"You can't teach an old dog new tricks." It's one of those sayings I've heard all my life and one I refuse to accept. Okay, grudgingly I will admit (only from observation of others of course!) that there may be some advantages to learning when you are a youth . . . but learning is not all about increasing your "fund of knowledge" (besides, who needs to know anything with Google around?) or developing a new skill set (I've learned a lot about wiring but I don't want to, nor will I ever have need of, becoming an electrician).
So, if "old dogs" don't need the knowledge or skills of new learning (except of course when they need to use the smart phone) then why pursue it at all? Well, it is my contention that those of us approaching the second half of our lives should pursue learning simply because . . . it changes you and how you will observe data all around you.
Those who study such things will tell you that knowledge and skill retention is directly related to the length of time and saturation one has with a certain knowledge area or skill. Thus something you learned and practiced since youth (let's say for five decades) is not likely to be lost easily while a relatively "new" skill or knowledge with limited exposure can lead to quick reversal in the learning and potential utter loss. Okay, but even this view, I think, still focuses on learning as acquiring a fund of knowledge or skill building.
I believe one of the greatest reasons to continue to challenge yourself with new learning then is that it changes what you will observe. It may not measure on a test of content or turn into a new expertise but it will change you.
Have you ever had an experience like this? Several years ago my daughter decided she wanted to have a horse. At the time I thought horses in my part of the country were a rarity . . . a relic of the past or the domain of a few breeders, maybe a few rogue left-over "cowboys" and some wealthy owners with show horses. Then we got horses and began to trailer them to various events. Suddenly, it seemed, I was seeing horses everywhere! I could not believe how many horses (and trailers) I drove past daily that I had never noticed before. (The same thing happened when I started keeping bees.)
Thus one of the things I have learned in recent years is to read music (at the advanced old age of 48). I also continue to take guitar lessons to this day. Why? Because it changes what I observe and it changes me. Flamingo-style and classical guitar music was something I could appreciate as a skill but did not enjoy as it sounded all the same to my ear. Now, after working hard to become a trained classical guitar player it is something richer and more enjoyable than I ever dreamed it could be.
So faithful reader, whether you are a young pup or an old dog, go out and learn . . . to change!