Can an old dog learn new tricks?

We decided to test the old dogs/new tricks cliche with our 14 1/2 year old Yorkie.

She never learned to "shake." A week ago we asked her to shake before she got her morning and afternoon treats. She's very good at sitting, but doesn't know shake.

We have her sit, say "shake" and lift her paw, then treat her. The 3 year old yorkie got it in 3 treat sessions. The old dog hasn't gotten it yet. We're giving her 2 weeks to catch on. We'll keep you posted.