In it he discusses the challenges and benefits of learning new things as an adult and in particular, debunking the long held scientific view called “critical-period effect”. Lucky for us old guys (and you too my dear readers!), Gary says "evidence for this belief was far weaker than widely supposed."
"The critical-period effect is the idea that you can’t do certain things—like learn a language, or learn an instrument—unless you start early in life. It’s a discouraging thought for anyone past adolescence. But, recently, the evidence for this idea had started to unwind."
When he decided to learn guitar at 40, Mr. Marcus said he did the best he could to "tackle the guitar bit-a-bit, keeping my expectations low and my persistence high." This should be the first commandment of music learning! And shortly after his book was published, he began finding new data that showed that the myth of critical periods itself had in fact kept people from even trying to learn new things.
By now we all know the power and far reaching benefits of learning music and casual music making - it's not just for 'school-kids' anymore. Folks of all ages are finding that learning music can "facilitate getting better at other things" with "results that last for decades." It's never too late to start and as Mr. Marcus says - the most important thing about learning something new is "...it can certainly make you happier." There's commandment #2!