Poisonous People
Leanne ten Brinke
Simon & Schuster

It seems only fitting that a book about dark personalities opens with the case study of a psychopath. But the author’s choice isn’t who you might have been expecting. Instead of a criminal whose misdeeds are on trial, it turns out to be the highly regarded judge hearing his case.

William O. Douglas, a US Supreme Court justice, is remembered as a towering figure of mid-20th-century liberal theory, but psychologist Leanne ten Brinke says in her new book Poisonous People that he would probably meet the “modern definitions of psychopathy”. While his misbehaviour never rose to the level of prosecutable offence, he left a trail of personal and professional wreckage that darkened every life he touched, writes ten Brinke.

The formal diagnosis of psychopathy was discontinued in 1952, in large part because of perceived stigma, supplanted by more nuanced diagnoses like antisocial personality disorder. But in the 1980s, the term was reintroduced in a criminal context, with criteria called the Psychopathy Checklist Revised used to evaluate the most dangerous criminals, whose brutal crimes and lack of empathy or compunction necessitated a way to tell how likely they were to reoffend or be rehabilitated. People whose score on this test identifies them as a psychopath account for around 1 per cent of the population, but by some estimates they are responsible for half of all serious crime, writes ten Brinke.

But ten Brinke, who directs the Truth and Trust Lab at the University of British Columbia in Canada, argues that, just because you don’t kill someone, doesn’t mean you don’t possess elevated levels of the same dark personality traits. “When we expand our view of psychopathy to include the larger slice of the population – perhaps 10 to 20 percent – who would score high on some traits related to psychopathy but not enough to be considered a ‘psychopath’ by clinical standards, we find these people everywhere,” she writes.

In Poisonous People, she tallies up the costs these “aggressive, predatory individuals” impose on society and puts together a playbook on how to minimise their impact on your life. But there is a catch.

Over the past two decades, personality researchers have developed a framework known as the dark tetrad. This describes the intersection of four personality traits: psychopathy (total imperviousness to the feelings of others), Machiavellianism (icy strategising and manipulation), narcissism and sadism.

While pop culture feeds the idea that psychopathy is a binary diagnosis in that you either have it or you don’t, ten Brinke explains that it is more of a sliding scale. We all fall somewhere on the spectrum, and our score on any single trait is independent of the others. The 10 to 20 per cent of us with high marks on those traits related to psychopathy have a unique affinity for “eroding ethical standards and sowing fear and mistrust”, she writes.

That’s the bad news, but surely the good news is that 80 per cent of us don’t hit those high scores. Right? Again, not so fast, says ten Brinke. In addition to being on a spectrum, the traits are malleable. That is, they are easily dialled up and down by our environment.

In meticulous case studies, she illustrates how “cultures of rot” can turn the 80 per cent into what she calls “situational psychopaths”. “Kind and empathic people are prone to infection by dark personalities,” she writes. Everything from excessive fatigue and extreme heat to the in-group dynamic propelled by sports fandom can lead people to view verbal and physical abuse of other people as an enjoyable pastime.

The book does dispense plenty of useful advice on how to protect ourselves from the “poisonous people” in our midst, such as establishing clear rules (because they love identifying and then taking advantage of unwritten rules). But more of the book is devoted to a stern call for self-reflection. How can we resist losing our own moral bearings? And how can we stop enabling malicious people? After all, we are the ones who elevate them to positions where they can wreak such havoc at an above average rate, as ten Brinke shows. Why do we vote for people with these traits? Why do we hire them to run businesses?

You may answer that dark traits make for effective leaders, but ten Brinke explodes this myth in an illuminating section of the book. She describes how her research on dark traits in investment bankers revealed an unexpected correlation between psychopathy and financial outcomes.

It turns out that “the most malicious and cunning managers generated returns 30 per cent lower than the average manager over a ten-year period”. And cooperative managers beat them all. “If you want to make less money as an investor,” she concludes, “you would do well to find the meanest, most cut-throat predator to manage your wealth.”

So where do we get our pop-sci fantasy of the ultra-competent psychopath? A lot of it comes from them. Dark-tetrad types tell far more lies, she writes, especially of the big self-aggrandising variety. Not only do they get a reward from it, called “duping delight”, but it furthers specific goals. As ten Brinke writes: “In the workplace, your employee might claim to be a highly effective leader, a clear communicator, or the team’s strongest performer. This could be true – or it could be narcissistic delusions and outright lies.”

The problem is that we are all too happy to believe them, she writes, and in so doing become complicit in their harm. We could at least make it a bit harder for them, she argues, by dialling up a small fraction of our own dark traits – specifically, a Machiavellian ability to engage in critical thinking. This would help us spot when we are being lied to.

Ten Brinke doesn’t promise low-effort approaches to rooting out liars. “If lying were so easy and straightforward to detect, there would be little point in doing it,” she reminds us.

But it can be done if you pay attention. If a minority of “bad apples”, as she calls them, ruin the barrel, the rest of us have some choice in whether or not to let the rot set in. Indeed, ten Brinke hints there may be some personality types within the 80 per cent who can not only stop the rot, but reverse it. These people pair dark traits with qualities that we don’t normally associate with them, like empathy and conscientiousness.

Their mere existence explodes another uncritically accepted axiom among the 80 per cent, that “absolute power corrupts absolutely”. In fact, this only holds true for the worst among us, says ten Brinke. Taking responsibility for your barrel of apples may require being more disciplined and honest about your own character. But there are rewards. Power is actually value neutral. It just makes us more of what we already are.

So we just need to figure out as a society how to cultivate what I’m going to call the “moral Machiavellis” among us. It would be a big improvement on a world that currrently seems to be an assembly line for psychopaths.

Three other great books on bad behaviour

Born Liars: Why we can’t live without deceit
Ian Leslie
Psychopaths might be inveterate liars, but the rest of us don’t come out so squeaky clean either. This book examines what it is that makes lying so irresistible for so many of us. Remember, it is also one of the developmental milestones of childhood.

Snakes in Suits: Understanding and surviving the psychopaths in your office
Paul Babiak and Robert D. Hare
This follows Robert Hare’s highly influential book Without Conscience: The disturbing world of the psychopaths among us. This time written with fellow psychologist Paul Babiak, Snakes in Suits concentrates far more on non-criminal psychopaths, who are probably working in an office.

The Prince
Niccolò Machiavelli (translated by N. H. Thompson)

The original treatise on unscrupulous politics was written by Niccolò Machiavelli, an Italian diplomat and scholar, in 1513. For many centuries, it was interpreted as an endorsement of manipulation and became synonymous with deviousness. In recent years, however, it has been rehabilitated as a self-defence manual against these dark arts.

Sally Adee is a science writer based in London