Joy Molecules: How Our Brain Creates Neural Connections and Shapes Habits and Intelligence
Hormones influence the mechanisms behind emotion formation and the action of various neurochemicals, and as a result, play a role in developing lasting habits. Loretta Graziano Breuning, distinguished professor at the University of California and author of the book Habits of a Happy Brain, suggests we reconsider our behavioral patterns and learn how to activate serotonin, dopamine, endorphin, and oxytocin.
Rewiring Neural Pathways
Every person is born with a multitude of neurons but very few connections between them. These connections are built as we interact with the world around us and ultimately shape who we are. Sometimes, you may want to modify these established connections. It might seem easy, since they formed effortlessly in our youth, but creating new neural pathways in adulthood turns out to be surprisingly difficult. Old connections are so efficient that abandoning them can feel like a threat to survival. Any new neural chains are fragile compared to the old ones. Once you understand how hard it is for the brain to form new neural pathways, you’ll appreciate your persistence in this area more than you’ll criticize yourself for slow progress.
Five Ways Your Brain Self-Adjusts
We mammals are able to create neural connections throughout our lives, unlike species with fixed connections. These connections form as the world around us stimulates our senses, which send electrical impulses to the brain. These impulses carve out neural pathways, making it easier and faster for future impulses to travel the same routes. Each person’s brain is tuned to their individual experiences. Here are five ways experience physically changes your brain:
Life Experience Insulates Young Neurons
A constantly active neuron eventually becomes coated with a special substance called myelin, which greatly increases its efficiency as a conductor of electrical impulses. Think of it like insulated wires carrying more current than bare ones. Myelinated neurons work effortlessly, unlike slow, “bare” neurons. Myelinated neurons appear white, which is why we distinguish between “white matter” and “gray matter” in the brain.
Most myelination of neurons is completed by age two, as a child learns to move, see, and hear. When a mammal is born, its brain must quickly form a mental model of the world to survive. That’s why myelin production is highest at birth and decreases by age seven. By then, you no longer need to relearn basic truths like fire burns or gravity makes you fall.
With the onset of puberty, myelination ramps up again. This is because mammals need to retune their brains to find the best mating partners. Animals often migrate to new groups during mating season, so they must adapt to new places and companions. Humans, too, often move to new tribes or clans and learn new customs and cultures in search of a mate. The increase in myelin production during puberty supports all this. Natural selection has designed the brain to change its mental model of the world during this period.
Everything you do deliberately and consistently during your “myelin bloom” years creates powerful, branched neural pathways in your brain. That’s why genius often shows up in childhood. That’s why young skiers can zip past you on slopes you can’t master, no matter how hard you try. That’s why learning foreign languages becomes so much harder after adolescence. As adults, you can memorize foreign words, but you often can’t recall them quickly to express your thoughts. That’s because your verbal memory is concentrated in thin, unmyelinated neurons, while your powerful myelinated connections are busy with higher-level thinking, making it hard for new impulses to find free neurons.
Fluctuations in myelination can help explain why people face different challenges at different life stages. Remember, the human brain doesn’t mature automatically. That’s why people say teenagers’ brains aren’t fully developed. The brain “myelinates” all our life experiences. So, if a teenager repeatedly receives unearned rewards, they’ll firmly remember that rewards can come without effort. Some parents excuse bad behavior by saying, “Their brain isn’t fully formed yet.” That’s why it’s so important to intentionally guide the experiences teens absorb. If you let a teen avoid responsibility for their actions, you may shape a mind that expects to dodge responsibility in the future.
Life Experience Increases Synapse Efficiency
A synapse is the contact point (a small gap) between two neurons. An electrical impulse in the brain can only move forward if it reaches the end of a neuron with enough strength to “jump” across this gap to the next neuron. These barriers help us filter truly important incoming information from meaningless “noise.” The process of an impulse crossing a synaptic gap is complex. Imagine a fleet of boats at the tip of one neuron, ferrying a neural “spark” to special docks on a neighboring neuron. With each repetition, the boats get better at their job. That’s why experience increases the chances of electrical signals passing between neurons. The human brain has over 100 trillion synaptic connections, and our life experience plays a crucial role in making sure impulses travel in ways that support our survival.
On a conscious level, you can’t decide which synaptic connections to develop. They form in two main ways:
- Gradually, through repeated practice.
- Instantly, under the influence of strong emotions.
Synaptic connections are built on repetition or emotions you’ve experienced in the past. Your mind exists because your neurons have formed connections that reflect both successful and unsuccessful experiences. Some episodes were “uploaded” to your brain thanks to “joy molecules” or “stress molecules,” while others were cemented by constant repetition. When your mental model of the world matches the information in your synaptic connections, electrical impulses flow easily, and you feel in tune with what’s happening around you.
Neural Chains Form Only from Active Neurons
Neurons that aren’t actively used start to weaken as early as age two. Strangely, this actually helps intelligence develop. Reducing the number of active neurons allows a toddler to focus on what’s familiar and rewarding, rather than being distracted by everything like a newborn. A two-year-old can already concentrate on things that brought pleasure before, like a familiar face or a favorite bottle. They can avoid things that previously caused negative emotions, like a quarrelsome playmate or a closed door. The young brain relies on its limited experience to meet needs and avoid threats.
How Neural Connections Feel Like “Truth”
Between ages two and seven, the brain continues to optimize itself, prompting the child to relate new experiences to old ones instead of storing new experiences as separate blocks. Closely intertwined neural connections and pathways form the basis of our intelligence. We create them by branching out old neural “trunks” rather than making entirely new ones. By age seven, we usually see what we’ve seen before and hear what we’ve already heard.
You might think this is a bad thing, but consider its value. Imagine you lie to a six-year-old—they believe you because their brain eagerly absorbs everything. But if you lie to an eight-year-old, they’re more likely to doubt you, comparing new information to what they already know. At eight, it’s harder to form new neural connections, so they rely on existing ones. This reliance helps them spot lies, which was crucial for survival when parents died young and children had to fend for themselves. In youth, we form certain neural connections and let others fade away, like autumn leaves in the wind. This makes our thinking more efficient and focused. Of course, you keep learning as you age, but new information tends to cluster in areas of the brain where active pathways already exist. For example, if our ancestors were born into hunting tribes, they quickly gained hunting experience; if born into farming tribes, they learned agriculture. The brain thus adapted for survival in the world they actually lived in.
New Synaptic Connections Form Between Actively Used Neurons
Each neuron can have many synapses because it has many branches, or dendrites. New branches form when a neuron is actively stimulated by electrical impulses. As dendrites grow toward points of electrical activity, they can get close enough for impulses from other neurons to bridge the gap. This is how new synaptic connections are born. When this happens, you consciously make connections between two ideas, for example.
You can’t feel your own synaptic connections, but you can easily see them in others. A dog lover sees the world through that passion. A tech enthusiast relates everything to technology. A political junkie interprets reality politically, while a religious person sees things through faith. One person sees the world positively, another negatively. However your neural connections are built, you don’t feel them as tentacle-like branches—you experience them as “truth.”
Emotion Receptors Develop or Atrophy
For an electrical impulse to cross a synaptic gap, a dendrite on one side must release chemical molecules that are caught by special receptors on the other neuron. Each neurochemical produced by our brain has a complex structure that fits only one specific receptor—like a key in a lock. When you’re overwhelmed by emotions, more neurochemicals are produced than the receptors can handle. You feel overwhelmed and disoriented until your brain creates more receptors. That’s how you adapt to what’s happening around you.
When a neuron’s receptor is inactive for a long time, it disappears, making room for other receptors you might need. Flexibility in nature means that neuron receptors must be used or they’ll be lost. “Joy hormones” are always present in the brain, searching for their receptors. That’s how you “recognize” the source of your positive feelings. A neuron “fires” because the right hormone molecules unlock its receptor. Then, a whole neural chain forms based on that neuron, teaching you where to expect joy in the future.