system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: My mind can make snap decisions or opinions instinctively, but it's very hard to articulate my reasoning. Why is that?

For example: I was just reading a post about female life expectancy being, in general and on average, longer than men.

One person chimed in 'there is a biological explanation for this, as grandmothers play a vital role in raising families and children'.

My mind instantly goes 'that is so incredibly stupid'. Now, whether or not that's true, somehow my brain leaps to a conclusion/opinion on the matter, and I even get annoyed by the statement.

But if someone challenged me back in conversation and asked me why that is such a bad argument, I find it difficult to respond and articulate why.


So, what is going in my head that 'enables' me to make snap reactions if there is no perfectly-formed conscious line of thought behind it?
gpt
Our brains have processes called heuristics. 

You know how when you walk across the same place in the grass a lot, the grass dies and turns into a path?  A heuristic is the same thing, but it's a pathway for thought.  A pathway that gives you a shortcut around logic, because it's easier.  

In your case, you've maybe heard a lot of people argue for an evolutionary basis for something they've noticed.  Maybe you associate those arguments with people who have certain beliefs with which you disagree. Maybe you've seen those arguments debunked often.

Whatever the case, you've worn down a shortcut in your brain where when someone makes that argument, you just cut across to the part where you think it's bullshit.