system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we curse as a reflex?

Well, when something gets messed up we often react by cursing. It's almost a reflex. I say almost because I never curse in front of my father and am otherwise doing it around friends.
gpt
That isn't a reflex. It's a habit.

Comparing the two introduces some really interesting neuroscience topics that have to do with habituation and learning.

A reflex is, broadly speaking, any response that happens *without* conscious thought. If you touch a hot stove, you're gonna pull your hand back *before* the fact that you just touched a hot stove even gets to your brain. It happens entirely without your input.

A habit, on the other hand, is kind of like a *learned reflex.*

Things happen in the nervous system because chemical reactions propagate from one nerve cell to another, like a row of dominos falling over. When an electrochemical reaction propagates from one neuron to another, a kind of feedback happens that ends up strengthening the connection between the two cells. That makes it easier for the same reaction to happen next time; it takes less energy, basically, to knock the next domino over.

That means when a "signal" (it's not really a signal in the sense you might be thinking, but that's a useful metaphor) propagates down a particular neuronal pathway just one time, it becomes *slightly easier* for a "signal" to propagate down that pathway the next time.

Neuroscientists say "What fires together, wires together."

This is the key to *all* learning. You know how you can't really learn something — a skill, or a fact you want to remember, or whatever — by just experiencing it once? You have to practice a skill, or review a fact multiple times before it "sticks." That's because you have to stimulate those particular cells in that particular way a number of times before they "grow together" enough to make it easy for that signal to propagate.

*Habituation* is the logical extreme of that process. It's when you do something *consciously* enough times that it becomes unconscious. Like biting your fingernails, or tapping your foot. You don't *decide* to do that — if that's your habit. Instead, it happens "automatically," because you've *so wired* those particular neurological pathways that signals propagate down them *all by themselves.*

So it isn't a reflex to swear when you hurt yourself or whatever. It's a habit. It's something you did enough times consciously that you've begun doing it without conscious intent. Cause you've *changed your brain.*

(For the record, unlike reflexes, habits can be broken. You just need to *interrupt* the action by conscious intent often enough, and the interruption will itself become habituated, breaking the habit.)