1 The Unfathomable Human Mind—A Millennia-Old Puzzle of Understanding Others

If there is one thing that is hardest to see through, it must be the human mind. Traditional Chinese culture has long had numerous descriptions of the unfathomable nature of the human mind: "In drawing a tiger, you can paint its skin but not its bones; in knowing a person, you can know their face but not their heart"; "The depth of the world's oceans can be known, but the human mind is hard to measure"; "The human mind is separated by a belly"... and countless others like these.

These sayings, passed down for thousands of years, actually point to the same fact: there is always an unbridgeable chasm between a person's external behavior and their true inner state—we can see a person's expressions, hear their words, and observe their behavior, but we cannot directly know: What do they truly believe? What do they truly fear? What do they truly want? Even, is the thought they express indeed their true inner thought?

Therefore, understanding the true inner state of others has long been an ability that humans yearn for, and it is constantly imagined and depicted in literature, film, and television. The most typical manifestation of this is giving characters in stories an ability that does not exist in reality—the ability to directly ”read” the minds of others.

The 2000 film What Women Want, starring Mel Gibson, tells the story of a man who accidentally gains the ability to read women's inner thoughts:

Although these works take different forms, they are all built on the same fantasy: if humans could break through normal information limitations and directly read another person's true thoughts, the natural information barrier between people would disappear. Consequently, misunderstandings could be reduced, lies could be exposed, and relationships between people would seem capable of being understood and predicted in advance.

But the reality is that humans cannot directly read the minds of others; we can only infer inner states through external behavior.。

2 The Inner World That Cannot Be Directly Observed

The reason humans can understand the world is that we possess a set of methods that are constantly accumulated and refined: when facing various objects in the external world, humans typically observe, measure, analyze, and build models to gradually understand the underlying laws.

For example, physics studies the motion of objects by observing changes in position, velocity, and forces to build models of the laws of motion; medicine studies human diseases by testing physiological indicators and observing tissue changes to gradually understand the mechanisms of disease occurrence and development.

In these processes, humans may not necessarily be able to directly see the entire process of how things operate, but we can at least gradually approach the true laws hidden behind the appearances by continuously acquiring new information and revising existing models.

However, when the object humans attempt to understand shifts from the external world to “another person's inner world,” the problem begins to complicate. This is because a person's inner state is not an object that can be directly observed from the outside, but rather a high-level information state generated by the complex system of the brain: tens of billions of neurons in the brain, through complex connection structures and dynamic activity patterns, together form a highly complex information processing system, and what we usually call thoughts, emotions, and various internal states are precisely generated during the operation of this system.

Today's technology is already capable of acquiring and analyzing partial brain activity and neural signals through techniques such as EEG, brain imaging, and brain-computer interfaces. For example, we can observe changes in the activity of certain brain regions during specific tasks, and we can also identify and predict some simple information patterns through machine learning models. These technologies allow humans, for the first time, to observe the operating state of the brain from the outside in a more direct and refined way.

However, there is still a huge gap between this and “mind reading” in the true sense. The reason is:Brain activity itself is not equivalent to a directly understandable psychological state. A person's complete inner state is not determined by a single neural signal: a thought, a memory, or an emotion is often the result of the combined action of a large amount of neural activity, personal experience, knowledge structure, and the current environment.

Therefore, even if certain changes in brain activity are observed, we still need to understand further: What do these signals represent? Why does this state occur? What does this state mean for this specific individual?

This is similar to how we can see a computer running and observe changes in the processor, memory, and data, but without understanding the data structures and operational logic of the entire system, merely seeing the low-level signals cannot directly reconstruct what task the user is completing—let alone the complexity of the human brain, which far exceeds most artificial systems created by humans today.

Therefore, although humans have begun to understand the physical basis of consciousness, we are still very far from fully decoding a person's inner world. This also dictates that, in the short term, humans cannot directly understand others through information reading, but can only make inferences based on limited information.

3 From Behavioral Signals to Models of Human Nature—Four Ways to Understand Others

1 From Limited Information to Understanding Others

So, in the absence of direct mind-reading, how exactly do humans make inferences based on limited information and gradually understand others?

If we observe closely, we will find that there is more than one way for humans to understand others: some are good at capturing subtle behavioral changes, some rely on long-term accumulated life experience, some use systematic theories such as psychology, and others go further to summarize universal laws of human nature from a large number of individual behaviors.

These abilities seem to vary greatly, but in fact, they can be classified according to the direction offrom concrete to abstractinto four levels:Behavioral Signal Level → Pattern Experience Level → Psychological Mechanism Level → Human Nature Structure Level, which are not four mutually exclusive methods, but rather four different levels of cognitive models that humans may use when understanding others.

2 Level 1: Behavioral Signals—What Do We See?

The starting point of understanding a person is what we can actually observe.

A person's inner state cannot be directly seen, but is often manifested through certain external behaviors: facial expressions, tone of voice, way of speaking, body language, behavioral choices, immediate reactions to specific events... These are the “behavioral signals”。

For example, a person says “I'm fine,” but their voice noticeably drops, their expression changes briefly, and they deliberately avoid a certain topic. We have not read their mind, yet we have already obtained some information related to their inner state.

This type of ability is very typically depicted in film and television works. The protagonist Lightman (played by Tim Roth) in the American TV series Lie to Me is an artistic representation of this ability:

By observing micro-expressions, voice, body language, and inconsistencies between words and actions, he judges what emotions or information a person might be hiding.

Of course, behavioral recognition in reality is far less magical than depicted in TV shows: a single glance or gesture in itself cannot directly prove that someone is lying, because the same behavior can correspond to completely different psychological states.

Therefore, the focus of behavioral signal analysis is not to find some “key evidence” that can directly reveal the truth, but to establish a preliminary judgment of a person's current state through a combination of multiple external clues. In other words, an isolated signal cannot be directly equated to a conclusion; a truly effective judgment comes from the combinational relationship among multiple behavioral signals, as well as the connection between these signals and the specific context.

What this level actually addresses is the first fundamental question of understanding others: What can we observe from a person's external performance?

3 Level 2: Pattern Experience—Have We Seen Similar Situations Before?

Humans do not start analyzing from scratch every time they face others. As we age and accumulate social experience, we constantly encounter various people and events, forming a large number of behavioral patterns in our memory. When a new situation arises, we often subconsciously make a comparison: “Have I seen this situation before?”

For example, a manager notices that an employee has suddenly become unusually cautious recently, repeatedly explaining their decisions during every report. A young person who has just started working might only notice: Why is he talking so strangely lately? But a manager who has experienced many similar situations may have already formed an empirical pattern: when a person suddenly starts over-explaining, it often means they are under some kind of pressure, or they worry that others might doubt their actions.

Forming such a judgment does not necessarily require psychological knowledge; it can also simply be the result of long-term accumulation of real-world experience. Sherlock Holmes in literature is a classic representative of this empirical judgment being dramatized: he is often able to quickly judge what a person might have gone through, what kind of work they do, or even where they have just been, based on their clothing, movements, habits, and traces of life.

Of course, Sherlock Holmes's reasoning also involves the artistic exaggeration of fiction, but it beautifully illustrates a real cognitive approach: humans compress a vast number of past cases into empirical patterns, and then use these patterns to understand new individuals.

This level answers the second fundamental question of understanding others: what does this expression usually mean?

4 Level 3: Psychological Mechanisms—Why Is It Like This?

Experiential patterns can help us judge “what this expression usually means,” but they cannot fully explain the reasons behind the behavior. Psychology, however, inquires further:Why do people exhibit such behavior?

For example, a person who is extremely afraid of failure will proactively downplay the importance of a task whenever they face something where they might fail, even telling themselves: “Actually, this thing wasn't very interesting to begin with.”

From an empirical perspective, we might judge: “This person is actually afraid of failure.” But psychology will continue to ask further:Why does a person who is afraid of failure protect themselves by denying the value of the thing itself?

This may involve psychological processes such as self-protection, defense mechanisms, and self-worth. When failure occurs, by telling themselves “it's not that I lack ability, but that this thing wasn't worth caring about in the first place,” a person can reduce the psychological pressure brought by failure, thereby maintaining a stable self-perception.

The depiction of the psychological counseling process between psychology professor Sean (played by Robin Williams) and the male protagonist Will (played by Matt Damon) in the movie *Good Will Hunting* can serve as a classic cinematic example of this way of understanding:

When facing a person's aggression, resistance, or seemingly irrational behavior, true psychological work is not simply about labeling the behavior, but about trying to understand the experiences, emotions, defenses, and psychological mechanisms behind these manifestations.

Therefore, the value of psychology lies not merely in classifying human behavior, but inEstablishing a set of theoretical models that can explain the causes of behavior。

This level focuses on the third question of understanding others: Why does such behavior occur?

5 Level 4: Structure of Human Nature—Why Are Humans Generally Like This?

When the subject of observation expands from “this person” to “many people,” we might discover common patterns that span across individuals, eras, and even cultures.

For example, why might people change their self-perception after gaining power? Why do people re-interpret their own behavior when their interests are threatened? Why do people in a group often make choices they wouldn't make when alone? Why might an originally kind person do cruel things under specific circumstances?

These questions are no longer just: “Why is this person like this?” but are asking:“Why are humans, as a species, prone to being like this under specific conditions?” This is the structural level of human nature.

This level does not focus on the specific experience of a particular individual, nor does it necessarily rely on a single psychological theory; instead, it attempts to abstract more stable laws of human nature from a large number of individual behaviors.

The reason why the movie *The Godfather* remains timeless is largely because it does not just tell the story of a family, but demonstrates how factors such as power, interest, loyalty, fear, dignity, and family collectively influence human choices:

Why does a person who originally did not want to become a certain kind of person eventually walk down that path? Why does a person make completely different decisions after possessing different resources, power, and choices? These are also the questions that philosophy, sociology, and long-term observations of human nature attempt to answer.

This level ultimately focuses on the fourth question of understanding others: Why are humans generally like this?

4 The Essence of Understanding Others: From Mind-Reading Fantasy to Cognitive Models

At this point, these four levels can be looked at together again:

These four levels are not four independent methods, nor are they a simple division of ability levels, but rather different levels of cognitive abstraction when humans understand others, collectively forming a process from the concrete to the abstract:From signals to patterns; from patterns to mechanisms; from mechanisms to structures.

However, a higher level of the model does not necessarily mean that the understanding is more accurate: Behavioral signals are easily interfered with by disguise, noise, and specific contexts; empirical judgments may be affected by sample bias and stereotypes; psychological mechanism analysis may also fall into over-interpretation; and the abstraction of human nature, if detached from specific individuals and realistic contexts, may likewise slide into fatalism or determinism. Therefore, a truly deep understanding of a person often requires a combination of different levels.

Of course, this does not mean that humans can only understand others by establishing such a systematic model. The cognitive approaches mentioned above can naturally form in long-term social life—long before the emergence of modern psychology, humans had already gradually formed a vast amount of understanding about human nature by observing others and accumulating experience.

As said in the fifth chapter of *Dream of the Red Chamber*: “A thorough understanding of worldly affairs is genuine knowledge; a full mastery of human relations is itself fine writing.”