Can you teach an old dog new tricks?

I taught my dog Tazzy how to give fives and she's 10 doggy years old. But people are always saying you can't teach an old dog new tricks.

Is this true? Have you ever taught your older dog a new trick?

This can also extend to adults. Is it possible to teach an older person who has been in the world for quite a few years new things, like playing the guitar or to not be so pessimistic, etc?

Absolutely yes. No questions here. It's all up to talent, desire and commitment. Don't know about dogs but I have no doubts regarding humans.
As for pessimism in particular...Emotions and feelings come from inside never from outside, meaning you're the only person in charge of how you feel and what you think. I know few people who went all the way down to the point of being nothing (or at least that was how they felt) and yet...where's a will there's way.

The Phoenix wrote:

Absolutely yes. No questions here. It's all up to talent, desire and commitment. Don't know about dogs but I have no doubts regarding humans.
As for pessimism in particular...Emotions and feelings come from inside never from outside, meaning you're the only person in charge of how you feel and what you think. I know few people who went all the way down to the point of being nothing (or at least that was how they felt) and yet...where's a will there's way.

That's a brilliant answer, Phoenix! If a person thinks that they won't succeed, chances are they won't.

It's a bit like me playing the guitar. I tried about two years ago, but the moment I held the guitar in my hands, I was saying: "hell no! This is way too complicated for me! I'll never be able to play!" I gave up soon after.
But I'm retrying with a more, "I can do it! If some of these talentless gits can play the bass I can play the guitar!" () attitude. I've already got further than I did the first time and I've only been playing a week.

My view is somewhat contradictory to Xiahou's; I believe Dogs have the ability to learn and absorb any amount of skills within their grasp up until their old age, however people...people are proud, stubborn and defeatist!