. from Peterson et al. 2015, JAMA Psychiatry, Author provided

What’s more, these disturbances in the brain were associated with slower reaction times during intelligent testing as well as more severe ADHD symptoms and conduct disorder.

Growing signs of trouble

This study’s findings add to a growing body of literature on air pollution and health, from which other studies report associations with autism spectrum disorders, schizophrenia and cognitive impairment.

For example, one study of Californian children showed that those exposed to the highest levels of traffic-related air pollution during pregnancy and in the first year of life were more likely to develop autistic spectrum disorders than those exposed to the lowest levels.

More direct evidence that air pollution affects the developing brain comes from animal studies. One study of the brains of young mice exposed to ultra-fine particles at concentrations similar to those found in rush-hour traffic found the mice displayed enlarged cavities in their brains – a condition which in humans is associated with autism and schizophrenia.

Particles – bad news for the brain

The mechanism by which air pollution is toxic to the brain is not yet fully understood, in particular, the pathway to the brain of particulate matter (PM) – small pollutants particles which can carry PAHs on their surface.

Ultrafine particles are believed to move to the brain either by travelling from the lung into the systemic circulation and across the blood brain barrier or by landing at the back of the nose then travelling to the brain via the olfactory nerve. Once in the brain, pollutant particles can cause inflammation and cellular damage.

Need for more research

As with any scientific project, there were limitations to the study: the sample size was small and it was not possible to exclude the possibility that the findings could have been caused by other environmental exposures. The researchers plan to scan many more children, and to assess the way PAH interact with other contaminants and their effects on the brain.

Cough cough – air pollution in London in 2014. David Holt/flickr, CC BY-SA

It’s also important to remember that the findings were made from a study of a specific population with a high level of poverty, low educational attainment and below-average maternal IQ – so the results may not easily generalise to other populations.

This study and much of the other research on air pollution and the brain originates from the US, where the proportion of one major source of urban air pollution – the diesel-powered car – is low compared to the UK. This makes it necessary to collect our own data here.

In our recently launched birth cohort study we will be collecting detailed information on 80,000 UK babies and their parents during pregnancy and the first year of children’s lives to work out which factors shape growth, development, health and well-being.

The cost of air pollution

Although there has been relatively little research on the negative effects of air pollution on the nervous system, evidence is already mounting. A unique feature of air pollution as a risk factor for disease is that exposure is almost universal.

Importantly, the study showed that the more the mother was exposed to PAH while pregnant, the larger the white matter disturbance in the child. This suggests that reduction in exposure to PAHs during pregnancy and just after birth has the potential to bring about an equivalent reduction in white matter disturbance in the child’s brain and its effects.

If further studies find similar results, the public health implications are significant given how widespread PAHs are and how little we know about the causes of mental health problems – an area that presents a large and growing disease burden on society.

The ever-accumulating evidence that so many components of air pollution contribute to such a diverse set of diseases confirms the urgent need to manage the quality of the air we breathe. Achieving this promises to be a significant and cost-effective way of improving our health and quality of life.

Threatening parents isn't the way to protect children from videogame violence

Trigger happy? Magnus Fröderberg/norden.org, CC BY

Headteachers from 16 schools in Cheshire have warned parents by letter that they would be reported to the authorities if they allowed their children to play videogames marked as suitable for adults with an 18 age rating.

The letter argued that not only did videogames subject children to violent scenes, but that they also increased sexualised behaviour and led children to be more vulnerable to sexual grooming. The letter stated that in the case of children allowed to play such games “we are advised to contact the police and children’s social care” as parents' actions would be “deemed neglectful”.

The letter’s author, Mary Hennessy Jones of the Nantwich Education Partnership, told The Sunday Times:

We are trying to help parents to keep their children as safe as possible in this digital era. It is so easy for children to end up in the wrong place and parents find it helpful to have some very clear guidelines.

The innocent days of Frogger and PacMan are largely gone, and popular videogames today often boast photo-realistic graphics depicting violence and other adult themes, which is why games such as Grand Theft Auto and Call of Duty are age rated in the same way as films.

I’m sure the letter was written with the best of intentions but as a parent of three “screenagers” and someone who has spent almost 30 years researching the effects of videogames on human behaviour, this is a heavy-handed way to deal with the issue.

Although it is illegal for any retailer to sell 18-rated games to minors, it’s not illegal for children to play them, nor is it illegal for parents to allow their children to do so. It’s true that many parents may benefit from an education in the positives and negatives of videogames, but threatening them with the “authorities” is not helpful.

Don’t blame the game

I’ve been researching the effects of videogames on children since the early 1990s and played a role in the introduction of age ratings to videogames, writing educational leaflets for parents that outlined the effects of excessive gaming. There’s no doubt that there are many positive benefits to videogaming too.

Children often play age-inappropriate videogames. My 13-year-old son moans that he is the only boy in his class that doesn’t own or play Call of Duty. This anecdotal evidence is borne out by research: in one study we found that almost two-thirds (63%) of children aged 11-13 had played an 18+ video game. Of the two-thirds who had played them, 8% reported playing them “all the time”, 22% reported playing them “most of the time”, 50% reported playing them “sometimes”, 18% reported playing them “hardly ever”. Unsurprisingly, boys were more likely than girls (76% vs 49%) to have played an 18+ video game – and more likely to play them more frequently.

How had they got access to the games in the first place? The majority had the games bought for them by family or friends (58%), played them at a friend’s house (35%), swapped them with friends (27%), or bought games themselves (5%). So this certainly suggests that parents and siblings are complicit in allowing children access to them.

Does it do what it says on the tin?

With the development of age rating and descriptors of the games content to be carried on the packaging, there is a growing amount of research studying the content of these games aimed at adults. For instance, one study led by Kimberley Thompson examined whether the description on the box of violence, blood, sexual themes, profanity, drugs and gambling in 18+ videogames matched the game’s content. The study found that although warnings for violence and gore were relatively well handled, 81% of games studied lacked descriptions of other adult themes in the game content. The same researchers have found adult content in lots of games aimed at young children and teenagers.

Another study led by David Walsh tested the validity and accuracy of media age ratings, including those for videogames. The findings suggested that when the entertainment industry rated a product as inappropriate for children, parents agreed. But parents disagreed with many industry ratings that designated material suitable for children, with those rated as appropriate for adolescents by the industry of greatest concern to parents.

In truth, there’s no difference between the issue of children and adolescents playing 18-rated games and that of children and teenagers watching 18-rated films. It does seem, however, that parents are more likely to act on ratings for films than for videogames. So while parents could be better informed and more responsible in how they monitor their children’s activities, threatening letters from schools are unlikely to have the intended effect on parents' attitudes.