Toxic People: 7 Psychological Strategies to Neutralize Their Dark Minds

Author Leanne ten Brinke · Publisher Ungjin Jisikhous · Published 2026-07-24 · ISBN 9788901300283

About the Book

"Psychopathy, Narcissism, Machiavellianism...
One in five people around you is a toxic person."
- A Canadian psychologist reveals the mechanisms of dark psychology through over 20 years of research on psychopaths.

Approximately 16,000 reports of workplace bullying were filed with the Ministry of Employment and Labor in one year. However, 55.7 percent of those who experienced bullying responded that they "endured it or pretended not to notice" (Workplace Bullying 119, 2025). The biggest reason was "because even if I responded, the situation wouldn't get better."

Tricia (pseudonym), a victim of workplace bullying interviewed by Canadian psychologist Leanne ten Brinke, was no different. Her boss, Kelly, was a person who habitually used verbal abuse and shifted the blame for prescription errors onto her subordinates. In the end, Tricia left the company and suffered from the after-effects for a long time, but Kelly continues to operate her pharmacy as if nothing happened.

The author refers to people like Kelly, who lack empathy and harm others through lies, incitement, and gaslighting, as 'toxic individuals.' Their personalities fall into the 'dark personality types' consisting of psychopathy, narcissism, Machiavellianism, and sadism. These individuals, who exist among us as lovers, bosses, colleagues, and neighbors, account for only about 20 percent of the population, but just as one rotten apple spoils the whole barrel, they sicken the people around them and the entire organization.

The conclusion that social psychologist Leanne ten Brinke reached after 20 years of studying toxic individuals is simple: toxic individuals have predictable tendencies and patterns, and these patterns can be learned and recognized. 『Toxic People』 is her first popular science book summarizing her research. In this book, the author psychologically dissects the mechanisms of manipulation and deception that are repeated in human relationships and provides realistic coping strategies for victims to reclaim control of their lives.

"Why are we most easily attracted to the most dangerous people?"
- Toxic individuals who approach with a complete mask and subtly exploit our instinct to trust.

Dark personality types, including psychopathy, are not as rare as one might think. Approximately 20 percent of the population, or one in five people, falls into this category. So how can we recognize 'toxic individuals' who exist among us with ordinary faces?

Recent psychology views psychopathy as a measurable personality trait across four domains: interpersonal relationships, emotions, risk assessment, and social norms (Chapter 1, Robert Hare). The typical characteristics observed in the PCL-R test, a tool for measuring psychopathy, are superficial charm, pathological lying, lack of empathy and guilt, impulsivity and irresponsibility, and violation of norms. However, the author explains that psychopathy is not an 'either/or' quality but a continuous trait that shows varying degrees, much like cholesterol levels. Narcissism, Machiavellianism, and sadism also share the common traits of manipulating others and lacking empathy, differing only in intensity.

So why do so many people fall for them? The author says the reason lies in the most powerful weapon of toxic individuals: 'superficial charm.' They approach wearing a 'mask of sanity' and exploit human psychology, which is designed to inherently trust people. In psychology, this is called the 'truth-default.' While we have evolved to assume that what others say is true, toxic individuals are precisely the ones who most effectively exploit that trust.

From the returns of ruthless fund managers to the downfall of lying politicians
"The illusion of rudeness and confidence,
toxic culture infects individuals, organizations, and society as a whole."

It often seems to us that toxic individuals always succeed, but that is an illusion. The author analyzed interview videos of 101 hedge fund managers, calculated their dark personality scores, and compared them with their actual operating performance over 10 years, yielding results contrary to common belief. Managers with strong dark traits had returns approximately 30 percent lower than the average (Chapter 2).

According to the author, toxic individuals actually impose enormous costs on individuals, organizations, and society as a whole. They pollute workplace culture, increase turnover rates, and reduce productivity. In fact, research has shown that a toxic organizational culture is 10.4 times more powerful a predictor of turnover than salary (Chapter 2). Furthermore, the cost incurred by psychopathic criminals in American society is estimated to be over 1 trillion dollars annually, and the damage they leave behind extends beyond economic losses, undermining the foundation of social trust and cooperation.

Yet, why do they often rise to positions of power? It's because humans tend to mistake rudeness and confidence for competence and leadership. If the man next to you on the subway spreads his legs wide, encroaching on your space, most people instinctively recoil rather than confront him. In this way, humans have a tendency to automatically conform to 'displays of dominance,' and toxic individuals exploit this gap to rise to power. However, contrary to this bias, leaders with high empathy actually achieve higher performance, while leaders with strong dark traits often diminish organizational performance (Chapter 3).

A similar phenomenon occurs in politics. The author's analysis of speeches by 151 U.S. senators showed that senators with stronger dark traits won elections more frequently and served longer. However, after taking public office, they struggled to secure cooperation from fellow legislators, leading to low legislative performance. The very traits that enabled their election paradoxically became obstacles to their job performance (Chapter 2).

A bigger problem is that toxicity is contagious. Toxicity spreads throughout an organization through three channels: imitation, emotional contagion, and zero-sum competition. People who see someone succeed through toxic means imitate them, coldness and hostility become the default emotions of the organization, and the norm of "I win if you lose" takes root. As seen in the case of former Uber CEO Travis Kalanick, a toxic culture spreads from being an individual's problem to an organization-wide problem. Ultimately, one rotten apple spoils the whole barrel.

"Gaslighting, lies... if you see through their patterns, you won't be fooled anymore."
- How to spot toxic people in 10 seconds and seven psychological strategies to neutralize them.

So how can one see through the mask of people who deceive and manipulate others? In 2008, a twelve-year-old girl named Karissa Boudreau went missing in a Canadian town. Her mother, Penny, appeared on television, desperately searching for her daughter, but the author, then a graduate student, noticed that the emotional expressions and actual facial expressions in the video were inconsistent. She was lying. Later, the investigation revealed that Penny was the one who had killed her daughter (Chapter 4).

We commonly think that liars avoid eye contact or fidget. However, research points to the real clues being in the specificity and consistency of statements rather than non-verbal behavior. This is because prepared lies easily falter when faced with unexpected questions. The author states that even untrained individuals can detect warning signs by observing behavior for about 10 seconds. To this end, the book also includes 'Dark Personality Detection Questions' and 'Dark Behavior Diagnostic Items' (Chapter 4).

Once you recognize a toxic individual, the next is a matter of choice: cut them off or stay. The author advises that if you decide to leave a toxic individual, don't mistake feelings of guilt and lingering attachment as signs of change. Dark personality traits are not easily altered, and love bombing and gaslighting are likely manipulative strategies to maintain the relationship. She also emphasizes that you should calculate the future costs you will incur rather than the time you have already invested (Chapter 6).

However, in reality, toxic individuals are often bosses, family members, or clients, making it difficult to sever ties. Therefore, the author also provides coping strategies for those who cannot leave and must maintain the relationship.

1. Set clear boundaries
- Clearly define the scope of the relationship and acceptable behavior standards.
2. Do not give them the authority to control others
- Do not surrender control over decision-making and emotional responses.
3. Find a win-win point
- When interests align, they won't make you their scapegoat.
4. Use carrots, not sticks
- For those who don't learn from punishment, rewards are more effective.
5. Emphasize common identity
- A sense of 'us' can elicit prosocial behavior even from them.
6. Verify facts over words
- Investigate and cross-reference like a detective, and document everything.
7. Negotiate in writing rather than face-to-face if possible
- Reduce the room for their most powerful weapon, persuasion, to operate.

Of particular note is the explanation of punishment. Research shows that individuals with strong psychopathic traits have a relatively low ability to learn from punishment. Therefore, the common belief that "strong scolding will change them" often does not work for them. This is also why punishment-centered organizational cultures and criminal policies show limitations (Chapter 7).

Ultimately, what the author emphasizes most is realistic expectations. She states that understanding their true nature as it is comes before hoping that they will change someday. The movement to reclaim control of one's life begins the moment one accepts that reality.

"Everyone becomes toxic sometimes."
- The true antidote to reclaiming control of life from toxic people, so as not to become situationally psychopathic.

『Toxic People』 finally turns its gaze to the reader. The author expresses caution against viewing toxic individuals solely as a problem of a born few. Timothy Kwong, the young man who impulsively set fire to a car during the 2011 Vancouver Stanley Cup riot, was not an inherently evil person but an ordinary citizen swept up in crowd psychology and anonymity. When frustration and stress combine with an "us vs. them" mentality and anonymity, anyone can temporarily exhibit callous and aggressive behavior.

The author describes this as 'situational psychopathy.' She candidly confesses her own experiences with road rage and how she transformed into a competitive and cold person under a toxic boss. If psychopaths are not entirely different from us, then we, too, might not be so different from them in certain situations.

Therefore, the author encourages readers to apply the standards they use to evaluate others to themselves. She suggests checking one's own behavior with the 'Dark Behavior Diagnostic Items' (Chapter 4) included in the book, reducing lies, expressing kindness and gratitude, and making sincere apologies when wrong. These small practices do not end with the individual but spread to change the culture of organizations and communities.

The focus extends beyond individuals to institutions. The author argues that success should be evaluated not only by results but also by process, and leaders should be selected based on character as well as competence. The most effective way to stop toxic individuals is to prevent them from monopolizing power in the first place.
In the epilogue, the author presents a solution in the form of a small bird called the Mexican jay. This bird did not completely eliminate the bacteria causing eye infections but succeeded in coexisting by developing both resistance and immunity so that even if infected, it would not suffer fatal damage. The author states that we, too, should not try to completely eliminate toxic individuals but rather develop the ability to recognize risks and minimize harm.

Cognitive psychologist Professor Kim Kyung-il, in his recommendation for this book, says, "The process of studying toxic individuals is ultimately the process of learning how to recognize good people." This is also the message the author emphasizes until the end. The most powerful antidote to toxic individuals is not special psychological techniques, but the strength of the good majority who trust and support each other.

Table of Contents

PROLOGUE | About the Darkness Lurking Beside Us

chapter 1 People Born with Dark Personalities
Meeting the Worst Control Freak Boss | Introducing Toxic People | Psychopathic Traits Exist on a Spectrum | The Anatomy of Psychopathy | Domain 1: How They Relate to Others | Domain 2: How They Experience Emotions | Domain 3: How They Assess Risk | Domain 4: How They Handle Social Rules and Conventions | 20 Percent of the Total Population | Four Types of Darkness | The Tyranny of the Few

chapter 2 How the Vicious Few Ruin Everyone
The Returns of a Ruthless Fund Manager | The Bill from Toxic People | Why Lying Politicians Win | Abuse Disguised as Love | When My Child Shows Dark Traits | The Man Who Lives on Talisman Drive

chapter 3 The Process of Toxicity Spreading
Why We Give Them Power | The Illusion that Cold-Blooded Leaders Are Competent | The Betrayal of Goodness | Machiavellian Mothers | How Corrupt Corporate Culture Spreads | Lift the Veil

chapter 4 How to Spot a Toxic Person in 10 Seconds
Her Face Tells a Lie | Detecting Liars | Charming First Impressions | Evaluating Casual Acquaintances | Listening to Your Own Dark Detector | Revising First Impressions

chapter 5 Everyone Becomes Toxic Sometimes
A Weekend Trip That Became a Nightmare | Situational Psychopathy | Becoming Anonymous in a Group | How to Keep Darkness at Bay

chapter 6 To Stay or to Leave
Harsh Truth 1: Confusing Emotions Are Normal | Harsh Truth 2: Dark Personalities Persist | Harsh Truth 3: Leaving Becomes Harder Over Time | Harsh Truth 4: No Guarantee of Change, No Matter How Hard You Try | Harsh Truth 5: You May Not Be the Only One Suffering | Harsh Truth 6: Therapy Is a Long and Arduous Journey | Harsh Truth 7: Leaving Can Also Be Risky | Moving to the Other Side

chapter 7 Seven Strategies for Dealing with Toxic People
Rule 1: Set Clear Boundaries | Rule 2: Do Not Give Them Authority to Control Others | Rule 3: Find a Win-Win Strategy | Rule 4: Use Carrots, Not Sticks | Rule 5: Emphasize Common Identity | Rule 6: Be a Detective | Rule 7: Avoid Face-to-Face Negotiations | The Power of Realistic Expectations

chapter 8 Facing the Darkness Within Us
My Inner Psychopathy | The Habit of Compassion and Kindness | The True Antidote | Better Leaders Definitely Exist | Redefining Success

EPILOGUE | The Antidote to Toxic People
Acknowledgments
Notes
Recommendation | Kim Kyung-il, Cognitive Psychologist