Yes, that means get of the house and stop coding (if you are).
Ballroom dancing, lyrical poetry, busking, popping-and-locking, figure sculpting, going up to strangers and trying to learn something about them, anything.
For bonus points, once you learn skills in the above, immediately start trying to teach them.
Success is one area is not directly transitive. However, the more success you have in multiple areas - the better off you will be. It's all about confidence.
Be open to new things. A closed mind is a terrible thing to see.
This is increasing breadth of knowledge. I'm not sure I agree that if we are going for mental sharpness that breadth of knowledge is the thing we want to train.
I'd look more into things that where the challenge is incrementally increasable and more focused on mental quickness: puzzles, math challenges, that sort of thing.
Unfamiliar situations are where we rely on intelligence rather than previously experienced situations, or physical challenges, or predictable scenarios. Parent's suggestion is increasing exposure to unfamiliar situations, which in turn increases utilization of your intelligence, which is basically exercise for it, like exercising any other body part or talent. Math challenges improve math talent, word games improve linguistic talent, etc. At first they all exercise your intelligence (like every other activity suggested), but after a certain threshold of competence the focus will be on increasing knowledge and familiarity with a specific domain.
This model of intelligence is based on analyzing the upbringing and patterns of time spent by the most intelligent people I have met in my life, and it seems consistent with the parent's suggestions.
Breadth of knowledge increases your mental sharpness just as depth of knowledge though, they both do.
If you only go for depth, you can do a PhD in a super narrow field and it will increase your mental sharpness significantly. However, it won't be easy for you to apply that sharpness in the real world, as it is very specific.
If you want to go for breadth, the best thing for that is definitely a startup, as you have to become really, really good across all disciplines. Having done that for a while now, I start to miss the challenge of depth, such as mathematics and physics, which I would like to do more once that has stabilized. :)
Yes, that means get of the house and stop coding (if you are).
Ballroom dancing, lyrical poetry, busking, popping-and-locking, figure sculpting, going up to strangers and trying to learn something about them, anything.
For bonus points, once you learn skills in the above, immediately start trying to teach them.
Success is one area is not directly transitive. However, the more success you have in multiple areas - the better off you will be. It's all about confidence.
Be open to new things. A closed mind is a terrible thing to see.