Seven and a Half Lessons About the Brain

1. Your brain's primary function is body regulation, not thinking

Your brain's most important job is to control your body​—​to manage allostasis​—by predicting energy needs before they arise so you can efficiently make worthwhile movements and survive.

Allostasis, not cognition. The brain evolved primarily to regulate the body's energy needs and resources, a process called allostasis. This involves predicting and preparing for the body's needs before they arise, ensuring efficient use of energy for survival and reproduction. The brain continually invests energy in anticipation of future needs, balancing withdrawals and deposits in the body's metaphorical energy budget.

Evolution of complexity. As animals evolved larger, more complex bodies, their brains developed increasingly sophisticated systems to manage internal bodily functions:

• Cardiovascular system (heart, blood vessels)
• Respiratory system (lungs, gas exchange)
• Immune system (fighting infections)
• Endocrine system (hormones, metabolism)

These complex systems required a central command center – the brain – to coordinate and regulate them efficiently. Thus, the primary purpose of the brain is to run the body, with cognitive functions like thinking, emotion, and creativity emerging as consequences of this foundational role.

2. The triune brain theory is a myth: You have one integrated brain

The triune brain idea and its epic battle between emotion, instinct, and rationality is a modern myth.

One integrated brain. The popular "triune brain" theory, which suggests the human brain evolved in three distinct layers (reptilian, emotional, and rational), is scientifically inaccurate. Modern neuroscience reveals that the human brain is a single, interconnected structure with no clear divisions between instinct, emotion, and rationality.

Evolutionary continuity. Recent research shows that:

• Reptiles and mammals share many of the same types of neurons
• Brain development follows a common "manufacturing plan" across species
• The human cerebral cortex is not disproportionately large compared to other mammals
• There is no dedicated "emotional" or "rational" brain system

This understanding challenges traditional notions of human nature and the idea that rationality must overcome emotion. Instead, it suggests a more integrated view of brain function, where cognition, emotion, and instinct work together as part of a unified system for body regulation and adaptive behavior.

3. Your brain is a complex, adaptable network, not a fixed structure

A brain network is not a metaphor. It's a description that comes from the best available science about how brains evolved, how they're structured, and how they function.

Dynamic neural networks. The brain is best understood as a complex, interconnected network of neurons rather than a fixed structure with dedicated components. This network is constantly changing and adapting, with neurons forming and breaking connections based on experience and need.

Key features of the brain network:

• Hubs: Densely connected regions that facilitate efficient communication
• Plasticity: The ability to change and reorganize connections over time
• Degeneracy: Multiple neural pathways can produce the same outcome
• Complexity: The capacity to create a vast number of distinct neural patterns

This network structure allows the brain to be incredibly flexible and efficient, adapting to new situations and environments while conserving energy. It explains how the brain can perform a wide range of functions with a single physical structure, and how it can recover from damage by rewiring itself.

4. Early experiences shape brain development through tuning and pruning

Little brains wire themselves to their world.

Experience-dependent development. A baby's brain is not fully formed at birth but continues to develop based on environmental inputs. This process involves two key mechanisms:

1. Tuning: Strengthening frequently used neural connections
2. Pruning: Eliminating unused or unnecessary connections

Critical role of caregivers. Parents and caregivers play a crucial role in shaping a child's brain development by:

• Regulating the baby's body budget (feeding, comforting, etc.)
• Guiding attention to important stimuli
• Providing rich sensory and social experiences

This developmental process allows the brain to adapt to its specific environment, but it also makes children vulnerable to negative experiences. Chronic stress, neglect, or poverty can have long-lasting effects on brain structure and function, potentially leading to physical and mental health issues later in life.

5. Your brain constantly predicts and constructs your reality

Scientists are now fairly certain that your brain actually begins to sense the moment-to-moment changes in the world around you before those light waves, chemicals, and other sense data hit your brain.

Predictive processing. Rather than passively reacting to sensory input, your brain actively constructs your perception of reality through constant prediction. It uses past experiences and current context to anticipate what you'll see, hear, feel, and do next.

Key aspects of predictive processing:

• Efficiency: Predictions allow faster responses to the environment
• Hallucination: Your conscious experience is a "controlled hallucination" constrained by sensory input
• Learning: Prediction errors drive learning and updating of mental models

This predictive nature of the brain has profound implications for understanding perception, action, and even concepts like free will. It suggests that our experiences and actions are heavily influenced by our past and current state, but also that we have the power to shape our future predictions through deliberate learning and exposure to new experiences.

6. Human brains are interconnected, regulating each other's body budgets

For your whole life, outside of your awareness, you make deposits of a sort into other people's body budgets, as well as withdrawals, and others do the same for you.

Social regulation. Human brains are fundamentally interconnected, constantly influencing each other's physiological states and energy budgets. This mutual regulation occurs through various channels:

• Physical proximity (e.g., touch, synchronized breathing)
• Emotional contagion
• Language and communication

Words as biological regulators. Language has a powerful effect on our biology:

• Kind words can calm and soothe
• Harsh words can trigger stress responses
• Even reading or hearing descriptions can activate corresponding brain regions

This interconnectedness has both positive and negative consequences:

• Benefits: Supportive relationships improve health and longevity
• Risks: Chronic stress from social sources can lead to physical and mental illness

Understanding this social nature of our brains highlights the importance of fostering positive relationships and considering the impact of our words and actions on others' well-being.

7. There is no universal human nature: Brains create diverse minds

Human brains make many different kinds of minds.

Variation is the norm. Rather than a single, universal human nature, our brains create a diverse array of minds shaped by culture, experience, and individual differences. This variation is crucial for the survival and adaptability of our species.

Examples of mind diversity:

• Cultural differences in emotional experiences and expression
• Varied cognitive styles and abilities (e.g., autism spectrum)
• Different ways of understanding and interacting with the world

Plasticity and acculturation. The human brain's plasticity allows for significant adaptation to new environments and cultures throughout life. This process, called acculturation, involves rewiring the brain to efficiently navigate new social and physical contexts.

Recognizing the diversity of human minds challenges simplistic notions of normal vs. abnormal and encourages a more nuanced understanding of mental health, education, and social interaction.

8. The human superpower: Creating shared social reality

Social reality is an incredible gift. You can simply make stuff up, like a meme or a tradition or a law, and if other people treat it as real, it becomes real.

Collective imagination. Humans have a unique ability to create and maintain shared social realities – collectively imagined concepts that shape our world and behavior. This capacity emerges from the interplay of five key abilities (the "Five Cs"):

1. Creativity
2. Communication
3. Copying
4. Cooperation
5. Compression (abstraction)

Power and responsibility. Social reality allows humans to:

• Create complex societies and institutions
• Collaborate on a massive scale
• Adapt to diverse environments

However, it also comes with risks:

• Potential for manipulation and oppression
• Mistaking social constructs for physical reality
• Unintended consequences on human evolution

Understanding the constructed nature of social reality empowers us to critically examine and shape the shared beliefs and institutions that govern our lives. It highlights both the remarkable adaptability of human societies and the responsibility we have in creating a world that promotes well-being for all.

Last updated: January 23, 2025