I’m just about to turn 65. I’ve been employed as an airline pilot for 36 years. I’m reasonably intelligent, but admittedly far from a wunderkind, and with no offers to work for the JPL or NASA. Pretty much an average guy who’s outstanding at being humble.
At at age 64, I had to learn how to fly the most complex and advanced airliner currently in service, the Airbus A350. I had flown the relatively simplistic Boeing 767 for the past 25 years, and had never flown an Airbus, which is completely different in almost every way from a Boeing.
I was the oldest person to attempt going through the Delta’s A350 Initial Qualification training program. I was warned that even much younger pilots were finding the training to be extremely challenging, and that because of my age, success might not be an option.
It was an extremely complex airplane. The training manual is literally 7000 pages long. Countless Training videos, 6 weeks of simulators, extremely difficult electronic and oral exams. “It can’t be done, old guy”, many said.
BULLSHIT! I went through the training and actually had an easy time of it. It was no more challenging than when I went through MD-11 training in 1991, at age 34, even though the A350 was a much more difficult training program.
I had no decline in my learning ability in 30 years, and aced the very challenging program without any trouble. If I can maintain my ability to easily learn complex tasks into my mid-60’s, hell, anyone can.
To answer the question:
For some it might be age 30, or 40, or 50, etc, etc. However, everyone is different. Some people are still extremely lucid and able to learn well into their 90’s.
Don’t assume. Don’t count yourself out at any age. Don’t be prejudiced against older people and sell them short, because many of them are still as sharp or even sharper than you. Treat all people well, especially older people, because in the blink of an eye you’re going to be one of them, and you’re going to love it when someone treats YOU with dignity and a little bit of respect.