Yanwen’s blog

8/7/2026

Recently I read an introduction to Criminal Behavior: A Psychological Approach, one of the classic textbooks in criminal and forensic psychology. First published in 1991 by Anne M. Bartol and Curt R. Bartol, it has been revised through 12 editions and has been widely used for decades in university courses on criminology, psychology, criminal justice, and forensic science.

What makes the book influential is its psychological approach to crime. Drawing on research from psychology, psychiatry, neuroscience, sociology, biology, and criminology, it explores questions such as why some people become violent, how personality and early life shape behavior, and how biological and environmental factors interact. It also discusses topics including psychopathy, juvenile delinquency, violent crime, sexual offending, mental illness, and offender rehabilitation.

What interests me most is what this research teaches us about human nature. Understanding why some people commit crimes helps us better protect ourselves and our children, while also giving us a deeper understanding of human behavior.

One question I had before reading about the book was: Are some people born evil?

The answer, according to modern psychology, is no. There are no absolute "born criminals." Some people are born with biological traits that increase their risk of criminal behavior—such as greater impulsivity, lower empathy, heightened aggression, or a stronger tendency toward risk-taking. These are risk factors, not destiny.

One well-known psychological framework is the Dark Triad, a combination of three personality traits associated with a greater likelihood of manipulative and antisocial behavior.

The first is Machiavellianism—a tendency to manipulate others for personal gain with little regard for morality and others.

The second is pathological narcissism—an exaggerated sense of self-importance coupled with intense anger when one's inflated self-image is threatened.

The third is psychopathy, characterized by having no feeling, lack of empathy and remorse, and a willingness to exploit others.

Yet possessing these traits does not inevitably lead to criminal behavior. Many people with some of these characteristics function successfully within society and never commit crimes.

That brings us to another important idea:

Genetics loads the gun, but the environment pulls the trigger.

Genes may create vulnerabilities, but whether those vulnerabilities develop into criminal behavior depends greatly on life experiences. A warm, supportive family, positive role models, and healthy social environments can become powerful protective factors.

Extensive research shows that many adult offenders experienced childhood adversity, including neglect, abuse, chronic family conflict, or parental absence. Such experiences do not guarantee criminal behavior, but they can significantly increase the risk.

A Chinese saying captures the role of external circumstances in shaping aggressive behavior: 兔子急了咬人 (Tùzi jí le yǎo rén), meaning that even a gentle rabbit will bite when cornered or pushed beyond its limits. This suggests that aggression or violence can arise from circumstances, not just innate disposition.

Another finding surprised me. In homicide cases, victims are often killed not by strangers but by people they know—family members, intimate partners, friends, acquaintances, or colleagues. The greatest danger frequently comes from within one's social circle rather than from an unknown assailant.

The motives for homicide are varied, including domestic conflict, jealousy, financial disputes, revenge, sexual violence, and, more rarely, thrill-seeking. While the specific motives differ, many murders arise from conflicts that gradually escalate rather than from random encounters.

This changes the way we think about personal safety. Staying indoors after dark or installing stronger locks certainly has its value, but safety also depends on recognizing warning signs in the people around us. Sometimes the greatest protection comes not from securing our homes against strangers, but from learning to recognize unhealthy, manipulative, or violent relationships before they turn dangerous.

My biggest takeaway from this book is that understanding crime is ultimately about understanding people. The better we understand human nature—both its strengths and its vulnerabilities—the better equipped we are to protect ourselves, raise our children wisely, and build healthier relationships.

8/6/2026

While watching my son take care of his new baby yesterday morning, two Chinese sayings came to mind:

丢了西瓜，捡了芝麻
Diū le xīguā, jiǎn le zhīma
Literally: “Throw away the watermelon and pick up the sesame seeds.”

It means giving up something much more valuable while focusing on something relatively trivial—losing sight of the big picture while worrying about the small things. It's like an English saying, "Penny wise and pound foolish."

Its opposite is 抓大放小 (zhuā dà fàng xiǎo): focus on what matters most and let go of what matters less.

There is a deeper parenting principle here: not every problem deserves the same amount of attention.

With a newborn, parents can easily become anxious about every small deviation: How long did the baby sleep? How much did he eat? Did he burp enough? Is his routine exactly right?

But the most important priorities are actually quite simple:

1. Keep the baby physically safe.

2. Make sure he is adequately fed and cared for.

3. Respond when he genuinely needs help.

4. Build a secure emotional attachment.

5. Give him room to sleep, grow, and develop at his own pace.

6. Create a warm and stable home.

7. As he grows, help him develop curiosity, independence, resilience, and good character.

These are the “watermelons.”

By contrast, parents don't need to become overly anxious about every “sesame seed”:

1. A particular nap doesn't go according to schedule.

2. The baby eats less than expected on one occasion.

3. He is unusually fussy one day.

4. The house isn't perfectly organized.

5. The daily routine doesn't follow the parenting book exactly.

6. The child doesn't reach every developmental milestone according to someone else's timetable.

Of course, this doesn't mean ignoring persistent feeding problems, unusual lethargy, breathing difficulties, injuries, or other genuine warning signs. 

抓大放小 requires judgment. The point is not to care less; it is to learn what deserves more care.

Keep in mind that as long as the baby is safe, healthy, and loved, many other things can be adjusted and caught up over time.

I think this principle becomes even more important as children grow.

Modern parenting creates a strong temptation to optimize everything: grades, extracurricular activities, sports, screen time, sleep schedules, social skills, college preparation, and even the child's personality and future career.

Parents can feel the pressure and become so focused on getting every detail right that they lose sight of the larger goal.

A child may have excellent grades, impressive extracurricular activities, perfect manners, and a carefully managed schedule, yet be afraid of making mistakes, dependent on parental approval, or unable to make decisions independently.

That would be 丢了西瓜，捡了芝麻.

And this connects to what I have been writing about perfectionism. When parents constantly correct, optimize, and worry about every little thing, children may gradually learn that mistakes are dangerous and that everything must be done perfectly. That can feed exactly the kind of fear-driven perfectionism we should be trying to prevent.

Good parenting isn't about getting every detail right.

It is about knowing which things matter most—and getting those things right.

8/5/2026

Many years ago, I read Seeing the Forest for the Trees: A Manager's Guide to Applying Systems Thinking by Dennis Sherwood, published in 2002.

The book introduced me to the idea of systems thinking—looking beyond individual events and symptoms to understand the larger system, the relationships among its parts, and the underlying causes that produce what we see on the surface.

It reminds me of a Chinese saying:

头痛医头、脚痛医脚
Tóu tòng yī tóu, jiǎo tòng yī jiǎo

Literally, it means: “Treat the head when the head hurts; treat the foot when the foot hurts.”

The saying describes the tendency to deal with a problem only where it appears, without asking what caused it in the first place. In English, there's a similar saying, “Treat the symptoms, not the root cause.”

This is exactly the kind of thinking that systems thinking tries to prevent.

A system is not simply a collection of independent parts. Its parts interrelate to and interact with one another, influence one another, and together produce outcomes that may not be obvious when we look at each part separately.

The human body is a good example. It is an integrated system made up of many interconnected subsystems —circulatory, respiratory, digestive, nervous, muscular, endocrine, immune, reproductive and others.

If we experience a headache, the pain is in the head. But the cause may not necessarily originate there. It could be related to dehydration, lack of sleep, stress, medication, blood pressure, vision, or many other factors.

The important lesson is not about diagnosing headaches. It is about how we think about problems.

If we see only the visible symptom, we may rush to fix whatever is immediately in front of us. But if we step back and ask, “What larger system produced this problem?”, we may see deeper than the surface and discover an entirely different solution.

We do this kind of “头痛医头、脚痛医脚” thinking more often than we realize.

A company has declining sales, so management pushes the salespeople harder—without asking whether the product, pricing, customer experience, or market has changed.

A child is doing poorly in school, so parents demand that the child study more—without asking whether the problem is motivation, sleep, anxiety, learning methods, or the relationship between parent and child or between teacher and child.

Someone keeps procrastinating, so they blame themselves for lacking discipline—without asking whether the task itself is unclear, overwhelming, or poorly structured.

In each case, the visible problem is real. But the root cause may be hidden elsewhere.

That is why systems thinking is useful far beyond business management.

When we encounter a difficult problem, the first question should not be: “How do I fix this?”

but: “Why is this happening? What's going on beneath the surface?”

And then: “What other parts of the system might be contributing to it?”

This way of thinking can prevent us from repeatedly facing and solving the wrong problem.

Sherwood's book title, Seeing the Forest for the Trees, tells us: don't become so focused on the tree in front of you that you forget to look at the forest that produced it.

8/4/2026

Yesterday I wrote that the prefrontal cortex is one of the last major brain regions to mature, with its structural and functional development continuing through adolescence and into the third decade of life.

But development doesn't stop there. The brain remains plastic throughout life. Learning, experience, and our environment can continue to reshape neural connections and brain function.

That means how we live matters.

Healthy habits such as adequate sleep, regular aerobic exercise, mindfulness, and sustained mental engagement can support cognitive and prefrontal function. 

Chronic stress, sleep deprivation, and prolonged social isolation, on the other hand, are associated with changes in brain structure and function, including in regions involved in decision-making, social cognition, and emotional regulation.

Studies indicate prolonged social isolation reduces grey matter density within the prefrontal cortex. Loneliness may feel like an emotion, but research suggests that chronic loneliness is associated with measurable changes in the brain, including areas involved in decision-making, social cognition, and emotional regulation. 

Another factor deserves special attention: our information diet.

Informational junk food: Short-form videos, constant notifications, and algorithmically curated feeds are designed to capture attention and encourage rapid, repeated engagement. They require little sustained concentration and can train us toward constant stimulation and instant gratification.

Just as our physical bodies are shaped by what we repeatedly consume, our minds are shaped by what we repeatedly pay attention to. If we spend hours jumping from one short video to another, our ability to sit quietly with a book, think through a difficult problem, or sustain a conversation may suffer.

That doesn't mean dopamine “pleasure chemical” simply “overpower” our PFC.

Dopamine plays an important role in motivation, learning, and reward prediction. It can increase the anticipation and pursuit of a rewarding experience. That's one reason an endless stream of potentially interesting videos can keep us scrolling: believing the next one might be better.

Over time, repeated behaviors can also become habits. Brain circuits involving the striatum and other regions help automate familiar behaviors, reducing the need for conscious deliberation each time we perform them.

That's why mindlessly opening a short-video app can feel almost automatic. We don't necessarily make a fresh decision every time. The habit has made the decision easier.

So perhaps the answer is to design our environment and habits so that our better judgment gets a chance to operate.

Get enough sleep. 

Exercise regularly. 

Spend time with real people. 

Read something longer than a few minutes.

Work on one thing without constantly switching. 

And protect some part of each day from algorithmic feeds and notifications.

Even thirty minutes of uninterrupted reading, writing, thinking, or face-to-face conversation can be a small act of resistance against constant stimulation.

We spend a great deal of effort taking care of our bodies. We should be equally taking care of the part of our brain that helps us pause, think, choose, and decide what kind of person we want to become.

8/3/2026

Recently I came across a buzzphrase on the Chinese internet:

“与前额叶健康的人做朋友”
Yǔ qián é yè jiànkāng de rén zuò péngyou
— “Make friends with people who have healthy prefrontal cortices.”

The phrase has spawned all kinds of humorous variations, such as “stay away from people with underdeveloped prefrontal cortices” and “check someone's prefrontal cortex before starting a relationship.”

Behind the joke is a fascinating piece of neuroscience.

The prefrontal cortex (PFC) is one of the most advanced regions of the human brain and one of the last to mature. It is heavily involved in what neuroscientists call executive functions: planning, decision-making, working toward long-term goals, inhibiting inappropriate impulses, and regulating behavior.

The PFC is also unusually large in humans. Depending on how it is defined, it has been estimated to account for up to about 29% of the human cerebral cortex, compared with about 17% in chimpanzees. The exact numbers vary according to the anatomical definition being used, but the broader point is clear: the human PFC is exceptionally expanded relative to that of other primates.

In everyday life, we might think of the PFC as the brain's management center.

It helps us pause before reacting in anger.

It helps us weigh costs and benefits before making a decision.

It helps us work backward from a goal and formulate a plan.

It helps us consider another person's perspective rather than seeing everything only from our own point of view.

It also helps us regulate our emotional responses.

This is where the PFC's relationship with the amygdala becomes interesting. The amygdala is involved in detecting emotionally significant or threatening stimuli and can contribute to rapid emotional responses such as fear. The PFC and other brain regions interact with the amygdala in regulating these responses.

In simple terms, however, the metaphor of the brake is useful. 

When someone insults us, our first impulse may be to strike back.

When we are angry, we may want to say something hurtful immediately.

When we see something we want, we may want it that moment.

A well-functioning regulatory system gives us the ability to pause, think of consequences and ask: “What happens if I act on this impulse?”

That may be what the Chinese internet saying is really getting at when it says, “Make friends with people who have healthy prefrontal cortices.”

It means we might want to spend time with people who can remain calm when emotions run high, think before they speak, consider consequences, listen to other perspectives, and resist every passing impulse.

We should choose friends not only for how much fun we have with them, but also for how they influence the way we think and behave.

And if the PFC is so important, an interesting question naturally follows:

What can we do to keep our own prefrontal cortex healthy and strengthen our ability to think before we act?

That's what I'll explore tomorrow.