After reading ‘Seven and a half lessons’
The book Seven and a Half Lessons About the Brain (subtitle: What Your Brain Can Tell You About Yourself) was written by Lisa Feldman Barrett, a world-renowned neuroscientist and director of the Center for Law, Brain, and Behavior at Harvard University. Barrett demystifies neuroscience by explaining complex concepts in everyday language, making it accessible for readers. In an era of rapid advancements in AI and cognitive science, this book is particularly valuable for prompting deep reflection on what it means to be human. It offers insights from anthropology and philosophy, providing readers with a fresh perspective.
Barrett explains that the brain is not just a tool for high-level cognition or reasoning, but also plays a critical role in efficiently managing the body’s energy resources. In other words, the brain is the central mechanism that regulates the body’s “budget.” This perspective challenges the traditional view of the mind-body relationship, emphasizing the deep connection between the brain and the body. Through this, readers gain a more profound understanding of the biological foundations and the importance of bodily functions.
Lesson $\frac{1}{2}$: The Brain Exists to Achieve Allostasis
From an evolutionary perspective, modern humans’ ancestors are thought to be very similar to present-day mammals. So why did our brains evolve the way they did? Common knowledge suggests that it was to “think.” In other words, humans evolved to perform high-level cognitive functions that other animals cannot, giving us dominance over them. This is why humans are often called “thinking animals.”
However, modern neuroscience finds no evidence to support this idea of “progressive evolution.” Instead, the brain exists to solve more fundamental problems, such as managing vital biological resources like water, salt, and oxygen. This process is not merely reactive or reflexive.
The brain’s most critical function is to predict when and how much energy is needed for survival and to control the body efficiently based on those predictions. This process of predictive resource management and control is called “allostasis.”
Lesson 1: The Brain is One
In Lesson 1, we learn that Plato’s classification of the mind is incorrect. Similarly, Aristotle thought the brain was a cooling system for the heart, medieval philosophers believed it was the seat of the soul, and 19th-century phrenologists treated it as a puzzle of functions like self-esteem and destructiveness. These errors mainly arose from metaphors.
Modern neuroscience understands the brain as a network. This network consists of about 128 billion neurons connected by over 500 trillion synapses, immersed in chemical substances called neurotransmitters. Neurons form clusters, and especially crucial are hubs that are highly connected with other clusters. When these hubs malfunction, mental disorders like depression, schizophrenia, and dyslexia can occur.
This network is constantly changing. Chemicals like glutamate, serotonin, and dopamine regulate these changes, speeding them up or slowing them down. Some neurotransmitters even affect the impact of others. If we compare this network to an airport system, neurotransmitters are like the airport staff or the weather.
The brain is highly energy-efficient, compact yet powerful, and designed to fit neatly within the skull. Most neurons are flexibly connected, allowing the brain to handle various tasks simultaneously. This phenomenon, known as “degeneracy,” is observed in systems like the immune system and olfactory genetics, where single units perform multiple functions. Moreover, the brain generates complex spatial and temporal patterns, maintaining high complexity. Our brain is much more intricate than a “meatloaf brain,” where all neurons are connected, or a “jackknife brain,” where major functions are simply stuck together.
Lesson 2: The Brain is a Network
In Lesson 2, we find that Plato’s classification of the mind was wrong. Aristotle, too, believed the brain was a cooling system for the heart, medieval philosophers considered it the seat of the soul, and 19th-century phrenologists thought of it as a puzzle of various functions like self-esteem or destructiveness. These errors were largely due to the use of metaphors.
Modern neuroscience sees the brain as a network. It consists of approximately 128 billion neurons connected by more than 500 trillion synapses, working in a fluid of neurotransmitters. Neurons are organized into clusters, and certain hubs, which are more connected than others, play a crucial role. If these hubs malfunction, it can lead to neurological or psychiatric disorders such as depression, schizophrenia, or dyslexia.
This network is dynamic, constantly changing. Neurotransmitters like glutamate, serotonin, and dopamine play roles in modulating the network’s speed of change. Some neurotransmitters can even affect how others work. The network structure is often compared to an airport system, with neurotransmitters acting like airport employees or weather conditions.
Lesson 3: The Young Brain Shapes Itself
Human babies are born in a relatively undeveloped state compared to other animals. The debate between nature and nurture is also critical in neuroscience. The brain undergoes changes in two major ways: tuning and pruning. Tuning relates to Hebb’s principle, which states that “neurons that fire together, wire together.” Pruning, on the other hand, refers to the idea that “what isn’t used is lost.”
Parents and caregivers play a vital role in shaping the developing brain. Babies cannot even burp on their own, so caregivers help regulate the infant’s bodily budget. Caregivers also teach babies what is important in their environment through shared attention, helping them create their own “niche.” The role of caregivers is also crucial in sensory development. Children exposed to multiple languages early on develop the ability to distinguish and learn them more easily. Without such exposure, learning new languages becomes much harder later in life.
Without caregivers, a young brain struggles to connect with the world. For example, children raised without caregivers in Romanian orphanages were more prone to language and attention difficulties, as well as psychological and behavioral problems. They even faced physical developmental issues. In conclusion, the human brain is designed to require both nature and nurture, making it meaningless to separate the two. Our genes are structured to complete brain development within the right physical and social environment—our “niche.”
Lesson 4: The Brain Predicts Almost Everything You Do
Cameras detect visual information and reconstruct it as images. But our brains work differently. Perception feels smooth and convincing, yet it is often inaccurate. The brain combines fragments of sensory input with memory to predict the experience of the world. Half of this experience comes from sensory input, and the other half is a “controlled hallucination” produced by the brain. This is similar to what Marcel Duchamp called the “beholder’s share.”
The brain uses sensory information to adjust the body budget and predict experiences accordingly. If predictions are wrong, the brain typically learns and corrects them, but when survival is at stake, prediction errors may be ignored. We often believe that perception guides our actions, but from a neuroscientific perspective, it may be that we act first for survival, and perception follows.
Does this mean we lack free will and, therefore, have no legal responsibility? Not at all. We can change our predictions through new experiences and creative ideas. In fact, we may have more control over our actions and experiences than we realize, which could lead to the conclusion that we bear even more responsibility.
Lesson 5: Your Brain Moves in Sync with Other Brains
Humans are social animals. We form groups, care for each other, and build civilizations together. Our brains regulate each other’s body budgets through cooperation, playing a key role in social connections. Poet Alfred Tennyson once said, “It is better to have loved and lost than never to have loved at all.” Research shows that couples who listen to each other, share intimacy, and support one another are not only happier but also less likely to fall ill. This also applies to the workplace, where trusting colleagues and managers can improve both performance and job satisfaction.
While animals rely on chemicals like pheromones, or senses like smell, sound, and touch to regulate each other’s nervous systems, humans primarily use language. The power of language over the body is significant. Many areas in the brain that process language are also involved in controlling the body’s internal functions, particularly the body budget. In fact, the brain’s language networks overlap significantly with the brain’s “default mode network,” which helps regulate systems like the autonomic nervous system, immune system, and endocrine system. This makes “words” an important tool for managing our bodies.
From a social and political standpoint, verbal aggression is a serious issue. Prolonged exposure to verbal abuse can lead to physical damage to our nervous systems by overtaxing the body budget. This raises the need for new perspectives on issues like freedom of expression and our reliance on others. Humans are highly interdependent, meaning that one person can either deplete or energize another person’s body budget. This hidden form of cooperation is essential to keeping us healthy.
Lesson 6: Your Brain Creates Many Kinds of Minds
People from the island of Bali in Indonesia respond to fear by falling asleep. Meanwhile, both Balinese and the Ilongot people of the Philippines experience what Westerners call “cognition” and “emotion” as a unified whole rather than as separate processes. In short, a brain shaped and developed within a specific culture produces a specific kind of mind. This doesn’t mean that the human brain is a blank slate (tabula rasa) that only learns from the environment, as in the metaphor of the “meatloaf brain.” Nor does it mean that the brain is born fully pre-programmed with universal human nature, as in the “jackknife brain.” Instead, humans are born with a “basic brain plan” that allows for a variety of mental configurations depending on how the brain is wired.
One of Charles Darwin’s key insights was that variation is a prerequisite for natural selection. Species with more variation are more likely to survive a catastrophe because of their diversity. Although variation is common and advantageous, many people find comfort in believing in universal human nature. This is why personality tests like the Myers-Briggs Type Indicator (MBTI), which categorize people into 16 personality types, are so popular.
One universal feature of the human mind is “affect”—the general feeling we get from our body, which science refers to as “affect.” Affect exists on a spectrum from pleasant to unpleasant (valence) and from activated to deactivated (arousal). Our brain is constantly generating affect, which acts as a summary of our bodily state and a barometer of our current situation. However, how physical processes turn into mental experiences remains one of the great mysteries of consciousness. When affect is combined with cultural adaptation (acculturation), the resulting mental experiences become far more complex. This is why people from different cultures have distinct mental experiences.
Lesson 7: Your Brain Constructs Your Reality
Humans create social realities like money, calendars, and nations. These concepts correspond to physical realities like paper and metal, the movement of the Earth and Sun, or the geography of continents and borders. Social realities can have profound effects on physical realities, such as in the case of wars or financial markets. Our ability to create these social realities is linked to five cognitive abilities known as the “5 Cs”: creativity, communication, copying, cooperation, and compression. Of these, creativity, communication, copying, and cooperation evolved alongside the large, complex human brain.
Compression, however, is unique to the human brain. The connection structures of layers 2 and 3 of the cerebral cortex enhance our brain’s ability to compress information. Sensory fragments are compressed into abstract representations, and creativity works as the reverse process—unpacking these abstractions. Abstraction and creativity are shared and spread through communication, copying, and cooperation within a cultural community.
While most animals evolved to be specialists in their niches, humans evolved to be generalists. We no longer merely select features from the physical world to adapt to; instead, we collectively add new functions as a group. Social reality is, in a way, a human-made niche.
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