Category: Forensic

Researchers chucked litter on the streets of New York and Bern to see if anyone would intervene

Trash can in New York CityBy Alex Fradera

To maintain pleasant public spaces requires that we all implicitly agree to certain civil behaviours, like pocketing our chocolate wrappers rather than leaving them strewn on the pavement, or turning the stereo down after eleven. But when these implicit agreements are too frequently ignored they can lose their force entirely, jeopardising the social order. To keep things together, one or more of us need to hold any miscreants to account… but who wants that hassle? A new paper in the journal Rationality and Society explores real-life littering norm enforcers, taking us from the streets of Switzerland to the New York underground.

Continue reading “Researchers chucked litter on the streets of New York and Bern to see if anyone would intervene”

Bad news for passport control: face-matching is harder than we realised

Passport Officer at Airport SecurityBy Alex Fradera

Experiments suggest that telling if two unfamiliar faces are the same or different is no easy task. Such research has sometimes presented participants with full body shots, has more commonly used cropped shots of people’s heads, but almost never placed the faces in a formal context, such as on a photographic ID card. But these are the situations in which face-to-photo matching is most relevant, when a shop assistant squints at a driver’s license before selling alcohol to a twitchy youth, or an emigration official scrutinises passports before their holders pass ports. Moreover, it’s plausible that the task is harder when juggling extra information, something already found in the realm of fingerprint matching, where biographical information can lead to more erroneous matches because it triggers observer prejudices. A new article in Applied Cognitive Psychology confirms these fears, suggesting that our real-world capacity to spot fakes in their natural setting is even worse than imagined.

Continue reading “Bad news for passport control: face-matching is harder than we realised”

Researchers have identified a simple bias that makes forgiveness so hard

Two cupped hands holding a stone with forgive written on itBy Alex Fradera

Tom Tate’s second visit to the German town of Pforzheim was a return to somewhere he hadn’t seen in fifty years. After bailing from a burning plane, he and his RAF squad had landed there, been captured, and his comrades executed by a Hitler Youth group incensed by the bombing the town had suffered. Tate himself had only escaped by moments, and swore never to return to a place that he believed bore only hate against him. But spurred by a magazine article that mentioned an annual service held to commemorate the atrocity, he decided to make the journey. Once there, he found himself welcomed by a population who deeply regretted their actions.

This story opens a new article in the Journal of Personality and Social Psychology, which investigates whether we underestimate how much our persecutors seek forgiveness. Relevant here is classic research that suggests a difference of perspective in how we judge people’s actions – we see our own actions as being strongly influenced by the situation we’re in, but when judging other another person’s actions we seem him or her as more directly responsible (sometimes described as the actor-observer bias). Researchers Gabrielle Adams and M. Ena Inesi thought that the same bias might be relevant to when one person harms another – that victims will typically assume the perpetrator intended his or her actions and will therefore remain unrepentant. Continue reading “Researchers have identified a simple bias that makes forgiveness so hard”

Training men to judge women’s sexual interest more accurately

Businessman Flirting Businesswoman
Researchers may have found a new way to combat sexual aggression

By Christian Jarrett

“You know I’m automatically attracted to beautiful — I just start kissing them. It’s like a magnet. Just kiss. I don’t even wait. And when you’re a star, they let you do it. You can do anything.”  Donald Trump, 2016 Republican Party nominee for US president, speaking in 2005 (full transcript).

The causes of sexual aggression are many, but anecdotal evidence (for example, as implied in the above quote), and research-based evidence, suggests that at least part of it has to do with when men overestimate women’s levels of sexual interest. A new study in the Psychology of Violence finds that men with a history of sexual aggression are especially likely to make this kind of misjudgment, in part because they focus on inappropriate cues, such as a woman’s attractiveness, rather than on her actual emotions. But promisingly, the research also suggests that it’s possible, through practice, to reduce this bias. This is an important finding considering previous research has shown that information-based educational programmes designed to reduce sexual aggression (through challenging rape myths, for example) are relatively ineffective. Continue reading “Training men to judge women’s sexual interest more accurately”

The Metropolitan Police’s elite super-recognisers are the real deal

Back view of metropolitan police officerBy Alex Fradera

Identifying people from video and photographs is a core task for a modern police force, and London – which led the world in implementing and using CCTV – has attempted to meet this need by developing a pool of 140 “police identifiers” made up of Metropolitan Police officers with a strong track record of making IDs from photographs. But who are these individuals? Are they really super-recognisers as the Met has claimed? True super-recognisers are usually identified by formal tests and their dramatic ability to recognise human faces outstrips typical performance to the same extent that many prosopagnosics (people with face-blindness) lag behind. Or, in identifying so many suspects, did the police identifiers just catch a string of lucky breaks? Addressing this through a battery of neuropsychological tests, Josh Davis and his UK-university collaborators scrutinise the scrutinisers in a new paper in Applied Cognitive Psychology. Continue reading “The Metropolitan Police’s elite super-recognisers are the real deal”

New power in the hands of the chronically powerless can be toxic

Toxic Chemical

In the 1970s, feminist theorists began to put forward what was then a controversial claim: that sexual aggression is essentially about power. This idea was important enough to launch experimental research, much of which has supported the claim – for instance, priming some men with a sense of power leads them to say they would be more prepared to coerce sex, and encourages men and women alike to believe a subordinate desired them sexually. However other research has suggested the opposite: that aggression is more likely when perpetrators feel less powerful, including in domestic violence and specifically sexual aggression contexts.

To make sense of these seemingly contradictory findings, researchers from Emory and Stanford universities have looked at power more carefully. Their work, published in the Journal of Personality and Social Psychology, suggests that a person’s experience of power in the past and their power right now in the current situation are distinct factors, and how they combine is key. Continue reading “New power in the hands of the chronically powerless can be toxic”

Killer wives are “wicked”, killer husbands are “stressed” –uncovering the sexism in judges’ closing remarks

Judges are not perfect, but we expect them to approach their cases clinically and with detachment, interpreting them on their merits, uninfluenced by stereotypes around skin colour, age, or … gender.

Unfortunately, a new study in Psychiatry, Psychology and Law has analysed the sentencing remarks made by judges in domestic murder cases (defined as murder between heterosexual spouses) and found that they framed killings by men in far more lenient and forgiving terms than killings by women. Continue reading “Killer wives are “wicked”, killer husbands are “stressed” –uncovering the sexism in judges’ closing remarks”

Does target shooting make teenagers aggressive?

When the dust settles on the tragedy of the latest mass shooting, gun clubs usually see a spike in their memberships as people look to arm and defend themselves. At the same time, many others argue for greater gun controls, and from their perspective, recreational target shooting is very much part of the problem, not the answer.

Anecdotally, this is borne out by the many killers who often turn out to have been target shooters. Indeed, in Germany after the teenage perpetrators of two spree atrocities, or their parents – in Erfurt in 2002 and in Winnenden in 2009 – were found to be shooting club members, the German Shooting Sport and Archery Federation decided to sponsor psychological research into the question of whether shooting club members are more aggressive than normal, and whether target shooting makes people more aggressive. Some of the initial findings have now been published in the journal Aggressive Behaviour and while the results are not conclusive, they do suggest there is reason to worry about the psychological effects of gun club membership.

The initial study involved 45 teenage target shooters (average age 13 years; they’d been a member of their clubs for about a year) completing measures of their aggression three times every six months over the course of the research. For example, they rated their agreement with statements like “I would rather hit somebody than be a coward”, and they took another test to reveal how readily they associated self-related words with words pertaining to violence and aggression – this supposedly providing an implicit or non-conscious measure of the aggressiveness of their self concept. They also answered questions about their emotional regulation abilities – for example, whether they deal with emotional problems by seeking help or through anger or aggression.

Although there was no control group – the research sponsors didn’t want to spread negative publicity among non-shooters – the aggression questionnaires used in the study have previously been throughly tested by psychologists on the general public, thus giving an idea of a “normal” level of aggression. The results showed that the teen shooting club members were significantly above average in their self-rated aggressive tendencies, and that this rose through the course of the study, so that by the end, they averaged a level of aggression higher than 84 per cent of the general population (in contrast, results on the implicit test suggested they associated their self concept more strongly with peace than aggression, but without a control group it’s difficult to interpret this finding. The teenage shooters also scored highly for maladaptive emotion regulation strategies, especially anger.

A second study involved teenage shooting club members and teenage basketball players spending around 40 minutes on target practice – four rounds of ten shots, either firing a gun at a target or throwing a ball at a basket, respectively. Before and after the training they all completed what’s known as a “Lexical Decision Task”. This involves looking at strings of letters and deciding if they’re real words or not. In this case, the researchers were particularly interested to how quick the participants were to recognise words pertaining to aggression and anxiety – greater speed at recognising words with these connotations after the training would be taken as a sign that aggression and anxiety had become more salient in the participants’ minds. The results were clear – for the shooting club members, but not the basketball players, training specifically increased the salience of aggressive and anxiety-related concepts.

The researchers cautioned that their results to not show there is a causal link between shooting club membership and acts of aggression – after all, they did not take any measures of actual aggressive behavior. Nonetheless, they said that the German Shooting Federation (and other shooting federations) “should feel strongly encouraged to counteract aggressive tendencies of their members based on the present results”.


Erle, T., Barth, N., Kälke, F., Duttler, G., Lange, H., Petko, A., & Topolinski, S. (2016). Are target-shooters more aggressive than the general population? Aggressive Behavior DOI: 10.1002/ab.21657

further reading
Are shooting club members more aggressive than most?

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

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Fingerprint matching is biased by the assessor’s prejudices

When we think of crime scene forensics, it’s easy to view it as the objective end of criminal investigation. Witnesses waffle, suspects slide around from the truth, and jurors can be misled by emotive evidence. but the physical evidence simply is what it is. Yet forensic work requires human judgment, and opens the door for human error: for example, a tendency to evaluate evidence differently depending on background information. Now a new study in Law and Human Behaviour suggests that investigators are more likely to match evidence to the wrong suspect when that suspect fits their prejudices.

Laura Smalarz of Williams College and her colleagues asked 225 American undergraduates (88 per cent white, 70 per cent women) to appraise evidence connected to a fictitious crime. Participants first read a mock police report outlining either a molestation of a child in a park, or a string of identity thefts across the city. They then looked at information about a suspect: their photo, name, and other biographic details, as well as a magnified image of their fingerprint and another supposedly found at the scene of the crime. The participants’ task was to judge whether these two very similar prints were a true match. In fact, the prints always differed, meaning the suspect should have been exonerated, rather than incriminated, by the evidence.

For some participants, the suspect was depicted photographically as a white man and labelled Steve Johnson, for others it was Mei Lee, an Asian woman. And this suspect information mattered. Overall, participants were quite accurate in spotting that the prints didn’t match, exonerating Mei Lee about 70 per cent of the time for both crimes, and at a similar rate for Steve Johnson when he was suspected of identity theft. But when considered in the context of child molestation, Steve Johnson’s prints were considered incriminating by fully half the participants.

Smalarz and her colleagues had predicted this result because in an earlier pilot study they found that child molestation conjures strong associations with white men. Most likely it was these associations that lead participants in the main study to make “false positive” errors of judgment (seeing a fingerprint match when there wasn’t one), whether by putting less effort into disproving their intuition, or actually finding it harder to detect such contraindications. Identity theft, meanwhile, wasn’t found to be strongly associated with stereotypes about race or gender in the pilot study, likely explaining why the main study showed no evidence of biased responding in this context.

These results wouldn’t be so worrying if people knew they were being biased – at least then they could try to self-correct. But the participants gave no indication of being conscious that their expectations were influencing their judgments. In fact, their self-ratings of how impartial they were scored marginally higher when investigating Steve Johnson’s role in the child molestation, suggesting that if anything, they saw themselves as acting more objectively in that instance. While it’s true that the participants in this study were not forensic professionals, it’s also the case that professionals often prove as vulnerable as laypeople to cognitive and social biases that skew their judgments – for example, past research has shown that judges give harsher sentences when they’re hungry and that professionals can be as poor as the public in detecting lies.

Salarz’s team argue their new findings may help to explain real-world miscarriages of justice, such as when suspicion for the 2004 Madrid train bombings fell on a convert to Islam who had professionally defended convicted terrorists, seemingly validated by a fingerprint match… that turned out to be wrong. Real-life forensic systems aren’t hermetically sealed; the FBI fingerprint system contains contextual information such as mug shots, biographies, and other content similar to this simulation. The researchers argue that the forensic process would be improved by managing more systematically when data is exposed to an investigator, keeping most of it veiled and only revealing it when the circumstances demand.


Smalarz, L., Madon, S., Yang, Y., Guyll, M., & Buck, S. (2016). The Perfect Match: Do Criminal Stereotypes Bias Forensic Evidence Analysis? Law and Human Behavior DOI: 10.1037/lhb0000190

further reading
how fingerprint experts are biased by context

Post written by Alex Fradera (@alexfradera) for the BPS Research Digest.

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Becoming a parent seems to make us less aggressive

To watch parents vie for parking spaces at the school gates, you might not think it, but a new study in Aggressive Behavior claims that becoming a parent reduces both men’s and women’s aggressive tendencies, although the caveat with men is that they need to be living with a partner too.

Lynda Boothroyd and Catharine Cross analysed all the sentences handed down for robbery or larceny by US federal courts between 1994 and 1999. They focused on these two crimes because both involve theft, but robbery includes the use of force – such as bank robbery or carjacking – whereas larceny – including crimes like theft from benefit plans or receiving stolen goods – does not. The records also included information on whether the 22,344 sentenced criminals had any dependents and the researchers used this as a proxy for parenthood.

Men were seven times more likely than women to be sentenced for robbery rather than nonviolent larceny, and violent theft was also more common among younger age groups, as you’d expect. But the novel revelation is that overall, non-parents were 1.6 times more likely to commit robbery than parents.

Note that sex trumps parental status: fathers were more violent than even childless women. Also, the data for one year (1999) included information on marital and habitation status, and this showed that parental status made no difference to the violent tendencies of single men, but was only associated with reduced violence among partnered men.

The study didn’t follow people over time, so it’s possible that less violent people are more likely to become parents, rather than that parenthood reduces violent tendencies. However, the researchers argue that their results match other research suggesting that parenthood leads to reduced testosterone levels, which favours the idea that parenthood really does cause reduced violence.

Also, the researchers say the notion that parenthood is associated with less aggression fits explanations for violence grounded in evolutionary psychology, whereby men are more violent than women because they have more to gain and less to lose. “Parents – of either sex – have more to lose from aggressive competition than non-parents, and very little to gain,” they said. Personally I can’t help wondering if most parents are simply too exhausted to get involved in any crime that involves physical exertion.

The impact of parenthood on physical aggression: Evidence from criminal data
Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

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