I'm at the age where half of the adult conversations in my life are about one teenager or another in my extended social circle doing something that lacks "common sense." This seems to frustrate and anger adults.
But it doesn't frustrate me, for the same reason I don't expect my toaster to mow my lawn. A young person's brain doesn't have a fully developed prefrontal cortex, and that's the part of the brain that imagines future consequences of current actions. (Please correct me if I got the brain region wrong.)
I've also noticed - and this is purely anecdotal - that some people seem to be born with full prefrontal cortex function, in terms of imagining the future, and others don't develop that ability until adulthood. In my case, by the age of six I was planning my entire life through retirement. (That's literally true.) Obviously I've had to revise the plan often, but I've never had less than a fully-practical lifelong plan.
That's why I worked hard in school to get good grades. It's why as a kid I managed to stay out of any kind of trouble that would follow me. It's why I've never had a serious injury doing dumbass things. The downside was that I worried about the future more than a kid should. It wasn't a healthy situation.
Despite my nerdish impulse for long-range planning, I had no "common sense" as a kid. And that's probably because what passes as common sense is nothing but pattern recognition - or "experience" as we like to say - and kids haven't seen enough of life to recognize many patterns.
I tell a story in my new book about going to my first real-world job interview at the age of 20. I had no mentors in my life to advise me in the ways of the business world. I grew up in a town with 2,000 residents and I had never even met a "business person" per se. My job interview was with a major international accounting firm.
My common sense told me that the last thing I wanted to do in a job interview was lie, especially if the lie would be easily detected. So instead of wearing a suit to the interview, which would have required acting like a huge phony, I wore my casual student clothes. The interviewer already knew I was a senior in college, so why would I present myself in some false way to a person I wished to impress? My "common sense" said I should be honest in my appearance, to get off on the right foot.
The interviewer took one look at me and showed me the door. He said, "I don't think you know why you're here." Ouch.
As the years passed, I saw enough patterns to realize that looks can often be more important than substance. But nothing about it is "common sense."
My point is that a normal, healthy brain doesn't have some magical ability called common sense. The pre-frontal cortex is either fully-formed or it isn't. And you have either seen a lot of patterns in life or you haven't. Sometimes logic matters in our decision-making, but not often.
The idea of "common sense" feels like magical thinking to me, similar to the notion that we have a "mind" that is more than the sum of our brain's chemistry and architecture.
As a descriptor, "common sense" feels dated.