A line in an old C&W song goes like this
“Someday I think I'll take up thinkin' and try my best to understand...”
The genre alone should have provided a sufficient clue, but just in case it hasn't, it is a man singing a song about a woman who "done him wrong".
But that's not the important thing about those words. What is, is the way they sum up the male's attitude toward thinking.
There is no sense in needlessly wasting energy thinking when none is required.
Save that energy for important things, such as cheering on your team, or hollering out to the kitchen for another beer, or pointing out to the referee/umpire/official how and why he just made an idiotic call.
When a man is hungry there is no need to think about what to do. He grabs some food and eats.
Or, when that man is tired, he goes to sleep.
Again, no need to think about what needs to be done to take care of the need. Men just naturally come up with the right answers without having to think.
Women, on the other hand, find thinking to be an exercise that brings them some sort of odd satisfaction regardless of the end results.
For instance, a woman, when asked for some sort of favor by a man, may respond with "I'll think about it".
Savvy men recognize that the most accurate interpretation of that statement is "It'll be a cold day in hell before I say yes to that one, Mister".
Thus it is true that many men's brains have not been used. At least not for “thinking”. It is seldom that a man will find such activity necessary. It is inherent in men to do the right thing reflexively unless the problem is extremely complex and the answer has serious ramifications, such as: If we find life on Mars, should we subsequently invade the planet and force them to install a democratic form of government? Or... is draft beer really that much better than bottled?
And if so, why, and what can be done to make bottled beer taste as good?
As the song referenced above makes clear, a man will schedule his thinking for a time when there are no other issues to be attended to. Men support one another in these endeavours and perform their thinking as a group action, when all energy can be concentrated in a single area. This is why a small party of men, meeting in the back corner of a dark tavern, absent distractions, can solve all the world's problems before closing time.
Sadly, women waste too much of their energy thinking, to no avail. “I 'thought' you said you would clean out the garage this weekend” a wife says to her husband.
The fact that he has been promising to attend to this little chore for months without moving an inch in that direction has not made an impression upon her. Had she been thinking productively, she would have moved the TV and his easy chair into the garage, placing the two on opposite side of a pile of trash that has blocked access to her parking spot for over a year.
And he, without having to think about it, would have carted that pile out to the curb before the game started.